DESCRIPTION
SIGNAL PROCESSING APPARATUS AND SIGNAL PROCESSING METHOD,
ENCODER AND ENCODING METHOD, DECODER AND DECODING METHOD, AND PROGRAM TECHNICAL FIELD ;
The present invention relates to a signal
processing apparatus and a signal processing method, an
encoder and an encoding method, a decoder and a decoding
method, and a program, and more particularly to a signal
processing apparatus and a signal processing method, an
encoder and an encoding method, a decoder and a decoding
method, and a program for reproducing a m.usic signal with
15 improved sound quality by expansion of a frequency band.
BACKGROUND ART
[0002]
Recently, music distribution services for
20 distributing music data via the internet have been
increased. The music distribution service distributes, :
as music data, encoded data obtained,, by encoding a music
signal. As an encoding method of the music signal, an
encoding method has been commonly used in which the
25 encoded data file size is suppressed to decrease a bit
rate so as to save time during download.
[0003]
Such an encoding method of the music signal is
broadly divided into an encoding method such as MPS .(MPEG
30 (Moving Picture Experts Group) Audio Layers 3)
(International Standard ISO/IEC 11172-3) and an encoding
1
a| SP248477WO01
method such as HE-AAC (High Efficiency MPEG4 AAC) J
(International Standard ISO/IEC 14496-3). [0004] I
The encoding method represented by MP3 cancels a I
5 signal component of a high frequency band (hereinafter,
referred to as a high band) having about' 15 kHz or more
in music signal that is almost imperceptible to humans,
and encodes the low frequency band (hereinafter, referred
to as a. low band) of the signal component of the
10 remainder. Therefore, the encoding method is referred to
as a high band cancelation encoding method. This kind of ?
high band cancelation encoding method can suppress the
file size of encoded data. However, since sound in a
high band can be perceived slightly by human, if sound is '
15 produced and output from the decoded music signal :
obtained by decoding the encoded data, suffers a loss of
sound quality whereby a sense of realism of an original ^
sound is lost and a sound quality deterioration such a
blur of sound occurs.
?0 [0005]
Unlike this, the encoding method represented by HEAAC
extracts specific information from a signal component
of the high band and encodes the information in
conjunction with a signal component of the low band. The
25 encoding method is referred to below as a high band
characteristic encoding method. Since the' high band •.-,
characteristic encoding method encodes only
characteristic information of the signal component of the
high band as information on the signal component of the
30 high band, deterioration of sound quality is suppressed
and encoding efficiency can be improved.
2
II SP248477WO01
[0006] j
In decoding data encoded by the high band •;
characteristic encoding method, the signal component of
the low band and characteristic information are decoded
5 and the signal component of the high band is produced
I I
from a signal component of the low band and
characteristic information after being decoded. - -
Accordingly, a technology that expands a frequency band
of the signal component of the high band by producing a
10 signal component of the high band from signal component
of the low band is referred to as a band expansion t
technology.
[0007] / ;
As an application example of a band expansion l
15 method, after decoding of data encoded by a high band
cancelation encoding method, a post process is performed. =
In the post process, the high band signal component lost
in the encoding is generated from the decoded low band :
signal component, thereby expanding the frequency band of
20 the signal component of the low band (see Patent Document
1) . The method of frequency band expansion of the
related art is referred below to as a band expansion
method of Patent Document 1.
[0008]
25 In a band expansion method of the Patent Document 1,
the apparatus estimates a power spectrum (hereinafter,
suitably referred to as a frequency envelope of the high
band) of the high band from the power spectrum of an
input signal by setting the signal component of the low
30 band after decoding as the input signal and produces the
signal component of the high band having the frequency
3
I
I
H^ SP248477WO01
envelope of the high band from the signal component of
the low band.
[0009]
Fig. 1 illustrates an example of a power spectrum t
5 of the low band after the decoding as an input signal and a frequency envelope of an estimated high band.
[0010] - - ;
In Fig. 1, the vertical axis illustrates a power as I
a logarithm and a horizontal axis illustrates a frequency.
10 [0011] The apparatus determines the band in the low band
of the signal' component of the high band (hereinafter,
referred to as an expansion start band) from a kind of an
encoding system on the input signal and information such
15 as a sampling rate, a bit rate and the like (hereinafter,
referred to as side information). Next, the apparatus
divides the input signal as signal component of the low
^ band into a plurality of sub-band signals. The apparatus
obtains a plurality of sub-band signals after division,
20 that is, an average of respective groups (hereinafter,
referred to as a group power) in a time direction of each
power of a plurality of sub-band signals of a low band
side lower than the expansion start band is obtained
(hereinafter, simply referred to as a low band side). As
25 illustrated in Fig. 1, according to the apparatus, it is
assumed that the average of respective group powers of
the signals of a plurality of sub-bands of.the low band
side is a power and a point making a frequency of a lower
end of the expansion start band be a frequency is a
30 starting point. The apparatus estimates a primary
straight line of a predetermined slope passing through
4
i
^ SP248477WO01
the starting point as the frequency envelope of'the high
band higher than the expansion start band (hereinafter,
simply referred to as a high band side). In addition, a ;
position in a power direction of the starting point may
5 be adjusted by a user. The apparatus produces each of a
plurality of signals of a sub-band of the high band side i
from a plurality of signals of a sub-band of the low band - r
side to be an estimated frequency envelope of the high ;
band side. The apparatus' adds a plurality of the i
10 produced signals of the sub-band of the high band side to
each other into the signal components of the high band
and adds the signal components of the low band to each
other to output the added signal components. Therefore,
the music signal after expansion of the frequency band is :
15 close to the original music signal. However, it is
possible to produce the music signal of a better quality.
[0012]
The band expansion method disclosed in the Patent
Document 1 has an advantage that the frequency band can
20 be expanded for the music signal after decoding of the
encoded data with respect to various high band
cancelation encoding methods and encoded data of various
bit rates.
25 CITATION LIST
PATENT DOCUMENT
[0013]
Patent Document 1: Japanese Patent Application Laid-Open
No. 2008-139844
30
SUMMARY OF THE INVENTION
5
^ SP248477WO01
PROBLEMS TO BE SOLVED BY THE INVENTION
[0014]
Accordingly, the band expansion method disclosed in
Patent Document 1 may be improved in that the estimated
5 frequency envelope of a high band side is a primary straight line of a predetermined slope, that is, a shape
of the frequency envelope is fixed.
[0015]
In other words, the power spectrum of the music
10 signal has various shapes and the music signal has a lot
of cases where the frequency envelope of the high band
side estimated by the band expansion method disclosed in
Patent Document 1 deviates considerably.
[0016]
15 Fig. 2 illustrates an example of an original power
spectrum of an attack music signal (attack music signal)
having a rapid change in time as a drum is strongly hit
once.
[0017]
20 In addition. Fig. 2 also illustrates the frequency
envelope of the high band side estimated from the input
signal by setting the signal component of the low band
side of the attack relative music signal as an input
signal by the band expansion method disclosed in the
25 Patent Document 1.
[0018]
As illustrated in Fig. 2, the power spectrum of the
original high band side of the attack music signal has a
substantially flat shape.
30 [0019]
Unlike this, the estimated frequency envelope of
6
^ SP248477WO01
the high band side has a predetermined negative slope and
even if the frequency is adjusted to have the power close
to the original power spectrum, difference between the
power and the original power spectrum becomes large as
5 the frequency becomes high. , :
[0020]
Accordingly, in the band expansion method disclosed
in Patent Document 1, the estimated frequency envelope of
the high band side cannot reproduce the frequency
10 envelope of the original high band side with high
accuracy. Therefore, if sound from the music signal
after the expansion of the frequency band is produced and
output, clarity of the sound in auditory is lower than
the original sound.
15 [0021]
In addition, in the high band characteristic
encoding method such as HE-AAC and the like described
above, the frequency envelope of the high band side is
used as characteristic information of the encoded high
20 band signal components. However, it needs to reproduce
the frequency envelope of the original high band side
with high accuracy in a decoding side.
[0022]
The present invention has been made in a
25 consideration of such a circumstance and provides a music
signal having a better sound quality by expanding a
frequency band.
SOLUTIONS TO PROBLEMS
30 [0023]
A signal processing apparatus according to a first
7
^ SP248477WO01
aspect of the present invention includes: a
demultiplexing unit that demultiplexes input encoded data
into data including information on a segment including
frames in which the same coefficient as a coefficient !
5 used in producing a high band signal is selected in a
section to be processed including a plurality of frames, and coefficient information for obtaining the coefficient
selected in the frames of the segment, and low band
encoded data; a low band decoding unit that decodes the
10 low band encoded data to produce a low band signal; a
selection unit that selects a coefficient of a frame to
be processed from a plurality of the coefficients based
on the data; a high band sub-band power calculation unit i
that calculates a high band sub-band power of a high band
15 sub-band signal of each sub-band constituting the high
band signal of the frame to be processed based on a low
band sub-band signal of each sub-band constituting the
low band signal of the frame to be processed and the
selected coefficient; and a high band signal production
2 0 unit that produces the high band signal of the frame to
be processed based on the high band sub-band power and
the low band sub-band signal.
[0024]
The section to be processed may be divided into the
25 segments so that positions of the frames adjacent to each
other in which different coefficients are selected are
set as boundary positions of the segments,.and
information indicating a length of each of the segments
may be set as information on the segments.
30 [0025]
The section to be processed may be divided into the
8
^ SP248477WO01
several segments having the same length so that a length i
of the segment is the longest and information indicating I
the length and information indicating whether the
selected coefficient is varied before and after each
5 boundary position of the segments may be set as
information on the segments.
[0026] - - ;
When the same coefficient is selected in continuous
several segments, the data may include one piece of
10 coefficient information for obtaining the coefficient
selected in the several continuous segments.
[0027]
The data may be produced for each section to be
processed by a system having a less data 'amount between a
15 first system and a second system, wherein, in the first
system, the section to be processed is divided into the
segments so that the positions of frames adjacent to each
other in which the different coefficients are selected,
are set as a boundary position of the segments and
2 0 information indicating a length of each of the segments
is set as information on the segments, wherein, in the
second system, the section to be processed is divided
into the several segments having the same length so that
a length of the segment is the longest and information
25 indicating the length and information indicating whether
the selected coefficient is varied before and after a
boundary position of the segments are set as information
on the segment, and wherein the data may further include
information indicating whether the data is obtained by
30 the first system or second system.
[0028]
9
4$ SP248477WO01
The data may further include reuse information ;
indicating whether the coefficient of an initial frame in
the section to be processed is the same as the
coefficient of a frame just before the initial frame, and l
5 when the data includes the reuse information indicating
that the coefficients are the same, the data may not
include coefficient information of the initial segment of - ;
the section to be processed.
[0029]
10 When a mode in which the coefficient information is
reused, is designated, the data may include the reuse
information, and when a mode in which the reuse of the
coefficient information is prohibited, is designated, the
data may not include the reuse information.
15 [0030]
A signal processing method or a program according
to the first aspect of the present invention includes the
steps of: demultiplexing input encoded data into data
including information on a segment including frames in
20 which the same coefficient as a coefficient used in
producing a high band signal is selected in^ a section to
be processed including a plurality of frames, and
coefficient information for obtaining the coefficient
selected in the frames of the segment, and low band
25 encoded data; decoding the low band encoded data to
produce a low band signal; selecting a coefficient of a -
frame to be processed from a plurality of the
coefficients based on the data; calculating a high band
sub-band power of a high band sub-band signal of each
30 sub-band constituting the high band signal of the frame
to be processed based on a low band sub-band signal of
10 .
^ SP248477WO01
each sub-band constituting the low band signal of the
frame to be processed and the selected .coefficient; and
producing the high band signal of the frame to be
processed based on the high band sub-band power ^nd the
5 low band sub-band signal.
[0031]
In the first aspect of the present invention, -input
encoded data is demultiplexed into data including
information on a segment including frames in which the
10 same coefficient as a coefficient used in producing a
high band signal is selected in a section to be processed
including a plurality of frames, and coefficient
information for obtaining the coefficient selected in the
frames of the segment and low band encoded data, the low
15 band encoded data is decoded to produce the low signal, a
coefficient of a frame to be processed is selected from a
plurality of the coefficients based on the data, the high
. band sub-band power of a high band sub-band signal of
each sub-band constituting the high band signal in the
20 frame to be processed is calculated based on a low band
sub-band signal of each sub-band constituting the low
band signal of the frame to be processed and the selected
coefficient, and the high band signal of the frames to be
processed is produced based on the high band sub-band
25 power and the low band sub-band signal.
[0032]
A signal processing apparatus according to a second
; aspect of the present invention includes: a sub-band
\ division unit that produces a low band sub-band signal of
: 30 a plurality of sub-bands in a low band side of an input
signal, and a high band sub-band signal of a plurality of
i 11 . •
W SP248477WO01
sub-bands in a high band side of the input signal; a
pseudo high band sub-band power calculation unit that
calculates a pseudo high band sub-band power which is.an
estimation value of power of the high band sub-band
5 signal based on the low band sub-band signal and a
predetermined coefficient; a selection unit that selects
any of a plurality of the coefficients for respective
frames of the input signal by comparing the high band
sub-band power of the high band sub-band signal and the
10 pseudo high band sub-band power; and a production unit
that produces data including information on a segment
having frames in v;hich the same coefficient is selected
in a section to be processed having a plurality of frames
of the input signal, and coefficient information for
15 obtaining the coefficient selected in frames of the
segment.
[0033]
The production unit may divide the section to be
processed into the segments so that the positions of
2 0 frames adjacent to each other in which different
coefficients are selected, are set as boundary positions
of the segments, and set information-indicating a length
of each of the segments as information on the segment.
[0034]
25 The production unit may divide the section to be
processed into the several segments having the same
length so that a length of the segment is the longest and
__^_^.information indicating the length and information
indicating whether the selected coefficient is varied
30 before and after boundary positions of the segments may
be set as information on the segments.
12
^ SP248477WO01
[0035]
The production unit may produce t.he data including
one piece of coefficient information for obtaining the
coefficient selected in the several continuous segments
5 when the same coefficient is selected in the several
continuous segments.
[0036]
The production unit may produce data for each
section to be processed with a system having a less data
10 amount between a first system and a second system,
wherein, in the first system, the section to be processed
is divided into the segments so that the positions of
frames adjacent to each other in which the different
coefficients are selected, are set as boundary positions
15 of the segments, and information indicating a length of
each of the segments is set as information on the
segments, and wherein, in the second system, the section
to be processed is divided into the several segments
having the same length so that a length of the segment is
20 the longest and information indicating the length and
information indicating whether the selected coefficient
is varied before and after a boundary position of the
segments are set as information on the segments.
[0037]
25 The data may further include information indicating
whether the data is obtained by the first system or the
second system.
[0038]
The production unit produces the data including the
30 reuse information indicating whether the coefficient of
an initial frame of the section to be processed is the
13
^ SP248477WO01
same as the coefficient of a frame just before the i
initial frame, and when the reuse information indicating I
that the coefficients are the same is included in the f
data, the data in which the coefficient information of an [
5 initial segment of the section to be processed is not
included, is produced. i
[0039] - i
When a mode in which the coefficient information is ?
reused, is designated, the production unit produces the
10 data including the reuse information, and when a mode in i
which the reuse of the coefficient information is
prohibited, is designated, the production unit produces
the data that the reuse information is not included.
[0040]
15 A signal processing method or a program according
to the second aspect of the present invention includes
the steps of: producing a low band sub-band signal of a
plurality of sub-bands in a low band side of an input
signal, and a high band sub-band signal of a plurality of
20 sub-bands in a high band side of the input signal;
calculating a pseudo high band sub-band power which is an
estimation value of power of the high band sub-band
signal based on the low band sub-band signal and a
predetermined coefficient; selecting any of a plurality
25 of the coefficients for respective frames of the input
signal by comparing the high band sub-band power of the . , -
high band sub-band signal and the pseudo high band subband
power; and producing data including information on a
segment having frames in which the same coefficient is
30 selected in a section to be processed having a plurality
of frames of the input signal, and coefficient
14
^ SP248477WO01
information for obtaining the coefficient selected in
frames of the segment.
[0041]
In the second aspect of the present invention, a
5 low band sub-band signal of a plurality of sub-bands in a
low band side of an input signal, and a high band subband
signal of a plurality of sub-bands in a high band
side of the input signal are provided, a pseudo high band
sub-band power is calculated as an estimation value of
10 power of the high band sub-band signal based on the low
band sub-band signal and a predetermined coefficient, any
of a plurality of the coefficients for respective frames
of the input signal is selected by comparing the high
band sub-band power of the high band sub-band signal and
15 the pseudo high band sub-band power, and information
interval segment having frames in which the same
coefficient is selected in an section to be processed
having a plurality of frames of the input signal, and
coefficient information for obtaining the coefficient
20 selected at frames of the segment are produced.
[0042]
A decoder according to a third-aspect of the
present invention includes: a demultiplexing unit that
demultiplexes input encoded data into data including
25 information on a segment including frames in which the
same coefficient as a coefficient used in producing a
high band signal is selected in a section to be processed
including a plurality of frames, and coefficient
information for obtaining the coefficient selected in the
30 frames of the segment, and low band encoded data; a low
band decoding unit that decodes the low band encoded data
15 -
i§ SP248477WO01
to produce a low band signal; a selection unit that
selects a coefficient of a frame to be processed from a
plurality of the coefficients based on the data; a high
band sub-band power calculation unit that calculates a
5 high band sub-band power of a high band sub-band signal
of each sub-band constituting the high band signal of the
frame to be processed based on a low band sub-band signal
of each sub-band constituting the low band signal of the
frame to be processed and the selected coefficient; a '
10 high band signal production unit that produces the high
band signal of the frame to be processed based on the
high band sub-band power and the low band sub-band
signal; and a synthesis unit that synthesizes the low
band signal and the high band signal to produce an output
15 signal.
[0043]
A decoding method of the third aspect of the
. prese5)% invention includes steps of demultiplexing input
encoded data into data including information on a segment
20 including frames in which the same coefficient as a
coefficient used in producing a high band signal are
selected in a section to be processed including a
plurality of frames, and coefficient information for
obtaining the coefficient selected in the frames of the
25 segment and low band encoded data, decoding the low band
encoded data to produce the low band signal, selecting a ,. -, -,
coefficient of a frame to be processed from a plurality
of coefficient based on the data, calculating a high band
sub-band power of a high band sub-band signal of each
30 sub-band including the high band signal of the frame to
be processed based on a low band sub-band signal of each
16
^ SP248477WO01
sub-band including the low band signal of the frame to be
processed and the selected coefficient, producing the
high band signal of the frame to be processed based on
the high band sub-band power and the low band sub-band
5 signal, and synthesizing the low band signal and the high
band signal to produce an output signal..
[0044]
In the third aspect of the present invention, input
encoded data is demultiplexed into data including
10 information on a segment including frames in which the
same coefficient as a coefficient used in producing a
high band signal is selected in a section to be processed
including a plurality, of frames, and coefficient
• . • i
information for obtaining the coefficient, selected at the
15 frames of the segment and low band encoded data, the low
band encoded data is decoded to produce the low signal, a
coefficient of a frame to be processed is selected from a
plurality of the coefficients based on the data, the high
band sub-band power of a high band sub-band.signal of
20 each sub-band constituting the high band signal in the
frame to be processed is calculated based on a low band
sub-band signal of each sub-band constituting the low
band signal of the frame to be processed and the selected
coefficient, and the high band signal of the frames to be
25 processed is produced based on the high band sub-band
pov.'er and the low band sub-band signal, and synthesizing
the low band signal and the high band signal to produce
an output signal.
[0045]
30 An encoder according to a fourth aspect of the
present invention includes: a sub-band division unit that
17
SP248477WO01 J
produces a low band sub-band signal of a plurality of [
sub-bands in a low band side of an input signal, and a high band sub-band signal of a plurality of sub-bands in !
a high band side of the input signal; a pseudo high band
5 sub-band power calculation unit that calculates a pseudo
high band sub-band power which is an estimation value of
power of the high band sub-band signal based on the low
band sub-band signal and a predetermined coefficient; a
selection unit that.. selects any of a plurality of the
10 coefficients for respective frames of the input signal by
comparing the high band sub-band power of the high band
sub-band signal and the pseudo high band sub-band power;
a high band encoding unit that produces high band encoded
data by encoding information on a segment having frames
15 in which the same coefficient is selected in a section to
be processed including a plurality of frames of the input
signal, and coefficient information for obtaining the
coefficient selected in the frames of the segment; a low
band encoding unit that encodes a low band signal of the
2 0 input signal and produces low band encoded data; and a
multiplexing unit that produces an output code string by
multiplexing the low band encoded data and the high band
encoded data.
[004-6]
25 An encoding method of the fourth aspect of the
present invention includes producing a low band sub-band
signal of a plurality of sub-bands in a low band side of
an'input signal, and a high band sub-band signal of a
plurality of sub-'bands in a high band side of. the input
30 signal, calculating a pseudo high band sub-band power
which is an estimation value of power of the high band
18
SP248477WO01
sub-band signal based on the low band sub-band signal and
a predetermined coefficient, selecting any of a plurality
of the coefficients for respective frames of the input
signal by comparing the high band sub-band power of the
5 high band sub-band signal and the pseudo high band subband
power, and producing high band encoded data by
encoding information on a segment including frames in
which the same coefficient is selected in a section to be
processed including.a plurality of frames of the input
10 signal and coefficient information for obtaining the
coefficient selected in frames of the segment, encoding a
low band signal of the input signal, producing the low
band encoded data and producing an output code string by
multiplexing the low band encoded data and the high band
15 encoded data.
[0047]
In the fourth aspect of the present invention, a
low band sub-band signal of a plurality of sub-bands in a •
low band side of an input signal, and a high band sub-
20 band signal of a plurality of sub-bands in a high band
side of the input signal are provided, a pseudo high band
sub-band power which is an estimation value of power of
the high band sub-band signal is calculated based on the
low band sub-band signal and a predetermined coefficient,
25 any of a plurality of coefficients for respective frames
of the input signal is selected by comparing the high
band sub-band power of the high band sub-band signal and
the pseudo ,high band sub-band power, the high band
encoded data is produced by encoding information on a
30 segment including frames in which the same coefficient is
selected and the coefficient information for obtaining
19
SP248477WO01
the coefficient selected in the frames of the segment,
the.low band signal of the input signal is encoded, the
low band encoded data is produced, and an output code
string is produced by multiplexing the low band encoded
- - 5 data and the high band encoded data.
EFFECTS 'OF THE INVENTION
[0048]
According to the first embodiment to the fourth
10 eiTibodiment, it is possible to reproduce music signal with
high sound quality by expansion of a frequency band.
BRIEF DESCRIPTION OF DRAWINGS
[0049]
15 Fig. 1 is a view an example of illustrating in an
example of a power spectrum of a low band after decoding
an input signal and a frequency envelope of a high band
estimated.
Fig. 2 is a view illustrating an example of an
20 original power spectrum of music signal of an attack
according to rapid change in time.
Fig. 3 is a block diagram illustrating a functional
configuration example of a frequency band expansion
apparatus in a first embodiment of the present invention.
25 Fig. 4 is a flowchart illustrating an example of a
frequency band expansion process by a frequency band
expansion apparatus in Fig. 3.
Fig. 5 is a view illustrating arrangement of a
power spectrum of- signal input to a frequency band
30 expansion apparatus in Fig. 3 and arrangement on a
frequency axis of a band pass filter.
20
SP248 477WO01 •
Fig. 6 is a view illustrating an example
illustrating frequency characteristics of a vocal region
and a power spectrum of a high band estimated.
Fig. 7 is a view illustrating an example of a power
._.:^^. 5 "spectrum of signal input to a frequency band expansion
apparatus in Fig. 3.
Fig. 8 is a view illustrating an example of a power
vector after liftering of an input signal in Fig. 7.
Fig. 9 is a block diagram illustrating a functional
10 configuration example of a coefficient learning apparatus
for performing learning of a coefficient used in a high
band signal production circuit of a frequency band
expansion apparatus in Fig. 3.
Fig. 10 is a flowchart describing an example of a
15 coefficient learning process by a coefficient learning
apparatus in Fig. 9.
Fig. 11 is a block diagram illustrating a
functional configuration example of an encoder in a
second embodiment of the present invention.
20 Fig. 12 is a flowchart describing an example of an
encoding process by an encoder in Fig. 11.
Fig. 13 is a block diagram illustrating a
functional configuration example of a decoder in a second
embo_diment of the present invention.
25 Fig. 14 is a flowchart describing an example of a
decoding'processing by a decoder in Fig. 13.
Fig. 15 is a block diagram illustrating a
functional configuration example of a coefficient
; learning apparatus for performing learning of a
\ 30 representative vector used in a high band encoding
; circuit of an encoder in Fig. 11 and decoded high band
J ' 21
SP248477WO01
#
sub-band power estimation coefficient used in a high band
decoding circuit of decoder in Fig. 13.
Fig. 16 is a flowchart describing an example of a
coefficient learning process by a coefficient learning
5 -apparatus in Fig. 15.
Fig. 17 is a view illustrating an example of an
encoded string to which an encoder in Fig. 11 is output.
Fig. 18 is a block diagram illustrating a
functional configuration example of the encoder.
10 Fig. 19 is a flowchart describing of encoding
processing.
Fig. 20 is a block diagram illustrating a
functional configuration example of a decoder.
Fig. 21 is a flowchart describing a decoding
15 process.
Fig. 22 is a flowchart describing an encoding
process.
Fig. 23 is a flowchart describing a decoding
process.
20 Fig. 24 is a flowchart describing an encoding
process.
Fig. 25 is a flowchart describing an encoding
process.
-Fig. 2 6 is a flowchart describing an encoding
25 process.
Fig. 27 is a flowchart describing an encoding
process.
Fig. 28 is a view illustrating a configuration
example of a coefficient learning apparatus.
30 Fig. 29 is a flowchart describing a coefficient
learning process.
i 22
SP248477WO01 •
Fig. 30 is a view describing an encoding amount
reduction of a coefficient index string.
Fig. 31 is a view describing an encoding amount
reduction of a coefficient index string.
. . V- :,, 5 .. " Fig. 32 is a view describing an encoding amount
reduction of a coefficient index string.
Fig. 33 is a block diagram illustrating a
functional configuration example of an encoder.
Fig. 34 is a flowchart describing an encoding
10 process.
Fig. 35 is a block diagram illustrating a
functional configuration example of a decoder.
Fig. 36 is a flowchart describing a decoding
process.
15 Fig. 37 is a view describing an encoding amount
reduction of a coefficient index string.
Fig. 3 8 is a block diagram illustrating a
functional configuration example of a decoder.
Fig. 3 9 is a flowchart describing an encoding
20 process.
Fig. 40 is a block diagram illustrating a
functional configuration example of a decoder.
Fig. 41 is a flowchart describing a decoding
process.
25 Fig. 42 is a block diagram illustrating a
functional configuration example of an encoder.
Fig. 43 is a flowchart describing an encoding
process.
; Fig. 44 is a block diagram illustrating a
30 functional configuration example of a decoder.
? Fig. 45 is a flowchart describing a decoding
; 23
SP248477WO01
#
process.
Fig. 4 6 is a diagram describing recycling of a
coefficient index.
Fig. 47 is a flowchart describing an encoding
5 process.
Fig. 48 is a flowchart describing a decoding
process."
Fig. 4 9 is a flowchart describing an encoding
process.
10 Fig. 50 is a flowchart describing the decoding
process.
Fig. 51 is a block diagram illustrating a
configuration example of hardware of a computer executing
a process to which the present invention is applied by a
15 program.
MODE FOR CARRYING OUT THE INVENTION
[0050]
An embodiment of the present invention will be
20 described with reference to the drawings. In addition,
the description thereof is performed in the following
! sequence.
1. First embodiment (when the present invention is
applied to a frequency band expansion apparatus)
! 25 2. Second embodiment (when the present invention is
applied to an encoder and a decoder)
,' 3. Third embodiment (when a coefficient index is
j included in high band encoded data)
; 4. Fourth embodiment (when a difference between
I 30 coefficient index and a pseudo high band sub-band power
j is included in high band encoded data)
24
^ SP248477WO01
5. Fifth embodiment (when a coefficient index is
selected using an estimation value).
6. Sixth embodiment (when a portion of a
coefficient is commons)
5 7. Seventh embodiment (v;hen an encoding amount of a
coefficient index string is reduced in time direction by
a variable length method)
8. Eighth embodiment (when an encoding amount of a
coefficient index string is reduced in time direction by
10 a fixed length method)
9. Ninth embodiment (when any of a variable length
method or a fixed length method is selected)
10. Tenth embodiment (when recycling of information
is performed by a variable method)
15 11. Eleventh embodiment (when recycling of
information is performed by a fixed length method)
[0051]
<1. First Embodiment>
In a first embodiment, a process that expands a
20 frequency band (hereinafter, referred to as a frequency
band expansion process) is performed with respect to a
signal component of a low band after decoding obtained by
decoding encoded data using a high cancelation encoding
method.
25 [0052]
[Functional Configuration Example of Frequency Band
Expansion Apparatus]
Fig. 3 illustrates a functional configuration
example of a frequency band expansion apparatus according
30 to the present invention.
[0053]
25
, SP248477WO01
A frequency band expansion apparatus 10 performs a
frequency band expansion process with respect to the
input signal by setting a signal component of the low
band after decoding as the input signal and outputs the
5 - 'signal after the frequency band expansion process
obtained by the result as an output signal.
[0054] -
The frequency band•expansion apparatus 10 includes
a low-pass filter 11, a delay circuit 12, a band pass
10 filter 13, a characteristic amount calculation circuit 14,
a high band sub-band power estimation circuit 15, a high
band signal production circuit 16, a high-pass filter 17
and a signal adder 18.
[0055]
15 The low-pass filter 11 filters an input signal by a
predetermined cut off frequency and supplies a low band
signal component, which is a signal component of the low
band as a signal after filtering to the delay circuit 12. .
[0056]
20 Since the delay circuit 12 is synchronized when
adding the low band signal component from the low-pass
filter 11 and a high band signal component which will be
described later to each other, it delays the low signal
comp.onent only a certain time and the low signal
25 component is supplied to the signal adder 18.
[0057]
The band pass filter 13 includes band pass filters
13-1 to 13-N having pass bands different from each other.
The band pass filter 13-i (
In a second embodiment, encoding processing and
5 decoding processing in the high band characteristic
encoding method by the encoder and the decoder are
performed.
[0184]
[Functional Configuration Example of Encoder]
10 Fig. 11 illustrates a functional configuration
example of the encoder to which the present invention is
applied.
[0185]
An encoder 30 includes a 31, a low band encoding
15 circuit 32, a sub-band division circuit 33, a
characteristic amount calculation circuit 34, a pseudo
high band sub-band power calculation circuit 35, a pseudo
high band sub-band power difference calculation circuit
36, a high band encoding circuit 37, a multiplexing
20 circuit 38 and a low band decoding circuit 39.
[0186]
The low-pass filter 31 filters an input signal
using a predetermined cutoff frequency and supplies a
signal of a low band lower than a cutoff frequency
25 (hereinafter, referred to as a low band signal) as signal '•
after filtering to the low band encoding circuit 32, a
sub-band division circuit 33, and a characteristic amount
calculation circuit 34.
[0187]
30 The low band encoding circuit 32 encodes a low band
signal from the low-pass filter 31 and supplies low band
59
^ SP248477WO01
encoded data obtained from the result to the multiplexing
circuit 38 and the low band decoding circuit 39.
[0188]
The sub-band division circuit 33 equally divides
5 the input signal and the low band signal from the lowpass
filter 31 into a plurality of sub-band signals
having a predetermined band width and supplies the
divided signals to the characteristic amount calculation
circuit 34 or the pseudo high band sub-band power
10 difference calculation circuit 36. In particular, the
sub-band division circuit 33 supplies a plurality of subband
signals (hereinafter, referred to as a low band subband
signal) obtained by inputting to the low band signal,
to the characteristic amount calculation circuit 34. In
15 addition, the sub-band division circuit 33 supplies the
sub-band signal (hereinafter, referred to as a high band
sub-band signal) of the high band higher than a cutoff
frequency set by the low-pass filter 31 among a plurality
of the sub-band signals obtained by inputting an input
20 signal to the pseudo high band sub-band power difference
calculation circuit 36.
[0189]
The characteristic amount calculation circuit 34
calculates one or more characteristic amounts using any
25 one of a plurality of sub-band signals of the low band
sub-band signal from the sub-band division circuit 33 and
the low band signal from the low-pass filter 31 and
supplies the calculated characteristic amounts to the
pseudo high band sub-band power calculation circuit 35.
30 [0190]
The pseudo high band sub-band power calculation
60
M| SP248477WO01
circuit 35 produces a pseudo high band sub-band power
based on one or more characteristic amounts from the
characteristic amount calculation circuit 34 and supplies
the produced pseudo high band sub-band power to the
5 pseudo high band sub-band power difference calculation
circuit 36.
[0191]
The pseudo high band sub-band power difference
calculation circuit 36 calculates a pseudo high band sub-
10 band power difference described below based on the high
band sub-band signal from the sub-band division circuit
33 and the pseudo high band sub-band power from the
pseudo high band sub-band power calculation circuit 35
and supplies the calculated pseudo high band sub-band
15 power difference to the high band encoding circuit 37.
[0192]
The high band encoding circuit 37 encodes the
pseudo high band sub-band power difference from the
pseudo high band sub-band power difference calculation
20 circuit 36 and supplies the high band encoded data
obtained from the result to the multiplexing circuit 38.
[0193]
The multiplexing circuit 38 multiples the low band
encoded data from the low band encoding circuit 32 and
25 the high band encoded data from the high band encoding
circuit 37 and outputs as an output code string.
[0194]
The low band decoding circuit 39 suitably decodes
the low band encoded data from the low band encoding
30 circuit 32 and supplies decoded data obtained from the
result to the sub-band division circuit 33 and the
61
m SP248477WO01
characteristic amount calculation circuit 34.
[0195]
[Encoding Processing of Encoder]
Next, referring to a flowchart in Fig. 12, the
5 encoding processing by the encoder 30 in Fig. 11 will be
described.
[0196]
In step Sill, the low-pass filter 31 filters the
input signal using a predetermined cutoff frequency and
10 supplies the low band signal as the signal after
filtering to the low band encoding circuit 32, the subband
division circuit 33 and the characteristic amount
calculation circuit 34.
[0197]
15 In step S112, the low band encoding circuit 32
encodes the low band signal from the low-pass filter 31
and supplies low band encoded data obtained from the
result to the multiplexing circuit 38.
[0198]
20 In addition, for encoding of the low band signal in
step S112, a suitable encoding method should be selected
according to an encoding efficiency and a obtained
circuit scale, and the present invention does not depend
on the encoding method.
25 [0199]
In step S113, the sub-band division circuit 33
equally divides the input signal and the low band signal
to a plurality of sub-band signals having a predetermined
bandwidth. The sub-band division circuit 33 supplies the
30 low band sub-band signal obtained by inputting the low
band signal to the characteristic amount calculation
62
^ SP248477WO01
circuit 34. In addition, the sub-band division circuit
33 supplies the high band sub-band signal of a band
higher than a frequency of the band limit, which is set
by the low-pass filter 31 of a plurality of sub-band
5 signals obtained by inputting the input signal to the
pseudo high band sub-band power difference calculation
circuit 36.
[0200]
In a step S114, the characteristic amount
10 calculation circuit 34 calculates one or more
characteristic amounts using at least any one of a
plurality of sub-band signals of the low band sub-band
signal from sub-band division circuit 33 and a low band
signal from the low-pass filter 31 and supplies the
15 calculated characteristic amounts to the pseudo high band
sub-band power calculation circuit 35. In addition, the
characteristic amount calculation circuit 34 in Fig. 11
has basically the same configuration and function as
those of the characteristic amount calculation circuit 14
20 in Fig. 3. Since a process in step S114 is substantially
identical with that of step S4 of a flowchart in Fig. 4,
the description thereof is omitted.
[0201]
In step S115, the pseudo high band sub-band power
25 calculation circuit 35 produces a pseudo high band subband
power based on one or more characteristic amounts
from the characteristic amount calculation circuit 34 and
supplies the produced pseudo high band sub-band power to
the pseudo high band sub-band power difference
30 calculation circuit 36. In addition, the pseudo high
band sub-band power calculation circuit 35 in Fig. 11 has
63
^ SP248477WO01
basically the same configuration and function as those of
the high band sub-band power estimation circuit 15 in Fig.
3. Therefore, since a process in step S115 is
substantially identical with that of step S5 of a
5 flowchart in Fig. 4, the description thereof is omitted.
[0202]
In step S116, a pseudo high band sub-band power
difference calculation circuit 36 calculates the pseudo
high band sub-band power difference based on the high
10 band sub-band signal from the sub-band division circuit
33 and the pseudo high band sub-band power from the
pseudo high band sub-band power calculation circuit 35
and supplies the calculated pseudo high band sub-band
power difference to the high band encoding circuit 37.
15 [0203]
Specifically, the pseudo high band sub-band power
difference calculation circuit 36 calculates the (high
band) sub-band power power(ib,J) in a constant time
frames J with respect to the high band sub-band signal
20 from the sub-band division circuit 33. In addition, in
an embodiment of the present invention, all the sub-band
of the low band sub-band signal and the sub-band of the
high band sub-band signal distinguishes using the index
ib. The calculation method of the sub-band power can
25 apply to the same method as first embodiment, that is,
the method used by Equation (1) thereto.
[0204]
Next, the pseudo high band sub-band power
difference calculation circuit 36 calculates a difference
30 value (pseudo high band sub-band power difference)
powerdiff (ib,J) between the high band sub-band power
64 ;
^ SP248477WO01
power (ib, J) and the pseudo high band sub-band power
powerih(ib,J) from the pseudo high band sub-band power
calculation circuit 35 in a time frame J. The pseudo
high band sub-band power difference powerdiff (ib,J) is
5 obtained by the following Equation (14).
[0205]
[Equation 14]
powerjiff (ib, J) =power( jb, J)-power|h(ib, J)
(J*FSIZE
25 [Functional Configuration Example of Encoder]
In addition, although it was described that the
pseudo high band sub-band power difference ID is output
from the encoder 3 0 to the decoder 4 0 as the high band
encoded data, the coefficient index for obtaining the
30 decoded high band sub-band power estimation coefficient
may be set as the high band encoded data.
81
^ SP248477WO01
[0262]
In this case, the encoder 30, for example, is
configured as illustrated in Fig. 18. In addition, in
Fig. 18, parts corresponding to parts in Fig. 11 has the
5 same numeral reference and the description thereof is
suitably omitted.
[0263]
The encoder 30 in Fig. 18 is the same expect that
the encoder 30 in Fig. 11 and the low band decoding
10 circuit 39 are not provided and the remainder is the same.
[0264]
In the encoder 30 in Fig. 18, the characteristic
amount calculation circuit 34 calculates the low band
sub-band power as the characteristic amount by using the
15 low band sub-band signal supplied from the sub-band
division circuit 33 and is supplied to the pseudo high
band sub-band power calculation circuit 35.
[0265] ?
In addition, in the pseudo high band sub-band power
20 calculation circuit 35, a plurality of decoded high band
sub-band power estimation coefficients obtained by the
predetermined regression analysis is corresponded to a
coefficient index specifying the decoded high band subband
power estimation coefficient to be recorded.
25 [0266]
Specifically, sets of a coefficient Aib(kb) and a
coefficient Bib for each sub-band used in operation of
Equation (2) described above are prepared in advance as
the decoded high band sub-band power estimation i
30 coefficient. For example, the coefficient Aib{kb) and the
coefficient Bib are calculated by an regression analysis
82
SP248477WO01
using a least-squares method by setting the low band subband
power to an explanation variable and the high band
sub-band power to an explained variable in advance. In
the regression analysis, an input signal including the
5 low band sub-band signal and the high band sub-band
signal is used as the broadband instruction signal.
[0267]
The pseudo high band sub-band power calculation
circuit 35 calculates the pseudo high band sub-band power
10 of each sub-band of the high band side by using the
decoded high band sub-band power estimation coefficient
and the characteristic amount from the characteristic
amount calculation circuit 34 for each of a decoded high
band sub-band power estimation coefficient recorded and
15 supplies the sub-band power to the pseudo high band subband
power difference calculation circuit 36.
[0268]
The pseudo high band sub-band power difference
calculation circuit 36 compares the high band sub-band
20 power obtained from the high band sub-band signal
supplied from the sub-band division circuit 33 with the
pseudo high band sub-band power from the pseudo high band
sub-band power calculation circuit 35.
[0269]
25 In addition, the pseudo high band sub-band power
difference calculation circuit 36 supplies the
coefficient index of the decoded high band sub-band power estimation coefficient, in which the pseudo high band
sub-band power closed to the highest pseudo high band :
30 sub-band power is obtained among the result of the *
comparison and a plurality of decoded high band sub-band
8 3
^ SP248477WO01
power estimation coefficient to the high band encoding
circuit 37. That is, the coefficient index of decoded
high band sub-band power estimation coefficient from
which the high band signal of the input signal to be
5 reproduced in decoding that is the decoded high band
signal closest to a true value is obtained.
[0270]
[Encoding Process of Encoder]
Next, referring to a flow chart in Fig. 19, an ;
10 encoding process performing by the encoder 30 in Fig. 18
will be described. In addition, processing of step S181
to step S183 are identical with those of step Sill to i
S113 in Fig 12. Therefore, the description thereof is |
omitted. i
15 [0271]
In step S184, the characteristic amount calculation circuit 34 calculates characteristic amount by using the
low band sub-band signal from the sub-band division i
circuit 33 and supplies the characteristic amount to the j
20 pseudo high band sub-band power calculation circuit 35.
[0272]
Specially, the characteristic amount calculation [
circuit 34 calculates as a characteristic amount, the low I
band sub-band power power(ib,J) of the frames J (where,
25 0
(6)described above using the gain amount G(ib, J) and the
decoded low band sub-band signal with respect to each
20 sub-band of the high band side.
[0303]
That is, the decoded high band signal production j
circuit 47 performs an amplitude modulation of the
decoded high band sub-band signal x{ib, n) in response to
25 the ratio of the low band sub-band power to the decoded
high band sub-band power and thus performs frequency- modulation the decoded low band sub-band signal (x2(ib, i
n)obtained. Therefore, the signal of the frequency !
component of the sub-band of the low band side is ;
30 converted to signal of the frequency component of the
sub-band of the high band side and the high band sub-band
93
I
I
^ SP248477WO01
signal x3(ib, n) is obtained. I
[0304] i
As described above, the processes for obtaining the !
high band sub-band signal of each sub-band is a process i
5 described blow in more detail.
[0305] i
The four sub-bands being a line in the frequency l
area is referred to as the band block and the frequency
band is divided so that one band block (hereinafter,
10 referred to as a low band block) is configured from four
sub-bands in which the index existed in the low side is
sb to sb-3. In this case, for example, the band
including the sub-band in which the index of the high
band side includes sb+1 to sb+4 is one band block. In
15 addition, the high band side, that is, a band block
including sub-band in which the index is sb+1 or more is
particularly referred to as the high band block.
[0306] In addition, attention is paid to one sub-band
20 constituting the high band block and the high band subband
signal of the sub-band (hereinafter, referred to as
attention sub-band) is produced. First, the decoded high
band signal production circuit 47 specifies the sub-band
of the low band block that has the same position relation
25 to the position of the attention sub-band in the high
band block.
[0307] ;
For example, if the index of the attention sub-band i
is sb+1, the sub-band of the low band block having the |
30 same position relation with the attention sub-band is set i
as the sub-band that the index is sb-3 since the !
94 j
^ SP248477WO01
attention sub-band is a band that the frequency is the j
lowest in the high band blocks.
[0308] As described above, the sub-band, if the sub-band
5 of the low band block sub-band having the same position
relationship of the attention sub-band is specific, the
low band sub-band power and the decoded low band sub-band i
signal and the decoded high band sub-band power is used ;
and the high band sub-band signal of the attention sub-
10 band is produced.
[0309]
That is, the decoded high band sub-band power and
the low band sub-band power are substituted for Equation
(3), so that the gain amount according to the rate of the
15 power thereof is calculated. In addition, the calculated
gain amount is multiplied by the decoded low band sub- i
band signal, the decoded low band sub-band signal
multiplied by the gain amount is set as the frequency
modulation by the operation of the Equation (6) to be set
20 as the high band sub-band signal of the attention subband.
[0310] ;
In the processes, the high band sub-band signal of ;
the each sub-band of the high band side is obtained. In •
25 addition, the decoded high band signal production circuit i
47 performs the Equation (7) described above to obtain
sum of the each high band sub-band signal and to produce j
the decoded high band signal. The decoded high band ]
signal production circuit 47 supplies the obtained i
30 decoded high band signal to the synthesis circuit 48 and ;
the process precedes from step S217 to the step S218 and
95 ;
m SP248477WO01
then the decoding process is terminated. ;
[0311]
In step S218, the synthesis circuit 48 synthesizes
the decoded low band signal from the low band decoding 5 circuit 42 and the decoded high band signal from the
decoded high band signal production circuit 47 and outputs as the output signal. i
[0312] f
As described above, since decoder 40 obtained the
10 coefficient index from the high band encoded data j
obtained from the demultiplexing of the input code string !
and calculates the decoded high band sub-band power by f
the decoded high band sub-band power estimation |
coefficient indicated by using the decoded high band sub- )
15 band power estimation coefficient indicated by the j
coefficient index, it is possible to improve the 3
estimation accuracy of the high band sub-band power. I
Therefore, it is possible to produce the music signal ;
having high quality.
20 [0313] l
<4. Fourth Embodiment> [Encoding Processes of Encoder]
First, in as described above, the case that only
the coefficient index is included in the high band
25 encoded data is described. However, the other
information may be included.
[0314] I
For example, if the coefficient index is included
in the high band encoded data, the decoding high band {
30 sub-band power estimation coefficient that the decoded high band sub-band power closest to the high band sub- I
9 6 i
m SP248477WO01
band power of the actual high band signal is notified of ^
the decoder 40 side. '
[0315]
Therefore, the actual high band sub-band power
5 (true value) and the decoded high band sub-band power
(estimation value) obtained from the decoder 40 produces
difference substantially equal to the pseudo high band
sub-band power difference poweraiff (ib, J) calculated from I
the pseudo high band sub-band power difference i
10 calculation circuit 36. ;
[0316] j
Herein, if the coefficient index and the pseudo J
high band sub-band power difference of the sub-band is ;
included in the high band encoded data, the error of the
15 decoded high band sub-band power regarding the actual ;
high band sub-band power is approximately known in the j
decoder 40 side. If so, it is possible to improve the
estimation accuracy of the high band sub-band power using
the difference. ?
20 [0317]
The encoding process and the decoding process in a
case where the pseudo high band sub-band power difference
is included in the high band encoded data will be
described with reference with a flow chart of Figs. 22
25 and 23.
[0318]
First, the encoding process performed by encoder 30
in Fig. 18 will be described with reference to the i
flowchart in Fig. 22. In addition-, the processes of step i
30 S241 to step S246 is identical with those of step SlBl to I
step S186 in Fig. 19. Therefore, the description thereof ;
97
|m SP248477WO01
is omitted.
[0319] I
In step S247, the pseudo high band sub-band power i
difference calculation circuit 36 performs operation of f
5 the Equation (15) described above to calculate sum E (J, I
id) of squares for difference for each decoded high band i
sub-band power estimation coefficient. {
[0320] I
In addition, the pseudo high band sub-band power
10 difference calculation circuit 36 selects sum of squares I
for difference where the sum of squares for difference is !
set as a minimum in the sum of squares for difference
among sum E(J, id) of squares for difference and supplies l
the coefficient index indicating the decoded high band
15 sub-band power estimation coefficient corresponding to
the sum of square for difference to the high band
encoding circuit 37.
[0321]
In addition, the pseudo high band sub-band power
20 difference calculation circuit 36 supplies the pseudo
high band sub-band power difference poweraiff (ib, J) of the
each sub-band obtained with respect to the decoded high
band sub-band power estimation coefficient corresponding
to selected sum of squares of residual error to the high
25 band encoding circuit 37. j
[0322] 1
In step S248, the high band encoding circuit 37 I
encodes the coefficient index and the pseudo high band !
sub-band power difference supplied from the pseudo high 1
30 band sub-band power difference calculation circuit 36 and I
supplies the high band encoded data obtained from the t
98 ?
^ SP248477WO01
result to the multiplexing circuit 38.
[0323] I
Therefore, the pseudo high band sub-band power
difference of the each sub-band power of the high band 5 side where the index is sb+1 to eb, that is, the I
estimation difference of the high band sub-band power is j
supplied as the high band encoded data to the decoder 40. j
[0324] I
If the high band encoded data is obtained, after i
10 this, encoding process of step S249 is performed to
terminate encoding process. However, the process of step i
S249 is identical with the process of step S189 in Fig.
19. Therefore, the description is omitted. ;
[0325] )
15 As described above, if the pseudo high band subband
power difference is included in the high band >
encoded data, it is possible to improve estimation j
accuracy of the high band sub-band power and to obtain f
music signal having good quality in the decoder 40. j
20 [0326] {
[Decoding Processing of Decoder] j
Next, a decoding process performed by the decoder i
40 in Fig. 20 will be described with reference to a t
flowchart in Fig. 23. In addition, the process of step ;
25 S271 to step S274 is identical with those of step S211 to '
step S214 in Fig. 21. Therefore, the description thereof
is omitted.
[0327]
In step S275, the high band decoding circuit 45
30 performs the decoding of the high band encoded data J
supplied from the demultiplexing circuit 41. In addition, ;
99 I
^ SP248477WO01
the high band decoding circuit 45 supplies the decoded ;.
high band sub-band power estimation coefficient indicated
by the coefficient index obtained by the decoding and the
pseudo high band sub-band power difference of each sub-
5 band obtained by the decoding to the decoded high band
sub-band power calculation circuit 46. J
[0328] ;
In a step S27 6, the decoded high band sub-band I
i
power calculation circuit 4 6 calculates the decoded high I
10 band sub-band power based on the characteristic amount I
I'
supplied from the characteristic amount calculation j
circuit 44 and the decoded high band sub-band power i
estimation coefficient 216 supplied from the high band
decoding circuit 45. In addition, step S27 6 has the same '
15 process as step S216 in Fig. 21.
[0329]
In step S277, the decoded high band sub-band power
calculation circuit 4 6 adds the pseudo high band sub-band
power difference supplied from the high band decoding
20 circuit 45 to the decoded high band sub-band power and
supplies the added result as an ultimate decoded high
band sub-band power to decoded high band signal
production circuit 47. ;
That is, the pseudo high band sub-band power
25 difference of the same sub-band is added to the decoding I
high band sub-band power of the each calculated sub-band.
[0330]
In addition, after that, processes of step S278 and
step S279 is performed and the decoding process is ,
30 terminated. However, their processes are identical with '•
step S217 and step S218 in Fig. 21. Therefore, the
100 {
t I
i:
^ SP248477WO01
description will be omitted. I
[0331] i
By doing the above, the decoder 40 obtains the
coefficient index and the pseudo high band sub-band power ;
5 from the high band encoded data obtained by the ;
demultiplexing of the input code string. In addition, :
decoder 4 0 calculates the decode high band sub-band power
using the decoded high band sub-band power estimation
coefficient indicated by the coefficient index and the
10 pseudo high band sub-band power difference. Therefore, j
it is possible to improve accuracy of the high band subband
power and to reproduce music signal having high
sound quality.
[0332] '
15 In addition, the difference of the estimation value
of the high band sub-band power producing between encoder j
30 and decoder 40, that is, the difference (hereinafter, I
referred to as an difference estimation between device)
between the pseudo high band sub-band power and decoded
20 high band sub-band power may be considered.
[0333]
In this case, for example, the pseudo high band
sub-band power difference serving as the high band
encoded data is corrected by the difference estimation
25 between devices and the estimation difference between
devices is included in the high band encoded data, the
pseudo high band sub-band power difference is corrected
by the estimation difference between apparatus in decoder
40 side. In addition, the estimation difference between
30 apparatus may be recorded in decoder 40 side in advance
and the decoder 40 may make correction by adding the
101
^ SP248477WO01
estimation difference between devices to the pseudo high t
band sub-band power difference. Therefore, it is i
possible to obtain the decoded high band signal closed to
the actual high band signal.
5 [0334]
<5. Fifth Embodiment>
In addition, in the encoder 30 in Fig. 18, it is
described that the pseudo high band sub-band power
difference calculation circuit 36 selects the optimal
10 index from a plurality of coefficient indices using the
square sum E(J,id) of for a difference. However, the
circuit may select the coefficient index using the index
different from the square sum for a difference.
[0335]
15 For example, as an index selecting a coefficient
index, mean square value, maximum value and an average
value of a residual error of the high band sub-band power
and the pseudo high band sub-band power may be used. In
this case, the encoder 30 in Fig. 18 performs encoding
20 process illustrated in a flowchart in Fig. 24.
[0336]
An encoding process using the encoder 30 will
described with reference to a flowchart in Fig. 24. In
addition, processes of step S301 to step S305 are
25 identical with those of step S181 to step S185 in Fig. 19.
Therefore, the description will be omitted. If the
processes of step S301 to step S305 are performed, the
pseudo high band sub-band power of each sub-band is
calculated for each K number of decoded high band sub-
30 band power estimation coefficient.
[0337]
102
^ SP248477WO01
In step S306, the pseudo high band sub-band power j
difference calculation circuit 36 calculates an estimation value Res(id,J) using a current frame J to be processed for each K number of decoded high band sub-band
5 power estimation coefficient.
[0338] I
In detail, the pseudo high band sub-band power
difference calculation circuit 36 calculates the high
band sub-band power power(ib,J) in frames J by performing
10 the same operation as the Equation (1) described above
using the high band sub-band signal of each sub-band
supplied from the sub-band division circuit 33. In
addition, in an embodiment of the present invention, it
is possible to discriminate all of the sub-band of the
15 low band sub-band signal and the high band sub-band using
index ib.
[0339]
If the high band sub-band power power(ib,J) is
obtained, the pseudo high band sub-band power difference
20 calculation circuit 36 calculates the following Equation
(16) and calculates the residual square mean square value
Resstd(id,J).
[0340] ;
[Equation 16]
eb „
Resstd(id. J) = Z {powerCib, J)-powerest(ib, id, J ) r
• • • 0 6 )
[ 0 3 4 1 ]
That is, the difference between the high band subband
power power(ib,J) and the pseudo high band sub-band
power powerest (ib,id,J) is obtained with respect to each
103
^ SP248477WO01
i.
sub-band on the high band side where the index sb+1 to eb l
and square sum for the difference becomes the residual s
square mean value Resgtd (id, J) . In addition, the pseudo <
high band sub-band power powerrest (ibh, id, J) indicates the i
5 pseudo high band sub-band power of the frames J of the J
sub-band where the index is ib, which is obtained with respect to the decoded high band sub-band power I
estimation coefficient where index is ib.
[0342] i
10 Continuously, the pseudo high band sub-band power ;
difference calculation circuit 36 calculates the j
following Equation (17) and calculates the residual
maximum value ReSmax(id,J). ;
[0343] ;
15 [Equation 17] j
Resmax(id. J)=maxib{|power(ib. J)—powerestCib, id, J)|l
• - • (17)
[0344] I
In addition, in an Equation (17), i
maxib{Ipower(ib,J)-powerest (ibfid,J)I} indicates a I
20 maximum value among absolute value of the difference >
between the high band sub-band power power(ib,J) of each
sub-band where the index is sb+1 to eb and the pseudo i
high band sub-band power powerest (ib,id,J). Therefore, a ;
maximum value of the absolute value of the difference !
25 between the high band sub-band power power(ib,J) in the ;
frames J and the pseudo high band sub-band power i
powerest (ib,id,J) is set as the residual difference J
maximum value ReSmax (id,J). *
[0345] t
104 [
I
j ^ SP248477WO01
In addition, the pseudo high band sub-band power
difference calculation circuit 36 calculates the *
following Equation (18) and calculates the residual '
average value ReSave (id, J) .
5 [0346] (
[Equation 18]
/ eb \ i
Resave(id, J) = I I {power(ib, J)-powerest(ib, id, J)}
Y ib=sb+1 J
/(eb-sb)l • • • (18)
[0347] f
That is, for each sub-band on the high band side in {
10 which the index is sb+1 to eb, the difference between the i
high band sub-band power power(ib,J) of the frames J and
the pseudo high band sub-band power powerest (ib,id,J) is I
obtained and the sum of the difference is obtained. In addition, the absolute value of a value obtained by ;
15 dividing the sum of the obtained difference by the number ;
of the sub-bands (eb - sb) of the high band side is set
as the residual average value ReSave (id,J) . The residual
average value ReSave(id,J) indicates a size of the average
value of the estimation error of each sub-band that a 20 symbol is considered. [0348] ?
In addition, if the residual square mean 5
Resstd(id,J), the residual difference maximum value I
Resmax (id,J), and the residual average value ReSave(id,J)
25 are obtained, the pseudo high band sub-band power s
difference calculation circuit 36 calculates the following Equation (19) and calculates an ultimate estimation value Res(id,J). 105 !
^ SP248477WO01
[0349]
[ E q u a t i o n 19]
Res (id, J) =ReSstd(icl, J) +Wmax>
In addition, if the encoding process described
above is performed for each frame of the input signal,
15 There may be a case where the coefficient index different
in each consecutive frame is selected in a stationary
region that the time variation of the high band sub-band
power of each sub-band of the high band side of the input
signal is small.
20 [0359]
That is, since the high band sub-band power of each
frame has almost identical values in consecutive frames
constituting the standard region of the input signal, the
same coefficient index should be continuously selected in
25 their frame. However, the coefficient index selected for
each frame in a section of the consecutive frames is
changed and thus the high band component of the voice
reproduced in the decoder 4 0 side may be no long
stationary. If so, incongruity in auditory occurs in the
30 reproduced sound.
[0360]
108
^ SP248477WO01
Accordingly, if the coefficient index is selected
in the encoder 30, the estimation result of the high band
component in the previous frame in time may be considered.
In this case, encoder 30 in Fig. 18 performs the encoding
5 process illustrated in the flowchart in Fig. 25.
[0361]
As described below, an encoding process by the
encoder 30 will be described with reference to the
flowchart in Fig. 25. In addition, the processes of step
10 S331 to step S336 are identical with those of step S301
to step S306 in Fig. 24. Therefore, the description
thereof will be omitted.
[0362]
The pseudo high band sub-band power difference
15 calculation circuit 36 calculates the estimation value
ResP(id,J) using a past frame and a current frame in step
S337.
[0363]
Specifically, the pseudo high band sub-band power
20 difference calculation circuit 36 records the pseudo high
band sub-band power of each sub-band obtained by the
decoded high band sub-band power estimation coefficient
of the coefficient index selected finally with respect to
frames J-1 earlier than frame J to be processed by one in
25 time. Herein, the finally selected coefficient index is
referred to as a coefficient index output to the decoder
40 by encoding using the high band encoding circuit 37.
[0364]
As described below, in particular, the coefficient
30 index id selected in frame (J-1) is set to as idseiected (J-
1) . In addition, the pseudo high band sub-band power of
109
^ SP248477WO01
the sub-band that the index obtained by using the decoded
high band sub-band power estimation coefficient of the
coefficient index idseiected(J-1) is ib (where, sb+l
30 By the way, in the frequency band expansion process,
if the sound having high quality is desired to be
117
1^ SP248477WO01
obtained, the sub-band of the lower band side is also
important in term of the audibility. That is, among subbands
on the high band side as the estimation accuracy of
the sub-band close to the low band side become larger, it
5 is possible to reproduce sound having high quality.
[0398]
Herein, when the estimation value with respect to
each decoded high band sub-band power estimation
coefficient is calculated, a weight may be placed on the
10 sub-band of the low band side. In this case, the encoder
30 in Fig. 18 performs the encoding process shown in the
flowchart in Fig. 26.
[0399]
Hereinafter, the encoding process by the encoder 30
15 will be described with reference to the flowchart in Fig.
26. In addition, the processes of steps S371 to step
S375 are identical with those of step S331 to step S335
in Fig. 25. Therefore, the description thereof will be
omitted.
20 [0400]
In step S376, the pseudo high band sub-band power
difference calculation circuit 36 calculates' estimation
value ResWband(id, J) using the current frame J to be
processed for each of the K number of decoded high band
25 sub-band power estimation coefficient.
[0401]
Specially, the pseudo high band sub-band power
difference calculation circuit 36 calculates high band
sub-band power power(ib,J) in the frames J performing the
30 same operation as the above-mentioned Equation (1) using
the high band sub-band signal of each sub-band supplied
118
^ SP248477WO01
from the sub-band division circuit 33.
[0402]
If the high band sub-band power power(ib,J) is
obtained, the pseudo high band sub-band power difference
5 calculation circuit 36 calculates the following Equation
27 and calculates the residual square average value
ResstdWband (id, J) .
[0403]
[Equation 27]
eb
Resstd Wband (i b. J) = I (Wband (I b) X {power (i b, J)
ib=sb+1
^Q -powerestCib. id. J)}}^ ---(27)
[0404]
That is, the difference between the high band subband
power power(ib,J) of the frames (J) and the pseudo
high band sub-band power (powerest (ib,id,J) is obtained
15 and the difference is multiplied by the weight Wband(ib)
for each sub-band, for each sub-band on the high band
side where the index is sb+1 to eb. In addition, the sum
of square for difference by which the weight Wband(ib) is
multiplied is set as the residual error square average
20 value ResstdWband(id,J).
[0405]
Herein, the weight Wband(ib)(where, sb+l
In addition, since the auditory of person has a
property that properly perceives a larger frequency band
10 of the amplitude (power), the estimation value with
respect to each decoded high band sub-band power
estimation coefficient may be calculated so that the
weight may be placed on the sub-band having a larger
power.
15 [0422]
In this case, the encoder 30 in Fig. 18 performs an
encoding process illustrated in a flowchart in Fig. 27.
The encoding process by the encoder 30 will be described
below with reference to the flowchart in Fig. 27. In
20 addition, since the processes of step S401 to step S405
are identical with those of step S331 to step S335 in Fig.
25, the description thereof will be omitted.
[0423]
In step S406, the pseudo high band sub-band power
25 difference calculation circuit 36 calculates the
estimation value ResWpower (id,J) using the current frame
J to be processed for the K number of decoded high band
sub-band power estimation coefficient.
[0424]
30 Specifically, the pseudo high band sub-band power
difference calculation circuit 36 calculates the high
124
^ SP248477WO01
band sub-band power power (ib,J) in the frames J by
performing the same operation as the Equation (1)
described above by using a high band sub-band signal of
each sub-band supplied from the sub-band division circuit
5 33.
[0425]
If the high band sub-band power power(ib,J) is
obtained, the pseudo high band sub-band power difference
calculation circuit 36 calculates the following Equation
10 (29) and calculates the residual error squares average
value ReSstdWpower(id,J).
[0426]
[Equation 29]
eb
Resstd Wpower ( i d, J) = I (Wpower (power (i b, J ) )
ib=sb+1
X (power (ib. J) -powerest(ib, id, J)}}^
- - - (29)
15 [0427]
That is, the difference between the high band subband
power powerest (it), J) and the pseudo high band subband
power powers (ib,id,J) is obtained and the weight
Wpower(power(ib,J) for each of the sub-bands is
20 multiplied by the difference thereof with respect to each
band of the high band side in which the index is sb+1 to
eb. In addition, the square sum of the difference by
which the weight Wpower(power(ib,J) is multiplied by set
as the residual error squares average value ReSstdWpo„er
25 (id,J).
[0428]
Herein, the weight Wpower (power (ib, J) (where,
sb+l
[Configuration of Coefficient Learning Apparatus]
By the way, a set of a coefficient Aib(kb) as the
decoded high band sub-band power estimation coefficient
20 and a coefficient Bib is recorded in a decoder 40 in Fig.
20 to correspond to the coefficient index. For example,
if the decoded high band sub-band power estimation
coefficient of 128 coefficient index is recorded in
decoder 40, a large area is needed as the recording area
25 such as memory for recording the decoded high band subband
power estimation coefficient thereof.
[0445]
Herein, a portion of a number of the decoded high
band sub-band power estimation coefficient is set as
30 common coefficient and the recording area necessary to
record the decoded high band sub-band power estimation
130
^ SP248477WO01
coefficient may be made smaller. In this case, the
coefficient learning apparatus obtained by learning the
decoded high band sub-band power estimation coefficient,
for example, is configured as illustrated in Fig. 28.
5 [0446]
The coefficient learning apparatus 81 includes a
sub-band division circuit 91, a high band sub-band power
calculation circuit 92, a characteristic amount
calculation circuit 93 and a coefficient estimation
10 circuit 94.
[0447]
A plurality of composition data using learning is
provided in a plurality of the coefficient learning
apparatus 81 as a broadband instruction signal. The
15 broadband instruction signal is a signal including a
plurality of sub-band component of the high band and a
plurality of the sub-band components of the low band.
[0448]
The sub-band division circuit 91 includes the band
20 pass filter and the like, divides the supplied broadband
instruction signal into a plurality of the sub-band
signals and supplies to the signals the high band subband
power calculation circuit 92 and the characteristic
amount calculation circuit 93. Specifically, the high
25 band sub-band signal of each sub-band of the high band
side in which the index is sb+1 to eb is supplied to the
high band sub-band power calculation circuit 92 and the
low band sub-band signal of each sub-band of the low band
in which the index is sb-3 to sb is supplied to the
30 characteristic amount calculation circuit 93.
[0449]
131
^ SP248477WO01
The high band sub-band power calculation circuit 92
calculates the high band sub-band power of each high band
sub-band signal supplied from the sub-band division
circuit 91 and supplies it to the coefficient estimation
5 circuit 94. The characteristic amount calculation
circuit 93 calculates the low band sub-band power as the
characteristic amount, the low band sub-band power based
on each low band sub-band signal supplied from the subband
division circuit 91 and supplies it to the
10 coefficient estimation circuit 94.
[0450]
The coefficient estimation circuit 94 produces the
decoded high band sub-band power estimation coefficient
by performing a regression analysis using the high band
15 sub-band power from the high band sub-band power
calculation circuit 92 and the characteristic amount from
the characteristic amount calculation circuit 93 and
outputs to decoder 40.
[0451]
20 [Description of Coefficient Learning Process]
Next, a coefficient learning process performed by a
coefficient learning apparatus 81 will be described with
reference to a flowchart in Fig. 29.
[0452]
25 In step S431, the sub-band division circuit 91
divides each of a plurality of the supplied broadband
instruction signal into a plurality of sub-band signals.
In addition, the sub-band division circuit 91 supplies a
high band sub-band signal of the sub-band that the index
30 is sb+1 to eb to the high band sub-band power calculation
circuit 92 and supplies the low band sub-band signal of
132
^ SP248477WO01
the sub-band that the index is sb-3 to sb to the
characteristic amount calculation circuit 93.
[0453]
In step S432, the high band sub-band power
5 calculation circuit 92 calculates the high band sub-band
power by performing the same operation as the Equation
(1) described above with respect to each high band subband
signal supplied from the sub-band division circuit
91 and supplies it to the coefficient estimation circuit
10 94.
[0454]
In step S433, the characteristic amount calculation
circuit 93 calculates the low band sub-band power as the
characteristic amount by performing the operation of the
15 Equation (1) described above with respect each low band
sub-band signal supplied from the sub-band division
circuit 91 and supplies to it the coefficient estimation
circuit 94.
[0455]
20 Accordingly, the high band sub-band power and the
low band sub-band power are supplied to the coefficient
estimation circuit 94 with respect to each frame of a
plurality of the broadband instruction signal.
[0456]
25 In step S434, the coefficient estimation circuit 94
calculates a coefficient Aib{kb) and a coefficient Bib by
performing the regression of analysis using least-squares
method for each of the sub-band ib (where, sb+l
[High Efficiency Encoding of Coefficient Index String]
In addition, as described above, the coefficient
25 index for obtaining the decoded high band sub-band power
estimation coefficient is included in the high band
encoded data (bit stream) and is transmitted to the
decoder 40 for each frame. However, in this case, the
bit amount of the coefficient index string included in
30 the bit stream increases and the encoding efficiency
decreases. That is, it is possible to perform encoding
142
^ SP248477WO01
or decoding of sound having a good efficiency.
[0488] :
Herein, when the coefficient index string is ;
included in the bit stream, the coefficient index string
5 is encoded by including time information in which the
coefficient index is changed and the value of the changed
coefficient index without including the value of the
coefficient index of each frame as it is, so that the bit
amount may be decreased.
10 [0489]
That is, as described above, one coefficient index
per frame is set as the high band encoded data and is
included in the bit stream. However, when a real world
signal, in particular, a stationary signal is encoded,
15 there are many cases in which the coefficient index is
continuous with the same value in a time direction as in
Fig. 30. An information amount reduction method of time
direction of the coefficient index is invented using
characteristic.
20 [0490]
Specifically, there is a method that transmits time
information on which the index is switched and the index
value thereof every plural (for example, 16) frames.
[0491]
25 Two pieces of time information are considered as
follows.
[0492]
(a) The length and the number of indices (see Fig.
30) are transmitted.
30 (b) The index of the length and a switching flag
are transmitted (see Fig. 31).
143
^ SP248477WO01
[0493] :
In addition, it is possible to correspond each or
both of (a) and (b) to one index as described below.
[0494]
5 A detailed embodiment in a case where each (a) and
(b), and both of thereof is selectively used will be
described.
[0495]
First, (a) a case where the length and the number
10 of the indices are transmitted, will be described.
[0496]
For example, as described in Fig. 32, it is assumed
that an output code string (bitstream) including the low
band encoded data and the high band encoded data is
15 output from the encoder as unit of a plurality frames.
In addition, in Fig. 32, a transverse direction shows
time and one rectangle shows one frame. In addition, the
numerical value within the rectangle showing a frame
shows the coefficient index specifying the decoded high
20 band sub-band power estimation coefficient of the frame.
[0497]
In an example of Fig. 32, the output code string is
output as a unit every 16 frames. For example, it is
assumed that the section from a position FSTl to a
25 position FSEl is the section to be processed and it is
considered that the output code string of 16 frames
included in the section to be processed is output.
[0498]
First, the section to be processed is divided into
30 the segments (hereinafter, referred to as consecutive
frame segments) including consecutive frames where the
144
^ SP248477WO01
same coefficient index is selected. That is, it is !
assumed that the boundary position of the frames adjacent !
to each other is a boundary position of each consecutive
frame segment in which a different coefficient index is
5 selected.
[0499]
In the example, the section to be processed is
divided into three segments, that is, a segment from a
position FSTl to a position FCl, a segment from a
10 position FCl to an position FC2, and a segment from a
position FC2 to a position FSEl.
For example, the coefficient index "2" is selected
in each frame in consecutive frame segments from the
position FSTl to the position FCl.
15 [0500]
Therefore, when the section to be processed is
divided into consecutive frame segments, data including
the number information indicating the number of
consecutive frame segments within the section to be
20 processed, a coefficient index selected at each
consecutive frame segment and segment information
indicating the length of each consecutive frame segment
is produced.
[0501]
25 For example, in an example in Fig. 32, since the
section to be processed is divided into three consecutive
frame segments, information indicating the number of the
consecutive frame segments "3" is set as the number
information and is expressed as "num_length=3" in Fig. 32.
30 For example, segment information of an initial
consecutive frame segment in the frame to be processed is
145
^ SP248477WO01
set as length "5" considering frames of the consecutive ;
frame segment to be an unit and is expressed as i
"length0=5" in Fig. 32.
[0502] 5 In addition, each piece of segment information can
be specified whether it is included in any segment
information of the consecutive frame segments from the {
lead of the section to be processed. That is, the [
segment information includes information specifying the r
10 position of consecutive frame segments in the section to (
be processed. ;
[0503] I
Therefore, in the section to be processed, when
data including the number information, the coefficient '
15 index and the segment information is produced, this data
is encoded to be set as the high band encoded data. In I
this case, when the same coefficient index is
continuously selected in a plurality of frames, since it
is not necessary to transmit the coefficient index for
20 each frame, it is possible to reduce the data amount of
bitstream transmitted and to perform encoding and '
decoding more efficiently. ;
[0504]
[Functional Configuration Example of Encoder]
25 When high band encoded data including the number
information, the coefficient index and the segment
information is produced, for example, the encoder is
configured as illustrated in Fig. 33. In addition, in f
Fig. 33, the same symbol is provided in part
30 corresponding to a case in Fig. 18 and thus the
description thereof is appropriately omitted.
146
^ SP248477WO01
[0505]
An encoder 111 in Fig. 33 and the encoder 30 in Fig.
18 are different in that the production unit 121 is disposed in the pseudo high band sub-band power ]
5 difference calculation circuit 3 6 of the encoder 111 and
other configurations are the same.
[0506]
The production unit 121 of the pseudo high band
sub-band power difference calculation circuit 36 produces
10 data including the number information, the coefficient
index and the segment information based on selection
result of the coefficient index in each frame in the
section to be processed and supplies the produced data to
the high band encoding circuit 37.
15 [0507]
[Description of Encoding Processing]
Next, an encoding process performed by the encoder
111 will be described with respect to a flowchart in Fig.
34. The encoding process is performed for each of a
20 predetermined number of frames, that is, a section to be
processed.
[0508]
In addition, since the processes of step S471 to
step S477 are identical with those of step S181 to step
25 S187 in Fig. 19, the description thereof is omitted. In
the processes of step S471 to step S477, each frame
constituting the section to be processed is set as a
frame to be processed in order and a sum of squares
E(J,id) of the pseudo high band sub-band power difference
30 is calculated for each decoded high band sub-band power
estimation coefficient with respect to the frame to be
147
SP248477WO01
processed.
[0509] ;
In step S478, the pseudo high band sub-band power ;
difference calculation circuit 36 selects the coefficient
5 index based on the sum of squares (a sum of squares for
difference) of the pseudo high band sub-band power
difference for each decoding high band sub-band power
estimation coefficient calculated with respect to the
frame to be processed.
10 [0510]
That is, the pseudo high band sub-band power
difference calculation circuit 3 6 selects the sum of i
squares for the difference having a minimum value among a -
plurality of the sums of squares for difference and sets
15 the coefficient index indicating the decoded high band
sub-band power estimation coefficient corresponding to
the sum of squares for difference as the selected
coefficient index. f
[0511] i
20 In step S479, the pseudo high band sub-band power f
difference calculation circuit 36 determines whether the f
i
only process of the length of a predetermined frame is (
performed. That is, it is determined whether the i
coefficient index is selected with respect to the whole i
25 frame constituting the section to be processed. {
[0512] '
In step S479, when it is determined that the
process of the length of a predetermined frame is still
not performed, the process returns to step S471 and the
30 process described above is repeated. That is, among the
section to be processed, the frame that is not still
148
^ SP248477WO01
processed is set as the frame to be processed next and
the coefficient index of the frame is selected.
[0513]
In the contrast, in step S479, if it is determined
5 that the process of the length of a predetermined frame
is performed, that is, if the coefficient index is
selected with respect to the whole frame in the section
to be processed, the process proceeds to step S480.
[0514]
10 In step S480, the production unit 121 produces the
data including the coefficient index, the segment
formation, and the number information based on the
selection result of the coefficient index of each frame
within the section to be processed and supplies the
15 produced data to the high band encoding circuit 37.
[0515]
For example, in the example in Fig. 32, the i
production unit 121 divides the section to be processed
from the position FSTl to the position FSEl into three j
20 consecutive frame segments. In addition, the production j
unit 121 produces the data including the number information "num_length=3" showing "3" of the number of I
the consecutive frame segments, the segment information {
•"length0=5", "lengthl=7", and "length2=4" showing the |
25 length of each consecutive frame segment and the i
coefficient index "2", "5" and "1" of the consecutive i
frame segment thereof. {
[0516] I
In addition, the coefficient index of each of the I
30 consecutive frame segments corresponds to the segment
information and it is possible to specify which of the
149 ;
^ SP248477WO01
consecutive frame segment includes the coefficient index. i
[0517]
Referring again to the flowchart in Fig. 34, in
step S481, the high band encoding circuit 37 encodes the
5 data including the coefficient index, the segment ;
information and the number information supplied from the ;
production unit 121 and produces the high band encoded
data. The high band encoding circuit 37 supplies the
produced high band encoded data to the multiplexing
10 circuit 38.
[0518] j
For example, in step S481, an entropy encoding is I
performed on some or all of the information of the I
I'
coefficient index, the segment information and the number i
15 information. In addition, if the high band encoded data *
is information from which the optimal decoded high band
sub-band power estimation coefficient is obtained, any J
information is preferable, for example, the data ;
including the coefficient index, the segment information I
2 0 and the number information may be set at the high band
encoded data as it is.
[0519]
In step S482, the multiplexing circuit 38
multiplexes the low band encoded data supplied from the
2 5 low band encoding circuit 32 and the high band encoded
data supplied from the high band encoding circuit 37, and
outputs the output code string obtained from the result
and then the encoding process is terminated.
[0520]
30 Therefore, the decoded high band sub-band power
estimation coefficient most suitable for performing the ;
150
^ SP248477WO01
frequency band expansion process can be obtained in the
decoder receiving the input of the output code string by
outputting the high band encoded data as the output code
string together with the low band encoded data.
5 Therefore, it is possible to obtain the signal having better sound quality. I
[0521] i
In addition, in the encoder 111, one coefficient {
index is selected with respect to the consecutive frame i
10 segments including one or more frames, and the high band
encoded data including the coefficient index thereof is !
output. For this reason, when the same coefficient index j
is continuously selected, it is possible to reduce the :
encoding amount of the output code string and to perform j
15 encoding or decoding of sound more efficiently.
[0522] ;
[Functional Configuration Example of Decoder]
The decoder that inputs as the output code string output from the encoder 111 in Fig. 33 decodes it, for
20 example, is configured as illustrated in Fig. 35. In
addition, in Fig. 35, the same symbol is provided for
parts corresponding to the case in Fig. 20. Therefore,
the description thereof is appropriately omitted.
[0523]
25 The decoder 151 in Fig. 35 is same as the decoder
40 in Fig. 20 in that it includes the demultiplexing
circuit 41 to the synthesis circuit 48, but is different
from the decoder 40 in Fig. 20 in that the selection unit
161 is disposed in the decoded high band sub-band power
30 calculation circuit 46.
[0524]
151
^ SP248477WO01
In the decoder 151, when the high band encoded data ;
is decoded by the high band decoding circuit 45, the segment information and the number information obtained j
from the result, and the decoded high band sub-band power 5 estimation coefficient specified by the coefficient index j
obtained by decoding of the high band encoded data are i
supplied to the selection unit 161.
[0525] I
The selection unit 161 selects the decoded high
10 band sub-band power estimation coefficient used in
calculating the decoded high band sub-band power based on j
the segment information and the number information •
supplied from the high band decoding circuit 45 with j
respect to the frame to be processed. ;
15 [0526]
[Description of Decoding Process] ;
Next, a decoding process performed by the decoder j
151 in Fig. 35 will be described with reference to a ;
flowchart in Fig. 36.
20 [0527] ;
The decoding process starts when the output code
string output from the encoder 111 is supplied as the j
input code string to the decoder 151, and is performed
for each of the predetermined number of frames, that is, ;
25 the section to be processed. In addition, since the
process of step S511 is the same process as that of step i
S211 in Fig. 21, the description thereof is omitted. '
[0528] [
In step S512, the high band decoding circuit 45
30 performs the decoding of the high band encoded data ;
supplied from the demultiplexing circuit 41 and supplies
152
^ SP248477WO01
the decoded high band sub-band power estimation
coefficient, the segment information and the number
information to the selection unit 161 of the decoded high
band sub-band power calculation circuit 46.
5 [0529]
That is, the high band decoding circuit 45 reads
the decoded high band sub-band power estimation
coefficient indicated by the coefficient index obtained
by decoding of the high band encoded data among the
10 decoded high band sub-band power estimation coefficient
recorded in advance and causes the decoded high band subband
power estimation coefficient to correspond to the
segment information. In addition, the high band decoding
circuit 45 supplies the corresponding decoded high band
15 sub-band power estimation coefficient, the segment
information and the number information to the selection
unit 161.
[0530]
In step S513, the low band decoding circuit 42
2 0 decodes the low band encoded data of the frame to be
processed by setting one frame to a frame to be processed
in the low band encoded data of each frame of the section
to be processed supplied from the demultiplexing circuit
41. For example, each frame of the section to be
25 processed is selected as a frame to be processed from the
lead to a tail of the section to be processed in this '_
order and the decoding with respect to the low band
encoded data of the frame to be processed is performed.
[0531] ;
30 The low band decoding circuit 42 supplies the
decoded low band signal obtained by the decoding of the
153 !
I
^ SP248477WO01 low band encoded data to the sub-band division circuit 43 j
and the synthesis circuit 48. [0532] f
When the low band encoded data is decoded, after j
5 that, the processes of step S514 and step S515 are j
performed and thus the characteristic amount is *
calculated from the decoded low band sub-band signal. I
However, since the processes thereof are the same as S
those of step S213 and step S214 in Fig. 21, the ;
10 description thereof is omitted. j
[0533] I
In step S516, the selection unit 161 selects the
decoded high band sub-band power estimation coefficient
of the frame to be processed from the decoded high band
15 sub-band power estimation coefficient supplied from the i
high band decoding circuit 45 based on the segment information and the number information supplied from the 1
high band decoding circuit 45.
[0534] }
20 For example, in an example in Fig. 32, when the
seventh frame from the lead of the section to be
processed is set to be processed, the selection unit 161
specifies the consecutive frame segment in which the {
frame to be processed is included from the number
25 information "num_length=3", the segment
information "length0=5" and "lengthl=7".
[0535]
In this case, since the consecutive frame segment
of the lead in the section to be processed includes 5
30 frames and a second consecutive frame segment includes 7
frames, it will be understood that seventh frames from
154 ;
^ SP248477WO01
the lead of the section to be processed are included in a
second consecutive frame segment from the lead of the J
section to be processed. Therefore, the selection unit
161 selects the decoded high band sub-band power ;
5 estimation coefficient specified by the coefficient index ;
"5" which corresponds to the segment information of the {
second consecutive frame segment as the decoded high band s
sub-band power estimation coefficient of frames to be
processed. 10 [0536] I
When the decoded high band sub-band power i
estimation coefficient of the frames to be processed is
selected, after that, the processes of step S517 to step S
S519 are performed. However, since the processes thereof 15 are the same as those of step S216 to step S218 in Fig.
21, the description thereof is omitted.
[0537] i
In the processes of step S517 to step S519, the
selected decoded high band sub-band power estimation
20 coefficient is used to produce decoded high band signal
of the frames to be processed and the produced decoded
high band signal and the decoded low band signal are
synthesized and output.
[0538]
25 In step S520, the decoder 151 determines whether
the process of a predetermined frame length is performed.
That is, it is determined whether the output signal
including the decoded high band signal and the decoded
low band signal is produced with respect to the whole
30 frame constituting the section to be processed.
[0539]
155 ^ SP248477WO01
In step S520, when it is determined that the i
process of a predetermined frames length is not performed, ;
the process returns to step S513 and the processes
described above are repeated. That is, the frame that is i
5 not still processed in spite of being processing is set
as frames to be processed next to produce the output
signal of the frames.
[0540]
In the contrast, in step S520, it is determined
10 that the process of a predetermined frame length is
performed, that is, if the output signal is produced with
respect to the whole frames in the section to be
processed is produced, the decoding processing is
terminated.
15 [0541]
As described above, according to the decoder 151,
since the coefficient index is obtained from the high
band encoded data obtained by a demultiplexing of the
input code string and thus the decoded high band sub-band
20 power is calculated by using the decoded high band subband
power estimation coefficient indicated by the
coefficient index, it is possible to improve estimation
accuracy of the high band sub-band power. Therefore, it
is possible to reproduce the sound signal having high
25 quality.
[0542]
In addition, since one coefficient index with
respect to the consecutive frame segment including one or
more frames is included in the high band encoded data, it
30 is possible to obtain the output signal having good
efficiency from the input code string which has less data
156 ;
^ SP248477WO01
amount.
[0543]
<8 . Eighth Einbodiment>
[High Efficiency Encoding of Coefficient Index String>
5 Next, a case in which an encoding amount of the
high band encoded data is reduced by forwarding the index
(b) of length (b) described above and the switching flag
and improves efficiency of the encoding or decoding of
the sound will be described. For example, in this case,
10 as illustrated in Fig. 37, a plurality of frames are set
as unit and thus the output code string (bitstream)
including the low band encoded data and the high band
encoded data is output from the encoder.
[0544]
15 In addition, in Fig. 37, a lateral direction
illustrates time and one rectangle illustrates one frame.
In addition, the numerical value in the rectangle
illustrating frames indicates the coefficient index
specifying the decoded high band sub-band power
20 estimation coefficient of the frames. In addition, in
Fig. 37, parts corresponding to a case in Fig. 32 are
designated with the same symbol. Therefore, the
description thereof is omitted.
[0545]
25 In an example in Fig. 37, 16 frames are set as a
unit to output the output code string. For example, the
segment from the position FSTl to the position FSEl is
set as the section to be processed and thus the output
code string of 16 frames included in the section to be
30 processed is output.
[0546]
157
^ SP248477WO01 i
W
Specifically, first, the section to be processed is equally divided into the segments (hereinafter, referred
to as a fixed length segment) including a predetermined
number of frames. Herein, the coefficient index selected
5 from each frame in the fixed length segment is the same ;
and the length of the fixed length segment is defined
such that the length of the fixed length segment is the
longest.
[0547]
10 In the example in Fig. 37, the length of the fixed
length segment (hereinafter, simply, referred to as a
fixed length) is set as 4 frames and the section to be
processed is equally divided into 4 fixed length segments.
That is, the section to be processed is divided into an
15 segment from the position FSTl to position FC21, a
segment from the position FC21 to the position FC22, an
segment from the position FC22 to the position FC23 and
an integral from the position FC23 to the position FSEl.
The coefficient index in these fixed length segments is
20 set as the coefficient index "1", "2", "2", "3" in this
order from the fixed length segment of the lead of the
section to be processed.
[0548]
Therefore, when the section to be processed is
25 divided into several fixed length segments, the data
including a fixed length index indicating a fixed length
of the fixed length segment of the section to be
processed, a coefficient index and a switching index are
produced.
30 [0549]
Herein, the switching flag is referred to as
158
I
I
^ SP248477WO01 information indicating whether the coefficient index is
changed at the boundary position of the fixed length l
segment, that is, a finish frame of a predetermined fixed [
frame and a leading frame of the next fixed length j
5 segment of the fixed length segment. For example, i-th i
(i=0, 1, 2. . .) switching flag gridflg_i is set as "1" when the coefficient index is changed and is set as "0" I
when the coefficient index is not changed in the boundary j
position of (i+l)th- and (i+2)th-fixed length segment 10 from the lead of the section to be processed. ;
[0550] j
In the example in Fig. 37, since the coefficient index "1" of a first fixed length segment and the I
coefficient index "2" of the second fixed length segment !
15 is different from each other, the value of the switching i
flag (gridflg_0) of the boundary position (the position j
FC21) of the first fixed length segment of the section to i
be processed is set as "1". :
In addition, since the coefficient index "2" of the S
20 second fixed length segment and the coefficient index "2" :
of a third fixed length segment is the same, the value of
the switching flag gridflg_l of the position FC22 is set J
as "0". ;
[0551] ;
25 In addition, the value of the fixed length index is
set as the value obtained from the fixed length. ;
Specially, for example, the fixed length index (length_id
is set as a value satisfying the fixed length
fixed_length=16/2^^"5^^-^^ . In an example in Fig. :
30 37, since the fixed length fixed_length=4 is
satisfied, the fixed length index length_id=2 is
159
I
^ SP248477WO01
satisfied.
[0552] :
When the section to be processed is divided into i
the fixed length segment and the data including a fixed
5 length index, a coefficient index and a switching flag is
produced, the data is encoded to be set as the high band
encoded data.
[0553] :
In the example in Fig. 37, the data including a
10 switching flag in the position FC21 to the position FC23
(gridflg_0=l, gridflg_l=0, and gridflg_2=l, the fixed
length index "2" and the coefficient of each fixed length
segment "1", " 2 " and "3" is encoded and thus is set as
the high band encoded data.
15 [0554]
Herein, the switching flag of the boundary position
of each fixed length segment specifies which number of
the switching of the boundary position is located in from
the lead of the section to be processed. That is, the
20 switching flag may include information for specifying the
boundary position of the fixed length segment in the
section to be processed.
[0555]
In addition, each coefficient index included in the
25 high band encoded data is disposed in sequence in which
the coefficient thereof is selected, that is, the fixed
length segment is disposed side by side in order. For
example, in an example of Fig. 37, the coefficient index |
is disposed in order of "1","2" and "3" and thus the
30 coefficient index thereof is included in the data.
[0556]
160 I
^ SP248477WO01
In addition, in an example in Fig. 37, the
coefficient index of a second and third fixed length
segment from the lead of the section to be processed is
"2", but in the high band encoded data, the coefficient
5 index "2" is set such that only 1 thereof is included.
When the coefficient index of the continuous fixed length
segment is the same, that is, the switching flag in the
boundary position of the continuous fixed length segment
is 0, the same coefficient index as many as the number of
10 the fixed length segment is not included in the high band
encoded data, but one coefficient index is included in
the high band encoded data.
[0557]
As described above, when the high band encoded data
15 is produced from data including the fixed index, the
coefficient index, and the switching flag, it is possible
to reduce the data amount of the bitstream to be
transmitted because it is not necessary to transmit the
coefficient index for receptive frames.
20 Accordingly, it is possible to perform encoding and
decoding more efficiently.
[0558]
[Functional Configuration Example of Encoders]
The high band encoded data including the fixed
25 length index, the coefficient index and the switching
flag described above is produced, for example, the
encoder is configured as illustrated in Fig. 38. In
addition, in Fig. 38, parts corresponding to those in Fig.
18 have the same symbol. Therefore, the description
30 thereof is appropriately omitted.
[0559]
161
^ SP248477WO01
The encoder 191 in Fig. 38 and the encoder 30 in
Fig. 18 have different configurations in that the .
production unit 201 is disposed in the pseudo high band
sub-band power difference calculation circuit 36 of the
5 encoder 191 and other configurations are the same.
[0560]
The production unit 201 produces data including the
fixed length index, the coefficient index and the
switching flag based on the selection result of the
10 coefficient index in each frame in the section to be
processed and supplies the produced data to the high band
encoding circuit 37.
[0561]
[Description of Encoding Process]
15 Next, an encoding process performed by the encoder
191 will be described with reference to the flowchart in
Fig. 39. The encoding process is performed for each of
the predetermined number of the frames, that is, the each
section to be processed.
20 [0562]
In addition, since the processes of step S551 to
step S559 are identical with those of step S471 to step
S479 in Fig. 34, the description thereof is omitted. In
the processes of step S551 to step S559, each frame
25 constituting the section to be processed is set as the
frame to be processed in order and the coefficient index
is selected with respect to the frame to be processed.
[0563]
In step S559, when it is determined that only a
30 process of a predetermined frame length is performed, the
process proceeds to step S560.
162
SP248477WO01
[0564]
In step S560, the production unit 201 produces data
including the fixed length index, the coefficient index
and the switching flag based on the selection result of
5 the coefficient index of each frame to be processed and
supplies the produced data to the high band encoding
circuit 37.
[0565]
For example, in the example in Fig. 37, the
10 production unit 201 sets the fixed length as four frames
to divide the section to be processed from the position
FSTl to the position FSEl into 4 fixed length segments.
In addition, the production unit 201 produce data
including the fixed length index "2", the coefficient
15 index "1", " 2 " and "3" and the switching flag "1", "0",
and "1".
[0566]
In addition, in Fig. 37, the coefficient indices of
the second and the third fixed length segment from the
20 lead of the section to be processed are "2" equally.
However, since the fixed length segments are continuously
disposed, only one of the coefficient indices "2" is
included in data output from the production unit 201.
[0567]
25 Referring again to the description of the flowchart
in Fig. 39, in step S561, the high band encoding circuit
37 encodes data including the coefficient index, and the
switching flag supplied from the production unit 201 and
produces the high band encoded data. The high band
30 encoding circuit 37 supplies the produced high band
encoded data to the multiplexing circuit 38. For example,
163
SP248477WO01
the entropy encoding is performed as needed with respect
to the some or all of the information fixed length index,
the coefficient index and the switching flag.
[0568]
5 When the process of step S561 is performed, after
that, the process of step S562 is performed to terminate
the encoding process. Since the process of step S562 has
the same process as in step S482 in Fig. 34. Therefore,
the description is omitted.
10 [0569]
Therefore, the decoded high band sub-band power
estimation coefficient most suitable for performing the
frequency band expansion process can be obtained in the
decoder receiving the input of the output code string by
15 outputting the high band encoded data as the output code
string together with the low band encoded data.
Therefore, it is possible to obtain the signal having a
good quality.
[0570]
20 In addition, in the encoder 191, one coefficient
index is selected with respect to one or more fixed
length segments and the high band encoded data including
the coefficient index is output. Therefore, in
particular, when the same coefficient index is
25 continuously selected, it is possible to reduce the
encoding amount of the output code string and to perform
the encoding or decoding sound more efficiently.
[0571]
[Functional Configuration Example of Decoder]
30 In addition, the output code string output from the
encoder 191 in Fig. 38 is input as the input code string
164
^ SP248477WO01
and the decoder, which performs decoding, for example, is
configured as in Fig. 40. The same symbol is used in Fig.
40 for parts corresponding to the case in Fig. 20 and the
description is adequately omitted.
5 [0572]
The decoder 231 in Fig. 40 is identical with the
decoder 40 in Fig. 20 in that it includes the
demultiplexing circuit 41 to the synthesis circuit 48,
but is different from the decoder 40 in Fig. 20 in that
10 the selection unit 241 is disposed in the decoded high
band sub-band power calculation circuit 46.
[0573]
In the decoder 231, when the high band encoded data
is decoded by the high band decoding circuit 45, the
15 fixed length index and the switch flag obtained from the
result, and decoded high band sub-band power estimation
coefficient specified by the coefficient index obtained
by decoding the high band encoded data are supplied to
the selection unit 241.
20 [0574]
The selection unit 241 selects the decoded high
band sub-band power estimation coefficient used in
calculating the decoded high band sub-band power with
respect to the frames to be processed based on the fixed
25 length index and the switchirig flag supplied from the
high band decoding circuit 45.
[0575]
[Description of Decoding Process]
Next, a decoding process performed by the decoder :
30 231 in Fig. 40 will be described with reference to the ;
flowchart in Fig. 41.
165
^ SP248477WO01
[0576]
The decoding process starts when the output code
string output from the encoder 191 is supplied to the
decoder 231 as the input code string and is performed for
5 each the predetermined number of the frames, that is, the
section to be processed. In addition, since the process
of step S591 is identical with that of step S511 in Fig.
36, the description thereof is omitted.
[0577]
10 In step S592, the high band decoding circuit 45
performs the decoding of the high band encoded data
supplied from the demultiplexing circuit 41, supplies the
decoded high band sub-band power estimation coefficient
the fixed index and the switching flag to the selection
15 unit 241 of the decoded high band sub-band power
calculation circuit 46.
[0578]
That is, the high band decoding circuit 45 reads
the decoded high band sub-band power estimation
20 coefficient indicated by the coefficient index obtained
by the decoding of the high band encoded data in the
decoded high band sub-band power estimation coefficient
recorded in advance. In this case, the decoded high band
sub-band power estimation coefficient is arranged in the
25 same sequence as the sequence in which the coefficient
index is arranged. In addition, high band decoding
circuit 45 supplies the decoded high band sub-band power
estimation coefficient, the fixed length index and the
switching flag to the selection unit 241.
30 [0579]
When the high band encoded data is decoded, after
166
^ SP248477WO01
that, the process of step S593 to step S595 is performed.
However, since the processes are the same as step S513 to
step S515 in Fig. 36, the description thereof is omitted.
[0580]
5 In step S596, the selection unit 241 selects the
decoded high band sub-band power estimation coefficient
of the frame to be processed from the decoded high band
sub-band power estimation coefficient supplied from the
high band decoding circuit 45 based on the fixed length
10 index and the switching flag supplied from the high band
decoding circuit 45.
[0581]
For example, in an example in Fig. 37, when the
fifth frame from the lead of the section to be processed
15 is set to be processed, the selection unit 241 specifies
which fixed length segment the frame to be processed from
the lead in the section to be processed includes from the
fixed length index 2. In this case, since the fixed
length is "4", the fifth frame is specified as being
2 0 included in the second fixed length segment.
[0582]
Next, the selection unit 241 specifies that a
second decoded high band sub-band power estimation
coefficient from the lead is a decoded high band sub-band
25 power estimation coefficient of the frame to be processed
in the decoded high band sub-band power estimation
coefficient provided in a sequence from the switching
flag (gridflg_0=l) of the position FC21. That is, since
the switching flag is "1", and thus coefficient index is
30 changed before and after the position FC21, the second
decoded high band sub-band power estimation coefficient
167
^ SP248477WO01
from the lead is specified as the decoded high band subband
power estimation coefficient of the frame to be
processed. In this case, the decoded high band sub-band
power estimation coefficient specified by the coefficient
5 index "2" is selected.
[0583]
In addition, in the example of Fig. 37, when the
ninth frame from the lead of the section to be processed
is set to be processed, the selection unit 241 specifies
10 which fixed length segment from the lead in the section
to be processed includes the frame to be processed from
the fixed length index "2". In this case, since the
fixed length is "4", ninth frame is specified as being
included in the third fixed length segment.
15 [0584]
Next, the selection unit 241 specifies that the
second decoded high band sub-band power estimation
coefficient from the lead is the decoded high band subband
power estimation coefficient of frame to be
20 processed in the decoded high band sub-band power I
estimation coefficient provided in a sequence from the
switching flag gridflg_l=0 of the position FC22. That is, since the switching flag is "0" and thus what is not
changed in the index before and after the position FC22 I
25 is specified, the second decoded high band sub-band power j
estimation coefficient from the lead is specified as the j
decoded high band sub-band power estimation coefficient j
of the frames to be processed. In this case, the decoded
high band sub-band power estimation coefficient specified 30 by the coefficient index "2" is selected.
[0585]
168
^ SP248477WO01
When the decoded high band sub-band power
estimation coefficient of the frames to be processed is
selected, the processes of step S597 to step S600 are
performed to complete the decoding processing. However,
5 since the processes are identical with those of step S517
to step S520 in Fig. 36, the description thereof is
omitted.
[0586]
In the processes of step S597 to step S600, the
10 selected decoded high band sub-band power estimation
coefficient is used to produce the decoded high band
signal of the frame to be processed, the produced decoded
high band signal and the decoded low band signal are
synthesized and is output.
15 [0587]
As described above, according to decoder 231, since the
coefficient index is obtained from the high band encoded
data obtained by demultiplexing of the input code string
and thus the decoded high band sub-band power estimation
20 coefficient indicated by the coefficient index is used to
produce the decoded high band sub-band power and thus, it
is possible to improve estimation accuracy of the high
band sub-band power. Therefore, it is possible to
reproduce a music signal having better sound quality.
25 [0588]
Further, since one coefficient index is included in
the high band encoded data with respect to one or more
fixed length segment, it is possible to obtain the output '
signal from the input code string of the lesser data
30 amount more efficiently.
[0589] i
169
^ SP248477WO01
<9. Ninth Embodiinent>
[Functional Configuration Example of Encoder]
In addition, as described above, a method
(hereinafter, referred to as a variable length method) of
5 producing data including a coefficient index, an segment
information and a number information is produced as data
for obtaining the high band component of sound and a
method of producing data including the fixed length index,
the coefficient index and the switching flag (hereinafter,
10 referred to as a fixed length method) was described.
[0590]
The method thereof can also reduce the encoding
amount of the high band encoded data similarly. However,
it is possible to further reduce the encoding amount of
15 the high band encoded data by selecting less encoding
amount among the these methods for each of the processing
sections.
[0591]
In this case, the encoder is configured as
20 illustrated in Fig. 42. In addition, in Fig. 42, the
same symbol is used for parts corresponding to a case in ;
Fig. 18. Therefore, the description is suitably omitted.
[0592]
The encoder 271 in Fig. 42 and the encoder 30 in i
25 Fig. 18 are different from each other in that the
production unit 281 is disposed in the pseudo high band |
sub-band power difference calculation circuit 36 of the
encoder 271 and the remainder of configuration has the
same configuration.
30 [0593]
The production unit 281 produces data for obtaining
170
^ SP248477WO01
the high band encoded data by a method selected in which
the switching of the variable length method or the fixed
length method is performed based on the selection result
of the coefficient index in each frame in the section to
5 be processed, and supplies the data to the high band
encoding circuit 37.
[0594]
[Description of Encoding Process]
Next, an encoding process performed by the encoder
10 271 will be described with reference to the flowchart in
Fig. 43. The encoding process is performed for each of
the predetermined number of the frames, that is, the
section to be processed.
[0595]
15 In addition, the processes of step S631 to step
S639 are identical with those of step S471 to step S479
in Fig. 34, therefore, the description thereof is omitted.
In the processes of step S631 to step S639, each frame
constituting the section to be processed is set as frames
20 to be processed in a sequence and the coefficient index
is selected with respect to frames to be processed.
[0596]
In step S639, when it is determined that only the
process of a predetermined frame length is performed, the
25 process proceeds to step S640.
[0597]
In step S640, the production unit 281 determines
whether the method, which produces the high band encoded
data, is set as the fixed length method.
30 [0598]
That is, the production unit 281 compares the
171
SP248477WO01
encoding amount of the high band encoded data at the time
of being produced by the fixed length method with the
encoding amount at the time of being produced by the
variable length method. In addition, the production unit
5 281 determines that the fixed length method is set when
the encoding amount of the high band encoded data of the
fixed length method is less than the encoding amount of
the high band encoded data of the variable length method.
[0599]
10 In step S640, when it is determined that the fixed
length method is set, the process proceeds to step S641.
In step S641, the production unit 281 produces data
including a method flag to the effect the fixed length
method is selected, a fixed length index, a coefficient
15 index and a switching flag and supplies it to the high
band encoding circuit 37.
[0600]
In step S642, the high band encoding circuit 37
encodes data including a method flag, a fixed length
20 index, a coefficient index and the switching flag
supplied from the production unit 281 and produces the
high band encoded data. The high band encoding circuit
37 supplies the produced high band encoded data to the
multiplexing circuit 38 and then the process proceeds to
25 the step S645.
[0601]
Unlike this, in step S640, when it is determined
that the fixed length method is not set, that is, it is
determined that the variable length method is set, the
30 process proceeds to step S643. In step S643, the
production unit 281 produces data including a method flag
172
^ SP248477WO01
to the effect that the variable length method is selected,
a coefficient index, segment information, and nuimber
information, and supplies the produced data to the high
band encoding circuit 37.
5 [0602]
In step S644, the high band encoding circuit 37
encodes data including a method flag, a coefficient index,
an segment information and number information supplied
from the production unit 281 and produces the high band
10 encoded data. The high band encoding circuit 37 supplies
the produced high band encoded data to the multiplexing
circuit 38 and then the process proceeds to step S645.
[0603]
In step S642 or step S644, when the high band
15 encoded data is produced, and then the process of step
S645 is performed to complete the encoding process.
However, since the processes are identical with those of
step S482 in Fig. 34, the description thereof is omitted.
[0604]
20 As described above, it is possible to reduce the
encoding amount of the output code string and to perform
encoding or decoding of sound more efficiently byproducing
the high-band encoded data by selecting the
system in which an encoding amount for each section to be
25 processed is less, between a fixed length system and a
variable length system.
[0605]
[Functional Configuration Example of Decoder]
In addition, the decoder that inputs and decodes
30 the output code string output from the encoder 271 in Fig.
42 as the input code string, for example, is configured
173
^ SP248477WO01
as in Fig. 44. In addition, in Fig. 44, the same symbols
are used for parts corresponding to a case in Fig. 20.
Therefore, the description thereof is omitted.
[0606]
5 The decoder 311 in Fig. 44 is the same as the.
decoder 40 in Fig. 20 in that it includes the
demultiplexing circuit 41 to the synthesis circuit 48,
but is different from the decoder 40 in Fig. 20 in that
the selection unit 321 is disposed in the decoded high
10 band sub-band power calculation circuit 46.
[0607]
In the decoder 311, when the high band encoded data
is decoded by the high band decoding circuit 45, the data
obtained from the result and the decoded high band sub-
15 band power estimation coefficient specified by the
coefficient index obtained by decoding of the high band
encoded data are supplied to the selection unit 321.
[0608]
The selection unit 321 specifies whether the high
20 band encoded data of the section to be processed is
produced by which method of the fixed length method or
the variable length based on data supplied from the high
band decoding circuit 45. In addition, the selection
unit 321 selects the decoding high band sub-band power
25 estimation coefficient used in calculating the decoded
high band sub-band power with respect to the frames to be
processed based on the specified result of the method
producing the high band encoded data and data supplied
from the high band decoding circuit 45.
30 [0609]
[Description of Decoding Process]
174
^ SP248477WO01
Next, a decoding process performing by the decoder
311 in Fig. 44 will be described with reference to the
flowchart in Fig. 45.
[0610]
5 The decoding processing starts when the output code
string output from the encoder 271 is supplied to the
decoder 311 as the input code string and is performed for
each of the predetermined number of the frames, that is,
the section to be processed. In addition, since the
10 process of step S671 is identical with that of step S591
in Fig. 41, the description is omitted.
[0611]
In a step S672, the high band decoding circuit 45
performs the decoding of the high band encoded data
15 supplied from the demultiplexing circuit 41 and supplies
data obtained from the result and the decoded high band
sub-band power estimation coefficient to the selection
unit 321 of the decoded high band sub-band power
calculation circuit 46.
20 [0612]
That is, the high band decoding circuit 45 reads
the decoded high band sub-band power estimation
coefficient indicated by the coefficient index obtained
by the decoding of the high band encoded data among the
25 decoded high band sub-band power estimation coefficients
recorded in advance. In addition, the high band decoding
circuit 45 supplies the decoded high band sub-band power
estimation coefficient and data obtained by the decoding
of the high band encoded data to the selection unit 321.
30 [0613]
In this case, when the fixed length system by the
175
^ SP248477WO01
system flag is indicated, a decoded high band sub-band
power estimation coefficient, a method flag, a fixed
length index and the switch flag are supplied to the
selection unit 321. In addition, when the method flag
5 indicates the variable length method, the decoded high
band sub-band power estimation coefficient, the method
flag, the segment information and the number information
is supplied to the selection unit 321.
[0614]
10 After the high band encoded data is decoded, the
processes of step S673 to step S675 are performed.
However, the processes are the same as step S593 to step
S595 in Fig. 41, the description thereof is omitted.
[0615]
15 In step S676, the selection unit 321 selects the
decoded high band sub-band power estimation coefficient
of the frame to be processed from the decoding high band
sub-band power estimation coefficient supplied from the
high band decoding circuit 45 based on data supplied from
20 the high band decoding circuit 45.
[0616]
For example, when the method flag supplied from the
high band decoding circuit 45 indicates the fixed length
method, the same process as step S596 in Fig. 41 is
25 performed and the decoded high band sub-band power
estimation coefficient is selected from the fixed length
index and the switching flag. Unlike this, when the
variable length method is indicated by the method flag
supplied from the high band decoding circuit 45, the same
30 process as in step S516 in Fig. 36 is performed, the
decoded high band sub-band power estimation coefficient
176
^^ SP248477WO01
is selected from the segment information and the number
information.
[0617]
When the decoding high frequency sub-band power
5 estimation coefficient of the frames to be processed is
selected, after that, the processes of step S677 to S680
are performed, the decoding processes are completed.
However, since the processed is identical with those of
step S597 to step S600 in Fig. 41, the description
10 thereof is omitted.
[0618]
The decoded high band sub-band power estimation
coefficient selected is used and thus the decoded high
band signal of the frames to be processed is produced in
15 the processes of step S677 to step S680 and the produced
decoded high band signal and decoded low band signal is
synthesized and output.
[0619]
As described, the high band encoded data is
2 0 produced by the method where the encoding amount is less
than the fixed length method and the variable length
method. Since one coefficient index with respect to one
or more frames is included in the high band encoded data,
it is possible to obtain the output signal having good
25 efficiency from the input code string with less data
amount.
[0620]
<10. Tenth Embodiment>
[High Performance Encoding of Coefficient Indexing
30 String]
Now, in the coding method of encoding sound,
177
^ SP248477WO01
information for decoding data of predetermined frames is
recycled as information for decoding data of frame later
the frame. In this case, a mode where the recycling of
information in time direction is performed and mode where
5 recycling is inhibited are selected.
[0621]
Herein, information reused in time direction is set
as the index and the like. Specially, for example, a
plurality of frames are set as unit and thus the output
10 code string including the low band encoded data and the
high band encoded data is output from the encoder as
illustrating in Fig. 46.
[0622]
In addition, in Fig 46, a lateral direction shows
15 time and one rectangle shows one frame. In addition, a
numeral in the rectangle showing the frame indicates the
coefficient index specifying the decoded high band subband
power estimation coefficient of the frame. In
addition, in Fig. 46, the same symbols are used for parts
20 corresponding to a case in Fig. 32. The description
thereof is omitted.
[0623]
An example in Fig. 46, 16 frames are set as a unit
to output the output code string. For example, an
25 segment from a position FSTl to a position FSEl is set as
an section to be processed and thus the output code string of 16 frames included in the section to be
processed is output.
[0624]
30 In this case, in the mode where the recycling of
information is performed, when the coefficient index of
118
^ SP248477WO01
the leading frame of the section to be processed is
identical with that of one previous frame, the recycling
flag "1" to the effect that the coefficient index is
recycled is included in the high band encoded data. In
5 an example in Fig. 4 6, since coefficient index of leading
frame of the section to be processed and that of the
previous frame are both "2", the recycling flag is set as
\> -1 //
[0625]
10 When the recycling flag is set as "1", since the
coefficient index of a last frame of a previous section
to be processed is recycled, the coefficient index of an
initial frame of the section to be processed is not
included in the high band encoded data of the section to
15 be processed.
[0626]
Unlike this, when the coefficient index of the
leading frame of the section to be processed is different
from that of a frame before one of the frames, the
20 recycling flag "0" to the effect that the coefficient
index is not recycled is included in the high band
encoded data. In this case, since the reuse of the
coefficient index is not possible, the coefficient index
of the initial frame to be processed is included in the
25 high band encoded data.
[0627]
In addition, in the mode where the information
recycling is inhibited, the recycling flag is not
included in the high band encoded data. When the
30 recycling flag is used, it is possible to reduce the
encoding amount of output code string and to perform
179
SP248477WO01
encoding or decoding of sound more efficiently.
[0628]
In addition, information recycled by the recycling
flag may be any information without the coefficient index
5 is limited.
[0629]
[Description of Decoding Processing]
Next, encoding and decoding processes performed in
a case where the reuse flag is used will be described.
10 First, a case where the high band encoded data is
produced by the variable length method will be described.
In this case, the encoding process and the decoding
process are performed by the encoder 111 in Fig. 33 and
the decoder 151 in Fig. 35.
15 [0630]
An encoding processing by the encoder 111 will be
described with reference to the flowchart in Fig. 47.
This encoding process is performed for each of the
predetermined number of the frames, that is, the section
20 to be processed.
[0631]
Since the processes of step S711 to step S719 are
identical with those of step S471 to step S479 in Fig. 34,
the description thereof is omitted. In the processes of
25 step S711 to step S719, each frame constituting the
section to be processed is set as the frame to be
processed in a sequence and the coefficient index is
selected with respect to the frame to be processed.
[0632]
30 In step S719, when only process of a predetermined
frame length is determined, the process proceeds to step
180
^ SP248477WO01
S720.
[0633]
In step S720, the production unit 121 determines
whether the recycling of information is performed. For
5 example, when the mode where the recycling of information
is performed by a user is assigned, it is determined that
the recycling of information is performed.
[0634]
In step S720, when it is determined that the
10 recycling of information is performed, the process
proceeds to S721.
[0635]
In step S721, the production unit 121 produces data
including the recycling flag, the coefficient index as
15 segment information and the number information based on
the selection result of the coefficient index of each
frame in the section to be processed and supplies the
produced data to the high band encoding circuit 37.
[0636]
20 For example, in an example in Fig. 32, since the
coefficient index of the leading frame of the section to
be processed is "2", whereas the coefficient index of the
frame just before the frame is "3" and the recycling flag
is set as "0" without the recycling of the coefficient
25 index.
[0637]
The production unit 121 produces data including the
recycling flag "0" and the number information
"num_length=3" and, the segment information of each
30 consecutive frame segment "length0=5", "lengthl=7", and
"length2=4", and the coefficient index of the consecutive
181
^ SP248477WO01
frame segment thereof "2", "5" and "1".
[0638]
In addition, when recycling flag is set as "1",
data where is not included in the coefficient index of
5 the initial consecutive frame of the section to be
processed is produced. For example, in the example in
Fig. 32, when the recycling flag of the section to be
processed is set as "1", data including the reuse flag
and the number information, the segment information
10 "length0=5", "lengthl=7" and "length2=4", and the
coefficient index "5", and "1".
[0639]
In step S722, the high band encoding circuit 37
encodes data including the recycling flag, the
15 coefficient index, the segment information, the
coefficient information and the number information
provided from the production unit 121 and produces the
high band encoded data. The high band encoding circuit
37 supplies the produced high band encoded data to the
20 multiplexing circuit 38 and then the process proceeds to '
step S725.
[0640]
Unlike this, in step S720, when it is determined
that the recycling of information is not performed, that i
25 is, when the mode where the recycling of information is inhibited by a user is assigned, the process proceeds to
step S723. i
[0641] In step S723, the production unit 121 produces data '
30 including the coefficient index, the segment information, ";
and the number information based on the selection result
182
^ SP248477WO01
of the coefficient index of each frame in the section to
be processed and supplies them to the high band encoding
circuit 37. The process of step S723 identical with that
of step S480 in Fig. 34 is performed.
5 [0642]
In step S724, the high band encoding circuit 37
encodes data including the coefficient index, the segment
information and the number information supplied from the
production unit 121 and produces the high band encoded
10 data. The high band encoding circuit 37 supplies the
produced high band encoded data to the multiplexing
circuit 38 and then the process proceeds to step S725.
[0643]
In step S722 or step S724, after the high band
15 encoded data is produced, the process of step S725 is
performed to terminate the encoding process. However,
since the process is identical with that of step S482 in
Fig. 34, the description thereof is omitted.
[0644]
2 0 As described above, when the mode where the reuse
of information is performed is assigned, it is possible
to reduce the encoding amount of the output code string
by producing the high band encoded data including the
reuse flag and to perform encoding or decoding of sound
25 more efficiently.
[0645]
[Description of Decoding Processing]
Next, a decoding process performed by the decoder
151 in Fig. 35 will be described with reference to a
30 flowchart in Fig. 48.
[0646] i
183
SP248477WO01
The decoding process starts when the encoding
process described with reference to Fig. 47 is performed
and the output code string output from the encoder 111 is
supplied to the decoder 151 as the input code string, and
5 is performed for each of a predetermined frame number,
that is, the section to be processed. In addition, the I
process of the step S751 is identical with that of step
S511 in Fig. 36, the description thereof is omitted. |
[0647] j
10 In step S752, the high band decoding circuit 45 performs decoding of the high band encoded data supplied
from the demultiplexing circuit 41 and supplies the data i
obtained from the result and the decoded high band sub- I
band power estimation coefficient to the selection unit i
15 161 of the decoded high band sub-band power calculation {
i
circuit 46. ;
[0648] j
That is, the high band decoding circuit 45 reads j
the decoded high band sub-band power estimation j
20 coefficient indicated with the coefficient index obtained i
by decoding of the high-band encoded data in the decoded •
high band sub-band power estimation coefficient recorded
in advance. In addition, the high band decoding circuit 45 supplies the decoded high band sub-band power '
25 estimation coefficient and data obtained by the decoding j
of the high band encoded data to the selection unit 161.
[0649]
In this case, when the mode where the recycling of
information is performed is assigned, the decoded high
30 band sub-band power estimation coefficient, the recycling
flag, the segment information and the number information
184
^ SP248477WO01
are supplied to the selection unit 161. In addition,
when the mode where the recycling of information is
inhibited is assigned, the decoded high band sub-band
power estimation coefficient, the segment information and
5 the number information are supplied to the selection unit
161.
[0650]
When the high band encoded data is decoded, after
that, the processes of step S753 to step S755 are 10 performed. However, since the processes are identical
with those of step S513 to step S515 in Fig. 36, the
description thereof is omitted. j
[0651] In step S756, the selection unit 161 selects the
15 decoded high band sub-band power estimation coefficient
of the frames to be processed from the decoded high band
sub-band power estimation coefficient supplied from the
high band decoding circuit 45 based on data supplied from
the high band decoding circuit 45.
20 [0652]
That is, when the recycling flag, the segment
information and the number information are supplied from
the high band decoding circuit 45, the selection unit 161
selects the decoded high band sub-band power estimation
25 coefficient of the frames to be processed based on the
recycling flag, the segment information and the number
information. For example, when the leading frame of the
section to be processed is the frame to be processed and
the recycling flag is "1", the decoded high band sub-band
30 power estimation coefficient of frame just before the
frame to be processed is selected as the decoded high
185
_ SP248477WO01
band sub-band power estimation coefficient of the frame
to be processed.
[0653]
In this case, in consecutive frame segment of the
5 lead of the section to be processed, the decoding high
band sub-band estimation coefficient identical with the
decoded high band sub-band power estimation coefficient
of the frames just before the section to be processed is '
selected in each frame. In addition, in a consecutive
10 frame segment subsequent to the second frame segment, the
decoded high band sub-band power estimation power
estimation coefficient of each frame is selected by the
same process as in the process of step S516 in Fig. 36,
that is, based on the segment information and the number
15 information.
[0654] I
In addition, in this case, the selection unit 161
keeps the decoded high band sub-band power estimation
coefficient of the frames just before the section to be
20 processed, which is supplied from the high band decoding
circuit 45 prior to starting the decoding processing. ;•
[0655] ;
In addition, when the recycling flag is "0" or the !
decoded high band sub-band power estimation coefficient,
25 the segment information and the number information are ;
supplied from the high band decoding circuit 45, the same
process as step S516 in Fig. 36 is performed and the
decoded high band sub-band power estimation coefficient
of the frame to be processed is selected. ;
30 [0656]
When the decoded high band sub-band power
18 6
^ SP248477WO01
estimation coefficient of the frames to be processed is
selected, after that, the process in step S757 to step
S7 60 is performed to complete the decoding process.
However, since the processes are identical with those of
5 step S517 to step S520 in Fig. 36, the description
thereof is omitted.
[0657]
In the processes of step S757 to step S760, the .
selected decoded high band sub-band power estimation
10 coefficient is used to produce the decoded high band
signal of the frame to be processed, and the produced
decoded high band signal and the decoded low band signal :
are synthesized and output.
[0658]
15 As described above, as needed, when the high band
encoded data including the reuse flag is used, it is
possible to obtain the output signal more efficiently
from the input code string of less amount of data.
[0659]
20 <11. Eleventh embodiment>
[Description of Decoding Processing]
Next, a case where the recycling of information is
performed as needed and the high band encoded data is
produced by the fixed length method will be described.
25 In this case, the encoding process and the decoding
process are performed by the encoder 191 in Fig. 38 and
decoder 231 in Fig. 40.
[0660]
As described below, an encoding process by the
30 encoder 191 will be described with reference to a
flowchart in Fig. 49. The encoding process is performed
187
^ SP248477WO01
for each of the predetermined number of the frames, that
is, the section to be processed.
[0661]
In addition, since the processes of step S791 to
5 step S799 are identical with those of step S551 to step
S559 in Fig. 39, the description thereof is omitted. In
the processes of step S791 to step S799, each frame
constituting the section to be processed is set as a
frame to be processed in a sequence and the coefficient
10 index is selected with respect to the frames to be
processed.
[0662]
In step S799, when it is determined that the
process of a predetermined frame length only is performed,
15 the process proceeds to step S800.
[0663]
In step S800, the production unit 201 determines
whether the recycling of information is performed. For
example, when the mode where the recycling of information
20 is performed by the user is assigned, it is determined
that the recycling of information is performed.
[0664]
In step S800, it is determined that the recycling
of information is performed, the process proceeds to step
25 S801.
[0665]
In step S801, the production unit 201 produces data
including the recycling flag, the coefficient index, the
fixed length index and the switching flag based on the
30 selection result of the coefficient index of each frame
in the section to be processed and supplies the produced
188 ;
^ SP248477WO01
data to the high band encoding circuit 37.
[0666]
For example, in an example in Fig. 37, since the
coefficient index of the leading frame of the processing
5 segment is "1", whereas the coefficient index of the
frame just before of the frame is "3", the recycling flag
is set as "0" without the recycling of the coefficient
index. The production unit 201 produces data including
the recycling flag "0", the fixed length index "2", the !
10 coefficient index "1", "2", "3" and the switching flag
[0667]
In addition, when the recycling flag is "1", data
which does not include the coefficient index of the
15 initial fixed length segment of the section to be
processed is produced. For example, in an example in Fig.
37, when the recycling flag of the section to be
processed is set as "1", data including the recycling ;
flag, the fixed length index is "2", the coefficient
20 index is "2", "3" and the switching flag is "1", "0", " 1"
is produced. ;
[0668] ;
In step S802, the high band encoding circuit 37
encodes data including the recycling flag, the
25 coefficient index, the fixed length index and the
switching flag supplied from the production unit 201 and
produces the high band encoded data. The high band
encoding circuit 37 supplies the produced high band i
encoded data to the multiplexing circuit 38, and after
30 that, the process proceeds to step S805.
[0669] i
189
SP248477WO01
Unlike this, in step S800, when it is determined i
that the recycling of information is not performed, that >
is, when the mode where the recycling of information is I
inhibited by user is assigned, the process proceeds to
5 step S803.
[0670] I
In step S803, the production unit 201 produces data
including the coefficient index, the fixed length index, !
and the switching flag based on the selection result of
10 the coefficient index of each frame in the section to be
processed and supplies them to the high band encoding :
circuit 37. In step S803, the same process as step S560
in Fig. 39 is performed.
[0671] •
15 In step S804, the high band encoding circuit 37
encodes data including the coefficient index, the fixed
length index and the switching flag supplied from the
production unit 201 and produces the high band encoded
signal. The high band encoding circuit 37 supplies the
20 produced high band encoded data to the multiplexing
circuit 38 and then the process proceeds to step S805.
[0672]
In step S802 or step S804, when the high band
encoded data is produced, after that, the process of step
25 S805 is performed to terminate the encoding process.
However, since these processes are identical with those
of step S562 in Fig. 39, the description thereof is
omitted.
[0673]
30 As described above, when the mode where the
recycling of information is performed is designated, it
190
_ SP248477WO01
is possible to reduce the encoded amount of the output
code string by producing the high band encoded data
including the recycling flag and to perform encoding and
decoding of sound more efficiently.
5 [0674]
[Description of Decoding Process]
Next, a decoding process performed by decoder 231
in Fig. 40 will be described with reference to a
flowchart in Fig. 50.
10 [0675]
The decoding process starts when the encoding
process described with reference to Fig. 4 9 is performed
and the output code string output from the encoder 191 is
supplied to the decoder 231 as the input code string and
15 is performed for each of the predetermined number of the
frames, that is, the section to be processed. In
addition, since the process of step S831 are identical
with those of step S591 in Fig. 41, the description
thereof is omitted.
20 [0676]
In step S832, the high band decoding circuit 45
performs the decoding of the high band encoded data
supplied from the demultiplexing circuit 41 and supplies
data obtained from the result and the decoded high band
25 sub-band power estimation coefficient to the selection
unit 241 of the decoded high band sub-band power
calculation circuit 46.
[0677]
That is, the high band decoding circuit 45 reads I
30 the decoded high band sub-band power estimation
coefficient indicated by the coefficient index obtained
191
^ SP248477WO01
by decoding of the high band encoded data in the decoded
high band sub-band power estimation coefficient that is
recorded in advance. In addition, the high band decoding
circuit 45 supplies the decoded high band sub-band power
5 estimation coefficient and data obtained by decoding of
the high band encoded data to the selection unit 241.
[0678]
In this case, when the mode where the reuse of
information is performed is designated, the decoded high
10 band sub-band power estimation coefficient, the reuse
flag, the fixed length index and switching flag are
supplied to the selection unit 241. In addition, when
the mode where the reuse of information is inhibited, is
designated, the decoded high band sub-band power
15 estimation coefficient, the fixed length index and the
switching flag is supplied to the selection unit 241.
[0679]
When high band encoded data is decoded, after that,
the process of step S833 to step S835 are performed.
20 However, since the processes are identical with those of step S593 to step S595 in Fig. 41, the description
thereof is omitted.
[0680] ;
In step S836, the selection unit 241 selects the
25 decoded high band sub-band power estimation coefficient of the frame to be processed from the decoded high band i
sub-band power estimation coefficient supplied from the
high band decoding circuit 45 based on data supplied from ?
the high band decoding circuit 45.
30 [0681] ;
That is, when the reuse flag, the fixed length i
192
SP248477WO01
index and the switching flag is supplied from the high
band decoding circuit 45, the selection unit 241 selects ;
the decoded high band sub-band power estimation
coefficient of the frames to be processed based on the •
5 reuse flag, the fixed length index and the switching flag. 5
For example, when the leading frames of the section to be ;
processed are frames to be processed and the reuse flag
is "1", the decoded high band sub-band power estimation
coefficient of the frames just before the frame to be
10 processed is selected as the decoded high band sub-band
power estimation coefficient of the frame to be processed.
[0 682]
In this case, in the fixed length segment of the
lead of the section to be processed, the decoded high
15 band sub-band estimation coefficient which is the same as
the decoded high band sub-band power estimation
coefficient of the frame just before the section to be
processed is selected in each frame. In addition, in a
fixed length segment subsequent to the second frame
20 segment, the decoded high band sub-band power estimation
coefficient of each frame is selected by the same process
as in the process of step S596 in Fig. 41, that is, based
on the fixed length index and the switching flag. :
[0683]
25 In addition, in this case, the selection unit 241 •
keeps the decoded high band sub-band power estimation
coefficient of the frame just before the section to be
processed supplied from the high band decoding circuit 45 i
prior to starting the decoding process.
30 [0684] ]
In addition, when the reuse flag is "0" and the i
193 }
^ SP248477WO01
decoded high band sub-band power estimation coefficient, j
the fixed length index and the switching flag are i
supplied from the high band decoding circuit 45, the same I
process as step S596 in Fig. 41 are performed and the ;
5 decoded high band sub-band power estimation coefficient
of the frame to be processed is selected.
[0685]
When the decoded high band sub-band power
estimation coefficient of the frames to be processed is :,
10 selected, after that, the processes of step S837 to step
S840 are performed to complete the decoding process.
However, since the processes are identical with those of ;
step S597 to step S600 Fig. 41, the description thereof
is omitted.
15 [0686] ;
In the processes of step S837 to step S840, the
selected decoded high band sub-band power estimation
coefficient is used to produce the decoded high band
signal of the frame to be processed and the produced
2 0 decoded high band signal and the decoded low band signal
is synthesized and output. j
[0687] , I
As described above, as needed, when the high band f
encoded data in which the reuse flag is included is used, j
i
25 it is possible to obtain the output signal more {
I I
efficiently from the input code string of less data. f
[0688] I
In addition, as described above, as an example l
i
where the reuse flag is used by using any one of the i
30 variable length'system and the fixed length system, a I
case where the high band encoded data is produced is i
194 ;
^ SP248477WO01
described. However, even in a case where the system
where the encoded amount is small is selected among these
systems, the reuse flag may be used.
[0689]
5 The serial process described above is performed by
a hardware and a software. When a serial process is
performed by the software, a program constituted by the
software is installed to a computer incorporated into an
indicated software or a general-purpose personal computer
10 capable of executing various functions by installing
various programs from a program recording medium.
[0690]
Fig. 51 is block diagram illustrating a
configuration example of the hardware of a computer
15 performing a series of processes described above by the
computer.
[0691]
In the computer, a CPU 501, a ROM (Read Only
Memory) 502 and a RAM (Random Access Memory) 503 are
20 connected each other by a bus 504.
[0 692]
In addition, an input/output interface 505 is
connected to the bus 504. An input unit 506 including a i
key board, an mouse a microphone and the like, an output
25 unit 507 including a display, a speaker and the like, a
storage unit 508 including a hard disk or non-volatile >
memory and the like, a communication unit 509 including a ;
network interface and the like, and a drive 510 that
drives a removable medium 511 of a magnetic disc, an ;
30 optical disc, a magneto-optical disc and semiconductor :
memory and the like are connected to the input/output
195
^ SP248477WO01
interface 505. [0693] !
In the computer configured as described above, for 5
example, the CPU 501 loads and executes the program i
5 stored in the storage unit 508 to the RAM 503 via the I
input/output interface 505 and the bus 504 to perform a
series of processes described above.
[0694]
The program to be executed by the computer (CPU -
10 501), for example, is recorded in a removable medium 511
such as a package medium including a magnetic disk,
(including a flexible disc), an optical disc ((CD-ROM
(Compact Disc-Read Only Memory)), DVD (Digital Versatile I
Disc) and the like) , a magneto-optical disc or a ]
15 semiconductor memory, or is provided via a wire or
wireless transmission medium including a local area
network, an internet and a digital satellite broadcasting.
[0695] ;
In addition, the program can be installed to the
20 storage unit 508 via the input/output interface 505 by
mounting the removable medium 511 to the drive 510. In :
addition, the program is received in the communication
unit 509 via the wire or wireless transmission medium and I
can be installed to the storage unit 508. In addition, 25 the program can be installed in the ROM 502 or the i
storage unit 508 in advance. I
[0696] {
In addition, the program performed by the computer j
may be a program where the process is performed in time {
30 sequence according the sequence described in the I
specification and a program where the process is
19 6
^ SP248477WO01
performed in parallel or in timing necessary when a call
is made.
[0697]
In addition, the embodiment of the present
5 invention is not limited the embodiment described above
and various modifications is possible within a scope
apart from a gist of the present invention.
REFERENCE SIGNS LIST
10 [0698]
10 Frequency Band Expansion Apparatus
11 Low-pass filter
12 Delay Circuit
13, 13-1 to 13-N Band Pass Filter
15 14 Characteristic Amount Calculation Circuit
15 High Band Sub-Band Power Estimation Circuit
16 High Band Signal Production Circuit
17 High-pass filter ;
18 Signal Adder
20 20 Coefficient Learning Apparatus
21, 21-1 to 21-(K+N) Band Pass Filter
22 High Band Sub-Band Power Calculation Circuit
23 Characteristic Amount Calculation Circuit i
24 Coefficient Estimation Circuit
25 30 Encoder
31 Low-pass filter
32 Low Band Encoding Circuit
33 Sub-Band Division Circuit ;
34 Characteristic Amount Calculation Circuit
30 35 Pseudo High Band Sub-Band Power Calculation Circuit
36 Pseudo High Band Sub-band Power Difference
197
^ SP248477WO01
Calculation Circuit
37 High Band Encoding Circuit
38 Multiplexing Circuit
40 Decoder ;
5 41 Demultiplexing Circuit
42 Low Band Decoding Circuit 43 Sub-Band Division Circuit
44 Characteristic Amount Calculation Circuit
45 High Band Decoding Circuit
10 4 6 Decoded High Band Sub-Band Power Calculation
Circuit ?
47 Decoded High Band Signal Production Circuit
48 Synthesis circuit
50 Coefficient Learning Apparatus ;
15 51 Low-pass filter j
52 Sub-Band Division Circuit j
53 Characteristic Amount Calculation Circuit j
54 Pseudo High Band Sub-Band Power Calculation Circuit f
55 Pseudo High Band Sub-Band Power Difference |
20 Calculation Circuit j
56 Pseudo High Band Sub-Band Power Difference {
Clustering Circuit
57 Coefficient Estimation Circuit 101 CPU 25 102 ROM
103 RAM
104 Bus
105 Input/Output Interface
106 Input Unit
30 107 Output Unit
108 Storage Unit
198
|k SP248477WO01
109 Communication Unit
110 Drive '•
111 Removable Medium
199 '

^ SP248477WO01
CLAIMS
1. A signal processing apparatus comprising:
a demultiplexing unit that demultiplexes input
5 encoded data into data including information on a segment
including frames in which the same coefficient as a
coefficient used in producing a high band signal is
selected in a section to be processed including a
plurality of frames, and coefficient information for
10 obtaining the coefficient selected in the frames of the
segment, and low band encoded data;
a low band decoding unit that decodes the low band
encoded data to produce a low band signal;
a selection unit that selects a coefficient of a
15 frame to be processed from a plurality of the
coefficients based on the data;
a high band sub-band power calculation unit that
calculates a high band sub-band power of a high band subband
signal of each sub-band constituting the high band
20 signal of the frame to be processed based on a low band
sub-band signal of each sub-band constituting the low
band signal of the frame to be processed and the selected
coefficient; and
a high band signal production unit that produces
25 the high band signal of the frame to be processed based
on the high band sub-band power and the low band sub-band
signal.
2. The signal processing apparatus according to claim
30 1,
wherein the section to be processed is divided into
200
^ SP248477WO01
the segments so that positions of the frames adjacent to
each other in which different coefficients are selected
are set as boundary positions of the segments, and
information indicating a length of each of the segments
5 is set as information on the segments.
3. The signal processing apparatus according to claim
1,
wherein the section to be processed is divided into
10 the several segments having the same length so that a
length of the segment is the longest and information
indicating the length and information indicating whether
the selected coefficient is varied before and after each
boundary position of the segments are set as information
15 on the segments.
4. The signal processing apparatus according to claim
3,
wherein when the same coefficient is selected in
20 continuous several segments, the data includes one piece
of coefficient information for obtaining the coefficient
selected in the several continuous segments.
5. The signal processing apparatus according to claim
25 1,
wherein the data is produced for each section to be
processed by a system having a less data amount between a
first system and a second system,
wherein, in the first system, the section to be
30 processed is divided into the segments so that the
positions of frames adjacent to each other in which the
201
^ SP248477WO01
different coefficients are selected, are set as a
boundary position of the segments and information
indicating a length of each of the segments is set as
information on the segments,
5 wherein, in the second system, the section to be
processed is divided into the several segments having the
same length so that a length of the segment is the
longest and information indicating the length and
information indicating whether the selected coefficient
10 is varied before and after a boundary position of the
segments are set as information on the segment, and
wherein the data further includes information
indicating whether the data is obtained by the first
system or second system.
15
6. The signal processing apparatus according to claim
1,
wherein the data further includes reuse information
indicating whether the coefficient of an initial frame in
20 the section to be processed is the same as the
coefficient of a frame just before the initial frame, and
when the data includes the reuse information
indicating that the coefficients are the same, the data
does not include coefficient information of the initial
25 segment of the section to be processed.
7. The signal processing apparatus according to claim
6,
wherein when a mode in which the coefficient
30 information is reused, is designated, the data includes
the reuse information, and when a mode in which the reuse
202
^ SP248477WO01
of the coefficient information is prohibited, is
designated, the data does not include the reuse
information.
5 8. A signal processing method for a signal processing
apparatus including:
a demultiplexing unit that demultiplexes input
encoded data into data including information on a segment
including frames in which the same coefficient as a
10 coefficient used in producing a high band signal is
selected in a section to be processed including a
plurality of frames, and coefficient information for
obtaining the coefficient selected in the frames of the
segment, and low band encoded data;
15 a low band decoding unit that decodes the low band
encoded data to produce a low band signal;
a selection unit that selects a coefficient of a
frame to be processed from a plurality of the
coefficients based on the data;
20 a high band sub-band power calculation unit that
calculates a high band sub-band power of a high band subband
signal of each sub-band constituting the high band
signal of the frame to be processed based on a low band
sub-band signal of each sub-band constituting the low
25 band signal of the frame to be processed and the selected
coefficient; and
a high band signal production unit that produces
the high band signal of the frame to be processed based
on the high band sub-band power and the low band sub-band
30 signal,
the signal processing method comprising the steps
203
^ SP248477WO01
of:
demultiplexing the encoded data into the data and
the low band encoded data by the demultiplexing unit;
decoding the low band encoded data by the low band
5 decoding unit;
selecting the coefficient of the frames to be
processed by the selection unit;
calculating the high band sub-band power by the
high band sub-band power calculation unit; and
10 producing the high band signal by the high band
signal production unit.
9. A program causing a computer to execute processes
comprising the steps of:
15 demultiplexing input encoded data into data
including information on a segment including frames in
which the same coefficient as a coefficient used in
producing a high band signal is selected in a section to
be processed including a plurality of frames, and
20 coefficient information for obtaining the coefficient
selected in the frames of the segment, and low band
encoded data;
decoding the low band encoded data to produce a low
band signal;
25 selecting a coefficient of a frame to be processed
from a plurality of the coefficients based on the data;
calculating a high band sub-band power of a high
band sub-band signal of each sub-band constituting the
high band signal of the frame to be processed based on a
30 low band sub-band signal of each sub-band constituting
the low band signal of the frame to be processed and the
204
^ SP248477WO01
selected coefficient; and
producing the high band signal of the frame to be
processed based on the high band sub-band power and the
low band sub-band signal.
5
10. A signal processing apparatus comprising:
a sub-band division unit that produces a low band
sub-band signal of a plurality of sub-bands in a low band
side of an input signal, and a high band sub-band signal
10 of a plurality of sub-bands in a high band side of the
input signal;
a pseudo high band sub-band power calculation unit
that calculates a pseudo high band sub-band power which
is an estimation value of power of the high band sub-band
15 signal based on the low band sub-band signal and a
predetermined coefficient;
a selection unit that selects any of a plurality of
the coefficients for respective frames of the input
signal by comparing the high band sub-band power of the
20 high band sub-band signal and the pseudo high band subband
power; and
a production unit that produces data including
information on a segment having frames in which the same
coefficient is selected in a section to be processed
25 having a plurality of frames of the input signal, and
coefficient information for obtaining the coefficient
selected in frames of the segment.
11. The signal processing apparatus according to claim
30 10,
wherein the production unit divides the section to
205
^ SP248477WO01
be processed into the segments so that the positions of
frames adjacent to each other in which different
coefficients are selected, are set as boundary positions
of the segments, and sets information indicating a length
5 of each of the segments as information on the segment.
12. The signal processing apparatus according to claim
10,
wherein the production unit divides the section to
10 be processed into the several segments having the same
length so that a length of the segment is the longest and
information indicating the length and information
indicating whether the selected coefficient is varied
before and after boundary positions of the segments are
15 set as information on the segments.
13. The signal processing apparatus according to claim
12,
wherein the production unit produces the data
20 including one piece of coefficient information for
obtaining the coefficient selected in the several
continuous segments when the same coefficient is selected
in the several continuous segments.
25 14. The signal processing apparatus according to claim
10,
wherein the production unit produces data for each
section to be processed with a system having a less data
amount between a first system and a second system,
30 wherein, in the first system, the section to be
processed is divided into the segments so that the
206
^ SP248477WO01
positions of frames adjacent to each other in which the
different coefficients are selected, are set as boundary
positions of the segments, and information indicating a
length of each of the segments is set as information on
5 the segments, and
wherein, in the second system, the section to be
processed is divided into the several segments having the
same length so that a length of the segment is the
longest and information indicating the length and
10 information indicating whether the selected coefficient
is varied before and after a boundary position of the
segments are set as information on the segments.
15. The signal processing apparatus according to claim
15 14,
wherein the data further includes information
indicating whether the data is obtained by the first
system or the second system.
20 16. The signal processing apparatus according to claim
10,
wherein the production unit produces the data
including reuse information indicating whether the
coefficient of an initial frame of the section to be
25 processed is the same as the coefficient of a frame just
before the initial frame, and
when the reuse information indicating that the
coefficients are the same is included in the data, the
data in which the coefficient information of an initial
30 segment of the section to be processed is not included,
is produced.
207
_ SP248477WO01
17. The signal processing apparatus according to claim
16,
wherein when a mode in which the coefficient
5 information is reused, is designated, the production unit
produces the data including the reuse information, and
when a mode in which the reuse of the coefficient
information is prohibited, is designated, the production
unit produces the data in which the reuse information is
10 not included.
18. A signal processing method for a signal processing
apparatus including:
a sub-band division unit that produces a low band
15 sub-band signal of a plurality of sub-bands in a low band
side of an input signal, and a high band sub-band signal
of a plurality of sub-bands in a high band side of the
input signal;
a pseudo high band sub-band power calculation unit
20 that calculates a pseudo high band sub-band power which
is an estimation value of power of the high band sub-band
signal based on the low band sub-band signal and a
predetermined coefficient;
a selection unit that selects any of a plurality of
25 the coefficients for respective frames of the input
signal by comparing the high band sub-band power of the
high band sub-band signal and the pseudo high band subband
power; and
a production unit that produces data including
30 information on a segment having frames in which the same
coefficient is selected in a section to be processed
208
^ SP248477WO01
having a plurality of frames of the input signal, and
coefficient information for obtaining the coefficient
selected in frames of the segment,
the signal processing method comprising the steps
5 of:
producing the low band sub-band signal and the high
band sub-band signal by the sub-band division unit;
calculating the pseudo high band sub-band power by
the pseudo high band sub-band power calculation unit;
10 selecting any of a plurality of the coefficients by
the selection unit; and
producing the data by the production unit.
19. A program causing a computer to execute processes
15 comprising the steps of:
producing a low band sub-band signal of a plurality
of sub-bands in a low band side of an input signal, and a
high band sub-band signal of a plurality of sub-bands in
a high band side of the input signal;
20 calculating a pseudo high band sub-band power which
is an estimation value of power of the high band sub-band
signal based on the low band sub-band signal and a
predetermined coefficient;
selecting any of a plurality of the coefficients
25 for respective frames of the input signal by comparing
the high band sub-band power of the high band sub-band
signal and the pseudo high band sub-band power; and
producing data including information on a segment
having frames in which the same coefficient is selected
30 in a section to be processed having a plurality of frames
of the input signal, and coefficient information for
209
^ SP248477WO01
obtaining the coefficient selected in frames of the
segment.
20. A decoder comprising:
5 a demultiplexing unit that demultiplexes input
encoded data into data including information on a segment
including frames in which the same coefficient as a
coefficient used in producing a high band signal is
selected in a section to be processed including a
10 plurality of frames, and coefficient information for
obtaining the coefficient selected in the frames of the
segment, and low band encoded data;
a low band decoding unit that decodes the low band
encoded data to produce a low band signal;
15 a selection unit that selects a coefficient of a
frame to be processed from a plurality of the
coefficients based on the data;
a high band sub-band power calculation unit that
calculates a high band sub-band power of a high band sub-
20 band signal of each sub-band constituting the high band
signal of the frame to be processed based on a low band
sub-band signal of each sub-band constituting the low
band signal of the frame to be processed and the selected
coefficient;
25 a high band signal production unit that produces
the high band signal of the frame to be processed based
on the high band sub-band power and the low band sub-band
signal; and
a synthesis unit that synthesizes the low band
30 signal and the high band signal to produce an output
signal.
210
^ SP248477WO01
21. A decoding method for a decoder including:
a demultiplexing unit that demultiplexes input
encoded data into data including information on a segment
5 including frames in which the same coefficient as a
coefficient used in producing a high band signal is
selected in a section to be processed including a
plurality of frames, and coefficient information for
obtaining the coefficient selected at the frames of the
10 segment, and low band encoded data;
a low band decoding unit that decodes the low band
encoded data to produce a low band signal;
a selection unit that selects a coefficient of a
frame to be processed from a plurality of the
15 coefficients based on the data;
a high band sub-band power calculation unit that
calculates a high band sub-band power of a high band subband
signal of each sub-band constituting the high band
signal of the frame to be processed based on a low band
20 sub-band signal of each sub-band constituting the low
band signal of the frame to be processed and the selected
coefficient;
a high band signal production unit that produces
the high band signal of the frame to be processed based
25 on the high band sub-band power and the low band sub-band
signal; and
a synthesis unit that synthesizes the low band
signal and the high band signal to produce an output
signal,
30 the decoding method comprising the steps of:
demultiplexing the encoded data into the data and
211
^ SP248477WO01
the low band encoded data by the demultiplexing unit;
decoding the low band encoded data by the low band
decoding unit;
selecting the coefficient of the frame to be
5 processed by the selection unit;
calculating the high band sub-band power by the
high band sub-band power calculation unit;
producing the high band signal by the high band
signal production unit; and
10 producing the output signal by the synthesis unit.
22. An encoder comprising:
a sub-band division unit that produces a low band
sub-band signal of a plurality of sub-bands in a low band
15 side of an input signal, and a high band sub-band signal
of a plurality of sub-bands in a high band side of the
input signal;
a pseudo high band sub-band power calculation unit
that calculates a pseudo high band sub-band power which
20 is an estimation value of power of the high band sub-band
signal based on the low band sub-band signal and a
predetermined coefficient;
a selection unit that selects any of a plurality of
the coefficients for respective frames of the input
25 signal by comparing the high band sub-band power of the
high band sub-band signal and the pseudo high band subband
power;
a high band encoding unit that produces high band
encoded data by encoding information on a segment having
30 frames in which the same coefficient is selected in a
section to be processed including a plurality of frames
212
^ SP248477WO01
of the input signal, and coefficient information for
obtaining the coefficient selected in the frames of the
segment;
a low band encoding unit that encodes a low band
5 signal of the input signal and produces low band encoded
data; and
a multiplexing unit that produces an output code
string by multiplexing the low band encoded data and the
high band encoded data.
10
23. An encoding method for an encoder including:
a sub-band division unit that produces a low band
sub-band signal of a plurality of sub-bands in a low band
side of an input signal, and a high band sub-band signal
15 of a plurality of sub-bands in a high band side of the
input signal;
a pseudo high band sub-band power calculation unit
that calculates a pseudo high band sub-band power which
is an estimation value of power of the high band sub-band
20 signal based on the low band sub-band signal and a
predetermined coefficient;
a selection unit that selects any of a plurality of
the coefficients for respective frames of the input
signal by comparing the high band sub-band power of the
25 high band sub-band signal and the pseudo high band subband
power;
a high band encoding unit that produces high band
encoded data by encoding information on a segment having
frames in which the same coefficient is selected in a
30 section to be processed including a plurality of frames
of the input signal, and coefficient information for
213
% SP248477WO01
^ - obtaining the coefficient selected in the frames of the
segment;
a low band encoding unit that encodes a low band'
signal of the input signal and produces low band encoded
5 data; and
a multiplexing unit that produces an output code
string by multiplexing the low band encoded data and^hehigh
band encoded data, m
^^ . the encoding method comprising the steps of:
10 producing the low band sub-band signal and the high
band sub-band signal by the sub-band division unit-
., • calculating the pseudo high band sub-band power by
the pseudo high band sub-band power calculation unit •
selecting any of a plurality of the coefficients by
15 the selection unit;
producing the high band encoded data by the high
band encoding unit;
producing the low band encoded data by the low band
encoding unit; and
^ 2 0 producing the output code string by the
multiplexing unit.