DESCRIPTION
Efficient Decisions for Deblocking
The present invention relates to the filtering of images. In particular, the present invention relates
to deblocking filtering and to decisions on enabling or disabling deblocking filtering for an image
block of a video image.
BACKGROUND OF THE INVENTION
At present, the majority of standardized video coding algorithms are based on hybrid video
coding. Hybrid video coding methods typically combine several different lossless and lossy
compression schemes in order to achieve the desired compression gain. Hybrid video coding is
also the basis for ITU-T standards (H.26x standards such as H.261 , H.263) as well as ISO/IEC
standards (MPEG-X standards such as MPEG-1, MPEG-2, and MPEG-4). The most recent and
advanced video coding standard is currently the standard denoted as H.264/MPEG-4 advanced
video coding (AVC) which is a result of standardization efforts by joint video team (JVT), a joint
team of ITU-T and ISO/IEC MPEG groups. This codec is being further developed by Joint
Collaborative Team on Video Coding (JCT-VC) under a name High-Efficiency Video Coding
(HEVC), aiming, in particular at improvements of efficiency regarding the high-resolution video
coding.
A video signal input to an encoder is a sequence of images called frames, each frame being a
two-dimensional matrix of pixels. All the above-mentioned standards based on hybrid video
coding include subdividing each individual video frame into smaller blocks consisting of a
plurality of pixels. The size of the blocks may vary, for instance, in accordance with the content
of the image. The way of coding may be typically varied on a per block basis. The largest
possible size for such a block, for instance in HEVC, is 64 x 64 pixels. It is then called the
largest coding unit (LCU). In H.264/MPEG-4 AVC, a macroblock (usually denoting a block of 16
x 16 pixels) was the basic image element, for which the encoding is performed, with a possibility
to further divide it in smaller subblocks to which some of the coding/decoding steps were
applied.
Typically, the encoding steps of a hybrid video coding include a spatial and/or a temporal
prediction. Accordingly, each block to be encoded is first predicted using either the blocks in its
spatial neighborhood or blocks from its temporal neighborhood, i.e. from previously encoded
video frames. A block of differences between the block to be encoded and its prediction, also
called block of prediction residuals, is then calculated. Another encoding step is a transformation
of a block of residuals from the spatial (pixel) domain into a frequency domain. The
transformation aims at reducing the correlation of the input block. Further encoding step is
quantization of the transform coefficients. In this step the actual lossy (irreversible) compression
takes place. Usually, the compressed transform coefficient values are further compacted
(losslessly compressed) by means of an entropy coding. In addition, side information necessary
for reconstruction of the encoded video signal is encoded and provided together with the
encoded video signal. This is for example information about the spatial and/or temporal
prediction, amount of quantization, etc.
Figure 1 is an example of a state of the art hybrid coder 100, as for example a typical
H.264/MPEG-4 AVC and/or HEVC video encoder. A subtractor 105 first determines differences
e between a current block to be encoded of an input video image (input signal s) and a
corresponding prediction block s, which is used as a prediction of the current block to be
encoded. The prediction signal may be obtained by a temporal or by a spatial prediction 180.
The type of prediction can be varied on a per frame basis or on a per block basis. Blocks and/or
frames predicted using temporal prediction are called "inter"-encoded and blocks and/or frames
predicted using spatial prediction are called "intra"-encoded. Prediction signal using temporal
prediction is derived from the previously encoded images, which are stored in a memory. The
prediction signal using spatial prediction is derived from the values of boundary pixels in the
neighboring blocks, which have been previously encoded, decoded, and stored in the memory.
The difference e between the input signal and the prediction signal, denoted prediction error or
residual, is transformed 1 0 resulting in coefficients, which are quantized 120. Entropy encoder
190 is then applied to the quantized coefficients in order to further reduce the amount of data to
be stored and/or transmitted in a lossless way. This is mainly achieved by applying a code with
code words of variable length wherein the length of a code word is chosen based on the
probability of its occurrence.
Within the video encoder 100, a decoding unit is incorporated for obtaining a decoded
(reconstructed) video signal s'. In compliance with the encoding steps, the decoding steps
include dequantization and inverse transformation 130. The so obtained prediction error signal
e' differs from the original prediction error signal due to the quantization error, called also
quantization noise. A reconstructed image signal s' is then obtained by adding 1 0 the decoded
prediction error signal e' to the prediction signal s. In order to maintain the compatibility between
the encoder side and the decoder side, the prediction signal s is obtained based on the encoded
and subsequently decoded video signal which is known at both sides the encoder and the
decoder.
Due to the quantization, quantization noise is superposed to the reconstructed video signal. Due
to the block-wise coding, the superposed noise often has blocking characteristics, which result,
in particular for strong quantization, in visible block boundaries in the decoded image. Such
blocking artifacts have a negative effect upon human visual perception. In order to reduce these
artifacts, a deblocking filter 150 is applied to every reconstructed image block. The deblocking
filter is applied to the reconstructed signal s'. Deblocking filter generally smoothes the block
edges leading to an improved subjective quality of the decoded images. Moreover, since the
filtered part of an image is used for the motion compensated prediction of further images, the
filtering also reduces the prediction errors, and thus enables improvement of coding efficiency.
After a deblocking filter, an adaptive loop filter 160 may be applied to the image including the
already deblocked signal s" for improving the pixel wise fidelity ("objective" quality). The adaptive
loop filter (ALF) is used to compensate image distortion caused by compression. Typically, the
adaptive loop filter is a Wiener Filter, as shown in Figure 1, with filter coefficiency determined
such that the mean square error (MSE) between the reconstructed s', and source images s is
minimized. The coefficients of ALF may be calculated and transmitted on a frame basis. ALF can
be applied to the entire frame (image of the video sequence) or the local areas (blocks). An
additional side information indicating which areas are to be filtered may be transmitted (blockbased,
frame-based or quadtree-based).
In order to be decoded, inter-encoded blocks require also storing the previously encoded and
subsequently decoded portions of image(s) in a reference frame buffer (not shown). An interencoded
block is predicted 180 by employing motion compensated prediction. First, a bestmatching
block is found for the current block within the previously encoded and decoded video
frames by a motion estimator. The best-matching block then becomes a prediction signal and
the relative displacement (motion) between the current block and its best match is then
signalized as motion data in the form of three-dimensional motion vectors within the side
information provided together with the encoded video data. The three dimensions consist of two
spatial dimensions and one temporal dimension. In order to optimize the prediction accuracy,
motion vectors may be determined with a spatial sub-pixel resolution e.g. half pixel or quarter
pixel resolution. A motion vector with spatial sub-pixel resolution may point to a spatial position
within an already decoded frame where no real pixel value is available, i.e. a sub-pixel position.
Hence, spatial interpolation of such pixel values is needed in order to perform motion
compensated prediction. This may be achieved by an interpolation filter (in Figure 1 integrated
within Prediction block 180).
For both, the intra- and the inter-encoding modes, the differences e between the current input
signal and the prediction signal are transformed 110 and quantized 120, resulting in the
quantized coefficients. Generally, an orthogonal transformation such as a two-dimensional
discrete cosine transformation (DCT) or an integer version thereof is employed since it reduces
the correlation of the natural video images efficiently. After the transformation, lower frequency
components are usually more important for image quality then high frequency components so
that more bits can be spent for coding the low frequency components than the high frequency
components. In the entropy coder, the two-dimensional matrix of quantized coefficients is
converted into a one-dimensional array. Typically, this conversion is performed by a so-called
zig-zag scanning, which starts with the DC-coefficient in the upper left corner of the twodimensional
array and scans the two-dimensional array in a predetermined sequence ending
with an AC coefficient in the lower right corner. As the energy is typically concentrated in the left
upper part of the two-dimensional matrix of coefficients, corresponding to the lower frequencies,
the zig-zag scanning results in an array where usually the last values are zero. This allows for
efficient encoding using run-length codes as a part of/before the actual entropy coding.
Figure 2 illustrates a state of the art decoder 200 according to the H.264/MPEG-4 AVC or HEVC
video coding standard. The encoded video signal (input signal to the decoder) first passes to
entropy decoder 990, which decodes the quantized coefficients, the information elements
necessary for decoding such as motion data, mode of prediction etc. The quantized coefficients
are inversely scanned in order to obtain a two-dimensional matrix, which is then fed to inverse
quantization and inverse transformation 230. After inverse quantization and inverse
transformation 230, a decoded (quantized) prediction error signal e' is obtained, which
corresponds to the differences obtained by subtracting the prediction signal from the signal input
to the encoder in the case no quantization noise is introduced and no error occurred.
The prediction signal is obtained from either a temporal or a spatial prediction 280. The
decoded information elements usually further include the information necessary for the
prediction such as prediction type in the case of intra-prediction and motion data in the case of
motion compensated prediction. The quantized prediction error signal in the spatial domain is
then added with an adder 240 to the prediction signal obtained either from the motion
compensated prediction or intra-frame prediction 280. The reconstructed image s' may be
passed through a deblocking filter 250, sample adaptive offset processing, and an adaptive loop
filter 260 and the resulting decoded signal is stored in the memory 270 to be applied for temporal
or spatial prediction of the following blocks/images
When compressing and decompressing an image, the blocking artifacts are typically the most
annoying artifacts for the user. The deblocking filtering helps to improve the perceptual
experience of the user by smoothing the edges between the blocks in the reconstructed image.
One of the difficulties in deblocking filtering is to correctly decide between an edge caused by
blocking due to the application of a quantizer and between edges which are part of the coded
signal. Application of the deblocking filter is only desirable if the edge on the block boundary is
due to compression artifacts. In other cases, by applying the deblocking filter, the reconstructed
signal may be despaired, distorted. Another difficulty is the selection of an appropriate filter for
deblocking filtering. Typically, the decision is made between several low pass filters with
different frequency responses resulting in strong or weak low pass filtering. In order to decide
whether deblocking filtering is to be applied and to select an appropriate filter, image data in the
proximity of the boundary of two blocks are considered.
To summarize, state of the art hybrid video coders, see e.g. Figure 1, apply block-wise
prediction and block-wise prediction error coding. The prediction error coding includes a
quantization step. Due to this block-wise processing, so called blocking artifacts occur,
especially in the case of coarse quantization. A blocking artifact is associated with a large signal
change at a block edge. These blocking artifacts are very annoying for the viewer. In order to
reduce these blocking artifacts, deblocking filtering is applied, e.g. in the H.264/MPEG-4 AVC
video coding standard or in the HM, which is the test model of the HEVC video coding
standardization activity. Deblocking filters decide for each sample at a block boundary if it is
filtered or not and apply a low pass filter in the case it is decided to filter. The aim of this decision
is to filter only those samples, for which the large signal change at the block boundary results
from the quantization applied in the block-wise processing. The result of this filtering is a
smoothed signal at the block boundary. The smoothed signal suppresses or reduces the
blocking artifacts. Those samples, for which the large signal change at the block boundary
belongs to the original signal to be coded, should not be filtered in order to keep high
frequencies and thus the visual sharpness. In the case of wrong decisions, the image is either
unnecessarily smoothened or remains blocky.
According to the above, it is desirable to reliably judge whether a deblocking filtering needs to be
applied at a block boundary between adjacent image blocks or not. The H.264/MPEG-4 AVC
standard provides decision operations for the deblocking filtering on a block basis for the pixels
close to the boundary in each individual pixel line, i.e., pixel row or pixel column respectively, at
a block boundary. In general, the block size of the image blocks for which deblocking filtering
processing is conducted in the H.264/MPEG-4 AVC standard is an 8 by 8 pixel block. It is noted,
that for other purposes the smallest block size may be different, as, for example, prediction is
supporting 4 by 4 blocks.
Figure 3 illustrates the decisions for horizontal filtering of a vertical boundary/edge for each
individual pixel line according to H.264/MPEG-4 AVC. Figure 3 depicts four 8 by 8 pixel image
blocks, the previously processed blocks 310, 320, 340 and the current block 330. At the vertical
boundary between previously processed block 340 and current block 330 it is decided, whether
deblocking filtering is applied or not. The pixel values of the pixel lines running perpendicular to
the vertical boundary serve as a basis for decision for each individual pixel line. In particular, the
pixel values in the marked area of each pixel line, as for instance the marked area 350 of the 5th
pixel line, are the basis for the filtering decision.
Similarly, as shown in Figure 4 , decisions for vertical filtering of a horizontal boundary/edge are
performed for each individual column of pixels. For instance, for the fifth column of the current
block 430, the decision on whether to filter or not, the pixels of this column close to the boundary
to the previously processed block 420 is performed based on the pixels marked by a dashed
rectangle 450.
The decision process for each sample of either each individual pixel column or each individual
pixel line, at the boundary is performed by utilizing pixel values of the adjacent blocks as shown
in Figure 5. In Figure 5, block p represents the previously processed block 340 or 440 as shown
in Figure 3 or Figure 4 with the pixel values pO, p 1 and p2 of one line (row or column). Block q
represents the current block 330 or 430, as in Figure 3 or Figure 4 , with the pixel values qO, q 1
and q2 in the same line. Pixel qO is the pixel in the line closest to the boundary with the block q.
Pixel q 1 is the pixel in the same line, second closest to the boundary with the block q, etc. In
particular, the pixels values pO and qO of the pixel line are filtered, if the following conditions are
satisfied:
< " P + Qffset )
QP + Q etB) _and
|«7, - <7o| < + OffsetB)
wherein, QP is a quantization parameter, OffsetA and OffsettB are slice level offsets, and is
chosen to be smaller than a. Further, pixel p 1 of the line is filtered, if additionally
< <2 + OffsetB) _
Further, the pixel of a pixel line or pixel column corresponding to the pixel value q 1 is filtered if
additionally
According to H.264/MPEG-4 AVC, for each individual pixel line (row or column for the respective
horizontal and vertical deblocking filtering), decision operations as above are performed. The
filtering can be switched on/off for each individual pixel line which is associated with a high
accuracy for the deblocking decision. However, this approach is also associated with a high
computational expense.
A decision process for application of a deblocking filtering with a lower computational expense
as for the above mentioned H.264/MPG-4 AVC standard, is suggested in "High Efficiency Video
Coding (HEVC) text specification Working Draft 1" (HM deblocking filter, JCTVC-C403), freely
available under http://wftp3.itu.int/av-arch/jctvc-site/2010_10_C_Guangzhou/, which is
incorporated herein by reference. Here, one deblocking filtering on/off decision is applied for the
entire block boundary between two adjacent image blocks based only on information of pixel
lines in the block. Also here the block size of the image blocks for which deblocking filtering
processing is conducted is an 8 by 8 pixel.
The decision for horizontal filtering of a vertical edge/boundary according to JCTVC-C403 is
described in the following by referring to Figs. 6, 8 and 9. Figure 6 depicts four 8 by 8 pixel
blocks, the previously processed blocks 610, 620, 640 and the current block 630. The vertical
boundary between the previous block 640 and the current block 630 is the boundary for which it
is decided, whether deblocking filtering is to be applied or not. The vertical boundary extends
over a boundary segment corresponding to 8 lines (rows) 660. The 3 d and the 6 pixel line,
which are oriented perpendicular to the vertical boundary, serve as a basis for a deblocking
filtering decision. In particular, the pixel values in the marked area 650 of the 3 d and the 6th pixel
line are used as a basis for the filtering decision. Hence, the filtering decision of the entire
boundary corresponding to the segment of 8 lines 660, will be based on only a subset of two out
of 8 pixel lines of the block.
Similarly, referring to Figure 7, the decision for vertical filtering of a horizontal edge/boundary
according to JCTVC-C403 is based on the pixel values of only two pixel columns 760 out of the
segment of 8 columns 750, which constitutes the horizontal boundary.
Figure 8 shows a matrix of pixel values, which corresponds to parts of the previous block 640
and the current block 630 of Figure 6. The pixel values in the matrix are p and q , with i being
an index varying perpendicular to the boundary between the blocks and with j being an index
varying along to the boundary between the blocks. Index i in Figure 8 varies only in the range
from 0 to 3, corresponding to the pixel positions within a line to be filtered, which are employed
for the decision and/or filtering. The remaining pixel positions of the previous and the current
block are not shown. Index j in Figure 8 varies in the range from 0 to 7, corresponding to the 8
pixel rows in the block, the vertical boundary of which is to be filtered. The two pixel lines 820
with indexes j=2 and j=5, which correspond to the respective 3rd and the 6th pixel lines, are used
as a basis for the filtering decision (on/off decision) for the entire block boundary and are marked
with dashed lines. In order to decide whether the segment of 8 pixel lines, which correspond to
the entire boundary, is filtered, the following condition is evaluated:
\p2 2 - 2 - p l 2 + < ,
wherein is a threshold value. If the above condition is true, it is decided that the filtering is to be
applied to all 8 lines of the boundary.
This decision process is further depicted in Figure 9. When the upper equation is separated into
a term di V .containing only pixel values of the pixel line with index j=2 and a term d2, .
containing only pixel values of the line with index j=5, the decision for filtering can be rewritten
as:
d + v < ,
wherein
and
d v = \p2 5 - 2 p l 5 + .
Hence, by use of the two values di,v and d 2 , it is decided by the threshold operation whether
the entire vertical boundary is to be filtered or not. The index v is used herein to indicate that a
decision for a vertical boundary is assessed.
Figure 8 shows a matrix of pixel values forming boundary portions of two neighbouring blocks A
and B. It is noted that this boundary may also be a horizontal boundary, so that the block A is a
previously processed block and block B is the current block, block A being the top neighbour of
block B. This arrangement corresponds to parts of the previous block 720 and the current block
730 in Figure 7. The pixel values in the matrix are p and qi with i being an index varying
perpendicular to the boundary between the blocks, the index i ranging from 0 to 3 in this
example corresponding to only the part of the block A and B shown, and with the index j varying
along the boundary between the blocks A and B, ranging from 0 to 7 corresponding to the
number of lines (in third case columns) to be processed by deblocking filtering. In this context,
"processing" or "deblocking processing" includes deciding whether deblocking filtering is to be
applied or not and/or selection of the filter type. The type of filter here refers to a weak, strong or
no filter for filtering pixels around the boundary in a particular line of the block. The derivation
process of boundary filtering strength is described, for instance, in section 8.1.6 of the above
mentioned "High Efficiency Video Coding (HEVC) text specification Working Draft 1". In
particular, when it is decided that the block is to be filtered, an individual decision is performed
for each line for deciding whether a strong filter or a weak filter is to be applied. If it is decided
that a weak filter is to be applied, it is tested whether it is to be applied to the line at all. A strong
filter in this sense is applied to more pixels around the boundary in the pixel line than the weak
filter. In general, a strong filter is a filter with a narrower pass-band than the weak filter.
The two pixel columns 820 with indexes j=2 and j=5, which correspond to the 3 d and the 6th pixel
column, are used as a basis for the filtering decision and are marked with dashed lines. The
horizontal boundary is filtered if
\p2 2 - 2 • - 2 ql + q 5 \ < ,
wherein is again a threshold value. If the above decision is true, filtering is applied to all 8
columns of the horizontal boundary, which corresponds to entire boundary. This decision
process is further depicted in Figure 10. When the upper equation is separated into a term d h
containing only pixel values of the pixel column with index j=2 and a term d2,h , containing only
pixel values of the pixel column with index j=5, the decision for filtering can be rewritten as:
d \.h + 2 < •
wherein
and
d = \P 25 - 2 • pl 5 + .
Hence, by the use of the two values di, and d2,h , it is decided by the threshold operation if the
entire horizontal boundary is filtered or not. The index h is hereby used to indicate that a
decision for a horizontal boundary is assessed.
To summarize, according to JVCT-D403, the filtering can be switched on/off for the entire
boundary based on only two pixel lines or pixel columns perpendicular to that boundary. For only
two positions of each segment of 8 lines/columns, a decision process is performed. The filtering
can be switched on/off for each segment of 8 lines/columns, corresponding to the entire block.
This is associated with a lower computational expense but also with a lower accuracy of the
decisions.
In contribution JCTVC-D263, "Parallel deblocking Filter", Daegu, January 201 1, freely available
at http://wftp3.itu.int/av-arch/jctvc-site/2011_01_D_Daegu/ which is incorporated herein by
reference, the decision operations for deblocking filtering of a block are performed similarly to
JCTVC-C403: One deblocking filtering on/off decision is applied for the entire block boundary
based only on pixel values of two pixel rows, or pixel columns respectively, of the two vertically
or horizontally adjacent image blocks. However, the difference between the two approaches is
that the pixel rows, or pixel columns respectively, which are used as a basis for the decision
whether the boundary is filtered or not, have a different position in the block.
The decision for horizontal filtering of a vertical boundary/edge according to JCTVC-D263 is
briefly described in the following by referring to Figures 11 and 13. In Figure 1 , the pixel lines
used as a basis for deciding on whether to filter or not, are the 4 h and 5th lines 1160 at the
boundary between the previous 1140 and the current block 1130. The entire vertical boundary
corresponds to a segment of 8 lines 1150.
Figure 13 shows a matrix of pixel values forming parts of the blocks A and B around a common
boundary. The blocks A and B correspond to the previous block 1140 and the current block
1130 of Figure 11, respectively. The pixel values in the matrix are pjj and q , with i being an
index varying perpendicular to the boundary between the blocks and ranging from 0 to 3 , and
with j being an index varying along to the boundary between the blocks and ranging from 0 to 7 .
The two pixel lines 1320 with indexes j=3 and j=4, which correspond to the 4th and the 5th pixel
line, are used as a basis for the filtering decision(s) and are marked with dashed lines. The
following condition is evaluated in order to judge whether to filter or not the pixels close to the
boundary in the current block:
| 23 - 2 • p l + < ,
wherein is a threshold value. If the above decision is true, filtering and/or further decision is
performed for all lines of the boundary which corresponds to a segment comprising 8 lines.
When the upper equation is separated into a term d , , containing only pixel values of the pixel
line with index j=3 and a term d2,v , containing only pixel values of the line with index j=4, the
decision for filtering can be rewritten as:
wherein
d v = + 0 |
and
d = |24 - 2 • 14 + 0 4 | + | 2 - 2 • 14 + 0 | .
Hence, by the use of the two values d v and d2, > it is decided by the threshold operation if all 8
lines of the corresponding segment are filtered or not. The index v is hereby used to indicate that
a decision for a vertical boundary is assessed.
Similarly, as shown in Figure 12, the decision for vertical filtering of a horizontal edge/boundary
between a current block 1230 and a previous block 1220 according to JCTVC-D263 is based on
the pixel values of only two columns 1260 out of the segment 1250 of pixels from 8 columns
which constitutes the horizontal boundary between the blocks 1230 and 1220.
Figure 13 may be also seen as corresponding to parts of the previous block 1220 and the
current block 1230 of Figure 12. The pixel values in the matrix are Pi and with i being an
index varying perpendicular to the boundary between the blocks, ranging from 0 to 3 and with j
being an index varying along to the boundary between the blocks, ranging from 0 to 7. The two
pixel columns 1320 with indexes j=3 and j=4, which in this example correspond to the 4th and the
5th pixel column, are used as a basis for the filtering decision and are marked with dashed lines.
Accordingly, the horizontal boundary is filtered when
\p2 3 - 2 - p \ 3 + + - 2 ql 4 + q0 \ < ,
wherein is a threshold value. If the above condition is true, filtering is applied to all columns of
the boundary corresponding to one segment which is composed of 8 columns. When the upper
equation is separated into a term d ,h, containing only pixel values of the column with index j=3
and a term d2,h , containing only pixel values of the column with index j=4, the decision for
filtering can be rewritten as:
,h + d h < ,
wherein
and
d ,h = .
Hence, by using the two values d ,hand d2,h , it is decided by the threshold operation whether all
8 columns of the segment 1010 are filtered or not. The index h is hereby used to indicate that a
decision for a horizontal boundary is assessed.
To summarize, similarly to the JVCT-C403, according to JVCT-D263, the filtering can be
switched on/off for the entire boundary segment based on only two pixel lines or pixel columns
from this segment. For only two positions of each segment of 8 lines (rows or columns), a
decision process is performed. Thus, the filtering can be switched on/off for each segment of 8
lines/columns. This is associated with a low computational expense but also with a low accuracy
of the decisions. An advantage of JCTVC-D263 over JCTVC-C403 is that the use of other
samples allows a higher degree of a parallel processing. However, both approaches JCTVCC403
and JCTVC-D263 provide a lower accuracy of decisions in comparison with, for example,
H.264/MPEG-4 AVC.
In H.264/MPEG-4 AVC , the decisions are performed as shown in Figure 2 to Figure 5. At each
pixel position at a block boundary, individual values are calculated using samples adjacent to the
block boundary. Based on these individual values, individual decision operations are performed
at each position of (for each line perpendicular to) the block boundary. This is associated with a
high computational expense while providing a high accuracy of the decisions. In JCTVC-C403,
pixels at the block edges form segments of 8 lines/columns (corresponding to the smallest block
size used for the deblocking filtering) as shown in Figure 6 and Figure 7. For each segment of 8
lines/columns, values are calculated only for a subset of positions, in the examples above for
only two positions rather than for all 8 positions. Based on these values, one single decision is
performed whether to filter all 8 lines/columns of the segment or not. Compared to
H.264/MPEG-4 AVC the computational expense is reduced since less values are calculated.
The term value refers to the measure based on values of the pixels in a line close to the
boundary such as d V and d2, or d h or d2,h as shown above. In addition, the memory bandwidth
is reduced since for the calculation of values, less samples need to be accessed from the
memory. However, also the accuracy of the decisions is reduced compared to the accuracy of
the decisions in H.264/MPEG-4 AVC. In JCTVC-D263, the calculation of values and the
decision operations are performed similar to the JCTVC-C403. The difference is that samples at
other positions of the segments of 8 lines/columns are used to calculate the values. The use of
these other samples allows a higher degree a parallel processing. Compared to JCTVC-C403,
the computational expense as well as the memory bandwidth is the same. However, the
accuracy of the decisions is further reduced. Details are explained in Figure 11 to Figure 13.
Thus, the known approaches are either associated with a high computational expense and high
memory bandwidth or with a low accuracy of the decisions. A low accuracy of the decisions, on
the other hand, may result to a low coding efficiency. High computational expense and high
memory bandwidth may both lead to high implementation costs.
SUMMARY OF THE INVENTION
In view of the above problems with the existing deblocking filtering approaches, the present
invention aims to provide a more efficient deblocking filtering with improved accuracy and
reduced computational expenses.
It is the particular approach of the present invention to judge whether or not to apply a
deblocking filter to segments of the boundary of a block by judging individually for each segment
of the boundary based on pixels comprised in a subset of pixel lines of the block.
According to an aspect of the present invention, a method for deblocking processing of an image
divided into blocks, of which the boundaries are to be processed, is provided, wherein each
block is composed of pixel lines perpendicular to a boundary with an adjacent block, the method
comprising the steps of judging whether or not to apply a deblocking filter to segments of the
boundary of the block by judging individually for each segment of the boundary based on pixels
comprised in a subset of pixel lines of the block, and applying or not applying the deblocking
filter to the segments of the boundary according to the result of the respective individual
judgements
According to another aspect of the present invention, an apparatus for deblocking processing of
an image divided into blocks, of which the boundaries are to be processed, is provided, wherein
each block is composed of pixel lines perpendicular to a boundary with an adjacent block, the
apparatus comprising a judging unit configured to judge whether or not to apply a deblocking
filter to segments of the boundary of the block by judging individually for each segment of the
boundary based on pixels comprised in a subset of pixel lines of the block, and a deblocking
filtering unit configured to apply or not apply the deblocking filter to the segments of the
boundary according to the result of the respective individual judgements.
The above and other objects and features of the present invention will become more apparent
from the following description and preferred embodiments given in conjunction with the
accompanying drawings in which:
Figure 1 is a block diagram illustrating an example of a state of the art hybrid coder;
Figure 2 is a block diagram illustrating an example of a state of the art hybrid decoder;
Figure 3 is a schematic drawing illustrating the decisions for horizontal deblocking filtering
of a vertical edge according to H.264/MPEG-4 AVC;
is a schematic drawing illustrating decisions for vertical deblocking filtering of a
horizontal edge according to H.264/MPEG-4 AVC;
is a schematic drawing illustrating the decision process for each sample at the
block boundary whether to filter or not according to H.264/MPEG-4AVC;
is a schematic drawing illustrating the decision process for each sample at the
block boundary whether to filter or not according to JCTVC-C403 for horizontal
filtering of a vertical edge;
is a schematic drawing illustrating a decision process for each sample at the block
boundary whether to filter or not according to JCTVC-C403 for vertical filtering of
a horizontal edge;
is a schematic drawing illustrating the decision process for each segment of 8
lines/columns whether to filter or not according to JCTVC-C403;
is a schematic drawing illustrating the decision process for each sample at the
block boundary whether to filter or not according to JCTVC-C403 for horizontal
filtering of a vertical edge;
is a schematic drawing illustrating a decision process for each sample at the block
boundary whether to filter or not according to JCTVC-C403 for vertical filtering of
a horizontal edge as according to Figure 7;
is a schematic drawing illustrating the decision process for each sample at the
block boundary whether to filter or not according to JCTVC-D263 for horizontal
filtering of a vertical boundary;
is a schematic drawing illustrating the decision process for each sample at the
block boundary whether to filter or not according to JCTVC-D263 for vertical
filtering of a horizontal boundary;
is a schematic drawing illustrating the decision process for each segment of 8
lines/columns whether to filter or not according to JCTVC-D263;
is a schematic drawing illustrating the decision process for horizontal filtering of a
vertical boundary according to an embodiment of the present invention;
is a schematic drawing illustrating the decisions for vertical filtering of a horizontal
boundary according to an embodiment of the present invention;
is a schematic drawing illustrating the decision process for horizontal filtering of a
vertical boundary according to an embodiment of the present invention;
is a schematic drawing illustrating the decisions for vertical filtering of a horizontal
boundary according to an embodiment of the present invention;
is a schematic drawing illustrating the decisions for horizontal filtering of a vertical
boundary according to an embodiment of the present invention;
is a schematic drawing illustrating the decision for vertical filtering of a horizontal
boundary according to an embodiment of the present invention;
is a schematic drawing illustrating the decision process according to an
embodiment of the present invention;
is a schematic drawing illustrating the decision process according to an
embodiment of the present invention;
is a schematic drawing illustrating the decision process according to an
embodiment of the present invention;
is a generalized block diagram of the hybrid video encoder according to the HM
2.0;
is an illustration of the signal before and after the deblocking filter for a region of
the example test sequence Kimono;
is a schematic drawing illustrating vertical edges and the horizontal edges of an
example coding unit (CU) of the size 16x16 samples ;
shows the notation of a part of a vertical edge for deblocking;
shows an illustration of the samples used to decide whether to filter or not
according to the HM2.0;
shows an illustration of the samples used to decide whether to filter or not similar
as in H.264/MPEG-4 AVC;
shows an illustration of the samples used to decide whether to filter or not
according to an embodiment of the invention;
shows BD-bit rates and run time ratios of the decisions similar as in H.264/MPEG-
4 AVC compared to the reference HM2.0;
shows BD-bit rates and run time ratios of the decisions compromising H 2.0 and
H.264/MPEG-4 AVC compared to the reference HM2.0;
illustrates subjective quality of the approach of an embodiment of the present
invention compared to the reference with the results shown in the table;
shows the cropped part of a deblocked frame of the test sequence Vidyo3 in the
case of the reference HM 2.0.Test case: Low delay, High Efficiency, QP37;
shows the cropped part of a deblocked frame of the test sequence Vidyo3 in the
case of the proposal. Test case: Low delay, High Efficiency, QP37;
shows the cropped part of a deblocked frame of the test sequence Vidyo3 in the
case of the reference HM 2.0. Test case: Low delay, High Efficiency, QP37;
shows the cropped part of a deblocked frame of the test sequence Vidyo3 in the
case of the proposal. Test case: Low delay, High Efficiency, QP37;
illustrates the BD-bit rate reduction averaged over all test cases and test
sequences versus additional number of required operations per edge segment
compared to the reference HM2.0 ;
is a schematic drawing illustrating an overall configuration of a content providing
system for implementing content distribution services;
is a schematic drawing illustrating an overall configuration of a digital
broadcasting system;
is a block diagram illustrating an example of a configuration of a television;
is a block diagram illustrating an example of a configuration of an information
reproducing/recording unit that reads and writes information from or on a
recording medium that is an optical disk;
Figure 42 is a schematic drawing showing an example of a configuration of a recording
medium that is an optical disk;
Figure 43A is a schematic drawing illustrating an example of a cellular phone;
Figure 43B is a block diagram showing an example of a configuration of the cellular phone;
Figure 44 is a schematic drawing showing a structure of multiplexed data;
Figure 45 is a drawing schematically illustrating how each of the streams is multiplexed in
multiplexed data;
Figure 46 is a schematic drawing illustrating how a video stream is stored in a stream of
PES packets in more detail;
Figure 47 is a schematic drawing showing a structure of TS packets and source packets in
the multiplexed data;
Figure 48 is a schematic drawing showing a data structure of a PMT;
Figure 49 is a schematic drawing showing an internal structure of multiplexed data
information;
Figure 50 is a schematic drawing showing an internal structure of stream attribute
information;
Figure 5 1 is a schematic drawing showing steps for identifying video data;
Figure 52 is a schematic block diagram illustrating an example of a configuration of an
integrated circuit for implementing the video coding method and the video
decoding method according to each of embodiments;
Figure 53 is a schematic drawing showing a configuration for switching between driving
frequencies;
Figure 54 is a schematic drawing showing steps for identifying video data and switching
between driving frequencies;
Figure 55 is a schematic drawing showing an example of a look-up table in which the
standards of video data are associated with the driving frequencies;
Figure 56A is a schematic drawing showing an example of a configuration for sharing a
module of a signal processing unit;
Figure 56B is a schematic drawing showing another example of a configuration for sharing a
module of a signal processing unit;
DETAILED DESCRIPTION
The problem underlying the present invention is based on the observation that the currently
employed approaches for deblocking filtering lead to either reduced filtering quality or to rather
high computational expenses.
In order to provide a more efficient filtering approach, according to the present invention, the
decisions related to the deblocking filtering are performed for segments of the blocks to be
filtered by the deblocking filter rather than for the entire blocks. Moreover, the decisions are
performed based on only a subset of the pixels in the block which are situated at the boundary.
In general, as also described in the background section, the decisions may be the decision on
whether or not to filter a segment of the boundary and/or whether to apply the filter to pixels at a
particular distance from the boundary (corresponding to the decision about the strength of the
filter), etc.
Herein, a block is a smallest block of pixels (samples) being confined by boundaries which are
processed by deblocking filtering. The processing at each boundary of a block includes decision
on whether to apply the filtering and/or what kind of filter to apply and/or applying or not the filter
according to the decision(s).As also described the backround section, the block size of which
the boundaries are processed by deblocking filtering is typically an 8 by 8 pixel similar to H.264
and the HEVC standards as JCTVC-D403 and JCTVC-D263. A block may be further seen as
being comprised of pixel lines perpendicular with respect to a specified boundary of the block.
The term boundary is referring to a logical line separating pixels of two neighbouring blocks. The
boundary of a smallest block to be processed by deblocking filtering, extends over all pixel lines
of the block oriented perpendicular to the boundary and also extends between two other
boundaries of the block which are oriented perpendicularly.
A segment is a portion of a block including one or more pixel lines oriented perpendicular to the
boundary with pixels to be processed by the deblocking filter. The segment of the block is a
subset of the pixel lines of entire block, i.e. a proper partial subset, meaning that it includes less
than all pixel lines of the block. Thus a segment extends over a certain number of pixel lines in a
direction parallel to the boundary. However, a segment does not extend over all pixel lines of a
block. Further, a segment of the boundary corresponds to the portion of the boundary where the
segment of the block portion is situated at the boundary.
Pixels at the boundary of a block are pixels in a block being situated close to the boundary to an
adjacent block. Pixels at the boundary may include the pixels directly at (closest to) the
boundary, the pixels which are second closest to the boundary, and/or the third closest, etc.
The deblocking filtering is typically performed by a 1-dimensional filter, vertical or horizontal.
The filter is applied orthogonally to the boundary, in particular, to the pixels at the boundary
included in a pixel line of the block perpendicular to the boundary.
Figures 14 and 16 illustrate the decision process for horizontal filtering of a vertical boundary
between two adjacent image blocks according to an embodiment of the present invention.
Similarly, Figures. 15 and 17 illustrate the decision process for vertical filtering of a horizontal
boundary between two adjacent image blocks according to an embodiment of the present
invention.
Figure 14 shows four 8x8 pixel image blocks, namely the previously processed blocks 1410,
1420, 1440 and the current block 1430 on the left hand side. Block 1410 is the top left
neighbour of the current block 1430, block 1420 is the top neighbour of the current block 1430
and block 1440 is the left neighbour of the current block 1430. The vertical boundary 1450
between the left adjacent block 1140 and the current block 1130 is the boundary for which the
decision for horizontal filtering is carried out. This boundary 1450 basically extends between and
is at the same time confined by an upper horizontal boundary 1470 and the lower horizontal
boundary 1480. The upper 1470 and lower 1480 horizontal boundaries may be filtered vertically.
The previous block 1440 and the current block 1430 adjacent to the boundary 1450 are
composed of 8 pixel lines oriented perpendicular to the boundary. Hence, the vertical boundary
for horizontal filtering in Figure 14 is extending over a segment of 8 pixel lines 1450. The
boundary can be divided into segments, wherein the smallest segment is extending over one
pixel line.
In order to decide whether or not to apply deblocking filter to segments of the block boundary
1450, pixels from a (proper partial) subset of the pixel lines from the current block 1430 and/or
the previous block 1440are used as a basis for decision. As also in the approaches described in
the background section, the pixels from the subset of lines (rows) in the previous block 1440 and
the current block 1430 are the pixels at the (close to) common boundary between these blocks.
In the example of Figure 14, two out of eight pixel lines are used for deciding whether or not to
apply a deblocking filter to each segment of the boundary. In this case the 3 d and 6th pixel line
is chosen. These two pixel lines represent a (proper partial) subset of the 8 pixel lines that the
previous 1440 and the current block 1430 are composed of. Herein, a proper partial subset of
pixel lines of a block is defined as any number of pixel lines which is smaller than the total
number of pixel lines that an image block is composed of. Subsequently, the samples from the
subset of lines, in this case, from the two pixel lines, are used for performing individual decisions
for segments of the boundary, as depicted on the right hand side of Figure 14. This is achieved,
for instance, by calculating line decision terms d ,v and d2,v as a function of the pixels from the
subset of lines. The values ,v and d2 may be calculated similar as the values d1 and d2,v
according to JCTVC-C403 or JCTVC-D263, as described above. These values may be
calculated, for instance, as gradients of the 1st or the 2 d order between the neighbouring pixels
in each respective of the two neighbouring blocks 1440 and 1430, or between pixels from both
blocks 1440 and 1430. These gradients may be calculated as differences between these pixels.
Such measures are advantageous for estimating the blocking effect between two blocks.
Further, an individual decision value FN, which corresponds to an individual function of the line
decision terms di, and d2,v , is compared with a threshold value for each segment of a number
of segment from 1 to N:
In the case the above condition is true, filtering is applied to the individual segment of the vertical
boundary 1450. It is noted that the line terms d and d2,v do not necessarily have to be
calculated in a separate step. The individual decision value may also be calculated without
having precalculated and stored the line decision terms separately before. In this example, each
boundary position corresponding to each line of the block(s) to be filtered is a segment and for
each of these lines it is decided based on individual function of the pixels from the subset of lines
whether the this boundary position is to be filtered or not. This corresponds in this example to
interpolation or extrapolation (depending on the segment position) of the individual decision term
based on 1) the pixels of the subset of block lines and 2) on the position of the segment.
Figure 15 illustrates the decisions for vertical filtering of a horizontal boundary similar to the
horizontal filtering of the vertical boundary described above with reference to Figure 14. Here,
instead of the 3rd and the 6th pixel line, the 3 d and the 6th pixel column are the basis for the
filtering decisions. The information obtained from the subset of lines formed by the 3 d and 6th
pixel columns corresponds to the calculated values, line decision terms, d and d2,h- Further, an
individual decision value (F ) , which is an individual function of the line decision terms d and
d2,h, is compared with a threshold value for each segment of a number of segment from 1 to N:
In the case the above condition is true, filtering is applied to the individual segment of the
horizontal boundary 1550. In this example, each line may be an individual segment, for which
an individual Function F is applied. The function is not necessarily computed as a function of
the line decision terms, it may be also directly computed from the individual pixels in the subset
lines.
Figure 16 exemplifies a particular solution and implementation for the above individual functions
of the calculated values based on the 3rd and 6th pixel line for individual segments of the
boundary. In this case, three individual decisions for three respective block (boundary) segments
are performed based on respective three individual decision values. In particular, Figure 16
shows on the right hand side, that for the first to the third pixel line, value d ,v obtained based on
the pixels of the 3rd pixel line is utilized for the following decision:
2 d v< .
In the case the above condition is true, filtering is applied to the segment extending over the first
to the third pixel line of the boundary 1650. However, this can also be seen as a same decision
for the individual segments extending over the first, the second or the third pixel line
respectively. Thus, the individual decision values for the first and the second pixel line can be
also seen as a nearest neighbor interpolation of the individual decision value of the third
segment. This means that the individual decision value used for the line for which the line
decision term is calculated, is also used for the other lines within the same segment. For a
further segment of the boundary, which corresponds to the fourth and fifth pixel line of the
boundary, information from both the third and the sixth pixel line is used. The values d V and d2,
are utilized for the following decision:
d ,v + d v v and d4, (line decision term) are calculated and used
for obtaining the individual decision values, as shown in Figure 22, for each segment constituting
the vertical boundary between the previous block 2140 and the current block 2130. In particular,
the condition for judging whether or not to apply a deblocking filter at the first segment which
corresponds to the 1ret pixel line is the following:
2 d v < .
The condition for judging whether or not to apply a deblocking filter for the second segment
which corresponds to the second pixel line is the following:
ά + ά < 
The condition for judging whether or not to apply a deblocking filter for the third segment which
corresponds to the third pixel line is the following:
d v < fi
The condition for judging whether or not to apply a deblocking filter for the fourth segment which
corresponds to the fourth pixel line is the following:
Alternatively, the condition for judging whether or not to apply a deblocking filter for the fourth
segment which corresponds to the fourth pixel line could be the following:
(4 2 + 2 3, ) < 3
The condition for judging whether or not to apply a deblocking filter for the fifth segment of the
boundary which is corresponding to the fifth pixel position is the following:
{2 + 4 )/3 < 
Alternatively, the condition for judging whether or not to apply a deblocking filter for the fifth
segment of the boundary which is corresponding to the fifth pixel position is the following:
The condition for judging whether or not to apply a deblocking filter for the sixth segment of the
boundary which corresponds to the sixth pixel position is the following:
The condition for judging whether or not to apply a deblocking filter for the seventh segment of
the boundary which corresponds to the seventh pixel position is the following:
d v + d v<
The condition for judging whether or not to apply a deblocking filter for the eighths segment of
the boundary which corresponds to the eight pixel position is the following:
In the case one of the above conditions is true, the filtering is applied to the respective individual
segment of the vertical boundary. According to the above approach, individual decisions for
segments, are performed by using linear combinations of the values d V , d2,v, d3, and d4,v (line
decision terms). Moreover, the above approach corresponds to an interpolation of individual
decision values obtained for segments extending over one pixel position at the boundary.
Further, it is understood that the same approach can be applied for judging whether or not to
apply a deblocking filter at a horizontal edge/boundary.
To summarize, in order to deblock with a high coding efficiency and low computational expense
and low memory bandwidth, decision and/or the line decision terms are calculated not for each
individual position (as also for JCTVC-C403 and JCTVC-D263). This leads to limited memory
bandwidth and limited computational expense. However, individual functions of the calculated
values (line decision terms) are used in order to perform individual and accurate decisions at
each position of an edge. A general example is shown in Figure 14 and Figure 15. A more
specific example is shown in Figure 16 and Figure 17. As a specific solution, also calculated
values of other, e.g. neighboring, segments are used in the function, see Figure 18 and Figure
19. It may be beneficial to use a regular distribution of the positions used to calculate the values,
see Figure 20. Specific a further specific solution, for each segment of an edge of 8 edge
positions, 4 values are calculated, see Figure 21-22. For each of the edge positions, individual
decisions are performed by the use of linear combinations of the 4 calculated values. The effect
of the invention is to increase of coding efficiency with same low computational expense and
same low memory bandwidth.
In the following, the efficiency of the present invention over prior art is shown as an example. In
the HM2.0, one single decision for enabling the deblocking is performed for an edge segment of
eight columns/lines using two calculated decision values. In contrast to the HM2.0,
H.264/MPEG-4 AVC uses eight individual decisions based on eight individually calculated
decision values for each edge segment. The change of the decisions to ones similar as in
H.264/MPEG-4 AVC can reduce the bit rate at the same quality by 0.2% in average over all test
cases. However, the calculation of additional decision values is associated with additional
computational expense. In order to achieve the same average bit rate reduction at a lower
additional computational expense, a modification of the decisions is invented. The invention
performs eight individual decisions but needs to calculate only four decision values for each
edge segment. The same average bit rate reduction of 0.2% is achieved compared to HM2.0 (IHE:
0.1%, l-LC: 0.1%, RA-HE: 0.2%, RA-LC: 0.2%, LD-HE: 0.3%, LD-LC: 0.3%) with
approximately no encoder/decoder run time increase in average. For the low delay high
efficiency configuration, an average bit rate reduction of 0.7% in achieved for the Class E
sequences. An increased subjective quality is noticeable at the same bit rate.
The current H 2.0 (see for instance, HM2.0 software:
http://hevc.kw.bbc.co.Uk/trac/browser/tags/HM-2.0 and T. Wiegand, W.-J. Han, J.-R. Ohm, G. J.
Sullivan, High Efficiency Video Coding (HEVC) text specification Working Draft 1, JCTVC-C403,
Guangzou, China, October 2010, both is in the following referred to as HM 2.0) applies hybrid
coding. In Figure 23 the generalized block diagram of the hybrid coder is shown. In a first step,
the input signal to be coded is predicted block-wise by either motion compensated prediction or
Intra prediction. The resulting prediction error is block-wise transform coded by applying an
approximation of the discrete cosine transform (Integer DCT) followed by a quantization of the
coefficients. Due to the block wise motion compensated prediction and a block wise prediction
error coding, so called blocking artifacts often become visible in the decoded images. These
blocking artifacts tend to be annoying for human observers. In order to reduce these annoying
blocking artifacts, an adaptive deblocking filter is applied. The deblocked signal is further filtered
by the use of an adaptive loop filter before being output and stored for further predictions. Figure
24 illustrates the signal before and after the deblocking filter for a region of the example test
sequence Kimono.
The deblocking of images is performed based on coding units (CU), which may have various
sizes, e.g. 8x8 samples, 16x16 samples. Vertical and horizontal edges of prediction and
transform blocks are deblocked. Each edge consists of one or several segments, whereas a
segment consists of 8 consecutive lines or columns. The segments v. of the vertical edges are
deblocked before the segments h of the horizontal edges. Figure 25 shows an example coding
unit of the size 16x16 samples and the positions of the corresponding 4 segments v,,...,v 4 and
four segments ¾,. . .,h4 . The order of deblocking the vertical edges is from top to bottom and
from left to right. The order of deblocking the horizontal edges is from left to right and from top to
bottom. In the following, the samples on the respective sides of the segments of the edges are
denoted as A and B , see Figure 26 (from JCT-VC, Test Model under Consideration, JCTVCB205_
draft007, Geneva, Switzerland, 21-28 July 2010). The segment A corresponds to the left
neighboring partition to B for vertical edges and to the above neighboring partition to B for
horizontal edges. For each segment of 8 lines/colums, the decisions and filtering operations are
performed as explained in the following section.
In a first step, in the decisions according to the HM2.0, the two vales d and d5 are calculated
by the use of the samples of two lines/columns as illustrated in Figure 27:
By the use of the two values d and d , it is decided by the threshold operation
d2 + d5 < 
if all 8 lines/columns of the corresponding segment are filtered or not. In order to perform the
decisions, 20 operations are required for each segment of 8 lines/columns.
In contrast to the HM2.0, H.264/MPEG-4 AVC applies individual decisions (decisions similar as
in H.264/MPEG-4 AVC) for each line/column. In order to investigate decisions similar as in
H.264/MPEG-4 AVC, an individual value d i is calculated for each of the 8 lines/columns as
illustrated in Figure 28:
di =\p2 i -2- p l + 0,...,7 .
By the use of the individual values di it is decided for each line/column by the threshold
operation
2 -d, < 
if a line/column of the corresponding segment is filtered or not. In order to perform the decisions,
88 operations are required for each segment of 8 lines/columns.
In order to perform the decisions for a segment of 8 lines/columns, HM2.0 requires 20
operations. If the decisions are performed similar as in H.264/MPEG-4 AVC, 88 operations are
required.
In this embodiment, decisions are proposed which compromise the ones of H 2.0 and
H.264/MPEG-4 AVC with respect to computational expense, measured by number of required
operations. Four values d , d , d 5 , and d are calculated for each segment of 8 lines/columns
as illustrated in Figure 29:
d, =\p2, -2- with = 0,2,5,7 .
By the use of these values, it is decided for each individual line/column by the threshold
operations
2 ά < for / = 0,2,5,7
d + d < 3 for i = 1
ά + ά < for = 6
(4 d 2 + 2 -d5 ) < 3 for = 3
(4• ί + 2 • 2 ) < 3 • for = 4
if a line/column of the corresponding segment is filtered or not. In order to perform the decisions,
only 58 operations are required for each segment of 8 lines/columns.
Experiments and results are described in the following. The decisions similar as in H.264/MPEG-
4 AVC, as well as the decisions compromising HM2.0 and H.264/MPEG-4 AVC, are both
integrated into the reference software of HM2.0.
Experiments and results for BD-bit rate and run time ratios are described in the following.
Following the common conditions (see for instance, F. Bossen, Common test conditions and
software reference configurations, JCTVC-D500, Daegu, Korea, January, 201 1) the
performance of all six test cases is evaluated, which is Intra, Random access, and Low delay,
each in high efficiency and low complexity operation mode. For all run time measurements,
computers of the same configuration are used.
The BD-rate results as well as the encoder-/decoder run time ratios compared to the reference
HM2.0 are shown in Figure 30 for the decisions similar as in H.264/MPEG-4 AVC and in Figure
3 1 for the decisions compromising HM2.0 and H.264/MPEG-4 AVC. Negative BD-rate numbers
show a gain compared to the reference. Run-time ratios less than 100% show reflect that the run
time is lower than the one of the reference. The following results can be observed for both
cases: The bit rate reduction is 0.2% in average of over all test sequences and configurations
and 0.7% in average for LD-LC, Class E. Approximately no encoder-/decoder run time increases
in average.
A subjective evaluation is described in the following. In CE12, various test sequences have been
selected for subjective evaluations. For these test sequences, the subjective quality of the
proposal compared to the reference has been performed with the results shown in the table of
Figure 32. For five out of the six test sequences, no difference in subjective quality is noticeable.
For one out of the six test sequences, the proposal is clearly sharper than the reference without
increased blocking. In addition, the proposal shows less color artifacts.
The increase of the sharpness is illustrated in Figure 33 and Figure 34. In Figure 33, a cropped
part of a deblocked frame of the test sequence Vidyo3 is shown for the case of the reference
HM2.0, low delay, high efficiency, QP37. Figure 34 shows the same cropped part for the case of
the proposed deblocking.
The reduction of color artifacts is illustrated in Figure 35, a cropped part of a deblocked frame of
the test sequence Vidyo3 is shown for the case of the reference HM2.0, low delay, high
efficiency, QP37. Figure 36 shows the same cropped part for the case of the proposed
deblocking.
In the following the coding efficiency versus the complexity is described. In Figure 37, the
achieved bit rate reduction averaged over all test cases and test sequences is shown versus the
additional number of required operations per edge segment of 8 lines/colums, both compared to
the reference HM2.0. It can be observed that the decisions compromising H.264/MPEG-4 AVC
achieve the same average bit rate reduction of 0.2% compared to the reference but with 44%
less operations than decisions similar as in H.264/MPEG-4 AVC.
All embodiments of the present invention as described above can be combined.
The processing described in each of embodiments can be simply implemented in an
independent computer system, by recording, in a recording medium, a program for implementing
the configurations of the video coding method and the video decoding method described in each
of embodiments. The recording media may be any recording media as long as the program can
be recorded, such as a magnetic disk, an optical disk, a magnetic optical disk, an IC card, and a
semiconductor memory.
Hereinafter, the applications to the video coding method and the video decoding method
described in each of embodiments and systems using thereof will be described.
Figure 38 illustrates an overall configuration of a content providing system ex100 for
implementing content distribution services. The area for providing communication services is
divided into cells of desired size, and base stations ex106, ex107, ex108, ex109, and ex1 10
which are fixed wireless stations are placed in each of the cells.
The content providing system ex100 is connected to devices, such as a computer ex1 11, a
personal digital assistant (PDA) ex1 12, a camera ex1 13, a cellular phone ex1 14 and a game
machine ex1 15, via the Internet ex101, an Internet service provider ex102, a telephone network
ex104, as well as the base stations ex106 to ex1 10, respectively.
However, the configuration of the content providing system ex100 is not limited to the
configuration shown in Figure 38, and a combination in which any of the elements are connected
is acceptable. In addition, each device may be directly connected to the telephone network
ex104, rather than via the base stations ex106 to ex1 10 which are the fixed wireless stations.
Furthermore, the devices may be interconnected to each other via a short distance wireless
communication and others.
The camera ex1 13, such as a digital video camera, is capable of capturing video. A camera
ex1 16, such as a digital video camera, is capable of capturing both still images and video.
Furthermore, the cellular phone ex1 may be the one that meets any of the standards such as
Global System for Mobile Communications (GSM), Code Division Multiple Access (CDMA),
Wideband-Code Division Multiple Access (W-CDMA), Long Term Evolution (LTE), and High
Speed Packet Access (HSPA). Alternatively, the cellular phone ex 4 may be a Personal
Handyphone System (PHS).
In the content providing system ex100, a streaming server ex103 is connected to the camera
ex1 3 and others via the telephone network ex104 and the base station ex109, which enables
distribution of images of a live show and others. In such a distribution, a content (for example,
video of a music live show) captured by the user using the camera ex1 13 is coded as described
above in each of embodiments, and the coded content is transmitted to the streaming server
ex103. On the other hand, the streaming server ex103 carries out stream distribution of the
transmitted content data to the clients upon their requests. The clients include the computer
ex1 11, the PDA ex1 12, the camera ex1 13, the cellular phone ex1 14, and the game machine
ex1 15 that are capable of decoding the above-mentioned coded data. Each of the devices that
have received the distributed data decodes and reproduces the coded data.
The captured data may be coded by the camera ex1 13 or the streaming server ex103 that
transmits the data, or the coding processes may be shared between the camera ex1 13 and the
streaming server ex103. Similarly, the distributed data may be decoded by the clients or the
streaming server ex103, or the decoding processes may be shared between the clients and the
streaming server ex103. Furthermore, the data of the still images and video captured by not
only the camera ex1 13 but also the camera ex1 16 may be transmitted to the streaming server
ex103 through the computer ex1 11. The coding processes may be performed by the camera
ex1 16, the computer ex1 11, or the streaming server ex103, or shared among them.
Furthermore, the coding and decoding processes may be performed by an LSI ex500 generally
included in each of the computer ex1 11 and the devices. The LSI ex500 may be configured of a
single chip or a plurality of chips. Software for coding and decoding video may be integrated into
some type of a recording medium (such as a CD-ROM, a flexible disk, and a hard disk) that is
readable by the computer ex1 11 and others, and the coding and decoding processes may be
performed using the software. Furthermore, when the cellular phone ex1 14 is equipped with a
camera, the image data obtained by the camera may be transmitted. The video data is data
coded by the LSI ex500 included in the cellular phone ex1 14.
Furthermore, the streaming server ex103 may be composed of servers and computers, and may
decentralize data and process the decentralized data, record, or distribute data.
As described above, the clients may receive and reproduce the coded data in the content
providing system ex100. In other words, the clients can receive and decode information
transmitted by the user, and reproduce the decoded data in real time in the content providing
system ex100, so that the user who does not have any particular right and equipment can
implement personal broadcasting.
Aside from the example of the content providing system ex100, at least one of the video coding
apparatus and the video decoding apparatus described in each of embodiments may be
implemented in a digital broadcasting system ex200 illustrated in Figure 39. More specifically, a
broadcast station ex201 communicates or transmits, via radio waves to a broadcast satellite
ex202, multiplexed data obtained by multiplexing audio data and others onto video data. The
video data is data coded by the video coding method described in each of embodiments. Upon
receipt of the multiplexed data, the broadcast satellite ex202 transmits radio waves for
broadcasting. Then, a home-use antenna ex204 with a satellite broadcast reception function
receives the radio waves.
Next, a device such as a television (receiver) ex300 and a set top box (STB) ex21 7 decodes the
received multiplexed data, and reproduces the decoded data.
Furthermore, a reader/recorder ex218 (i) reads and decodes the multiplexed data recorded on a
recording media ex215, such as a DVD and a BD, or (i) codes video signals in the recording
medium ex215, and in some cases, writes data obtained by multiplexing an audio signal on the
coded data. The reader/recorder ex218 can include the video decoding apparatus or the video
coding apparatus as shown in each of embodiments. In this case, the reproduced video signals
are displayed on the monitor ex219, and can be reproduced by another device or system using
the recording medium ex215 on which the multiplexed data is recorded. It is also possible to
implement the video decoding apparatus in the set top box ex217 connected to the cable ex203
for a cable television or to the antenna ex204 for satellite and/or terrestrial broadcasting, so as to
display the video signals on the monitor ex219 of the television ex300. The video decoding
apparatus may be implemented not in the set top box but in the television ex300.
Figure 40 illustrates the television (receiver) ex300 that uses the video coding method and the
video decoding method described in each of embodiments. The television ex300 includes: a
tuner ex301 that obtains or provides multiplexed data obtained by multiplexing audio data onto
video data, through the antenna ex204 or the cable ex203, etc. that receives a broadcast; a
modulation/demodulation unit ex302 that demodulates the received multiplexed data or
modulates data into multiplexed data to be supplied outside; and a multiplexing/demultiplexing
unit ex303 that demultiplexes the modulated multiplexed data into video data and audio data, or
multiplexes video data and audio data coded by a signal processing unit ex306 into data.
The television ex300 further includes: a signal processing unit ex306 including an audio signal
processing unit ex304 and a video signal processing unit ex305 that decode audio data and
video data and code audio data and video data, respectively; and an output unit ex309 including
a speaker ex307 that provides the decoded audio signal, and a display unit ex308 that displays
the decoded video signal, such as a display. Furthermore, the television ex300 includes an
interface unit ex317 including an operation input unit ex312 that receives an input of a user
operation. Furthermore, the television ex300 includes a control unit ex310 that controls overall
each constituent element of the television ex300, and a power supply circuit unit ex31 that
supplies power to each of the elements. Other than the operation input unit ex312, the interface
unit ex317 may include: a bridge ex313 that is connected to an external device, such as the
reader/recorder ex218; a slot unit ex314 for enabling attachment of the recording medium
ex216, such as an SD card; a driver ex315 to be connected to an external recording medium,
such as a hard disk; and a modem ex316 to be connected to a telephone network. Here, the
recording medium ex216 can electrically record information using a non-volatile/volatile
semiconductor memory element for storage. The constituent elements of the television ex300
are connected to each other through a synchronous bus.
First, the configuration in which the television ex300 decodes multiplexed data obtained from
outside through the antenna ex204 and others and reproduces the decoded data will be
described. In the television ex300, upon a user operation through a remote controller ex220 and
others, the multiplexing/demultiplexing unit ex303 demultiplexes the multiplexed data
demodulated by the modulation/demodulation unit ex302, under control of the control unit ex310
including a CPU. Furthermore, the audio signal processing unit ex304 decodes the
demultiplexed audio data, and the video signal processing unit ex305 decodes the demultiplexed
video data, using the decoding method described in each of embodiments, in the television
ex300. The output unit ex309 provides the decoded video signal and audio signal outside,
respectively. When the output unit ex309 provides the video signal and the audio signal, the
signals may be temporarily stored in buffers ex318 and ex319, and others so that the signals are
reproduced in synchronization with each other. Furthermore, the television ex300 may read
multiplexed data not through a broadcast and others but from the recording media ex215 and
ex216, such as a magnetic disk, an optical disk, and a SD card. Next, a configuration in which
the television ex300 codes an audio signal and a video signal, and transmits the data outside or
writes the data on a recording medium will be described. In the television ex300, upon a user
operation through the remote controller ex220 and others, the audio signal processing unit
ex304 codes an audio signal, and the video signal processing unit ex305 codes a video signal,
under control of the control unit ex310 using the coding method described in each of
embodiments. The multiplexing/demultiplexing unit ex303 multiplexes the coded video signal
and audio signal, and provides the resulting signal outside. When the
multiplexing/demultiplexing unit ex303 multiplexes the video signal and the audio signal, the
signals may be temporarily stored in the buffers ex320 and ex321, and others so that the signals
are reproduced in synchronization with each other. Here, the buffers ex318, ex319, ex320, and
ex321 may be plural as illustrated, or at least one buffer may be shared in the television ex300.
Furthermore, data may be stored in a buffer so that the system overflow and underflow may be
avoided between the modulation/demodulation unit ex302 and the multiplexing/demultiplexing
unit ex303, for example.
Furthermore, the television ex300 may include a configuration for receiving an AV input from a
microphone or a camera other than the configuration for obtaining audio and video data from a
broadcast or a recording medium, and may code the obtained data. Although the television
ex300 can code, multiplex, and provide outside data in the description, it may be capable of only
receiving, decoding, and providing outside data but not the coding, multiplexing, and providing
outside data.
Furthermore, when the reader/recorder ex218 reads or writes multiplexed data from or on a
recording medium, one of the television ex300 and the reader/recorder ex218 may decode or
code the multiplexed data, and the television ex300 and the reader/recorder ex218 may share
the decoding or coding.
As an example, Figure 4 1 illustrates a configuration of an information reproducing/recording unit
ex400 when data is read or written from or on an optical disk. The information
reproducing/recording unit ex400 includes constituent elements ex401, ex402, ex403, ex404,
ex405, ex406, and ex407 to be described hereinafter. The optical head ex401 irradiates a laser
spot in a recording surface of the recording medium ex215 that is an optical disk to write
information, and detects reflected light from the recording surface of the recording medium
ex215 to read the information. The modulation recording unit ex402 electrically drives a
semiconductor laser included in the optical head ex401 , and modulates the laser light according
to recorded data. The reproduction demodulating unit ex403 amplifies a reproduction signal
obtained by electrically detecting the reflected light from the recording surface using a photo
detector included in the optical head ex401 , and demodulates the reproduction signal by
separating a signal component recorded on the recording medium ex215 to reproduce the
necessary information. The buffer ex404 temporarily holds the information to be recorded on the
recording medium ex215 and the information reproduced from the recording medium ex215.
The disk motor ex405 rotates the recording medium ex215. The servo control unit ex406 moves
the optical head ex401 to a predetermined information track while controlling the rotation drive of
the disk motor ex405 so as to follow the laser spot. The system control unit ex407 controls
overall the information reproducing/recording unit ex400. The reading and writing processes can
be implemented by the system control unit ex407 using various information stored in the buffer
ex404 and generating and adding new information as necessary, and by the modulation
recording unit ex402, the reproduction demodulating unit ex403, and the servo control unit
ex406 that record and reproduce information through the optical head ex401 while being
operated in a coordinated manner. The system control unit ex407 includes, for example, a
microprocessor, and executes processing by causing a computer to execute a program for read
and write.
Although the optical head ex401 irradiates a laser spot in the description, it may perform highdensity
recording using near field light.
Figure 42 illustrates the recording medium ex215 that is the optical disk. On the recording
surface of the recording medium ex215, guide grooves are spirally formed, and an information
track ex230 records, in advance, address information indicating an absolute position on the disk
according to change in a shape of the guide grooves. The address information includes
information for determining positions of recording blocks ex231 that are a unit for recording data.
Reproducing the information track ex230 and reading the address information in an apparatus
that records and reproduces data can lead to determination of the positions of the recording
blocks. Furthermore, the recording medium ex215 includes a data recording area ex233, an
inner circumference area ex232, and an outer circumference area ex234. The data recording
area ex233 is an area for use in recording the user data. The inner circumference area ex232
and the outer circumference area ex234 that are inside and outside of the data recording area
ex233, respectively are for specific use except for recording the user data. The information
reproducing/recording unit 400 reads and writes coded audio, coded video data, or multiplexed
data obtained by multiplexing the coded audio and video data, from and on the data recording
area ex233 of the recording medium ex215.
Although an optical disk having a layer, such as a DVD and a BD is described as an example in
the description, the optical disk is not limited to such, and may be an optical disk having a
multilayer structure and capable of being recorded on a part other than the surface.
Furthermore, the optical disk may have a structure for multidimensional recording/reproduction,
such as recording of information using light of colors with different wavelengths in the same
portion of the optical disk and for recording information having different layers from various
angles.
Furthermore, a car ex210 having an antenna ex205 can receive data from the satellite ex202
and others, and reproduce video on a display device such as a car navigation system ex21 1 set
in the car ex210, in the digital broadcasting system ex200. Here, a configuration of the car
navigation system ex21 will be a configuration, for example, including a GPS receiving unit
from the configuration illustrated in Figure 40. The same will be true for the configuration of the
computer ex1 , the cellular phone ex1 4, and others.
Figure 43A illustrates the cellular phone ex1 14 that uses the video coding method and the video
decoding method described in embodiments. The cellular phone ex1 14 includes: an antenna
ex350 for transmitting and receiving radio waves through the base station ex1 10; a camera unit
ex365 capable of capturing moving and still images; and a display unit ex358 such as a liquid
crystal display for displaying the data such as decoded video captured by the camera unit ex365
or received by the antenna ex350. The cellular phone ex1 4 further includes: a main body unit
including an operation key unit ex366; an audio output unit ex357 such as a speaker for output
of audio; an audio input unit ex356 such as a microphone for input of audio; a memory unit
ex367 for storing captured video or still pictures, recorded audio, coded or decoded data of the
received video, the still pictures, e-mails, or others; and a slot unit ex364 that is an interface unit
for a recording medium that stores data in the same manner as the memory unit ex367.
Next, an example of a configuration of the cellular phone ex1 14 will be described with reference
to Figure 43B. In the cellular phone ex1 14, a main control unit ex360 designed to control overall
each unit of the main body including the display unit ex358 as well as the operation key unit
ex366 is connected mutually, via a synchronous bus ex370, to a power supply circuit unit ex361,
an operation input control unit ex362, a video signal processing unit ex355, a camera interface
unit ex363, a liquid crystal display (LCD) control unit ex359, a modulation/demodulation unit
ex352, a multiplexing/demultiplexing unit ex353, an audio signal processing unit ex354, the slot
unit ex364, and the memory unit ex367.
When a call-end key or a power key is turned ON by a user's operation, the power supply circuit
unit ex361 supplies the respective units with power from a battery pack so as to activate the cell
phone ex1 14.
In the cellular phone ex1 14, the audio signal processing unit ex354 converts the audio signals
collected by the audio input unit ex356 in voice conversation mode into digital audio signals
under the control of the main control unit ex360 including a CPU, ROM, and RAM. Then, the
modulation/demodulation unit ex352 performs spread spectrum processing on the digital audio
signals, and the transmitting and receiving unit ex351 performs digital-to-analog conversion and
frequency conversion on the data, so as to transmit the resulting data via the antenna ex350.
Also, in the cellular phone ex1 14, the transmitting and receiving unit ex351 amplifies the data
received by the antenna ex350 in voice conversation mode and performs frequency conversion
and the analog-to-digital conversion on the data. Then, the modulation/demodulation unit ex352
performs inverse spread spectrum processing on the data, and the audio signal processing unit
ex354 converts it into analog audio signals, so as to output them via the audio output unit ex356.
Furthermore, when an e-mail in data communication mode is transmitted, text data of the e-mail
inputted by operating the operation key unit ex366 and others of the main body is sent out to the
main control unit ex360 via the operation input control unit ex362. The main control unit ex360
causes the modulation/demodulation unit ex352 to perform spread spectrum processing on the
text data, and the transmitting and receiving unit ex351 performs the digital-to-analog conversion
and the frequency conversion on the resulting data to transmit the data to the base station ex1 10
via the antenna ex350. When an e-mail is received, processing that is approximately inverse to
the processing for transmitting an e-mail is performed on the received data, and the resulting
data is provided to the display unit ex358.
When video, still images, or video and audio in data communication mode is or are transmitted,
the video signal processing unit ex355 compresses and codes video signals supplied from the
camera unit ex365 using the video coding method shown in each of embodiments, and transmits
the coded video data to the multiplexing/demultiplexing unit ex353. In contrast, during when the
camera unit ex365 captures video, still images, and others, the audio signal processing unit
ex354 codes audio signals collected by the audio input unit ex356, and transmits the coded
audio data to the multiplexing/demultiplexing unit ex353.
The multiplexing/demultiplexing unit ex353 multiplexes the coded video data supplied from the
video signal processing unit ex355 and the coded audio data supplied from the audio signal
processing unit ex354, using a predetermined method.
Then, the modulation/demodulation unit ex352 performs spread spectrum processing on the
multiplexed data, and the transmitting and receiving unit ex351 performs digital-to-analog
conversion and frequency conversion on the data so as to transmit the resulting data via the
antenna ex350.
When receiving data of a video file which is linked to a Web page and others in data
communication mode or when receiving an e-mail with video and/or audio attached, in order to
decode the multiplexed data received via the antenna ex350, the multiplexing/demultiplexing
unit ex353 demultiplexes the multiplexed data into a video data bit stream and an audio data bit
stream, and supplies the video signal processing unit ex355 with the coded video data and the
audio signal processing unit ex354 with the coded audio data, through the synchronous bus
ex370. The video signal processing unit ex355 decodes the video signal using a video decoding
method corresponding to the coding method shown in each of embodiments, and then the
display unit ex358 displays, for instance, the video and still images included in the video file
linked to the Web page via the LCD control unit ex359. Furthermore, the audio signal
processing unit ex354 decodes the audio signal, and the audio output unit ex357 provides the
audio.
Furthermore, similarly to the television ex300, a terminal such as the cellular phone ex1 14
probably have 3 types of implementation configurations including not only (i) a transmitting and
receiving terminal including both a coding apparatus and a decoding apparatus, but also (ii) a
transmitting terminal including only a coding apparatus and (iii) a receiving terminal including
only a decoding apparatus. Although the digital broadcasting system ex200 receives and
transmits the multiplexed data obtained by multiplexing audio data onto video data in the
description, the multiplexed data may be data obtained by multiplexing not audio data but
character data related to video onto video data, and may be not multiplexed data but video data
itself.
As such, the video coding method and the video decoding method in each of embodiments can
be used in any of the devices and systems described. Thus, the advantages described in each
of embodiments can be obtained.
Furthermore, the present invention is not limited to embodiments, and various modifications and
revisions are possible without departing from the scope of the present invention.
Video data can be generated by switching, as necessary, between (i) the video coding method
or the video coding apparatus shown in each of embodiments and (ii) a video coding method or
a video coding apparatus in conformity with a different standard, such as MPEG-2, H.264/AVC,
and VC-1.
Here, when a plurality of video data that conforms to the different standards is generated and is
then decoded, the decoding methods need to be selected to conform to the different standards.
However, since to which standard each of the plurality of the video data to be decoded conform
cannot be detected, there is a problem that an appropriate decoding method cannot be selected.
In order to solve the problem, multiplexed data obtained by multiplexing audio data and others
onto video data has a structure including identification information indicating to which standard
the video data conforms. The specific structure of the multiplexed data including the video data
generated in the video coding method and by the video coding apparatus shown in each of
embodiments will be hereinafter described. The multiplexed data is a digital stream in the
MPEG2-Transport Stream format.
Figure 44 illustrates a structure of the multiplexed data. As illustrated in Figure 44, the
multiplexed data can be obtained by multiplexing at least one of a video stream, an audio
stream, a presentation graphics stream (PG), and an interactive graphics stream. The video
stream represents primary video and secondary video of a movie, the audio stream (IG)
represents a primary audio part and a secondary audio part to be mixed with the primary audio
part, and the presentation graphics stream represents subtitles of the movie. Here, the primary
video is normal video to be displayed on a screen, and the secondary video is video to be
displayed on a smaller window in the primary video. Furthermore, the interactive graphics
stream represents an interactive screen to be generated by arranging the GUI components on a
screen. The video stream is coded in the video coding method or by the video coding apparatus
shown in each of embodiments, or in a video coding method or by a video coding apparatus in
conformity with a conventional standard, such as MPEG-2, H.264/AVC, and VC-1 . The audio
stream is coded in accordance with a standard, such as Dolby-AC-3, Dolby Digital Plus, MLP,
DTS, DTS-HD, and linear PCM.
Each stream included in the multiplexed data is identified by PID. For example, 0x101 1 is
allocated to the video stream to be used for video of a movie, 0x1 100 to 0x1 11F are allocated to
the audio streams, 0x1200 to 0x121 F are allocated to the presentation graphics streams,
0x1400 to 0x141 F are allocated to the interactive graphics streams, 0x1 B00 to 0x1 B1F are
allocated to the video streams to be used for secondary video of the movie, and 0x1 A00 to
0x1 A 1F are allocated to the audio streams to be used for the secondary video to be mixed with
the primary audio.
Figure 45 schematically illustrates how data is multiplexed. First, a video stream ex235
composed of video frames and an audio stream ex238 composed of audio frames are
transformed into a stream of PES packets ex236 and a stream of PES packets ex239, and
further into TS packets ex237 and TS packets ex240, respectively. Similarly, data of a
presentation graphics stream ex241 and data of an interactive graphics stream ex244 are
transformed into a stream of PES packets ex242 and a stream of PES packets ex245, and
further into TS packets ex243 and TS packets ex246, respectively. These TS packets are
multiplexed into a stream to obtain multiplexed data ex247.
Figure 46 illustrates how a video stream is stored in a stream of PES packets in more detail.
The first bar in Figure 20 shows a video frame stream in a video stream. The second bar shows
the stream of PES packets. As indicated by arrows denoted as yy1 , yy2, yy3, and yy4 in Figure
20, the video stream is divided into pictures as I pictures, B pictures, and P pictures each of
which is a video presentation unit, and the pictures are stored in a payload of each of the PES
packets. Each of the PES packets has a PES header, and the PES header stores a Presentation
Time-Stamp (PTS) indicating a display time of the picture, and a Decoding Time-Stamp (DTS)
indicating a decoding time of the picture.
Figure 47 illustrates a format of TS packets to be finally written on the multiplexed data. Each of
the TS packets is a 188-byte fixed length packet including a 4-byte TS header having
information, such as a PID for identifying a stream and a 184-byte TS payload for storing data.
The PES packets are divided, and stored in the TS payloads, respectively. When a BD ROM is
used, each of the TS packets is given a 4-byte TP_Extra_Header, thus resulting in 192-byte
source packets. The source packets are written on the multiplexed data. The TP_Extra_Header
stores information such as an Arrival_Time_Stamp (ATS). The ATS shows a transfer start time
at which each of the TS packets is to be transferred to a PID filter. The source packets are
arranged in the multiplexed data as shown at the bottom of Figure 47. The numbers
incrementing from the head of the multiplexed data are called source packet numbers (SPNs).
Each of the TS packets included in the multiplexed data includes not only streams of audio,
video, subtitles and others, but also a Program Association Table (PAT), a Program Map Table
(PMT), and a Program Clock Reference (PCR). The PAT shows what a PID in a PMT used in
the multiplexed data indicates, and a PID of the PAT itself is registered as zero. The PMT stores
PIDs of the streams of video, audio, subtitles and others included in the multiplexed data, and
attribute information of the streams corresponding to the PIDs. The PMT also has various
descriptors relating to the multiplexed data. The descriptors have information such as copy
control information showing whether copying of the multiplexed data is permitted or not. The
PCR stores STC time information corresponding to an ATS showing when the PCR packet is
transferred to a decoder, in order to achieve synchronization between an Arrival Time Clock
(ATC) that is a time axis of ATSs, and an System Time Clock (STC) that is a time axis of PTSs
and DTSs.
Figure 48 illustrates the data structure of the PMT in detail. A PMT header is disposed at the top
of the PMT. The PMT header describes the length of data included in the PMT and others. A
plurality of descriptors relating to the multiplexed data is disposed after the PMT header.
Information such as the copy control information is described in the descriptors. After the
descriptors, a plurality of pieces of stream information relating to the streams included in the
multiplexed data is disposed. Each piece of stream information includes stream descriptors
each describing information, such as a stream type for identifying a compression codec of a
stream, a stream PID, and stream attribute information (such as a frame rate or an aspect ratio).
The stream descriptors are equal in number to the number of streams in the multiplexed data.
When the multiplexed data is recorded on a recording medium and others, it is recorded
together with multiplexed data information files.
Each of the multiplexed data information files is management information of the multiplexed data
as shown in Figure 49. The multiplexed data information files are in one to one correspondence
with the multiplexed data, and each of the files includes multiplexed data information, stream
attribute information, and an entry map.
As illustrated in Figure 49, the multiplexed data includes a system rate, a reproduction start time,
and a reproduction end time. The system rate indicates the maximum transfer rate at which a
system target decoder to be described later transfers the multiplexed data to a PID filter. The
intervals of the ATSs included in the multiplexed data are set to not higher than a system rate.
The reproduction start time indicates a PTS in a video frame at the head of the multiplexed data.
An interval of one frame is added to a PTS in a video frame at the end of the multiplexed data,
and the PTS is set to the reproduction end time.
As shown in Figure 50, a piece of attribute information is registered in the stream attribute
information, for each PID of each stream included in the multiplexed data. Each piece of
attribute information has different information depending on whether the corresponding stream is
a video stream, an audio stream, a presentation graphics stream, or an interactive graphics
stream. Each piece of video stream attribute information carries information including what kind
of compression codec is used for compressing the video stream, and the resolution, aspect ratio
and frame rate of the pieces of picture data that is included in the video stream. Each piece of
audio stream attribute information carries information including what kind of compression codec
is used for compressing the audio stream, how many channels are included in the audio stream,
which language the audio stream supports, and how high the sampling frequency is. The video
stream attribute information and the audio stream attribute information are used for initialization
of a decoder before the player plays back the information.
The multiplexed data to be used is of a stream type included in the P T. Furthermore, when the
multiplexed data is recorded on a recording medium, the video stream attribute information
included in the multiplexed data information is used. More specifically, the video coding method
or the video coding apparatus described in each of embodiments includes a step or a unit for
allocating unique information indicating video data generated by the video coding method or the
video coding apparatus in each of embodiments, to the stream type included in the PMT or the
video stream attribute information. With the configuration, the video data generated by the video
coding method or the video coding apparatus described in each of embodiments can be
distinguished from video data that conforms to another standard.
Furthermore, Figure 5 1 illustrates steps of the video decoding method. In Step exS100, the
stream type included in the PMT or the video stream attribute information is obtained from the
multiplexed data. Next, in Step exS101 , it is determined whether or not the stream type or the
video stream attribute information indicates that the multiplexed data is generated by the video
coding method or the video coding apparatus in each of embodiments. When it is determined
that the stream type or the video stream attribute information indicates that the multiplexed data
is generated by the video coding method or the video coding apparatus in each of embodiments,
in Step exS102, decoding is performed by the video decoding method in each of embodiments.
Furthermore, when the stream type or the video stream attribute information indicates
conformance to the conventional standards, such as MPEG-2, H.264/AVC, and VC-1, in Step
exS103, decoding is performed by a video decoding method in conformity with the conventional
standards.
As such, allocating a new unique value to the stream type or the video stream attribute
information enables determination whether or not the video decoding method or the video
decoding apparatus that is described in each of embodiments can perform decoding. Even
when multiplexed data that conforms to a different standard, an appropriate decoding method or
apparatus can be selected. Thus, it becomes possible to decode information without any error.
Furthermore, the video coding method or apparatus, or the video decoding method or apparatus
can be used in the devices and systems described above.
Each of the video coding method, the video coding apparatus, the video decoding method, and
the video decoding apparatus in each of embodiments is typically achieved in the form of an
integrated circuit or a Large Scale Integrated (LSI) circuit. As an example of the LSI, Figure 52
illustrates a configuration of the LSI ex500 that is made into one chip. The LSI ex500 includes
elements ex501 , ex502, ex503, ex504, ex505, ex506, ex507, ex508, and ex509 to be described
below, and the elements are connected to each other through a bus ex510. The power supply
circuit unit ex505 is activated by supplying each of the elements with power when the power
supply circuit unit ex505 is turned on.
For example, when coding is performed, the LSI ex500 receives an AV signal from a
microphone ex1 17, a camera ex1 13, and others through an AV IO ex509 under control of a
control unit ex501 including a CPU ex502, a memory controller ex503, a stream controller
ex504, and a driving frequency control unit ex512. The received AV signal is temporarily stored
in an external memory ex51 1, such as an SDRAM. Under control of the control unit ex501, the
stored data is segmented into data portions according to the processing amount and speed to be
transmitted to a signal processing unit ex507. Then, the signal processing unit ex507 codes an
audio signal and/or a video signal. Here, the coding of the video signal is the coding described
in each of embodiments. Furthermore, the signal processing unit ex507 sometimes multiplexes
the coded audio data and the coded video data, and a stream IO ex506 provides the multiplexed
data outside. The provided multiplexed data is transmitted to the base station ex107, or written
on the recording media ex215. When data sets are multiplexed, the data should be temporarily
stored in the buffer ex508 so that the data sets are synchronized with each other.
Although the memory ex51 1 is an element outside the LSI ex500, it may be included in the LSI
ex500. The buffer ex508 is not limited to one buffer, but may be composed of buffers.
Furthermore, the LSI ex500 may be made into one chip or a plurality of chips.
Furthermore, although the control unit ex510 includes the CPU ex502, the memory controller
ex503, the stream controller ex504, the driving frequency control unit ex512, the configuration of
the control unit ex510 is not limited to such. For example, the signal processing unit ex507 may
further include a CPU. Inclusion of another CPU in the signal processing unit ex507 can
improve the processing speed. Furthermore, as another example, the CPU ex502 may serve as
or be a part of the signal processing unit ex507, and, for example, may include an audio signal
processing unit. In such a case, the control unit ex501 includes the signal processing unit ex507
or the CPU ex502 including a part of the signal processing unit ex507.
The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI
depending on the degree of integration.
Moreover, ways to achieve integration are not limited to the LSI, and a special circuit or a
general purpose processor and so forth can also achieve the integration. Field Programmable
Gate Array (FPGA) that can be programmed after manufacturing LSIs or a reconfigurable
processor that allows re-configuration of the connection or configuration of an LSI can be used
for the same purpose.
In the future, with advancement in semiconductor technology, a brand-new technology may
replace LSI. The functional blocks can be integrated using such a technology. The possibility is
that the present invention is applied to biotechnology.
When video data generated in the video coding method or by the video coding apparatus
described in each of embodiments is decoded, compared to when video data that conforms to a
conventional standard, such as MPEG-2, H.264/AVC, and VC-1 is decoded, the processing
amount probably increases. Thus, the LSI ex500 needs to be set to a driving frequency higher
than that of the CPU ex502 to be used when video data in conformity with the conventional
standard is decoded. However, when the driving frequency is set higher, there is a problem that
the power consumption increases.
In order to solve the problem, the video decoding apparatus, such as the television ex300 and
the LSI ex500 is configured to determine to which standard the video data conforms, and switch
between the driving frequencies according to the determined standard. Figure 53 illustrates a
configuration ex800. A driving frequency switching unit ex803 sets a driving frequency to a
higher driving frequency when video data is generated by the video coding method or the video
coding apparatus described in each of embodiments. Then, the driving frequency switching unit
ex803 instructs a decoding processing unit ex801 that executes the video decoding method
described in each of embodiments to decode the video data. When the video data conforms to
the conventional standard, the driving frequency switching unit ex803 sets a driving frequency to
a lower driving frequency than that of the video data generated by the video coding method or
the video coding apparatus described in each of embodiments. Then, the driving frequency
switching unit ex803 instructs the decoding processing unit ex802 that conforms to the
conventional standard to decode the video data.
More specifically, the driving frequency switching unit ex803 includes the CPU ex502 and the
driving frequency control unit ex512 in Figure 26. Here, each of the decoding processing unit
ex801 that executes the video decoding method described in each of embodiments and the
decoding processing unit ex802 that conforms to the conventional standard corresponds to the
signal processing unit ex507 in Figure 50. The CPU ex502 determines to which standard the
video data conforms. Then, the driving frequency control unit ex512 determines a driving
frequency based on a signal from the CPU ex502. Furthermore, the signal processing unit
ex507 decodes the video data based on the signal from the CPU ex502. For example, the
identification information described is probably used for identifying the video data. The
identification information is not limited to the one described above but may be any information as
long as the information indicates to which standard the video data conforms. For example, when
which standard video data conforms to can be determined based on an external signal for
determining that the video data is used for a television or a disk, etc., the determination may be
made based on such an external signal. Furthermore, the CPU ex502 selects a driving
frequency based on, for example, a look-up table in which the standards of the video data are
associated with the driving frequencies as shown in Figure 55. The driving frequency can be
selected by storing the look-up table in the buffer ex508 and in an internal memory of an LSI,
and with reference to the look-up table by the CPU ex502.
Figure 54 illustrates steps for executing a method. First, in Step exS200, the signal processing
unit ex507 obtains identification information from the multiplexed data. Next, in Step exS201 ,
the CPU ex502 determines whether or not the video data is generated by the coding method
and the coding apparatus described in each of embodiments, based on the identification
information. When the video data is generated by the video coding method and the video coding
apparatus described in each of embodiments, in Step exS202, the CPU ex502 transmits a signal
for setting the driving frequency to a higher driving frequency to the driving frequency control unit
ex512. Then, the driving frequency control unit ex512 sets the driving frequency to the higher
driving frequency. On the other hand, when the identification information indicates that the video
data conforms to the conventional standard, such as MPEG-2, H.264/AVC, and VC-1, in Step
exS203, the CPU ex502 transmits a signal for setting the driving frequency to a lower driving
frequency to the driving frequency control unit ex512. Then, the driving frequency control unit
ex512 sets the driving frequency to the lower driving frequency than that in the case where the
video data is generated by the video coding method and the video coding apparatus described
in each of embodiment.
Furthermore, along with the switching of the driving frequencies, the power conservation effect
can be improved by changing the voltage to be applied to the LSI ex500 or an apparatus
including the LSI ex500. For example, when the driving frequency is set lower, the voltage to be
applied to the LSI ex500 or the apparatus including the LSI ex500 is probably set to a voltage
lower than that in the case where the driving frequency is set higher.
Furthermore, when the processing amount for decoding is larger, the driving frequency may be
set higher, and when the processing amount for decoding is smaller, the driving frequency may
be set lower as the method for setting the driving frequency. Thus, the setting method is not
limited to the ones described above. For example, when the processing amount for decoding
video data in conformity with H.264/AVC is larger than the processing amount for decoding
video data generated by the video coding method and the video coding apparatus described in
each of embodiments, the driving frequency is probably set in reverse order to the setting
described above.
Furthermore, the method for setting the driving frequency is not limited to the method for setting
the driving frequency lower. For example, when the identification information indicates that the
video data is generated by the video coding method and the video coding apparatus described
in each of embodiments, the voltage to be applied to the LSI ex500 or the apparatus including
the LSI ex500 is probably set higher. When the identification information indicates that the video
data conforms to the conventional standard, such as MPEG-2, H.264/AVC, and VC-1, the
voltage to be applied to the LSI ex500 or the apparatus including the LSI ex500 is probably set
lower. As another example, when the identification information indicates that the video data is
generated by the video coding method and the video coding apparatus described in each of
embodiments, the driving of the CPU ex502 does not probably have to be suspended. When
the identification information indicates that the video data conforms to the conventional standard,
such as MPEG-2, H.264/AVC, and VC-1, the driving of the CPU ex502 is probably suspended at
a given time because the CPU ex502 has extra processing capacity. Even when the
identification information indicates that the video data is generated by the video coding method
and the video coding apparatus described in each of embodiments, in the case where the CPU
ex502 has extra processing capacity, the driving of the CPU ex502 is probably suspended at a
given time. In such a case, the suspending time is probably set shorter than that in the case
where when the identification information indicates that the video data conforms to the
conventional standard, such as MPEG-2, H.264/AVC, and VC-1.
Accordingly, the power conservation effect can be improved by switching between the driving
frequencies in accordance with the standard to which the video data conforms. Furthermore,
when the LSI ex500 or the apparatus including the LSI ex500 is driven using a battery, the
battery life can be extended with the power conservation effect.
There are cases where a plurality of video data that conforms to different standards, is provided
to the devices and systems, such as a television and a mobile phone. In order to enable
decoding the plurality of video data that conforms to the different standards, the signal
processing unit ex507 of the LSI ex500 needs to conform to the different standards. However,
the problems of increase in the scale of the circuit of the LSI ex500 and increase in the cost
arise with the individual use of the signal processing units ex507 that conform to the respective
standards.
In order to solve the problem, what is conceived is a configuration in which the decoding
processing unit for implementing the video decoding method described in each of embodiments
and the decoding processing unit that conforms to the conventional standard, such as MPEG-2,
H.264/AVC, and VC-1 are partly shared. Ex900 in Figure 56A shows an example of the
configuration. For example, the video decoding method described in each of embodiments and
the video decoding method that conforms to H.264/AVC have, partly in common, the details of
processing, such as entropy coding, inverse quantization, deblocking filtering, and motion
compensated prediction. The details of processing to be shared may include use of a decoding
processing unit ex902 that conforms to H.264/AVC. In contrast, a dedicated decoding
processing unit ex901 is probably used for other processing unique to the present invention.
Since the present invention is characterized by application of deblocking filtering, for example,
the dedicated decoding processing unit ex901 is used for such filtering. Otherwise, the decoding
processing unit is probably shared for one of the entropy decoding, inverse quantization, spatial
or motion compensated prediction, or all of the processing. The decoding processing unit for
implementing the video decoding method described in each of embodiments may be shared for
the processing to be shared, and a dedicated decoding processing unit may be used for
processing unique to that of H.264/AVC.
Furthermore, ex1000 in Figure 56B shows another example in that processing is partly shared.
This example uses a configuration including a dedicated decoding processing unit ex1001 that
supports the processing unique to the present invention, a dedicated decoding processing unit
ex1002 that supports the processing unique to another conventional standard, and a decoding
processing unit ex1003 that supports processing to be shared between the video decoding
method in the present invention and the conventional video decoding method. Here, the
dedicated decoding processing units ex1001 and ex1002 are not necessarily specialized for the
processing of the present invention and the processing of the conventional standard,
respectively, and may be the ones capable of implementing general processing. Furthermore,
the configuration can be implemented by the LSI ex500.
As such, reducing the scale of the circuit of an LSI and reducing the cost are possible by sharing
the decoding processing unit for the processing to be shared between the video decoding
method in the present invention and the video decoding method in conformity with the
conventional standard.
Most of the examples have been outlined in relation to an H.264/AVC based video coding
system, and the terminology mainly relates to the H.264/AVC terminology. However, this
terminology and the description of the various embodiments with respect to H.264/AVC based
coding is not intended to limit the principles and ideas of the invention to such systems. Also the
detailed explanations of the encoding and decoding in compliance with the H.264/AVC standard
are intended to better understand the exemplary embodiments described herein and should not
be understood as limiting the invention to the described specific implementations of processes
and functions in the video coding. Nevertheless, the improvements proposed herein may be
readily applied in the video coding described. Furthermore the concept of the invention may be
also readily used in the enhancements of H.264/AVC coding and/or HEVC currently discussed
by the JCT-VC.
To summarize, the present invention relates to deblocking filtering, which may be
advantageously applied for block-wise encoding and decoding of image or video signal. In
particular, the present invention relates to performing an efficient and accurate decision on
whether or not to apply deblocking filtering on an image block. The efficient and accurate
decision is achieved by performing individual decisions on whether or not to apply deblocking
filtering for segments of a boundary between adjacent image blocks, wherein the individual
decision are based on pixels comprised in a subset of the pixel lines that the image blocks are
composed of.
CLAIMS
A method for deblocking processing of an image divided into smallest blocks of which the
boundaries are to be processed, wherein each block is composed of pixel lines
perpendicular to a boundary with an adjacent block, the method comprising the steps of:
judging whether or not to apply a deblocking filter to segments of the boundary of the
block by judging individually for each segment of the boundary based on pixels
comprised in a subset of pixel lines of the block,
applying or not applying the deblocking filter to the segments of the boundary according
to the result of the respective individual judgements.
The method according to claim 1, wherein said step of judging whether or not to apply a
deblocking filter to segments of the boundary of the block includes the steps of:
obtaining an individual decision value for each segment of the boundary by using pixel
values of pixels comprised in at least one pixel line of the subset of the pixel lines of the
block, and
comparing the individual decision value with a threshold value for each individual
segment of the boundary.
The method according to claim 2, wherein the step of obtaining an individual decision
value for each segment of the boundary includes the step of:
obtaining at least one of the individual decision values based on a single pixel line of the
subset of the pixel lines.
The method according to claim 3, wherein the step of obtaining an individual decision
value for each segment of the boundary includes the step of:
obtaining at least an individual decision value based on the single pixel line of the subset
of the pixel lines by applying nearest neighbour interpolation to the at least one individual
decision value based on the single pixel line of the subset of the pixel lines.
The method according to claims 3 or 4, wherein the step of obtaining an individual
decision value for each segment of the boundary further includes the step of:
obtaining at least one individual decision value based on at least two pixel lines of the
subset of the pixel lines.
The method according to claim 5, wherein the step of obtaining at least one individual
decision value based on at least two pixel lines includes the step of:
obtaining the individual decision value by linear combinations of individual decision
values which are based on a single pixel line of the subset of the pixel lines.
The method according to claim 5, wherein the step of obtaining at least one individual
decision value based on at least two pixel lines of the subset of the pixel lines includes
the step of:
interpolating individual decision values based on a single pixel line of the subset of the
pixel lines linearly.
The method according to any of the claims 1 to 7, wherein in the step of judging whether
or not to apply a deblocking filter to segments of the boundary of the block, the judging is
based on pixels comprised in pixel lines of another block, which is adjacent to the block
and situated across another boundary perpendicular to the boundary, in addition to being
based on pixels comprised in a subset of the pixel lines of the block.
The method according to any of claims 1 to 8, wherein, in the step of judging whether or
not to apply a deblocking filter to segments of the boundary of the block, the pixel lines
serving as a basis forjudging are regularly distributed in a direction parallel to the
boundary.
The method according to any of the claims 1 to 9 further comprising the step of:
judging which type deblocking filtering is applied at each segment of the boundary of the
block.
A method for encoding an image block of an image including a plurality of pixels, the
method comprising the steps of:
compressing and reconstructing the image block, and
applying filtering to the reconstructed block according to any of the claims 1 to 10.
A method for decoding a coded image block of an image including a plurality of pixels,
the method comprising the steps of:
reconstructing the coded image block, and
applying filtering according to any of the claims 1 to 10 to the reconstructed image block.
A computer program product comprising a computer-readable medium having a
computer-readable program code embodied thereon, the program code being adapted to
carry out the method according to any of the claims 1 to 10.
An apparatus for deblocking processing of an image divided into smallest blocks of which
the boundaries are to be processed, wherein each block is composed of pixel lines
perpendicular to a boundary with an adjacent block, the apparatus comprising:
a judging unit configured to judge whether or not to apply a deblocking filter to segments
of the boundary of the block by judging individually for each segment of the boundary
based on pixels comprised in a subset of pixel lines of the block, and
a deblocking filtering unit configured to apply or not apply the deblocking filter to the
segments of the boundary according to the result of the respective individual judgements.
The apparatus according to claim 14, wherein the judging unit further comprises:
an processing unit configured to obtain an individual decision value for each segment of
the boundary by using pixel values of pixels comprised in at least one pixel line of the
subset of the pixel lines of the block, and
a comparing unit configured to compare the individual decision value with a threshold
value for each individual segment of the boundary.
The apparatus according to claim 15, wherein said processing unit is configured to obtain
at least one of the individual decision values based on a single pixel line of the subset of
the pixel lines.
The apparatus according to claim 6, wherein said processing unit is configured to obtain
at least a further individual decision value based on the single pixel line of the subset of
the pixel lines by applying nearest neighbour interpolation to the at least one individual
decision value based on the single pixel line of the subset of the pixel lines.
The apparatus according to claim 16 or 17, wherein said processing unit is configured to
obtain at least one individual decision value based on at least two pixel lines of the
subset of the pixel lines.
The apparatus according to claim 18, wherein said processing unit is configured to obtain
said at least one individual decision value based on at least two pixel lines of the subset
of the pixel lines by utilizing linear combinations of individual decision values which are
based on a single pixel line of the subset of the pixel lines.
The apparatus according to claim 18, wherein said processing unit is configured to obtain
said at least one individual decision value based on at least two pixel lines of the subset
of the pixel lines by interpolating individual decision values based on a single pixel line of
the subset of the pixel lines linearly.
The apparatus according to any of the claims 14 to 20, wherein said judging unit is
configured to judge whether or not to apply a deblocking filter to segments of the
boundary based on pixels comprised in pixel lines of another block, which is adjacent to
the block and situated across another boundary perpendicular to the boundary, in
addition to being based on pixels comprised in a subset of the pixel lines of the block.
The apparatus according to any of the claims 14 to 2 1, wherein said judging unit is
configured to decide whether or not to apply a deblocking filter to segments of the
boundary, wherein the pixel lines serving as a basis for judging are regularly distributed
in a direction parallel to the boundary.
The apparatus according to any of the claims 14 to 22, wherein said judging unit is
configured to judge which type deblocking filtering is applied to each segment of the
boundary.
An apparatus for encoding an image block of an image including a plurality of pixels, the
apparatus comprising:
an encoder with a decoder for compressing and reconstructing the current block, and
an apparatus for filtering the reconstructed block according to any of the claims 14 to 23.
An apparatus for decoding a coded image block of an image including a plurality of
pixels, the apparatus comprising:
a decoder for reconstructing the coded image block, and
an apparatus for filtering the reconstructed image block according to any of the claims 14
to 23.
An integrated circuit for embodying the apparatus according to any of the claims 14 to 23,
comprising a memory for storing pixels to be filtered.