Technical Field [0001]
The present invention relates to a signal processing apparatus and method, a program, and a data recording medium, and more particularly, relates to a signal processing apparatus and method, a program, and a data recording medium configured such that the playback level of an audio signal can be easily and effectively enhanced without requiring additional information given by prior analysis. Background Art [0002]
For example, in the case where movie content or music content with a large dynamic range in audio volume is played back on a portable device with compact built-in speakers, not only does the audio volume become lower overall, but audio such as low-volume dialogue in particular becomes difficult to hear. [0003]
Thus, although normalization and automatic gain control technology does exist as technology for making the audio of such content easier to hear, volume control becomes audibly unstable unless data is read sufficiently far enough ahead. [0004]
There also exists technology that boosts low-volume portions and compresses high-volume portions of audio by
2

means of a dynamic range compression process for volume. However, with a compression process, it is difficult to obtain large audio enhancement effects if generalized volume boost and compression settings are used. In order to obtain large effects, it is necessary to vary settings on a per-content basis. [0005]
For example, there exists technology that takes a sound pressure level specified by dialogue normalization as a basis, boosting signals with a lower sound pressure level and compressing signals with a higher sound pressure level. With this technology, however, it is necessary to specify boost and compression settings and a sound pressure level for dialogue normalization at the time of encoding the audio signal in order to obtain sufficient effects. [0006]
Furthermore, technology has also been proposed in which, in the case of compressing the dynamic range of audio voliame, faint sounds in an audio signal are made easier to hear by multiplying the audio signal by coefficients determined by the average of the absolute values of the audio signal (see PTL 1, for example). Citation List Patent Literature [0007]
3

PTL 1: Japanese Unexamined Patent Application Publication No. 5-275950 Summary of Invention Technical Problem [0008]
Meanwhile, various types of content such as movies, music, and self-recorded content are coming to be played back on portable devices with compact built-in speakers. However, much of such content lacks additional information for effective voliome control given by prior analysis done at the time of encoding, etc. as discussed above. For this reason, there is a need for technology that effectively conducts volume control even in cases where additional information obtained by prior analysis is not included in the audio signal of given content, [0009]
Accordingly, if the technology described in PTL 1 discussed above is used, it becomes possible to suppress sudden changes in loudness while making faint sounds in an audio signal easier to hear by means of a compression process, without requiring prior analysis of the audio signal. However, the playback level of an audio signal cannot be sufficiently enhanced with this technology. [0010]
For example, with the technology described in PTL 1,
4

since amplitude is simply damped by multiplying an audio signal l^y a constant, there is little freedom in amplitude conversion settings, and it cannot be said that the playback level of an audio signal can be effectively enhanced. Also, this technology can only be used in the case of narrowing the dynamic range of volume by amplitude conversion of an audio signal. Converting amplitude without changing the dynamic range of volume or widening the dynamic range of volume cannot be conducted. [0011]
The present invention, being devised in light of such circumstances, is configured such that the playback level of an audio signal can be easily and effectively enhanced without requiring additional information given by prior analysis.
Solution to Problem [0012]
A signal processing apparatus of a first aspect of the present invention comprises analyzing means analyzing input signal characteristics, mapping processing means conducting amplitude conversion of the input signal on the basis of a predetermined linear function or nonlinear function, weighting controlling means respectively multiplying a plurality of the input signals, which have been respectively amplitude-converted on the basis of mutually different
5

functions by a plurality of the mapping processing means, by weights determined by the analysis result for the input signal characteristics, and adding means generating an output signal by adding together the plurality of input signals which have been multiplied by the weights. [0013]
The analyzing means may be made to compute a value expressing the average sample value of samples included in a given segment of the input signal as the analysis result. [0014]
The analysis result may be taken to be the root mean square or a moving average of sample values of samples included in the given segment. [0015]
In the case where amplitude conversion is conducted on the input signal for each of a plurality of channels to generate an output signal for each channel, the analyzing means may be made to compute one analysis result shared by all channels. [0016]
It may be configured such that the weights are determined by the analysis result for every single sample of the input signal. [0017]
It may be configured such that the weights are
6

determined by the analysis result for every given number of two or more consecutive samples of the input signal. [0018]
A signal processing method or program of a first aspect of the present invention includes the steps of analyzing input signal characteristics, conducting amplitude conversion of the input signal on the basis of a predetermined linear function or nonlinear function, respectively multiplying a plurality of the input signals, which have been amplitude-converted on the basis of a plurality of mutually different functions, by weights determined by the analysis result for the input signal characteristics, and generating an output signal by adding together the plurality of input signals which have been multiplied by the weights. [0019]
In a first aspect of the present invention, input signal characteristics are analyzed, amplitude conversion of the input signal is conducted on the basis of a predetermined linear function or nonlinear function, a plurality of the input signals, which have been respectively amplitude-converted on the basis of mutually different functions by a plurality of the mapping processing means, are respectively multiplied by weights determined by the analysis result for the input signal characteristics, and an
7

output signal is generated by adding together the plurality of input signals which have been multiplied by the weights. [0020]
A data recording mediiom of a second aspect of the present invention has recorded thereon an output signal obtained by analyzing input signal characteristics, conducting amplitude conversion of the input signal on the basis of a predetermined linear function or nonlinear function, respectively multiplying a plurality of the input signals, which have been amplitude-converted on the basis of a plurality of mutually different functions, by weights determined by the analysis result for the input signal characteristics, and adding together the plurality of input signals which have been multiplied by the weights. [0021]
A signal processing apparatus of a third aspect of the present invention comprises analyzing means analyzing input signal characteristics, and mapping processing means generating an output signal by conducting amplitude conversion of the input signal on the basis of a nonlinear function determined by the analysis result for the input signal characteristics. [0022]
The analyzing means may be made to compute a value expressing the average sample value of samples included in a
8

given segment of the input signal as the analysis result. [0023]
The analysis result may be taken to be the root mean square or a moving average of sample values of samples included in the given segment. [0024]
In the case where amplitude conversion is conducted on the input signal for each of a plurality of channels to generate an output signal for each channel, the analyzing means may be made to compute one analysis result shared by all channels on the basis of the input signals in the plurality of channels. [0025]
The nonlinear function may be determined by the analysis result for every single sample of the input signal. [0026]
The nonlinear function may be determined by the analysis result for every given number of two or more consecutive samples of the input signal. [0027]
A signal processing method or program of a third aspect of the present invention includes the steps of analyzing input signal characteristics, and generating an output signal by conducting amplitude conversion of the input signal on the basis of a nonlinear function determined by
9

the analysis result for the input signal characteristics. [0028]
In a third aspect of the present invention, input signal characteristics are analyzed, and an output signal is generated by conducting amplitude conversion of the input signal on the basis of a nonlinear function determined by the analysis result for the input signal characteristics. [0029]
A data recording medium of a fourth aspect of the present invention has recorded thereon an output signal obtained by analyzing input signal characteristics, and conducting amplitude conversion of the input signal on the basis of a nonlinear function determined by the analysis result for the input signal characteristics. Advantageous Effects of Invention [0030]
According to the first through fourth aspects of the present invention, the playback level of an audio signal can be easily and effectively enhanced without requiring additional information given by prior analysis. Brief Description of Drawings [0031]
[Fig. 1] Fig. 1 is a diagram illustrating an exemplary configuration of a first embodiment of an audio signal processing apparatus applying the present invention.
10

[Fig. 2] Fig. 2 is a flowchart explaining a conversion process.
[Fig. 3] Fig. 3 is a diagram illustrating exemplary mapping functions.
[Fig. 4] Fig. 4 is a diagram illustrating exemplary mapping functions.
[Fig. 5] Fig. 5 is a diagram illustrating exemplary mapping functions.
[Fig. 6] Fig. 6 is a diagram illustrating another exemplary configuration of an audio signal processing apparatus.
[Fig. 7] Fig. 7 is a flowchart explaining a conversion process.
[Fig. 8] Fig. 8 is a diagram illustrating another exemplary configuration of an audio signal processing apparatus.
[Fig. 9] Fig. 9 is a flowchart explaining a conversion process.
[Fig. 10] Fig. 10 is a diagram illustrating exemplary mapping functions.
[Fig. 11] Fig. 11 is a diagram illustrating another exemplary configuration of an audio signal processing apparatus.
[Fig. 12] Fig. 12 is a flowchart explaining a conversion process.
11

[Fig. 13] Fig. 13 is a block diagram illustrating an
exemplary configuration of a computer.
Description of Embodiments
[0032]
Hereinafter, embodiments applying the present invention
will be described with reference to the drawings, throughout
which like parts are referred to by like references, and in
which:
[0033]

[Configuration of audio signal processing apparatus]
Fig. 1 is a diagram illustrating an exemplary configuration of an embodiment of an audio signal processing • apparatus applying the present invention. [0034]
The audio signal processing apparatus 11 is provided in a portable playback apparatus that plays back content consisting of video signals and audio signals, for example, and conducts amplitude conversion on an input audio signal such that the playback level is enhanced, and outputs the amplitude-converted audio signal. Note that hereinafter, an audio signal input specifically input into the audio signal processing apparatus 11 is designated an input signal, while an audio signal obtained by amplitude-converting an input signal is designated an output signal.
12

[0035]
The audio signal processing apparatus 11 is composed of an analyzer 21, a mapping processor 22, an output unit 23, and a drive 24.
[0036]
The analyzer 21 analyzes the characteristics of a supplied input signal, and supplies mapping control information indicating the analysis results to the mapping processor 22.
[0037]
The mapping processor 22 uses mapping control information supplied from the analyzer 21 to conduct a mapping process on a supplied input signal and enhance the playback level of the input signal. In the mapping process, linear or non-linear amplitude conversion is conducted on an input signal. The mapping processor 22 supplies the output unit 23 with an output signal obtained by the mapping process.
[0038]
The output unit 23 may output an output signal supplied from the mapping processor 22 to a subsequent audio output unit, etc. or supply it to the drive 24. The drive 24 records an output signal supplied from the output unit 23 to a removable medium 25, which is a recording medium able to be freely inserted into and removed from the drive 24.
13

[0039]
[Description of conversion process]
Next, operation of the audio signal processing apparatus 11 in Fig. 1 will be described. [0040]
The audio signal processing apparatus 11 conducts a conversion process upon being supplied with an input signal, and generates and outputs an output signal. Hereinafter, a conversion process conducted by the audio signal processing apparatus 11 will be described with reference to the flowchart in Fig. 2. [0041]
In step Sll, the analyzer 21 analyzes the characteristics of a supplied input signal, and generates mapping control information. [0042]
Specifically, the analyzer 21 may, for example, perform the computation in the following Eq. 1, and compute the root mean square RMS(n) for the nth sample of the input signal as mapping control information for the nth sample. [0043] [Expression 1]
r, m+N/2-t
RMS (n) =20.0 x Iogio J ij- * I (x(m))^ - - - (i)
» N m=n-N/2
V )
14

[0044]
In Eq. 1 herein, x(m) represents the sample value of the mth sample of the input signal (the input signal value). Also, in Eq. 1, the input signal values, or in other words the sample values of each input signal sample, are taken to be normalized such that -l [Configuration of audio signal processing apparatus]
Meanwhile, in the case where an audio signal given as an input signal has two or more channels, inter-channel volume balance of audio based on the output signal may change if analysis of input signal characteristics or a mapping process is conducted independently on each channel. [0099]
For this reason, it is desirable to conduct identical analyses and mapping processes on the input signals in all channels. Thus, it may also be configured such that characteristics are analyzed for the input signals in all channels, and a mapping process is conducted using one set of mapping control information obtained from the analysis results. In such cases, the audio signal processing apparatus may be configured as illustrated in Fig. 6, for example. [0100]
The audio signal processing apparatus 51 is composed of
31

an analyzer 21, a mapping processor 22, a mapping processor 61, an output unit 23, and a drive 24. In Fig. 6 herein, like numerals are given to portions corresponding to the case in Fig. 1, and description of such portions will be reduced or omitted. [0101]
Input signals are supplied to the audio signal processing apparatus 51 as a left-channel audio signal and a right-channel audio signal constituting a movie or other content, for example. In other words, the left-channel input signal is supplied to the analyzer 21 and the mapping processor 22, while the right-channel input signal is supplied to the analyzer 21 and the mapping processor 61. [0102]
The analyzer 21 analyzes the respective characteristics of the supplied left- and right-channel input signals, generates mapping control information on the basis of the two sets of analysis results thus obtained, and supplies the mapping control information to the mapping processor 22 and the mapping processor 61. [0103]
The mapping processor 61 uses the mapping control information supplied from the analyzer 21 to conduct a mapping process on the supplied right-channel input signal and generates a right-channel output signal. At this point,
32

a process similar to that of the mapping processor 22 is conducted in the mapping processor 61. The mapping processor 61 supplies the right-channel output signal obtained by the mapping process to the output unit 23. [0104]
In this way, in the audio signal processing apparatus 51, shared mapping control information is used to conduct mapping processes in the mapping processor 22 and the mapping processor 61. [0105]
The output unit 23 may output the left- and right-channel output signals supplied from the mapping processor 22 and the mapping processor 61 to a subsequent unit or to the drive 24 for recording to the removable medium 25. [0106] [Description of conversion process]
Next, a conversion process conducted by the audio signal processing apparatus 51 will be described with reference to the flowchart in Fig. 7. [0107]
In step S41, the analyzer 21 analyzes the characteristics of supplied left- and right-channel input signals. For example, the analyzer 21 may perform the computation in Eq. 1 discussed earlier, and compute a left-channel root mean square RMS(n) and a right-channel root
33

mean square RMS(n). [0108]
In step S42, the analyzer 21 generates mapping control information on the basis of the input signal characteristics analysis results, and supplies the mapping control information to the mapping processor 22 and the mapping processor 61. For example, the analyzer 21 may compute the average of the left-channel root mean square RMS(n) and the right-channel root mean square RMS(n), and take the obtained average to be the mapping control information. [0109]
However, it may also be configured such that the larger value of the left-channel root mean square RMS(n) and the right-channel root mean square RMS{n) may be taken without change as the mapping control information. Also, samples from the left-channel input signal and samples from the right-channel input signal may be used to compute a single root mean square RMS(n), etc. as the mapping control information. [0110]
Once the operation in step S42 is conducted and mapping control information is generated, the operations in steps S43 and S44 are subsequently conducted and the conversion process ends. However, since these processing operations are similar to the operations in steps S12 and S13 of Fig. 2,
34

their description will be reduced or omitted. [0111]
However, in step S43, the mapping control information is used in the mapping processor 22 and the mapping processor 61, and a left-channel output signal and a right-channel output signal are respectively generated with identical mapping functions and control factors. [0112]
In so doing, the audio signal processing apparatus 51 analyzes the characteristics of left- and right-channel input signals, generates common mapping control information for the left and right channels, and uses the obtained mapping control information to conduct an identical mapping process on each channel. By using common mapping control information for the left and right channels to conduct an identical mapping process on per-channel input signals in this way, the playback level of an audio signal can be enhanced without changing the inter-channel volume balance. [0113]
Although the foregoing describes a case where two left-and right-channel input signals are input, an input signal may also be composed of three or more channels. Even in such cases, common mapping control information is generated for all channels. [0114]
35

[Configuration of audio signal processing apparatus]
Also, although the foregoing describes using a single mapping function to generating an output signal, a plurality of linear or nonlinear mapping functions may be prepared, and it may be configured such that an output signal is generated by selectively using those mapping functions according to the mapping control information. In such cases, changes in the output that occur due to switching the mapping function used to generate the output signal can be made smoother by taking the output signal to be a weighted sum of outputs from plural mapping functions depending on the mapping control information. [0115]
In this way, in the case of generating an output signal by using a plurality of mapping functions, an audio signal processing apparatus may take the configuration illustrated in Fig. 8, for example. [0116]
Namely, the audio signal processing apparatus 91 is composed of an analyzer 21, mapping processors 101-1 to 101-M, a weighting controller 102, an adder 103, an output unit 23, and a drive 24. In Fig. 8 herein, like numerals are given to portions corresponding to the case in Fig. 1, and description of such portions will be reduced or omitted.
36

[0117]
The mapping processors 101-1 to 101-M each conduct a mapping process on a supplied input signal using respectively different mapping functions, and supply the output signals obtained as a result to the weighting controller 102. Note that hereinafter, the mapping processors 101-1 to 101-M will also be simply designated the mapping processors 101 in cases where it is not necessary to individually distinguish them,
[0118]
The weighting controller 102 multiplies output signals supplied from the mapping processors 101 by distribution ratios, which are weights determined by mapping control information supplied from the analyzer 21, and supplies the result to the adder 103. In other words, the weighting controller 102 is provided with multipliers 111-1 to 111-M. The multipliers 111-1 to 111-M multiply output signals supplied from the mapping processors 101-1 to 101-M by distribution ratios ai to UM determined by mapping control information, and supply the results to the adder 103.
[0119]
Note that hereinafter, the multipliers 111-1 to 111-M will also be simply designated the multipliers 111 in cases where it is not necessary to individually distinguish them,
[0120]
37

The adder 103 adds together M output signals supplied from the multipliers 111, and supplies the final output signal obtained as a result to the output unit 23. [0121] [Description of conversion process]
Next, a conversion process conducted by the audio signal processing apparatus 91 will be described with reference to the flowchart in Fig. 9. [0122]
In step S71, the analyzer 21 analyzes the characteristics of a supplied input signal. For example, the analyzer 21 may perform the computation in Eq. 1 discussed earlier, compute the root mean square RMS{n) for the nth sample of the input signal as mapping control information, and supply the mapping control information to the weighting controller 102. [0123]
In step S72, the mapping processors 101 conduct a mapping process on supplied input signals, and supply the obtained output signals to the multipliers 111. [0124]
For example, assume that the audio signal processing apparatus 91 is provided with four mapping processors 101-1 to 101-4. In this case, the mapping processors 101-1 to 101-4 conduct a mapping process on supplied input signals by
38

using the mapping functions fi(x) to f4(x) expressed in the following Eqs. 8 to 11. In other words, the value obtained by substituting in a mapping function for the sample value x of the nth sample of an input signal is taken to be the sample value of the nth sample of an output signal. [0125] [Expression 8]
fi(x)=x (-1.0^x^1.0) ••■(8)
f2(x)=^_^^^^ -1 (-1.0^X^1.0) • • " (9)
f3(x)=-j:j|z^-i (-1.0^x^^1.0) . . . (10)
f4(x) = ^_^^^,o^-l (-1.0^x^1,0) • • ■ (11)
[0126]
In Eqs. 8 to 11 herein, x represents the sample value of an input signal sample. In Eqs. 8 to 11, the input signal sample value x is taken to be normalized to a value from -1 to 1. [0127]
These mapping functions fi(x) to f4(x) are functions ordered from the mapping function f4(x) to the mapping function fi(x) in order of steepest characteristics. [0128]
In Fig. 10 herein, the mapping functions fi(x) to f4(x)
39

are illustrated in the upper-left, the upper-right, the lower-left, and the lower-right, respectively. Also, in Fig. 10, the horizontal axis represents the sample value x of an input signal, while the vertical axis represents the value of a mapping function. [0129]
For example, in the drawing, the mapping function fi(x)=x illustrated in the upper-left is a linear first-order function, in which a sample value x in an input signal is taken without change as a sample value in an output signal. Also, the mapping functions f2(x) to f4(x) are nonlinear exponential functions ordered from the mapping function f4(x) to the mapping function f2(x) in order of steepest characteristics in the segment for most sample values X, including sample values x equal to 0, In other words, the mapping functions are ordered from the mapping function f4 (x) to the mapping function f2(x) in order of the highest rate of change in the mapping function output versus change in the sample value x. [0130]
Returning to description of the flowchart in Fig. 9, in step S73, the weighting controller 102 multiplies output signals supplied from the mapping processors 101 by distribution ratios acting as weights, on the basis of mapping control information supplied from the analyzer 21.
40

[0131]
For example, assume that the audio signal processing apparatus 91 is provided with four mapping processors 101-1 to 101-4. In this case, the weighting controller 102 performs the computation expressed in the following Eq. 12 and computes distribution ratios aito a4 for the mapping functions fi(x) to f4(x), on the basis of the root mean square RMS(n) given as mapping control information. [0132] [Expression 9]
ai=1.0-^|y. ff2=1.0-ff|, (I3=ff4=0.0 (-12.0 [Configuration of audio signal processing apparatus]
Also, although the case of a one-channel input signal as the audio signal was described with Fig. 8, an input signal may also be taken to have plural channels. For example, in the case where a two-channel input signal is input, the audio signal processing apparatus may take the configuration illustrated in Fig. 11. [0152]
The audio signal processing apparatus 141 in Fig. 11 is composed of an analyzer 21, mapping processors 101-1 to 101-M, a weighting controller 102, an adder 103, mapping processors 151-1 to 151-M, a weighting controller 152, and adder 153, an output unit 23, and a drive 24. In Fig. 11 herein, like numerals are given to portions corresponding to the case in Fig. 8, and description of such portions will be
47

reduced or omitted. [0153]
Input signals are supplied to the audio signal processing apparatus 141 as a left-channel audio signal and a right-channel audio signal constituting a movie or other content, for example. In other words, the left-channel input signal is supplied to the analyzer 21 and the mapping processors 101-1 to 101-M, while the right-channel input signal is supplied to the analyzer 21 and the mapping processors 151-1 to 151-M. [0154]
The analyzer 21 analyzes the respective characteristics of the supplied left- and right-channel input signals, generates mapping control information on the basis of the two sets of analysis results thus obtained, and supplies the mapping control information to the weighting controller 102 and the weighting controller 152. [0155]
The mapping processors 151-1 to 151-M conduct mapping processes on a supplied input signal using the same respective mapping functions used by the mapping processors 101-1 to 101-M. Also, the mapping processors 151-1 to 151-M supply output signals obtained by the mapping processes to the weighting controller 152. Note that hereinafter, the mapping processors 151-1 to 151-M will also be simply
48

designated the mapping processors 151 in cases where it is
not necessary to individually distinguish them.
[0156]
The weighting controller 152 conducts the same operation as the weighting controller 102. In other words, multipliers 161-1 to 161-M constituting the weighting controller 152 correspond to the multipliers 111-1 to 111-M, multiplying output signals supplied from the mapping processors 151-1 to 151-M by distribution ratios ai to ttM and supplying the results to the adder 153. Note that hereinafter, the multipliers 161-1 to 161-M will also be simply designated the multipliers 161 in cases where it is not necessary to individually distinguish them. [0157]
The adder 153 adds together M output signals supplied from the multipliers 161, and supplies the final output signal obtained as a result to the output unit 23. [0158] [Description of conversion process]
Next, a conversion process conducted by the audio signal processing apparatus 141 will be described with reference to the flowchart in Fig. 12. [0159]
In step SlOl, the analyzer 21 analyzes the characteristics of supplied left- and right-channel input
49

signals. For example, the analyzer 21 may perform the computation in Eq. 1 discussed earlier, and compute a left-channel root mean square RiyiS(n) and a right-channel root mean square RMS(n). [0160]
In step S102, the analyzer 21 generates mapping control information on the basis of the input signal characteristics analysis results, and supplies the mapping control information to the weighting controller 102 and the weighting controller 152. For example, the analyzer 21 may compute the average of the left-channel root mean square RMS(n) and the right-channel root mean square RMS(n), and take the obtained average to be the mapping control information. [0161]
Once the operation in step S102 is conducted and mapping control information is generated, the operations in steps S103 to S106 are subsequently conducted and the conversion process ends. However, since these processing operations are similar to the operations in steps S72 to S75 of Fig. 9, their description will be reduced or omitted. [0162]
However, in steps S103 to S105, mapping processes are conducted in the mapping processors 101, the obtained output signals are multiplied by distribution ratios in the
50

multipliers 111, the output signals which have been multiplied by the distribution ratios are added together in the adder 103, and the result is taken to be the final left-channel output signal. Similarly, mapping processes are conducted in the mapping processors 151, the obtained output signals are multiplied by distribution ratios in the multipliers 161, the output signals which have been multiplied by the distribution ratios are added together in the adder 153, and the result is taken to be the final right-channel output signal. [0163]
In so doing, the audio signal processing apparatus 141 analyzes the characteristics of left- and right-channel input signals, generates common mapping control information for the left and right channels, and uses the obtained mapping control information to compute a common distribution ratio for the left and right channels for each mapping function. By using common mapping control information for the left and right channels to compute common distribution ratios for the left and right channels for each mapping function in this way, the playback level of an audio signal can be Enhanced without changing the inter-channel volume balance. [0164]
The series of processes discussed in the foregoing may
51

be executed in hardware, but may also be executed in software. In the case of executing the series of processes in software, a program constituting such software is installed from a program recording medium to a computer built into special-purpose hardware, or a computer such as a general-purpose personal computer, for example, able to execute various functions by installing various programs thereon. [0165]
Fig. 13 is a block diagram illustrating an exemplary hardware configuration of a computer that executes the series of processes discussed in the foregoing with a program. [0166]
In a computer, a CPU (Central Processing Unit) 201, ROM (Read-only Memory) 202, and RAM (Random Access Memory) 203 are connected to each other by a bus 204. [0167]
An input/output interface 205 is additionally connected to the bus 204. Connected to the input/output interface 205 are an input unit 206 comprising a keyboard, mouse, microphone, etc., an output unit 207 comprising a display, speakers, etc., a recording unit 208 comprising a hard disk, non-volatile memory, etc., a communication unit 209 comprising a network interface, etc., and a drive 210 that
52

drives a removable medium 211 such as a magnetic disk, an optical disc, a magneto-optical disc, or semiconductor memory. [0168]
In a computer configured as above, the series of process discussed in the foregoing is conducted due to the CPU 201 loading a program recorded in the recording unit 208 into the RAM 203 via the input/output interface 205 and the bus 204, and executing the program, for example. [0169]
A program executed by the computer (CPU 201) may for example be provided by being recorded onto a removable medium 211 as an instance of packaged media consisting of magnetic disks (including flexible disks), optical discs (including CD-ROMs (Compact Disc - Read-Only Memory), DVDs (Digital Versatile Disc), etc.), magneto-optical discs, or semiconductor memory. Alternatively, a program may be provided via a wired or wireless transmission mediiom such as a local area network, the Internet, or digital satellite broadcasting. [0170]
Additionally, a program may be installed to the recording unit 208 via the input/output interface 205 by loading the removable medium 211 into the drive 210. Also, a program may be received by the communication unit 209 via
53

a wired or wireless transmission medium and installed to the
recording unit 208. Otherwise, a program may be installed
in advance to the ROM 202 or the recording unit 208.
[0171]
Herein, a program executed by a computer may be a
program in which operations are conducted in a time series
following the order described in this specification, but may
also be a program in which operations are executed in
parallel or at required timings, such as upon being called.
[0172]
Furthermore, an embodiment of the present invention is
not limited to the embodiments discussed in the foregoing,
and various modifications are possible within a scope that
does not depart from the principal matter of the present
invention.
Reference Signs List [0173]
11 audio signal processing apparatus
21 analyzer
22 mapping processor 61 mapping processor
101-1 to 101-M, 101 mapping processors
102 weighting controller
103 adder
151-1 to 151-M, 151 mapping processors
54

152 weighting controller
153 adder
In so far as the embodiments of the invention described
above are implemented, at least in part, using software-controlled data processing apparatus, it will be appreciated that a computer program providing such software control and a transmission, storage or other medium by which such a computer program is provided are envisaged as aspects of the present invention.
55

CLAIMS
[Claim 1]
A signal processing apparatus comprising:
analyzing means analyzing input signal characteristics;
mapping processing means conducting amplitude conversion of the input signal on the basis of a predetermined linear function or nonlinear function;
weighting controlling means respectively multiplying a plurality of the input signals, which have been respectively amplitude-converted on the basis of mutually different functions by a plurality of the mapping processing means, by weights determined by the analysis result for the input signal characteristics; and
adding means generating an output signal by adding together the plurality of input signals which have been multiplied by the weights. [Claim 2]
The signal processing apparatus according to Claim 1, wherein
the analyzing means computes a value expressing the average sample value of samples included in a given segment of the input signal as the analysis result. [Claim 3]
The signal processing apparatus according to Claim 2, wherein
56

the analysis result is the root mean square or a moving average of sample values of samples included in the given segment. [Claim 4]
The signal processing apparatus according to Claim 1, wherein
in the case where amplitude conversion is conducted on the input signal for each of a plurality of channels to generate an output signal for each channel, the analyzing means computes one analysis result shared by all channels. [Claim 5]
The signal processing apparatus according to Claim 1, wherein
the weights are determined by the analysis result for every single sample of the input signal. [Claim 6]
The signal processing apparatus according to Claim 1, wherein
the weights are determined by the analysis result for every given number of two or more consecutive samples of the input signal. [Claim 7]
A signal processing method for a signal processing apparatus provided with
analyzing means analyzing input signal characteristics,
57

mapping processing means conducting amplitude conversion of the input signal on the basis of a predetermined linear function or nonlinear function,
weighting controlling means respectively multiplying a plurality of the input signals, which have been respectively amplitude-converted on the basis of mutually different functions by a plurality of the mapping processing means, by weights determined by the analysis result for the input signal characteristics, and
adding means generating an output signal by adding together the plurality of input signals which have been multiplied by the weights, the signal processing method including the steps of:
the analyzing means analyzing the input signal characteristics;
the plurality of mapping processing means conducting amplitude conversion of the input signal;
the weighting controlling means multiplying the amplitude-converted input signals by the weights determined by the analysis result; and
the adding means generating the output signal by adding together the input signals which have been multiplied by the weights. [Claim 8]
A program causing a computer to execute processing
58

including the steps of:
analyzing input signal characteristics;
conducting amplitude conversion of the input signal on the basis of a predetermined linear function or nonlinear function;
respectively multiplying a plurality of the input signals, which have been amplitude-converted on the basis of a plurality of mutually different functions, by weights determined by the analysis result for the input signal characteristics; and
generating an output signal by adding together the plurality of input signals which have been multiplied by the weights. [Claim 9]
A data recording medium recording an output signal obtained by
analyzing input signal characteristics,
conducting amplitude conversion of the input signal on the basis of a predetermined linear function or nonlinear function,
respectively multiplying a plurality of the input signals, which have been amplitude-converted on the basis of a plurality of mutually different functions, by weights determined by the analysis result for the input signal characteristics, and
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adding together the plurality of input signals which have been multiplied by the weights. [Claim 10]
A signal processing apparatus comprising:
analyzing means analyzing input signal characteristics; and
mapping processing means generating an output signal by conducting amplitude conversion of the input signal on the basis of a nonlinear function determined by the analysis result for the input signal characteristics. [Claim 11]
The signal processing apparatus according to Claim 10, wherein
the analyzing means computes a value expressing the average sample value of samples included in a given segment of the input signal as the analysis result. [Claim 12]
The signal processing apparatus according to Claim 11, wherein
the analysis result is the root mean square or a moving average of sample values of samples included in the given segment. [Claim 13]
The signal processing apparatus according to Claim 10, wherein
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in the case where amplitude conversion is conducted on the input signal for each of a plurality of channels to generate an output signal for each channel, the analyzing means computes one analysis result shared by all channels on the basis of the input signals in the plurality of channels. [Claim 14]
The signal processing apparatus according to Claim 10, wherein
the nonlinear function is determined by the analysis result for every single sample of the input signal. [Claim 15]
The signal processing apparatus according to Claim 10, wherein
the nonlinear function is determined by the analysis result for every given number of two or more consecutive samples of the input signal. [Claim 16]
A signal processing method for a signal processing apparatus provided with
analyzing means analyzing input signal characteristics, and
mapping processing means generating an output signal by conducting amplitude conversion of the input signal on the basis of a nonlinear function determined by the analysis result for the input signal characteristics,
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the signal processing method including the steps of: the analyzing means analyzing the input signal
characteristics; and
the mapping processing means conducting amplitude
conversion of the input signal on the basis of the nonlinear
function.
[Claim 17]
A program causing a computer to execute processing
including the steps of:
analyzing input signal characteristics; and generating an output signal by conducting amplitude
conversion of the input signal on the basis of a nonlinear
function determined by the analysis result for the input
signal characteristics.
[Claim 18]
A data recording mediiom recording an output signal
obtained by
analyzing input signal characteristics, and conducting amplitude conversion of the input signal on
the basis of a nonlinear function determined by the analysis
result for the input signal characteristics.