JP2011242788A - Signal encoding device and method, signal decoding device and method, program, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow an encoding side to generate information for generating a high sub-band signal of high quality when expanding a frequency band on a decoding side.SOLUTION: A signal encoding device 10 divides an inputted time-series signal into a plurality of sub-bands, encodes a low sub-band signal to generate low sub-band signal encoded data, compares a frequency amplitude peak of a new high sub-band signal generated from the low sub-band signal with that of the original high sub-band signal to generate high sub-band signal frequency amplitude peak information, and compares a gain of the new high sub-band signal generated by using the low sub-band signal with that of the original high sub-band signal to generate high sub-band signal gain information. Then, the signal encoding device 10 multiplexes the low sub-band signal encoded data, the high sub-band signal frequency amplitude peak information and the high sub-band signal gain information and outputs compressed data.

Description

  INDUSTRIAL APPLICABILITY The present invention provides a signal encoding apparatus and method, a signal decoding apparatus and method suitable for use in expanding a subband signal limited to a frequency band on the encoding side to a wider frequency band on the decoding side. And a program and a recording medium.

  In recent years, high-efficiency encoding of audio signals has made it possible to compress the sound quality equivalent to a CD (Compact disk) to about 1/10 the amount of data of the original CD by utilizing the mechanism of human hearing. ing. At present, products using these technologies are distributed in the market, and it has been realized that they can be recorded on a smaller recording medium or distributed through a network.

  In such high-efficiency compression, a unique format is employed, and within the format range, the sound quality and bit rate can be freely controlled to some extent on the encoding side. For example, the mini-disc (MD) (trademark of Sony Corporation) also has two modes, LP2 and LP4, which employ the same high-efficiency compression technology as the long-time recording mode. By compressing to, the recording time is twice as long as LP2 although the sound quality is inferior.

  However, since such high-efficiency compression technology is designed and standardized with a clear target for bit rate and sound quality, if the bit rate is further lowered while maintaining the standard (format), the sound quality will be extremely low. It will deteriorate. To avoid this situation, improve the high-efficiency encoding algorithm on the encoding side, limit high-frequency signals that are insensitive to human hearing, and distribute extra bits to low-frequency signals. The method is generally taken.

Information technology -Coding of audio-visual objects-Part3: Audio ISO / IEC 14496-3: 2001

  By the way, there is also an attempt to reproduce the high frequency signal on the decoding side when the high frequency signal is limited in order to maintain the sound quality and reduce the bit rate while maintaining the format as described above. For example, a technique for doubling the reproduction band of a 44.1 kHz sampling PCM signal described in Japanese Patent Laid-Open No. 2-311006, or a telephone frequency band described in Japanese Patent Laid-Open No. 9-55778 is expanded on the receiving side. There is such a technology.

  This technology has the advantage that the format does not need to be changed and only the decoding side needs to be improved. However, since the band needs to be expanded only from the received signal, it has a dramatic effect on sound quality. In addition, depending on the input sound source, an auditory distortion may be heard in the high range, particularly when there is not much correlation between the low range and the high range.

  On the other hand, there is an attempt to extend the band by expanding the format, encoding information for expanding the band on the encoding side, and using information for expanding the band on the decoding side. For example, there is a technique for expanding a band using an LPC filter described in US Pat. No. 5,068,899 and a technique for expanding a band using a subband filter bank and a nonlinear device described in US Pat. No. 5,127,054. .

  Such a technique provides an improvement effect for an audio signal, but an audio signal is perceived by an auditory distortion and an adequate quality cannot be obtained.

  On the other hand, there is a technique that can obtain a certain level of quality for an audio signal. For example, the ISO international standard HE-AAC (ISO / IEC 14496-3: 2001) provides a certain level of quality for audio signals.

  FIG. 7 shows the configuration of a signal decoding apparatus that performs band expansion by HE-AAC.

In the signal decoding device 70 that performs band expansion by HE-AAC, the demultiplexing circuit 71 includes:
The compressed data output from the encoding device is separated into low frequency information and high frequency information, and the low frequency information and the high frequency information are supplied to the low frequency information decoding circuit 72 and the band expansion circuit 74, respectively.

  The low frequency information decoding circuit 72 decodes the low frequency information to generate a low frequency time series signal, and supplies the low frequency time series signal to the subband division filter bank 73.

  The sub-band division filter bank 73 divides the low-frequency time-series signal into a plurality of bands to generate a low-frequency sub-band signal, and the low-frequency sub-band signal is transmitted to the band expansion circuit 74 and the sub-band synthesis filter bank 75. Supply.

  The band expanding circuit 74 expands the band using the high band information and the low band subband signal, and generates a high band subband signal. Thereafter, the band expansion circuit 74 supplies this high-frequency subband signal to the subband synthesis filter bank 75.

  The subband synthesis filter bank 75 subband synthesizes the low frequency subband signal and the high frequency subband signal to generate a time series signal that is an output signal.

  The band expansion circuit 74 described above whitens the low-frequency subband signal using a linear prediction filter. Thereafter, the band expansion circuit 74 adjusts the gain of the whitened low-frequency subband signal using high-frequency information composed of gain values of the high-frequency subband signal to generate a high-frequency subband signal. .

  Here, whitening has the effect of suppressing the frequency amplitude peak of the low-frequency subband signal. In general, however, the audio signal is higher in the high-frequency subband signal than in the low-frequency subband signal. This is based on statistical properties such as whitening. However, it cannot be said that the high frequency sub-band signal is whitened for an input signal having a large non-stationary characteristic such as a voice, and whitening does not give a good result.

The present invention has been proposed in view of such a conventional situation, and a signal encoding apparatus and method for expanding a frequency band with sufficient quality for an audio signal and a voice signal, and a signal code are provided. Decoding apparatus and method for decoding compressed data output from an encoding apparatus, a program for causing a computer to execute such signal encoding processing and signal decoding processing, and a computer-readable recording medium on which the program is recorded The purpose is to provide.

  In order to achieve the above-described object, a signal encoding apparatus and method according to the present invention divides a time-series signal into a plurality of subbands and a high frequency subband signal composed of low frequency subbands. A high-frequency subband signal composed of subbands on the band side, and then encoding the low-frequency subband signal to generate low-frequency subband signal encoded data. Generates a new high frequency subband signal, compares the frequency amplitude of the new high frequency subband signal with the original high frequency subband signal, generates high frequency subband signal frequency amplitude information, Compares the gain of the new high frequency subband signal generated from the low frequency subband signal with the original high frequency subband signal to generate high frequency subband signal gain information, and then generates the low frequency subband signal code. Data and high frequency subvan Multiplexes the signal frequency amplitude information and high frequency subband signal gain information and outputs the compressed data.

  In addition, in order to achieve the above-described object, the signal decoding apparatus and method according to the present invention includes a low-frequency subband encoded data, a high-frequency subband signal frequency amplitude information, and a high-frequency subband by demultiplexing the compressed data. After being separated into signal gain information, the low-frequency subband signal encoded data is decoded to generate a low-frequency subband signal, and then the low-frequency subband signal is folded back to the high frequency side to generate the frequency of the subband signal. Performs band expansion and adjusts the frequency amplitude using the high frequency subband signal frequency amplitude information, and then adjusts the gain of the high frequency subband signal whose frequency amplitude has been adjusted using the high frequency subband signal gain information After that, the low-frequency sub-band signal and the high-frequency sub-band signal whose frequency amplitude peak and gain are adjusted are sub-band synthesized to output a time-series signal.

  A program according to the present invention causes a computer to execute the above-described signal encoding process or signal decoding process, and a recording medium according to the present invention can be read by a computer in which such a program is recorded. It is.

  According to the signal encoding apparatus and method, the signal decoding apparatus and method, the program, and the recording medium according to the present invention, when the frequency band is limited on the encoding side, the high frequency subband signal frequency amplitude information and the high frequency subband signal The frequency of the high frequency subband signal generated on the decoding side is generated by adjusting the frequency amplitude and gain of the high frequency subband signal using the two pieces of information when generating gain information and expanding the frequency band on the decoding side. Since the amplitude and gain coincide with the frequency amplitude and gain of the original high-frequency subband signal, the time-series signal can be reproduced with high quality.

It is a figure which shows the structure of the signal encoding apparatus in this Embodiment. It is a figure which shows the frequency return of the subband signal by a frequency aliasing method. It is a 3-bit quantization table used for quantization of high frequency subband signal frequency amplitude peak information. It is a figure which shows the structure of the signal encoding apparatus in this Embodiment. It is a figure which shows the structure of the signal decoding apparatus in this Embodiment. It is a 2-bit quantization table used for quantization of high frequency subband signal frequency amplitude peak information. It is a figure which shows the structure of the signal decoding apparatus which performs the band expansion by HE-AAC.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  First, the signal encoding apparatus in the present embodiment will be described.

  As shown in FIG. 1, the signal encoding device 10 according to the present embodiment includes a subband division filter bank 11, a low frequency subband signal encoding circuit 12, and a high frequency subband signal frequency amplitude peak information generation circuit 13. And a high frequency sub-band signal gain information generation circuit 14 and a multiplexing circuit 15.

  The subband division filter bank 11 divides an input time-series signal into a plurality of subbands, and converts a lowband subband signal composed of a plurality of lowband subbands into a lowband subband signal encoding circuit. 12, the high frequency subband signal frequency amplitude peak information generation circuit 13, and the high frequency subband signal gain information generation circuit 14.

  The subband division filter bank 11 converts a highband subband signal composed of a plurality of highband subbands into a highband subband signal frequency amplitude peak information generation circuit 13 and highband subband signal gain information. This is supplied to the generation circuit 14.

  Here, the subband signal is x (k, n), and the value of k is k = 0, 1, 2,..., N−1. k indicates a subband, and N indicates the number of subband divisions. N represents a time index. Regarding the value of k, 0 indicates the lowest subband and N-1 indicates the highest subband. Further, in x (k, n), the entire subband signal with k = 0, 1, 2,..., N / 2−1 is a low frequency subband signal, and k = N / 2, N / 2 + 1. , N / 2 + 2,..., N−1 are all high-band subband signals.

  Although the number of subbands is set to N / 2 on both the low frequency side and the high frequency side, in the present embodiment, the number of subbands on the low frequency side and the high frequency side need not be the same. Of the subbands, the ratio of the number of subbands between the low frequency side and the high frequency side is not limited.

  The low frequency subband signal encoding circuit 12 encodes the low frequency subband signal x (k, n) and supplies the low frequency subband signal encoded data to the multiplexing circuit 15.

  The high frequency subband signal frequency amplitude peak information generation circuit 13 generates a new high frequency subband signal generated from the low frequency subband signal x (k, n) and the original high frequency subband signal x (k, n). ) And the frequency amplitude peak for each subband, and the high frequency subband signal frequency amplitude peak information is generated. Thereafter, the high frequency subband signal frequency amplitude peak information generation circuit 13 supplies the high frequency subband signal frequency amplitude peak information to the multiplexing circuit 15. The details of the method in which the high frequency subband signal frequency amplitude peak information generation circuit 13 generates the high frequency subband signal frequency amplitude peak information will be described later.

  The high frequency subband signal gain information generation circuit 14 generates a new high frequency subband signal generated from the low frequency subband signal x (k, n), the original high frequency subband signal x (k, n), and Are compared with each other to generate high frequency subband signal gain information. Thereafter, the high frequency subband signal gain information generation circuit 14 supplies the high frequency subband signal gain information to the multiplexing circuit 15. The details of the method in which the high frequency subband signal gain information generation circuit 14 generates the high frequency subband signal gain information will be described later.

  The multiplexing circuit 15 multiplexes the low frequency subband signal encoded data, the high frequency subband signal frequency amplitude peak information, and the high frequency subband signal gain information, and outputs compressed data.

  Here, the above-described high frequency subband signal frequency amplitude peak information generation circuit 13 and high frequency subband signal gain information generation circuit 14 generate high frequency subband signal frequency amplitude peak information and high frequency subband signal gain information, respectively. The method of performing will be described in detail.

  First, a method in which the high frequency subband signal frequency amplitude peak information generation circuit 13 described above generates high frequency subband signal frequency amplitude peak information will be described.

  The high frequency subband signal frequency amplitude peak information generation circuit 13 first folds back the low frequency subband signal x (k, n) by a frequency aliasing method (see, for example, US Pat. No. 5,068,899).

  In this frequency aliasing method, as shown in FIG. 2, the high frequency subband signal frequency amplitude peak information generation circuit 13 folds back the low frequency subband signal x (k, n) in the N / 2th subband. . For example, a high frequency subband signal with i = N-1 corresponds to a low frequency subband signal with k = 0, and a high frequency subband signal with i = N-3 is a low frequency subband signal with k = 2. Corresponding to

  When the high frequency subband signal obtained by the frequency folding is xa (i, n), the high frequency subband signal xa (i, n) and the low frequency subband signal x (k, n) are as follows. It has the relationship represented by Formula (1).

  Next, the high-frequency subband signal frequency amplitude peak information generation circuit 13 obtains Xa (i, ω) by performing a discrete Fourier transform on the high-frequency subband signal xa (i, n) obtained by frequency folding. Here, ω = 0, 1, 2,..., M−1, ω represents a frequency index of discrete Fourier transform, and M represents a transform block length of discrete Fourier transform. The high frequency subband signal frequency amplitude peak information generation circuit 13 performs discrete Fourier transform on the original high frequency subband signal x (k, n) to obtain X (k, ω). Here, ω = 0, 1, 2,..., M−1.

  Subsequently, the high frequency subband signal frequency amplitude peak information generation circuit 13 determines the maximum value of the frequency amplitude | Xa (i, ω) | of the high frequency subband signal xa (i, n) obtained by frequency folding as Xa. Let (i) max be the maximum value of the frequency amplitude | X (k, ω) | of the original high-frequency subband signal x (k, n) is X (k) max. The high frequency subband signal frequency amplitude peak information generation circuit 13 generates a subband of the high frequency subband signal xa (i, n) obtained by frequency folding and the original high frequency subband signal x (k, n). Since the gain is different for each, Xa (i) max is normalized by the following equation (2).

  Thereafter, the high frequency subband signal frequency amplitude peak information generation circuit 13 calculates the high frequency subband signal frequency amplitude peak information p (i) by the following equation (3).

  The high frequency sub-band signal frequency amplitude peak information generation circuit 13 quantizes the high frequency sub-band signal frequency amplitude peak information p (i) using, for example, a 3-bit quantization table shown in FIG. The subband signal frequency amplitude peak information p (i) is supplied to the multiplexing circuit 15.

  As a method for newly generating a high frequency subband signal xa (i, n) using a low frequency subband signal, in addition to the frequency aliasing method, a frequency shift method (for example, US Pat. No. 4,667,730) Or the like may be used.

  Next, a method for generating the high frequency subband signal gain information g (i) by the high frequency subband signal gain information generation circuit 14 described above will be described in detail.

  First, the high frequency subband signal gain information generation circuit 14 folds back the low frequency subband signal x (k, n) by the above-described frequency aliasing method.

  Next, the high frequency band sub-band signal gain information generation circuit 14 subtracts the high frequency band sub-band signal xa (i, n) obtained by the frequency folding and the original high frequency band sub-band signal x (k, n). High frequency sub-band signal gain information g (i) indicating a gain difference for each band is calculated by the following equation (4).

  Here, B represents a sample interval, and g (i) represents high frequency subband signal gain information from a certain time b to the B sample interval.

  Thereafter, the high frequency sub-band signal gain information generation circuit 14 encodes the high frequency sub-band signal gain information g (i), and the encoded high frequency sub-band signal gain information g (i) is sent to the multiplexing circuit 15. Supply. Note that differential quantization and Huffman coding can be used for encoding g (i), and methods well known by those skilled in the art may also be used.

  As described above, the signal encoding apparatus 10 according to the present embodiment includes the high frequency subband signal frequency amplitude peak information p (i) and the high frequency subband signal gain information g in addition to the low frequency subband signal encoded data. (I) is generated, and the low-frequency sub-band signal encoded data and the two pieces of information are sent to a signal decoding device to be described later. Based on these two pieces of information, the signal decoding apparatus adjusts the frequency amplitude peak and gain of the high-frequency subband signal xa (i, n) obtained by frequency band expansion.

By the way, in the signal encoding device 10 described above, the low-frequency subband signal x (k, k) before encoding.
n) generated high frequency subband signal xa (i, n) is compared with the original high frequency subband signal x (k, n), high frequency subband signal frequency amplitude peak information, Subband signal gain information. On the other hand, in the signal decoding apparatus, the frequency amplitude peak and gain of the high frequency subband signal xa (i, n) generated from the encoded and decoded low frequency subband signal x (k, n) are Adjustment is made by subband signal frequency amplitude peak information and high frequency subband signal gain information.

  Since the low-frequency subband signal x (k, n) is strictly different between before and after encoding, the original high-frequency subband signal and a high frequency amplitude peak and gain adjusted by the signal decoding apparatus are used. Strictly speaking, the frequency amplitude peak and gain of the subband signal are different.

  Therefore, the signal encoding apparatus may generate high frequency subband signal frequency amplitude peak information and high frequency subband signal gain information from the encoded and decoded low frequency subband signal decoded data.

  FIG. 4 shows the configuration of the signal encoding apparatus in this case. The same components as those of the signal encoding device 10 of FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the signal encoding device 20, after the low frequency subband signal encoding circuit 12 generates the low frequency subband signal encoded data, the low frequency subband signal decoding circuit 26 decodes the low frequency subband signal encoded data. To do. The low frequency subband signal decoding circuit 26 supplies the low frequency subband signal decoded data to the low frequency subband signal frequency amplitude peak information generation circuit 13 and the high frequency subband signal gain information generation circuit 14. Thereafter, the high frequency subband signal frequency amplitude peak information generation circuit 13 generates a new high frequency subband signal xa (i, n) generated from the low frequency subband signal decoded data and the original high frequency subband signal x ( k, n) and the frequency amplitude peak for each subband are compared, and high frequency subband signal frequency amplitude peak information is generated. Further, the high frequency subband signal gain information generation circuit 14 generates a new high frequency subband signal xa (i, n) generated from the low frequency subband signal decoded data and the original high frequency subband signal x (k, The gain in each subband is compared with n), and high frequency subband signal gain information is generated.

  As a result, it is possible to relieve the distortion of the processing of encoding and decoding of the low frequency subband signal, and to generate high frequency subband signal frequency amplitude peak information and high frequency subband signal gain information with high quality.

  Next, a signal decoding apparatus according to the present embodiment that generates a high-frequency subband signal using the compressed data described above will be described.

As shown in FIG. 5, the signal decoding device 30 in the present embodiment includes a demultiplexing circuit 31,
The low band subband signal decoding circuit 32, the high band subband signal frequency amplitude peak adjustment circuit 33, the high band subband signal gain adjustment circuit 34, and the subband synthesis filter bank 35 are configured.

  The demultiplexing circuit 31 demultiplexes the compressed data input from the signal encoding device 10, and performs low frequency subband encoded data, high frequency subband signal frequency amplitude peak information p (i), and high frequency subbands. The band signal gain information g (i) is supplied to the low frequency subband signal decoding circuit 32, the high frequency subband signal frequency amplitude peak adjustment circuit 33, and the high frequency subband signal gain adjustment circuit 34, respectively.

  The low frequency subband signal decoding circuit 32 decodes the low frequency subband signal encoded data, converts the low frequency subband signal x (k, n) to the high frequency subband signal frequency amplitude peak adjustment circuit 33, and subband synthesis. To the filter bank 35.

  Note that the low frequency subband signal generated by the low frequency subband signal decoding circuit 32 is supplied from the subband division filter bank 11 in the signal encoding device 10 and is supplied with the low frequency subband signal x (k, n ) Is strictly different, but here, it is assumed that there is no change in the low-frequency subband signal in the process of encoding and decoding, and x (k) which is the same notation as the low-frequency subband signal before encoding. , N).

  The high frequency sub-band signal frequency amplitude peak adjustment circuit 33 performs frequency band expansion using the low frequency sub-band signal x (k, n), and the high frequency sub-band signal xa (i, i, i) obtained by the frequency band expansion. The frequency amplitude peak of n) is adjusted by high frequency subband signal frequency amplitude peak information. Then, the high frequency sub-band signal xap (i, n) having the frequency amplitude peak adjusted is supplied to the high frequency sub-band signal gain adjusting circuit 34. Details of how the high frequency subband signal frequency amplitude peak adjustment circuit 33 adjusts the frequency amplitude peak will be described later.

  The high frequency subband signal gain adjustment circuit 34 adjusts the gain of the high frequency subband signal xap (i, n) whose frequency amplitude peak has been adjusted according to the high frequency subband signal gain information, and the frequency amplitude peak and gain are adjusted. The high frequency sub-band signal xapg (i, n) thus supplied is supplied to the sub-band synthesis filter bank 35. Details of how the high frequency subband signal gain adjustment circuit 34 adjusts the gain will be described later.

  The subband synthesis filter bank 35 performs subband synthesis on the low frequency subband signal x (k, n) and the high frequency subband signal xapg (i, n), and outputs a time series signal.

  Here, the above-described method in which the high frequency subband signal frequency amplitude peak adjustment circuit 33 adjusts the frequency amplitude peak of the high frequency subband signal xa (i, n), and the high frequency subband signal gain adjustment circuit 34 include: Each method for adjusting the gain of the high frequency subband signal xap (i, n) whose frequency amplitude peak has been adjusted will be described in detail.

  First, a method in which the high frequency subband signal frequency amplitude peak adjustment circuit 33 adjusts the frequency amplitude peak of the high frequency subband signal xa (i, n) will be described.

  First, the high frequency sub-band signal frequency amplitude peak adjustment circuit 33 uses the low frequency sub-band signal x (k, n) to expand the frequency band by the above-described frequency aliasing method, and the high frequency sub-band signal xa ( i, n).

  Next, the high frequency subband signal frequency amplitude peak adjustment circuit 33 adjusts the gain of the frequency amplitude peak for the high frequency subband signal xa (i, n) obtained by the frequency band expansion by the following equation (5). Do.

  Here, noise (n) is a signal uncorrelated with xa (k, n) and has an average gain G. C (k) is a normalization coefficient for making the power of noise (n) equal to the power of xa (k, n), and is calculated by the following equation (6).

  The power of the uncorrelated signal noise (n) having the average gain G becomes equal to the power of xa (k, n) in the T sample interval by multiplying the normalization coefficient c (k). In Expression (5), the powers of xa (k, n) and noise (n) * c (k) are the same, and xa (k, n) is determined by the high frequency subband signal frequency amplitude peak information p (i). ) And noise (n) * c (k) are adjusted.

  Thereafter, the high frequency sub-band signal frequency amplitude peak adjustment circuit 33 supplies the high frequency sub-band signal xap (i, n) having the frequency amplitude peak adjusted to the high frequency sub-band signal gain adjustment circuit 34.

  Next, a method in which the high frequency sub-band signal gain adjustment circuit 34 adjusts the gain of the high frequency sub-band signal xap (i, n) whose frequency amplitude peak has been adjusted will be described.

  The high frequency subband signal gain adjustment circuit 34 uses the high frequency subband signal gain information g (i) to calculate the gain of the high frequency subband signal xap (i, n) whose frequency amplitude peak has been adjusted as follows: The high frequency sub-band signal xapg (i, n) is generated by adjusting according to (7).

  As a result, the gain of the high frequency subband signal xapg (i, n) is the same as the gain of the original high frequency subband signal x (k, n).

  Thus, the subband signal generated by the signal decoding device 30 has the same frequency amplitude peak and gain over the entire frequency band as the original subband signal x (k, n) used in the signal encoding device 10. Become. As a result, the signal decoding device 30 can output a time-series signal with high quality.

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

  In the embodiment described above, 3 bits are used when quantizing the high frequency subband signal frequency amplitude peak information p (i), but the high frequency subband signal xapg (i) obtained by frequency band expansion is used. And the original high frequency sub-band signal x (k, n) only need to have the same timbre tone, so that a quantization bit length that cannot be detected by human hearing may be used.

  For example, the quantization bit length of the high frequency subband signal frequency amplitude peak information p (i) may be shortened on the high frequency side by utilizing the characteristic that human auditory sensitivity becomes dull at high frequency. As an example of this, the 3-bit quantization table shown in FIG. 3 is used for subbands less than i = 3 / 4N, and the 2-bit quantization shown in FIG. 6 is used for subbands greater than i = 3 / 4N. A table may be used.

  In addition, for example, by utilizing the characteristic that the human auditory sensitivity becomes dull for a subband signal with a weak power level, the frequency amplitude of the high frequency subband signal corresponding to the power level of the subband signal is set for each subband. The quantization bit length of the peak information p (i) may be changed. As an example of this, in the case of a subband signal of a certain power level or higher, the 3-bit quantization table shown in FIG. 3 is used, and for the subband signal of less than a certain power level, the 2-bit quantization table of FIG. 6 is used. May be.

  Furthermore, in the above-described embodiment, the high frequency subband signal frequency amplitude peak information generation circuit 13 supplies the high frequency subband signal frequency amplitude peak information p (i) for each subband to the multiplexing circuit 15. By utilizing the characteristic that the human auditory sensitivity becomes dull at the frequency band, the high frequency subband signal frequency amplitude peak information p (i) is shared by a plurality of subbands, and the high frequency subband signal frequency amplitude peak information p ( The data amount of i) may be reduced. As an example of this, when a 16-band high-frequency subband signal xa (i, n) is obtained by frequency band expansion, it is divided into 3 subbands, 3 subbands, 5 subbands, and 8 subbands from the low frequency side. The high frequency subband signal frequency amplitude peak information p (i) may be shared by the plurality of subbands and supplied to the multiplexing circuit 15.

  In the above-described embodiment, the hardware configuration has been described. However, the present invention is not limited to this, and any processing can be realized by causing a CPU (Central Processing Unit) to execute a computer program. It is. In this case, the computer program can be provided by being recorded on a recording medium, or can be provided by being transmitted via the Internet or another transmission medium.

  DESCRIPTION OF SYMBOLS 10 Signal coding apparatus, 11 Subband division | segmentation filter bank, 12 Low frequency subband signal encoding circuit, 13 High frequency subband signal frequency amplitude peak information generation circuit, 14 High frequency subband signal gain information generation circuit, 15 Multiplexing Circuit, 20 signal encoding device, 26 low frequency subband signal decoding circuit, 30 signal decoding device, 31 demultiplexing circuit, 32 low frequency subband signal decoding circuit, 33 high frequency subband signal frequency amplitude peak adjusting circuit, 34 High frequency subband signal gain adjustment circuit, 35 subband synthesis filter bank

Claims (8)

In a signal encoding device that encodes an input time-series signal,
The time-series signal is divided into a plurality of subbands, and a low-frequency subband signal composed of a plurality of low-frequency subbands and a high-frequency subband signal composed of a plurality of high-frequency subbands. A dividing means to generate;
Encoding means for encoding the low frequency subband signal and generating low frequency subband signal encoded data;
A new high frequency subband signal is generated from the low frequency subband signal, the frequency amplitude of the new high frequency subband signal and the high frequency subband signal are compared, and the high frequency subband signal frequency amplitude information is obtained. High frequency subband signal frequency amplitude information generating means for generating;
A new high frequency sub-band signal is generated from the low frequency sub-band signal, and the gains of the new high frequency sub-band signal and the high frequency sub-band signal are compared for each sub-band, and the high frequency sub-band signal gain High frequency subband signal gain information generating means for generating information;
A signal encoding device comprising: output means for multiplexing the low frequency subband signal encoded data, the high frequency subband signal frequency amplitude information, and the high frequency subband signal gain information and outputting compressed data. In a signal encoding method for encoding an input time series signal,
The time-series signal is divided into a plurality of subbands, and a low-frequency subband signal composed of a plurality of low-frequency subbands and a high-frequency subband signal composed of a plurality of high-frequency subbands. A splitting process to be generated;
An encoding process for encoding the low frequency subband signal and generating low frequency subband signal encoded data;
A new high frequency subband signal is generated from the low frequency subband signal, the frequency amplitude of the new high frequency subband signal and the high frequency subband signal are compared, and the high frequency subband signal frequency amplitude information is obtained. A high frequency sub-band signal frequency amplitude information generation step to generate;
A new high-frequency sub-band signal is generated from the low-frequency sub-band signal, and the gains of the new high-frequency sub-band signal and the high-frequency sub-band signal are compared for each sub-band. A high frequency sub-band signal gain information generating step for generating information;
A signal encoding method comprising: an output step of multiplexing the low frequency subband signal encoded data, the high frequency subband signal frequency amplitude information, and the high frequency subband signal gain information and outputting compressed data. In a program for causing a computer to execute signal encoding processing for encoding an input time-series signal,
The time-series signal is divided into a plurality of subbands, and a low-frequency subband signal composed of a plurality of low-frequency subbands and a high-frequency subband signal composed of a plurality of high-frequency subbands. A splitting process to be generated;
An encoding process for encoding the low frequency subband signal and generating low frequency subband signal encoded data;
A new high frequency subband signal is generated from the low frequency subband signal, the frequency amplitudes of the new high frequency subband signal and the high frequency subband signal are compared, and the high frequency subband signal frequency amplitude information is obtained. A high frequency sub-band signal frequency amplitude information generation step to generate;
A new high frequency sub-band signal is generated from the low frequency sub-band signal, and the gains of the new high frequency sub-band signal and the high frequency sub-band signal are compared for each sub-band, and the high frequency sub-band signal gain A high frequency sub-band signal gain information generating step for generating information;
A signal encoding process including: an output step of multiplexing the low frequency sub-band signal encoded data, the high frequency sub-band signal frequency amplitude information, and the high frequency sub-band signal gain information and outputting compressed data is executed on a computer Program to make. In a computer-readable recording medium on which a program for causing a computer to execute a signal encoding process for encoding an input time-series signal is recorded,
The time-series signal is divided into a plurality of subbands, and a low-frequency subband signal composed of a plurality of low-frequency subbands and a high-frequency subband signal composed of a plurality of high-frequency subbands. A splitting process to be generated;
An encoding process for encoding the low frequency subband signal and generating low frequency subband signal encoded data;
A new high frequency subband signal is generated from the low frequency subband signal, the frequency amplitudes of the new high frequency subband signal and the high frequency subband signal are compared, and the high frequency subband signal frequency amplitude information is obtained. A high frequency sub-band signal frequency amplitude information generation step to generate;
A new high frequency sub-band signal is generated from the low frequency sub-band signal, and the gains of the new high frequency sub-band signal and the high frequency sub-band signal are compared for each sub-band, and the high frequency sub-band signal gain A high frequency sub-band signal gain information generating step for generating information;
A signal encoding process including: an output step of multiplexing the low frequency sub-band signal encoded data, the high frequency sub-band signal frequency amplitude information, and the high frequency sub-band signal gain information and outputting compressed data is executed on a computer A recording medium on which a program to be recorded is recorded. In a signal decoding apparatus that decodes compressed data input from the encoding side and outputs a time-series signal,
Separating means for demultiplexing the compressed data and separating it into low band sub-band encoded data, high band sub-band signal frequency amplitude information and high band sub-band signal gain information,
A low frequency subband signal decoding means for decoding the low frequency subband signal encoded data and generating a low frequency subband signal;
High frequency subband signal frequency amplitude adjusting means for performing frequency band expansion of the subband signal by folding the low frequency subband signal to the high frequency side and adjusting the frequency amplitude using the high frequency subband signal frequency amplitude information; ,
High frequency subband signal gain adjusting means for adjusting the gain of the high frequency subband signal whose frequency amplitude has been adjusted by the high frequency subband signal frequency amplitude adjusting means, using the high frequency subband signal gain information;
A signal decoding device comprising: output means for combining the low frequency subband signal and the high frequency subband signal whose gain is adjusted by the high frequency subband signal gain adjusting means and outputting a time-series signal. In a signal decoding method for decoding compressed data input from an encoding side and outputting a time-series signal,
A demultiplexing step of demultiplexing the compressed data into low band subband encoded data, high band subband signal frequency amplitude information, and high band subband signal gain information;
A low frequency subband signal decoding step of decoding the low frequency subband signal encoded data and generating a low frequency subband signal;
A high-frequency sub-band signal frequency amplitude adjusting step for performing frequency band expansion of the sub-band signal by folding the low-frequency sub-band signal to the high frequency side and adjusting the frequency amplitude using the high-frequency sub-band signal frequency amplitude information; ,
A high-frequency sub-band signal gain adjusting step for adjusting a gain of the high-frequency sub-band signal whose frequency amplitude is adjusted by the high-frequency sub-band signal frequency amplitude adjusting step using the high-frequency sub-band signal gain information;
An output step of combining the low frequency subband signal and the high frequency subband signal whose gain is adjusted by the high frequency subband signal gain adjustment step, and outputting a time-series signal. In a program for causing a computer to execute signal decoding processing for decoding compressed data input from an encoding side and outputting a time-series signal,
A demultiplexing step of demultiplexing the compressed data into low band subband encoded data, high band subband signal frequency amplitude information, and high band subband signal gain information;
A low frequency subband signal decoding step of decoding the low frequency subband signal encoded data and generating a low frequency subband signal;
A high-frequency sub-band signal frequency amplitude adjusting step for performing frequency band expansion of the sub-band signal by folding the low-frequency sub-band signal to the high frequency side and adjusting the frequency amplitude using the high-frequency sub-band signal frequency amplitude information; ,
A high-frequency sub-band signal gain adjusting step for adjusting a gain of the high-frequency sub-band signal whose frequency amplitude is adjusted by the high-frequency sub-band signal frequency amplitude adjusting step using the high-frequency sub-band signal gain information;
An output step of combining the low-frequency subband signal and the high-frequency subband signal whose gain has been adjusted by the high-frequency subband signal gain adjustment step and outputting a time-series signal to a computer. The program to be executed. In a computer-readable recording medium recorded with a program for causing a computer to execute a signal decoding process for decoding compressed data input from the encoding side and outputting a time-series signal,
A demultiplexing step of demultiplexing the compressed data into low band subband encoded data, high band subband signal frequency amplitude information, and high band subband signal gain information;
A low frequency subband signal decoding step of decoding the low frequency subband signal encoded data and generating a low frequency subband signal;
A high-frequency sub-band signal frequency amplitude adjusting step for performing frequency band expansion of the sub-band signal by folding the low-frequency sub-band signal to the high frequency side and adjusting the frequency amplitude using the high-frequency sub-band signal frequency amplitude information; ,
A high-frequency sub-band signal gain adjusting step for adjusting a gain of the high-frequency sub-band signal whose frequency amplitude is adjusted by the high-frequency sub-band signal frequency amplitude adjusting step using the high-frequency sub-band signal gain information;
An output step of combining the low-frequency subband signal and the high-frequency subband signal whose gain is adjusted by the high-frequency subband signal gain adjustment step and outputting a time-series signal to a computer. A recording medium on which a program to be executed is recorded.

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