JP3230365B2 - Information encoding method and apparatus, and information decoding method and apparatus - Google Patents

Abstract

PURPOSE:To reduce a processing amount at the time of encoding, to simplify constitution and to reduce the cost by performing an actual conversion processing only in a required band and encoding signals based on specified band information or the like. CONSTITUTION:Processing band control information from a terminal 706 is supplied to a processing band control circuit 704 and the processing bands of a frequency component decomposition circuit 701, a normalization and quantization circuit 702 and a code sequence generation circuit 703 are controlled based on the information. Then, the frquency component decomposition circuit 701 performs the processing of only the required band based on the control information sent from the processing band control circuit 704 to the frequency component decomposition circuit 701. Also, the normalization and quantization circuit 702 and the code sequence generation circuit 703 similarly perform only the processing in the required band based on the respective pieces of the control information from the processing band control circuit 704. By performing only the processings in the required band in such a manner, an arithmetic processing amount is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information encoding method which encodes input digital data by so-called high-efficiency encoding, and transmits, records, reproduces and decodes the data to obtain a reproduced signal. The present invention relates to an apparatus and an information decoding method and apparatus.

[0002]

2. Description of the Related Art Hitherto, various methods for highly efficient encoding of a signal such as audio or voice have been known. For example, an audio signal or the like on a time axis is divided into a plurality of frequency bands without being blocked. Division coding (sub-band coding: SBC), which is a non-blocking frequency band division method for performing coding, and converting a signal on the time axis into a signal on the frequency axis (spectral conversion) to generate a plurality of frequency bands , And a coding frequency band division method for encoding for each band, so-called conversion encoding. Further, a high-efficiency coding method combining the above-described band division coding and transform coding is also considered.In this case, for example, after performing band division by the band division coding, The spectrum of the signal for each band is converted into a signal on the frequency axis, and coding is performed for each band that has been subjected to the spectrum conversion.

Here, as a band dividing filter used in the above-mentioned band dividing coding, for example, QM
There is an F filter, and this QMF filter is described in the document "Digital Coding of Speech in
Subbands "(Digital coding of speech in subbands,
RECrochiere, Bell Syst.Tech.J., Vol.55, No.819
76).

[0004] Also, a document "Polyphase Quadrature Filters-New Band Division Coding Technology" (PoPo
lyphase Quadrature filters -A new subband coding t
echnique, Joseph H. Rothweiler, ICASSP 83 BOSTON)
Describes an equal bandwidth filter division technique.

[0005] The above-mentioned spectral conversion includes:
For example, an input audio signal is divided into blocks in a predetermined unit time (frame), and a discrete Fourier transform (DFT), a cosine transform (DCT), a modified DCT transform (MDCT), or the like is performed for each block, so that the time axis is changed to the frequency axis. There is a spectrum conversion to be performed. The above MDCT is described in the document “Time domain aliasing.
Subband / Transform Coding Using Cancellation-Based Filter Bank Design "(Subband / TransformCoding
Using Filter Bank Designs Based on Time Domain Ali
asing Cancellation, JPPrincen, ABBradley, Uni
v. of Surrey, Royal Melbourne Inst. of Tech. ICASSP
1987).

As described above, by quantizing the signal divided for each band by the filter or the spectrum conversion, the band in which the quantization noise occurs can be controlled.
Aurally more efficient encoding can be performed by utilizing properties such as a masking effect. Further, if the normalization is performed for each band, for example, with the maximum value of the absolute value of the signal component in that band before the quantization is performed, more efficient encoding can be performed.

Here, as a frequency division width when quantizing each frequency component divided into frequency bands, for example, a bandwidth in consideration of human auditory characteristics is often used. That is, an audio signal may be divided into a plurality of bands (for example, 25 bands) in a band called a critical band (critical band) in which the band becomes generally wider as the frequency becomes higher. When encoding data for each band at this time, a predetermined bit distribution for each band or
Encoding by adaptive bit allocation (bit allocation) is performed for each band. For example, when the coefficient data obtained by the MDCT processing is encoded by the bit allocation, the MD of each block is encoded.
The MDCT coefficient data for each band obtained by the CT processing is encoded with an adaptive number of allocated bits. The following two methods are known as bit allocation methods.

[0008] For example, in the document "Adaptive Transform Coding of Speech Signals,
R. Zelinski, P. Noll, IEEE Transactions of Accoust
ics, Speech, and Signal Processing, vol.ASSP-25, N
o.4, August 1977), bit allocation is performed based on the signal magnitude for each band. In this method, the quantization noise spectrum is flattened and the noise energy is minimized, but the actual noise sensation is not optimal because the masking effect is not utilized from the auditory point of view.

Further, for example, in the document “Critical band encoder—
Digital Encoding of Perceptual Requirements of the Auditory System (The critical band coder --digital encodi
ng of the perceptual requirements of the auditory
system, MAKransner MIT, ICASSP 1980) describes a method of obtaining a required signal-to-noise ratio for each band and performing fixed bit allocation by using auditory masking. However, in this method, even when the characteristic is measured with a sine wave input, the characteristic value is not so good because the bit allocation is fixed.

[0010] In order to solve these problems, all bits that can be used for bit allocation include a fixed bit allocation pattern predetermined for each small block and a bit allocation depending on the signal size of each block. A high-efficiency coding apparatus has been proposed in which a division ratio is used to perform the division, the division ratio is made dependent on a signal related to an input signal, and the division ratio into the fixed bit allocation pattern is increased as the spectrum of the signal is smoother. ing.

According to this method, when energy is concentrated on a specific spectrum such as a sine wave input, a large number of bits are allocated to a block including the spectrum, thereby significantly improving the entire signal-to-noise characteristic. can do. In general, human hearing is extremely sensitive to signals having steep spectral components. Therefore, using such a method to improve the signal-to-noise characteristics merely improves the numerical values measured. But not
This is effective for improving sound quality in terms of hearing.

Numerous other methods have been proposed for the bit allocation method. Further, models relating to hearing are refined, and if the capability of the coding device is increased, more efficient coding can be perceived perceptually. Will be possible.

[0013]

However, in order to realize these encoding and decoding means, larger hardware is required as compared with a case where the signal sample value is recorded as it is. In particular, when the signal to be handled covers a wide band including high-frequency components, the number of spectral components to be handled increases, and the sampling frequency also increases.Therefore, the necessary buffer capacity and the amount of arithmetic processing per time become large. Would.

On the other hand, these encoding means and decoding means are generally realized by a circuit composed of a semiconductor. However, the degree of integration and the price of the semiconductor rapidly decrease, and at the same time, the sound quality is reduced. Demand levels are increasing. For example, when encoding a human voice for efficient recording, even if the initial requirement is to understand the content, a more faithful presence is required as the technology level rises. Go. Of course, it is conceivable to raise the standard level by, for example, increasing the bandwidth of the signal to be handled in accordance with the improvement of the technical level. However, when the standard is changed in this way, the signal recorded between the signal and the decoding device is changed. Will be incompatible. In particular, there arises a problem that a decoding means configured based on the old standard cannot reproduce a signal encoded according to the new standard.

The present invention has been made in view of such circumstances, and can simplify processing in accordance with the required quality of a reproduced signal, and can perform coding and encoding at low cost or at high speed. It is an object of the present invention to provide an information encoding method and apparatus and an information decoding method and apparatus capable of performing decoding.

Another object of the present invention is to enable a decoding means to reproduce a signal of a band corresponding to its ability from the same recorded code, and to provide a scale corresponding to the purpose,
An object of the present invention is to make it possible to configure a price decoding means, and to expand the bandwidth of a signal to be recorded while maintaining compatibility in accordance with the capability of a widely used decoding means.

[0017]

In order to solve the above-mentioned problems, an information encoding method according to the present invention performs actual conversion processing only in a necessary band based on designated band information and the like. It encodes the signal.

Further, the information decoding method according to the present invention reproduces a signal by performing conversion processing for actual decoding only in a necessary band based on information described in a code to be decoded. It is.

Further, in another information decoding method according to the present invention, the decoding means selects a necessary code portion from the input code based on a band which can be actually decoded by the decoding means itself. It reproduces a signal of a bandwidth corresponding to the capability.

That is, an information encoding method according to the present invention comprises a frequency component decomposing means, and a means for encoding the frequency component obtained by the frequency component decomposing means. The processing of the component decomposition may be omitted. An information encoding device to which this method is applied can be configured.

Further, the information decoding method according to the present invention comprises a processing band control means, a frequency component code decoding means, and a waveform signal synthesizing means for synthesizing a waveform signal from the frequency component obtained by the frequency component decoding means. The waveform signal synthesizing unit may omit the process of synthesizing the waveform signal for some bands based on the control of the processing band control unit. An information decoding device to which this method is applied can be configured.

Further, another information decoding method according to the present invention comprises an information selecting means, a frequency component code decoding means,
A waveform signal synthesizing unit for synthesizing a waveform signal from the frequency component obtained by the frequency component decoding unit, wherein the waveform signal synthesizing unit extracts only a part of information included in the input code string selected by the information selecting unit. In this case, the process of synthesizing the waveform signal is omitted for some bands. An information decoding device to which this method is applied can be configured.

In these methods or apparatuses, a processing band control means is provided, and the control as to whether or not to omit the frequency component decomposition processing for some of the bands is performed by the processing band control means. . Further, it is preferable that the band from which the processing of the frequency component decomposition is omitted is a band on the high frequency side. Further, it is preferable that the frequency decomposition means is constituted by a band division filter means and a spectrum conversion means.

The input signal or the output signal may be an audio signal or an image signal.

[0025]

By performing actual conversion processing for encoding or decoding only in a necessary band, the processing is simplified, and encoding and decoding can be performed at low cost or at high speed. Also, the decoding means can reproduce a signal of a band corresponding to the capability from the same recorded code, and according to the purpose, it is possible to configure a decoding means of a scale and a price corresponding to the purpose. The bandwidth of the signal to be recorded can be expanded while maintaining compatibility in accordance with the capability of the widely used decoding means.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining an embodiment of an information encoding method according to the present invention. In the embodiment shown in FIG. 1, the input signal is a modified discrete cosine transform,
It is decomposed into spectral components obtained by so-called MDCT or other spectral transformation. The spectral coefficients are grouped for each predetermined band (in this example, nine bands from b1 to b9) and subjected to normalization processing. Here, the normalization processing means that each spectrum coefficient is divided by a normalization coefficient determined by the maximum absolute value of the spectrum coefficient in each band.

Next, the spectral coefficients normalized for each band are requantized with the given number of bits. The method of giving the number of bits may be constant regardless of the input signal, or may be determined depending on the input signal in consideration of masking or the like. By performing the normalization processing, it is possible to efficiently requantize the spectral coefficient in a band including only low-level frequency components with a small number of bits. The original signal can be compressed by reducing the number of bits for requantization.

FIG. 2 is a block diagram schematically showing a configuration to which an embodiment of the information encoding apparatus according to the present invention can be applied. An audio signal input via an input terminal 100 of the encoding device is decomposed into frequency components by a frequency component decomposing means circuit 101. This frequency component is subjected to normalization and requantization for each fixed band by the normalization quantization circuit 102, and thereafter, by the code string generation circuit 103, quantization accuracy information, normalization coefficient information, normalization and The quantized frequency component information is converted into a code string, and extracted from the output terminal 104.

On the other hand, FIG. 3 is a block diagram showing a schematic configuration to which the embodiment of the decoding apparatus according to the present invention corresponding to the encoding apparatus shown in FIG. 2 is applied. Input terminal 2
00 is output to the output terminal 104 shown in FIG.
Corresponding to the output from the code string decoding circuit 20.
The information is separated into quantization accuracy information, normalization coefficient information, and normalized and quantized frequency component information by 1 and sent to an inverse quantization / inverse normalization circuit 202 to generate a frequency component signal. The generated frequency component signal is supplied to a waveform signal synthesis circuit 2
03, is converted into a waveform signal, and is output to an output terminal 204.
Output.

As a method of decomposing into frequency components, spectral conversion means such as the above-described DFT, DCT, MDCT or the like, or a band division filter may be used, but as shown in FIG. A combination of the division filter and the above-described spectrum conversion may be used.

In the example of FIG. 4, the waveform signal input from the input terminal 300 is divided by the band division filter circuit 301 into four bands. Each terminal 331, 33
In 2, 333 and 334, signals in the band from the lower frequency are obtained in this order. These signals have a bandwidth of 1/4 of the input waveform signal at the terminal 300, and each sampling rate is 1/4 of the input waveform signal. Therefore, the spectrum conversion circuits 311, 312, 313, and 314 that perform spectrum conversion of these signals are actually １ ／ of the case where the input signal is directly subjected to spectrum conversion.
With the conversion length of, the same frequency resolution can be obtained.
Each spectrum conversion circuit 311, 312, 313, 314
Output from each of the output terminals 321, 322,
323 and 324 respectively.

FIG. 5 shows an example of a waveform signal synthesizing means corresponding to the frequency component decomposing means of FIG. Each input terminal 401, 402, 40 of this waveform signal synthesizing means
3 and 404 are input to each output terminal 32 in FIG.
1, 322, 323, and 324, respectively.

Here, each inverse spectrum conversion circuit 411,
Output terminals 441, 44 from 412, 413, 414
The sampling rates of the signals of the respective bands obtained at 2, 443 and 444 correspond to the respective terminals 331, 332 and 33 in FIG.
3 and 334, respectively. By combining the signals of the respective bands obtained at these terminals 441, 442, 443, and 444 with the band combining filter 421, a waveform signal can be reproduced, and the combined waveform signal is output from the output terminal 431. Taken out.

FIGS. 6 and 7 show examples of the configuration of the band division filter circuit 301 of FIG. 4 and the band synthesis filter circuit 421 of FIG. 5, respectively. That is, FIG.
, A QMF circuit 501, 511, 512 for dividing an input signal from a terminal 500 into a high-frequency signal and a low-frequency signal.
Are combined, for example, the band division filter circuit 3 of FIG.
01, each terminal 521, 522, 523, 52
From No. 4, signals in the band from the lower frequency are obtained in this order. In FIG. 7, three IQMF circuits 611, 612, and 621 for combining signals in two bands divided by one QMF are combined to form, for example, a band combining filter circuit 421 in FIG. .

As described above, by using the QMF and the IQMF to configure the band division filter means and the band synthesis filter means, it is possible to cancel the effect of aliasing caused by lowering the sampling rate after band division.

Now, consider a case where an audio signal is recorded / reproduced using the above-described encoding apparatus and decoding apparatus. In many acoustic signals, important signal components are concentrated on a specific band, particularly on a low frequency side. Of course, by reproducing higher frequency signal components, the sound quality is improved,
Although a more realistic sound signal can be obtained, it is possible to understand the content of the speech even if only the low-frequency side signal is reproduced, and it is also possible to enjoy music with moderate sound quality.

The above-mentioned encoding / decoding requires a great deal of processing as compared with the case where the waveform signal sample of the original waveform signal is recorded as it is. It would be very useful if you could play it. Such simple encoding means and decoding means are particularly useful in the following cases.

The first case is a case where, for the above-described reason, at the stage of performing signal compression for a certain application, it is finally determined that only the low-frequency side signal is necessary. This is the case when the band of the input signal is restricted in advance, or when the encoding means is instructed to ignore the high-frequency signal. And in terms of decryption,
This is the case where the input code string is composed only of information on the low-frequency side signal, or the case where it is instructed to the decoding means that the high-frequency side signal can be ignored.

The second case is a case where the band reproduced by the decoding means is determined according to the capability of the decoding means.
In this case, decoding is performed by selecting information on a band that can be reproduced by the decoding means itself from the given code string. In this case, different signals are reproduced from the same code string depending on the type of decoding means, but these appear as differences in the sound quality of the reproduced signals. This means that in the process where the cost of the decoding means decreases over time, it is possible to introduce a decoding means that gradually improves the sound quality without causing a compatibility problem. I have.

A method of the present invention for easily encoding or decoding a sound in such a limited band will be described below with reference to the drawings.

FIG. 8 is a block diagram of an embodiment of an encoding apparatus according to the present invention for coping with the first case. The processing band control circuit 704 is provided with processing band control information from the terminal 706, and controls the processing band of the frequency component decomposition circuit 701, the normalization / quantization circuit 702, and the code string generation circuit 703 based on this information. . The processing band control information from the terminal 706 may be input by the operator of the encoding unit, or may be supplied from a band limiting filter (not shown in FIG. 8) that supplies an input signal to the terminal 700. good.

The frequency component decomposing circuit 701 has the same configuration as the frequency component decomposing circuit 101 of FIG. 2, but has only the necessary band based on the control information sent from the processing band control circuit 704 to the frequency component decomposing circuit 101. Perform processing. For example, when encoding a signal only in the band from b1 to b6 in FIG. 1, the spectrum conversion means 313 and 314 in FIG. 4 that processes a high-frequency signal do not perform processing. In the case where the band division filter means of FIG. 4 has the configuration of FIG. 6, the processing of the QMF circuit 512 of FIG.

Similarly, the normalization / quantization circuit 702 and the code string generation circuit 703 shown in FIG.
Only the processing in the necessary band is performed based on each control information from. By performing only the processing in the necessary band in this way, the amount of calculation processing can be significantly reduced,
High-speed processing can be performed at low cost, and the power consumed by the circuit can be reduced when the processing is performed by an electric circuit.

Note that this encoding device or method is not necessarily limited to one that processes an input audio signal or the like in real time. For example, when compressing the information of a file in which the sample value of a waveform signal is recorded as it is and recording the information on a magneto-optical disk or the like, the earlier the processing is, the more convenient the processing is. Doing it has a great meaning.

The configuration of the frequency component decomposing circuit 701 does not necessarily have to be the same as that shown in FIGS. 4 and 6, but can be smaller than the initial configuration, for example, the configuration shown in FIGS. 11 and 12. It may be. FIG.
4 receives the same signal as the band division filter circuit 301 of FIG. 4, but outputs only the low-frequency side signal, and sends them to the spectrum conversion circuits 811 and 812. Spectrum conversion circuit 81
1, 812 are the spectrum conversion circuits 311, 31 of FIG.
The same processing as in step 2 is performed. FIG. 12 shows an example of the configuration of the band division filter circuit 801. Except that the output of the QMF circuit 821 is only on the low band side, the QMF circuit 821,
831 performs the same processing as the QMF circuits 501 and 511 in FIG. 6, respectively. In this case, the processing band control circuit 704 in FIG. 8 does not need to be particularly provided.

FIG. 15 shows an example of a code string for one block obtained by performing the encoding process in this manner. In this example, first, the number n _Q of quantization accuracy information, for example, a value of n _Q = 6, is recorded at the head, and then the quantization accuracy information Q and the normalization coefficient information K up to the band actually coded. , Spectrum coefficient information S is recorded. Various other methods are possible for recording the encoded sequence, for example,
Instead of recording the number of quantization accuracy information, dummy quantization accuracy information, for example, information that the number of quantization bits is 0 may be recorded in the bands b7, b8, and b9.

Next, FIG. 9 is a block diagram of an embodiment of a decoding device according to the present invention for coping with the first case. The code string decoding circuit 711 takes, for example, a code string as shown in FIG. 15 as an input signal, and supplies information for restoring the normalized and quantized spectral coefficients to the inverse quantization / inverse normalization circuit 712. At the same time, the number of quantization accuracy information is sent to the processing band control circuit 714. The processing band control 714 calculates a band required for processing necessary for decoding from the number of pieces of quantization accuracy information, and performs inverse quantization and inverse normalization 712.
The control is performed so that the processing of the waveform signal synthesizing circuit 713 is performed only in a necessary band. As in the case of the encoding device shown in FIG. 8, for example, the processing of the inverse spectrum conversion circuits 413 and 414 in FIG. 5 and the IQMF circuit 612 in FIG. 7 can be omitted, and the amount of arithmetic processing can be greatly reduced. Therefore, high-speed processing can be performed at low cost, and the power consumed by the circuit can be reduced when the processing is performed by an electric circuit.

It should be noted that the decoding means or method is not limited to processing and outputting audio signals and the like in real time. For example, in the case of decoding a code string that has been compressed into a file and recording the sample value of the waveform signal as it is on a magneto-optical disk or the like, the earlier the processing is, the more convenient it is. Processing has great significance.

Next, FIG. 10 is a block diagram of an embodiment of the decoding means according to the present invention for coping with the second case. The decoding means of this embodiment accepts, for example, a code string as shown in FIG.

The waveform signal synthesizing circuit 724 shown in FIG.
3 and the band combining filter circuit 851 in FIG. 13 has the structure shown in FIG. Here, the inverse spectrum conversion circuits 841 and 842 perform the same processing as the inverse spectrum conversion circuits 411 and 412 in FIG. 5, respectively, and the IQMF circuit 861 performs the same processing as the IQMF circuit 611 in FIG. Also, the IQMF circuit 871
Performs the same processing as the IQMF circuit 621 in FIG. 7 using a signal having a value of 0 instead of the input signal from the terminal 642.

Here, the information selection circuit 722 in FIG.
From the output of the code string decoding circuit 721, information on a band that can be processed by the decoding device is selected. That is, since the decoding means can process only the bands from b1 to b6 in FIG. 1, the information selection circuit 722 selectively reverses only the information in the portions not shaded in FIG. The result is sent to the quantization inverse normalization circuit 723. The inverse quantization / inverse normalization circuit 723 forms each spectral coefficient based on the information, and the waveform signal synthesizing circuit 724 converts these spectral coefficients to synthesize a waveform signal. The processing amount of the waveform signal synthesizing circuit 724 is much smaller than the case of synthesizing signals of all bands, and can be configured by the simple means as described above, or can perform high-speed processing. This decoding means or method is not necessarily limited to processing and outputting an audio signal or the like in real time as in the case of the first case.

As described above, the method of the present invention is effective in both the first case and the second case.
As described above, the effect is great when the spectrum is obtained by dividing the band and then performing spectrum conversion. For example, as described in Japanese Patent Application Laid-Open No. Hei 5-183442, which has been proposed by the present applicant, when performing spectral transformation and inverse spectrum transformation such as MDCT and IMDCT, an arithmetic method of fast Fourier transform (FFT) is used. It is known that these conversions can be realized with a small amount of arithmetic processing by using.
When performing the FFT, for example, as described in the document “Fast Fourier Transform”, E. OranBringham, Miyagawa, Imai translation, Science and Technology Publishing Company, the results of arithmetic processing in the middle are stored. A work area proportional to the length is required, and information in the work area is processed while being shuffled. For this reason, if spectrum conversion is performed using FFT without band division, a large work area is required, and the effect of reduction in arithmetic processing is also reduced.
It is smaller than a method of performing spectrum conversion by performing band division that can omit spectrum conversion in a band where processing is not performed.

The same applies to the decoding, and the inverse conversion of the spectral coefficients subjected to spectrum division after band division into a waveform signal inversely converts the spectral coefficient subjected to spectrum conversion without band division into a waveform signal. A smaller work area is required, and the effect of reducing the arithmetic processing is great. F
In order to perform FT at high speed, these work areas need to be configured so that reading and writing can be performed at sufficiently high speed. However, shortening the conversion length means that the required work area can be reduced. This means that the encoding device and the decoding device can be configured at a lower cost.

FIG. 17 is a processing example of an encoding method for performing processing using the present invention. In this processing example, it is explicitly shown that the processing is performed only by the band of the spectrum conversion. However, the processing is also simplified in the band division filter processing in step S11 as in the case of the above-described encoding means. It is possible to

In FIG. 17, after performing band division filter processing in step S11, steps S12 and S1 are executed.
3. In S14, whether the designated band is larger than Fs / 8 or 2Fs
/ 8 or greater than 3Fs / 8. Then, when the specified bandwidth is larger than 3Fs / 8 performs orthogonal transform of the band b ₄ ~b ₁ at step S15 to S18, it specifies the bandwidth is large than 2Fs / 8 3Fs
/ 8 band b ₃ in step S16~S18 when the following
Performs a spectrum conversion ~b _1, when the specified band is 2Fs / 8 or less large than Fs / 8 step S17, S1
At 8, the spectrum conversion of the bands b ₂ and b ₁ is performed, and when the designated band is equal to or less than Fs / 8, the spectrum conversion of the band b ₁ is performed at step S18. In the next step S19, normalization and quantization of the spectrum signal are performed, and then, in step S20, a code string is generated.

Next, FIG. 18 is a processing example of a decoding method for performing processing using the present invention. In this processing example, it is explicitly shown that processing is performed only by the band of the inverse spectrum transform. However, as in the case of the above-described encoding unit, the processing is also performed in the band synthesis filter processing in step S30. It can be simplified.

In FIG. 18, the code string is decoded in step S21, the spectrum signal is dequantized and denormalized in step S22, and the quantization accuracy is calculated in steps S23, S24 and S25. It is determined whether the number of information is greater than 4, 6, or 8 respectively. When quantizer accuracy information is larger than 8 performs inverse orthogonal transform of a band b ₄ ~b ₁ at step S26 to S29, the bandwidth in step S27~S29 when quantization accuracy information is 8 or less larger than 6 Inverse spectrum conversion of b _{3 to} b ₁ is performed, and when the number of quantization precision information is larger than 4 and equal to or smaller than 6, the inverse spectrum conversion of the bands b ₂ and b ₁ is performed in steps S28 and S29, and and performing inverse orthogonal transform of the band b ₁ in step S29 when the 4 below. In the last step S30, band synthesis filter processing is performed.

Next, FIG. 19 is a processing example of another decoding method for performing processing using the present invention. In the example of FIG. 19, the decoding process of the code string is performed in step S31, and the necessary information is selected in step S32. Only the information selected here is used in the following process. That is, after performing the inverse quantization and inverse normalization processing of the spectrum signal in step S33, step S3
4, S35 is performed only inverse spectrum transform for band b _2, b _1, a is performed band synthesis filtering process in step S36.

Although the above description has been made with respect to the case where the MDCT is used as the spectrum transform, the method of the present invention can be applied to the case where the discrete Fourier transform (DFT) or the discrete cosine transform (DCT) is used. Can be. Further, the method of the present invention can be applied to encoding after band division by a filter without using such special spectral transformation.

Also, the case where the lower band is taken as the band to be actually processed has been described. In addition to this, for example, only the band having a higher actual signal level may be processed. Is also possible. However, in actuality, as described above, for example, an important signal component is distributed in the low frequency side in a normal acoustic signal or the like, and a simple processing is performed by always processing only the low frequency side. A great effect can be obtained by the configuration.

Note that the method of the present invention is applicable to multi-channel audio signals. Further, in the above description, the case where the audio signal is encoded / decoded has been described, but the method of the present invention is also effective when processing other types of signals. However, especially when applied to audio signals and image signals in which important information is concentrated in the low frequency range, the effect is great.

[0063]

As is apparent from the above description, the information encoding method and apparatus according to the present invention omit the above-mentioned frequency component decomposition processing for some bands, and By performing the processing only in the necessary band, the processing amount at the time of encoding can be reduced, the configuration can be simplified, and the cost can be reduced.

Further, the information decoding method and apparatus according to the present invention omit the processing of waveform signal synthesis for some bands under the control of the processing band control means, or Only a part of the information included in the input code string selected by the means is used, and the processing of waveform signal synthesis is omitted for some bands. That is, signal reproduction can be realized by simple processing by performing actual conversion processing only in a necessary band based on information described in a code to be decoded. In addition, the decoding means selects the necessary code portion based on the band that the decoding means itself can actually decode from the input code, and reproduces a signal of a bandwidth corresponding to the capability, thereby reducing the cost. And a compatible decoding method can be provided.

Therefore, the actual processing for encoding or decoding is performed only in the necessary band in accordance with the required quality of the reproduced signal, so that the processing is simplified and the cost is reduced or the speed is increased. , Encoding and decoding. Also, the decoding means can reproduce a signal of a band corresponding to the capability from the same recorded code, and according to the purpose, it is possible to configure a decoding means of a scale and a price corresponding to the purpose. The bandwidth of the signal to be recorded can be expanded while maintaining compatibility in accordance with the capability of the widely used decoding means.

Further, by setting the band for which the processing is omitted to be on the high frequency side, the processing is always performed only on the low frequency side where important signal components are distributed, for example, in a normal audio signal or image signal. The reduction effect can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing a frequency spectrum for describing an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a schematic configuration of an encoding device to which an embodiment of the present invention is applied.

FIG. 3 is a block diagram illustrating a schematic configuration of a decoding device to which an embodiment of the present invention is applied.

FIG. 4 is a block circuit diagram illustrating a schematic configuration of a frequency component decomposition circuit used in the encoding device of FIG. 2;

FIG. 5 is a block circuit diagram showing a schematic configuration of a waveform signal synthesis circuit used in the decoding device of FIG. 3;

FIG. 6 is a block circuit diagram illustrating an example of a configuration of a band decomposition filter circuit.

FIG. 7 is a block circuit diagram illustrating an example of a configuration of a band synthesis filter circuit.

FIG. 8 is a block circuit diagram illustrating a schematic configuration of an encoding device according to an embodiment of the present invention.

FIG. 9 is a block circuit diagram illustrating a schematic configuration of a decoding device according to an embodiment of the present invention.

FIG. 10 is a block circuit diagram showing a schematic configuration of a decoding device according to another embodiment of the present invention.

FIG. 11 is a block circuit diagram illustrating a schematic configuration of a frequency component decomposition circuit used in the encoding device according to the embodiment of the present invention.

FIG. 12 is a block circuit diagram illustrating an example of a configuration of a band decomposition filter circuit used in an embodiment of the present invention.

FIG. 13 is a block circuit diagram illustrating a schematic configuration of a waveform signal synthesis circuit used in the decoding device according to the embodiment of the present invention.

FIG. 14 is a block circuit diagram showing an example of a configuration of a band synthesis filter circuit used in the embodiment of the present invention.

FIG. 15 is a diagram illustrating an example of a code string according to an embodiment of the present invention.

FIG. 16 is a diagram showing another example of a code string according to the embodiment of the present invention.

FIG. 17 is a flowchart schematically showing an example of a part of a processing procedure of an encoding method according to an embodiment of the present invention.

FIG. 18 is a flowchart schematically illustrating a part of an example of a processing procedure of a decoding method according to an embodiment of the present invention.

FIG. 19 is a flowchart schematically showing an example of a part of a processing procedure of a decoding method according to another embodiment of the present invention.

[Explanation of symbols]

 101, 701 Frequency component decomposition circuit 102, 702 Normalization / quantization circuit 103, 703 Code string generation circuit 201, 711, 721 Code string decoding circuit 202, 712, 723 Denormalization / dequantization circuit 203, 713, 724 Waveform signal synthesis circuit 704, 714 Processing band control circuit 722 Information selection circuit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03M 7/30 G10L 19/02

Claims (9)

(57) [Claims] An input signal is divided into a plurality of bands.
In an information encoding method in which a frequency- divided signal is decomposed into frequency components for each band and encoded, a band in which no frequency component decomposition processing is performed is selected, and the frequency component decomposition processing of the selected band is omitted. An information encoding method, wherein a value of a frequency component in a band in which the frequency component decomposition processing is not performed is set to 0. 2. The information encoding method according to claim 1, wherein a band for which the processing of the frequency component decomposition is omitted is a band on a high frequency side. 3. The information encoding method according to claim 1, wherein the frequency decomposition processing is a spectrum conversion processing. 4. An input signal is divided into a plurality of bands.
Decompose the divided signal into frequency components for each band and code
In the information encoding method for performing frequency division , a band in which frequency component decomposition processing is not performed is selected , and the frequency component decomposition processing of the selected band is omitted.
In addition, the coding of the band in which the frequency component decomposition process is not performed is performed.
An information encoding method characterized in that there is no information. 5. A band for dividing an input signal into a plurality of bands.
Dividing means, frequency component decomposition processing means for decomposing the band-divided signal into frequency components for each band, means for encoding the frequency components obtained by the frequency component decomposition means, and performing frequency component decomposition processing And a processing band control unit for selecting a non-existing band, wherein the frequency component decomposing unit omits the frequency component decomposing process of the selected band and sets the value of the frequency component of the band in which the frequency component decomposing process is not performed to 0. An information encoding device characterized by the above-mentioned. 6. The waveform signal is divided into a plurality of bands, and divided.
In the information decoding method of receiving a code string decomposed into frequency components for each band and coding the decoded frequency component code and synthesizing a waveform signal, a band in which frequency component synthesis processing is not performed is determined. Select, omit the frequency component synthesis in the selected band, and set the value of the waveform signal in the band in which the frequency component synthesis is not performed to 0.
An information decoding method, characterized in that: 7. The information decoding method according to claim 6, wherein a band for which the processing of the frequency component synthesis is omitted is a band on a high frequency side. 8. The information decoding method according to claim 6, wherein the frequency component synthesizing process is an inverse spectrum transform process. 9. A waveform signal is divided into a plurality of bands, and divided.
And receive a code sequence coded is decomposed into frequency components for each band, the information decoding apparatus for synthesizing a waveform signal by decoding the encoded frequency component codes, the bandwidth is not performed frequency component synthesis process It includes a processing bandwidth control means for selecting, omitting the frequency component synthesis processing for the selected band, the frequency
An information decoding apparatus characterized in that the value of a waveform signal in a band in which a number component synthesis process is not performed is set to 0.