JPH07336231A - Method and device for coding signal, method and device for decoding signal and recording medium - Google Patents

Abstract

PURPOSE:To eliminate the occurrence of an adverse effect (sound swing) in a listening sense onto a sound obtained by decoding even when a bit is not allocated to the noise component of a coding unit in the case of coding. CONSTITUTION:This decoding device is provided with a tone component decoding circuit 702 decoding a coded tone component, a code string decomposition circuit 701 separating the coded noise component and a scale factor, a 1st noise component decoding circuit 731 decoding the coded noise component, a pseudo signal generating circuit 7 generating a prescribed pseudo signal, and a 2nd noise component decoding circuit decoding the coded scale factor, normalizing the pseudo signal with the scale factor and using the normalized signal for a decoded frequency component in the coding unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal coding method and apparatus for coding an input signal such as digital data by so-called high efficiency coding, a recording medium on which the high efficiency coded signal is recorded, and The present invention relates to a signal decoding method and apparatus for decoding a coded signal transmitted via a transmission path or a coded signal reproduced from a recording medium to obtain a reproduced signal.

[0002]

2. Description of the Related Art Conventionally, there are various techniques for highly efficient encoding of a signal such as audio or voice. For example, a time axis signal is framed in a predetermined time unit and the time axis signal of each frame is Converting to a signal on the frequency axis (spectral conversion), dividing into multiple frequency bands, and coding for each band, a so-called conversion coding method, or audio signals on the time axis are not framed, Examples include so-called band division coding (sub-band coding: SBC) in which the data is divided into frequency bands for coding. Further, a method of high efficiency coding in which the above band division coding and transform coding are combined is also considered, and in this case, for example, after performing band division by the band division coding, A signal for each band is spectrum-converted into a signal on the frequency axis, and each spectrum-converted band is encoded.

Here, as a band division filter used in the above-mentioned band division encoding, for example, QMF is used.
, And this QMF filter is described in the document "Digital Coding of Speech in.
Subbands "(" Digital coding of speech in subband "
s "RE Crochiere, Bell Syst.Tech. J., Vol.55, No.8
1976). The filter of this QMF is
The band is divided into two equal bandwidths, and the filter is characterized in that so-called aliasing does not occur when the divided bands are combined later.

In addition, the document "Polyphase Quadrature Filters-New Band Division Coding Technology"("Po
lyphase Quadrature filters -A new subband coding t
echnique ", Joseph H. Rothweiler ICASSP 83, BOSTON)
Describes an equal bandwidth filter partitioning technique.
This polyphase quadrature filter is characterized in that when a signal is divided into a plurality of bands of equal bandwidth, it can be divided at one time.

Further, as the above-mentioned spectrum conversion,
For example, an input audio signal is framed in a predetermined unit time, and a discrete Fourier transform (DFT) is performed for each frame.
There is a spectrum conversion in which a time axis is converted into a frequency axis by performing discrete cosine transform (DCT) or modified discrete cosine transform (MDCT). Regarding the MDCT, refer to the document “Time Domain Aliasing.
"Subband / Transform Coding with Cancellation-Based Filter Bank Design"
Using Filter Bank Designs Based on Time Domain Al
iasing Cancellation, "JPPrincen ABBradley, Uni
v. of Surrey Royal Melbourne Inst. of Tech. ICASSP
1987).

In this way, by quantizing the signal divided for each band by the filter and the spectrum conversion,
It is possible to control the band in which the quantization noise is generated, and it is possible to perform auditory and more efficient encoding by utilizing the properties such as the so-called masking effect. In addition, if the normalization is performed for each band, for example, with the maximum absolute value of the signal component in that band before performing the quantization here,
Furthermore, highly efficient encoding can be performed.

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

For example, the document "Adaptive Transform Coding of Speech Signal"
s ", IEEE Transactions of Accoustics, Speech, and S
ignal Processing, vol.ASSP-25, No.4, August 1977
), Bit allocation is performed based on the signal size of each band. In this method, the quantization noise spectrum becomes flat and the noise energy becomes the minimum, but the actual noise feeling is not optimal because the masking effect is not used auditorily.

In addition, for example, the document "Critical band encoder-
Digital encoding of the auditory system's perceptual requirements "
("The critical band coder --digital encoding of
the perceptual requirements of the auditory syste
m ", MAKransner MIT, ICASSP 1980) describes a method of performing fixed bit allocation by obtaining the required signal-to-noise ratio for each band by using auditory masking. Even when the characteristic is measured with a sine wave input, the characteristic value is not so good because the bit allocation is fixed.

In order to solve these problems, all bits that can be used for bit allocation are assigned a fixed bit allocation pattern predetermined for each band or each block obtained by subdividing each band, and within each block. Of the fixed bit allocation pattern as the signal spectrum is smoothed, and the divided ratio depends on the signal related to the input signal. A high-efficiency coding apparatus has been proposed which increases the division ratio into minutes.

According to this method, when energy is concentrated on a specific spectrum such as a sine wave input, by allocating a large number of bits to a block including the spectrum, the total signal-to-noise is increased. The properties can be significantly improved. In general, human hearing for a signal having a steep spectral component is extremely sensitive. Therefore, improving the signal-to-noise characteristic by using such a method does not only improve the numerical value in measurement. , It is effective in improving the sound quality in terms of hearing.

Note that many other methods have been proposed for the bit allocation method, and if the model relating to hearing is further refined and the performance of the coding apparatus is improved, it will be more efficient in terms of hearing. Coding is possible.

However, in the above-mentioned conventional method, since the band for quantizing the frequency component is fixed, for example, when the spectrum is concentrated in the vicinity of some specific frequencies, those frequencies are reduced. In order to quantize the spectral components with sufficient accuracy, many bits have to be allocated to a large number of spectra belonging to the same band as those spectral components, resulting in reduced efficiency.

That is, generally, noise contained in a tone-like acoustic signal in which spectral energy is concentrated at a specific frequency is very high compared with noise added to an acoustic signal in which energy is gently distributed over a wide frequency band. It easily hits the ears and is a great obstacle to hearing. Furthermore, if the spectral components with large energy, that is, the tone components, are not quantized with sufficient accuracy, when those spectral components are returned to the waveform signal on the time axis and combined with the preceding and following frames, the Distortion becomes large (a large connection distortion occurs when it is combined with a waveform signal of an adjacent time frame), which also causes a great hearing loss. For this reason, it has been difficult for the conventional method to improve the coding efficiency without deteriorating the sound quality particularly for the tone-like acoustic signal.

In order to solve this problem, the applicant of the present application has previously mentioned that in the specification and drawings of Japanese Patent Application No. 5-152865, a tone-like component in which energy is concentrated on an input acoustic signal at a specific frequency. It proposes a method for realizing high coding efficiency by separating and coding into a component (noise component or non-tone component) in which energy is distributed gently over a wide band.

That is, in the previously proposed method, the input acoustic signal is frequency-converted and divided into, for example, a seaside band, and the spectral components of each of these divided bands are divided into tone components and noise components (non-tone components). Component), and the efficient encoding that normalizes and quantizes each separated tone component (a spectral component in a very narrow range on the frequency axis where the tone component in the band exists) To give. In addition, as a very narrow range on the frequency axis in which the tonal component in which the above-mentioned efficient encoding is performed exists, for example, a certain number around a spectrum having maximum energy which is each tonal component The range of spectral components can be mentioned as an example.

According to the above-proposed method, by performing the above-mentioned operation, the efficiency is improved as compared with the above-mentioned method of quantizing the frequency component inside each fixed band. It is possible to achieve good coding. The frequency component coded as described above is recorded on a recording medium or transmitted to a transmission line together with corresponding position information on the frequency axis of the tone component.

[0018]

By the way, as described above, a signal is converted into a frequency component, and the obtained frequency component is separated into a tone component and a noise component (non-tone component) and encoded. In the method, for example, the input acoustic signal is framed in the _order of frame F _n-1 , frame F _n , and frame F _{n + 1 in} the time direction, and frequency conversion is performed on each of these frames F, for example, as shown in FIG. It is assumed that various frequency components are obtained. Note that FIG. 8 shows, for example, the level of the absolute value of the spectrum signal (frequency component) obtained by the MDCT converted into a dB value, and the input acoustic signal is, for example, 64 spectrum signals for each frame. Has been converted to.

When the frequency components of each of these frames are encoded, the frequency components in the frame are grouped in groups of five bands shown by b ₁ to b ₅ in FIG. summarized in unit or will be referred to as block), and separated into TC _a to Tc _D) and other noise components NC in the example of the frequency components in units of coding tone component TC (FIG. 8, the The separated tone characteristic component TC and the separated noise component NC are encoded with different allocated bits.

At this time, the total number of bits that can be used when encoding the frequency component in one frame is predetermined, but for the noise component NC, the maximum value of the spectrum component in it is used as a normalization factor. By performing normalization and quantization with a numerical value (scale factor), the number of bits assigned to the noise component can be reduced, and more bits are added to the tone component TC that is important for hearing. I am able to assign a number. In the example of FIG. 8, the bandwidth of each coding unit b is set to be narrow on the low frequency side and wide on the high frequency side in consideration of the waterfront frequency band according to human auditory characteristics. This makes it possible to control the generation of quantization noise so as to match the auditory characteristics.

Here, as described above, the total number of bits that can be used when encoding the frequency components in one frame is predetermined, so that, for example, the encoded data may be temporarily changed depending on the content of the input signal. The capacity of the transmission buffer memory for accumulating and keeping the transmission rate constant becomes excessive (overflowing), or the total number of bits allocated to the frame when encoding one frame. May be exceeded (that is, the total number of bits may be insufficient).

In order to prevent the above-mentioned overflow and shortage of the number of bits, a bit for coding is not assigned to a noise component of a coding unit which has a less audible influence on the perceptual effect in a frame ( That is, the number of allocated bits is set to 0 so that no noise component is transmitted). For example, as shown in FIG.
respect might be masked eg fourth encoding units b ₄ of the noise components NC with less high range and tone characteristic component TC _D of audibility affected in _n, the bits for coding Do not assign.

Here, if, for example, the allocation of bits to a certain coding unit (block) occurs or disappears in, for example, frames that are temporally adjacent or close to each other for the reasons described above, the coding is performed. The frequency corresponding to the unit becomes subject to modulation, and when the sound signal obtained by the subsequent decoding is reproduced, an undesired sound fluctuation may be perceived.

Therefore, the present invention has been made in view of such a situation, and even in the case where no bit is allocated to the noise component of the encoding unit at the time of encoding. , A signal encoding method and apparatus capable of preventing a sound obtained by the subsequent decoding from adversely affecting the audibility, and a signal decoding method and apparatus corresponding thereto,
Another object of the present invention is to provide a recording medium on which an encoded signal is recorded.

[0025]

The present invention has been made in view of the above circumstances, and a signal coding method of the present invention converts an input signal into frequency components and converts the frequency components into tone components. Is a signal encoding method and apparatus for separating the first signal and the second signal including other components, and encoding the first signal and the second signal, respectively. At the time of encoding, a frequency component encoding process for encoding a frequency component in the encoding unit and a standardized information encoding process for encoding only standardized information based on the frequency component in the encoding unit are performed. , Is selectively switched for each encoding unit.

Further, the signal coding apparatus of the present invention comprises a conversion means for converting an input signal into frequency components, and the frequency components into a first signal composed of tone components and a second signal composed of other components. The second code includes a separation means for separating, a first encoding means for encoding the first signal, and a second encoding means for encoding the second signal. The encoding unit encodes the frequency component in the encoding unit, the frequency component encoding unit, the standardization information encoding unit that encodes only the standardization information based on the frequency component in the encoding unit, and the second unit. The present invention is characterized by comprising switching means for selectively switching a signal for each coding unit and sending it to the frequency component coding means or the standardized information coding means.

In these signal coding method and apparatus of the present invention, the scale factor and the word length of the coding unit are used in the frequency component coding process when coding the second signal. The standardization information is a scale factor of the coding unit, a maximum value of frequency components in the coding unit, or an average value.

Next, the recording medium of the present invention is a recording medium on which an encoded signal is recorded. The input signal is converted into a frequency component and the frequency component is used as a first signal composed of a tone component. Separated into a second signal consisting of other components,
The first signal is encoded, and the frequency component in the encoding unit of the second signal and only the standardization information based on the frequency component in the encoding unit are selectively switched for each encoding unit. And the encoded first signal and second coded signal are recorded.

Here, in the recording medium of the present invention, the encoded frequency component of the second signal has a scale factor and a word length of the encoding unit. The standardization information is a scale factor of the coding unit, a maximum value of frequency components in the coding unit, or an average value.

Next, according to the signal decoding method of the present invention, a first coded signal obtained by coding a first signal having a tone characteristic frequency component and a second coded signal having a frequency component other than tone characteristic are encoded.
The frequency component coded signal obtained by coding the frequency component in the coding unit and the standardized information coded signal obtained by coding only the standardized information based on the frequency component in the coding unit are selectively switched. A signal decoding method for decoding a second coded signal, wherein when the second coded signal of the coding unit is decoded, the standardized information coded signal is decoded and the decoding is performed. It is characterized in that a predetermined pseudo signal is standardized by the standardized information to be a frequency component in the coding unit.

Further, the signal decoding apparatus of the present invention comprises first decoding means for decoding a first coded signal obtained by coding a first signal composed of tone-like frequency components, and other than tone-like characteristics. Of the second signal composed of frequency components of the frequency unit, the frequency component encoded signal obtained by encoding the frequency component in the encoding unit, and the normalization information encoding obtained by encoding only the standardization information based on the frequency component in the encoding unit. Separating means for selectively separating the signal, frequency component coded signal decoding means for decoding the frequency component coded signal separated by the separating means, and pseudo signal generating means for generating a predetermined pseudo signal, The standardized information coded signal separated by the separating means is decoded, and the pseudo signal is standardized by the decoded standardized information to obtain a frequency component in the coding unit. It is characterized in that it has a No. decoding means.

Here, in the signal decoding method and apparatus of the present invention, the frequency component obtained by decoding the frequency component coded signal of the predetermined time is used as the predetermined pseudo signal of the current time. Further, the predetermined time corresponds to one unit time for converting the time axis signal into the frequency axis frequency component at the time of encoding. Furthermore, the signal obtained by decoding the frequency component coded signal has the scale factor and word length of the coding unit, and the standardization information is the scale factor of the coding unit, the maximum value of the frequency component in the coding unit. , Or the average value. Furthermore, in the signal decoding method and apparatus of the present invention, a random sequence signal is generated and the random sequence signal is used as the predetermined pseudo signal.

[0033]

According to the signal coding method and apparatus of the present invention, when the second signal is coded, the frequency component coding process for coding the frequency component in the coding unit and the coding process in the coding unit are performed. Since the standardized information encoding process that encodes only the standardized information based on the frequency component of is selectively switched for each encoding unit, the total number of allocated bits required for encoding is There is no shortage, and the amount of information transmitted or recorded does not increase.

Further, according to the recording medium of the present invention, only the frequency component in the coding unit of the second signal and the standardization information based on the frequency component in the coding unit are selectively selected for each coding unit. Since the information is switched and encoded and recorded, the recorded information does not increase too much.

Further, according to the signal decoding method and apparatus of the present invention, when the second coded signal of the coding unit is decoded, the standardized information coded signal is decoded and this decoding is performed. Since the predetermined pseudo signal is standardized by the standardization information to be the decoded frequency component in this coding unit, even if the coding units that did not include the frequency component are alternately supplied, the decoding is performed. The pseudo signal exists in the encoded unit as a frequency component, and the reproduced signal is not modulated by the encoding unit that did not include the frequency component.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of a signal coding apparatus of an embodiment of the present invention to which the signal coding method of the present invention is applied.

That is, the signal coding apparatus of the present invention comprises a conversion circuit 601 for converting an input signal into a frequency component, and the frequency component into a first signal composed of a tone component and a second signal composed of other components. A signal component separating circuit 602 which is a separating means for separating, a tone characteristic component encoding circuit 603 which is a first encoding means for encoding the first signal, that is, a tone characteristic component, and the second signal or noise. And a second encoding means for encoding the sex component. Here, the second coding means includes a first noise component coding circuit 641 which is a frequency component coding means for coding a frequency component in the coding unit and a frequency component in the coding unit. A second noisy component coding circuit 642, which is a standardized information coding means for coding only standardized information (scale factor or maximum value or average value described later) based on the second signal, and a second signal for each coding unit. And a noise component selection circuit 640 which is a switching means for selectively switching to the first noise component encoding circuit 641 or the second noise component encoding circuit 642. .

In FIG. 1, an acoustic waveform signal is supplied to the terminal 600. This acoustic signal waveform is converted into a signal frequency component by the conversion circuit 601, and then sent to the signal component separation circuit 602. The conversion circuit 6
The detailed configuration of 01 will be described later.

In the signal component separation circuit 602,
The signal frequency component obtained by the conversion circuit 601 is a tone component which is a first signal having a steep spectrum distribution, and a signal frequency component other than that is a noise which is a second signal having a flat spectrum distribution. Separated into sex components (non-tone components).

Of these separated frequency components, the tone component having the steep spectrum distribution is coded by the tone component coding circuit 603, and the code string generation circuit 6 is produced.
Sent to 05. On the other hand, the noise component, which is a signal frequency component other than the tone component, is sent to the noise component selection circuit 640.

In the noise component selection circuit 640, the noise component supplied from the signal component separation circuit 602 is converted into a noise component to be encoded by the first noise component encoding circuit 641 in the subsequent stage (hereinafter referred to as "noise component"). , The first noise component) and the second noise component encoding circuit 642 to encode the noise component (hereinafter referred to as the second noise component).

That is, the noise component selection circuit 64
At 0, as shown in FIG.
Frame (eg, arbitrary frame F_n) Each
The noise component NC of the encoding unit (block) b,
The frame F_nFor example, the frame immediately before in time
(Frame F_n-1) Corresponding to each encoding unit
By comparing the noise component NC of
Room F_nThe frame F one before_n-1Corresponding encoding unit of
Knit b_mThe noise component NC of the frame F _nPair of
Corresponding coding unit b_mReplaces the noise component NC of
Even if you get the frame F_nCorresponding encoding uni
T b_mIt is determined that the noise amount allowed for
If it is turned off, the second noise component encoding circuit 64
Select 2. On the contrary, the noise component selection circuit 640
By the comparison, the frame F _nThe previous frame
Mu F_n-1Corresponding encoding unit b of_mNoise component of
Frame F in NC_nCorresponding encoding unit b of_m
If the noise component NC of_n
Corresponding encoding unit b of_mThe amount of noise allowed for
When it is determined that the number of bits exceeds the maximum (that is, the encoding unit
B_m(When it is determined that cannot be replaced)
To select the first noise component encoding circuit 641.
It

In the noise component selection circuit 640, even if the comparison condition for replacing the noise component is not met, for example, when the total bit amount of the frame F _n is insufficient, human hearing is performed. It is also possible to make a selection such that the noise component is supplied to the second noise component encoding circuit 642 in order from the encoding unit having the lowest auditory sensitivity according to the characteristics of the above.

The noise component selected by the noise component selection circuit 640 and sent to the second noise component encoding circuit 642 is encoded by the second noise component encoding circuit 642. Only the scale factor used for normalizing the frequency component (noise component) in the unit b _m as the standardization information is encoded. Alternatively, in the second noise component encoding circuit 642, the encoding unit b _{m is used} instead of the scale factor.
It is also possible to encode only the maximum value or average value of the noisy components in the above. Here, when only the maximum value or the average value is coded, in the second noise component coding circuit 642, each of the noise components sent from the noise component selection circuit 640 is Looking at the distribution of the components, if the deviation between each component is relatively small (for example, if the deviation is smaller than a predetermined threshold), the maximum value is coded, and if the deviation is relatively large (for example, smaller than the predetermined threshold, If the change is large), the average value is encoded.

On the other hand, the noise component selected by the noise component selection circuit 640 and sent to the first noise component encoding circuit 641 is scaled by the first noise component encoding circuit 641. The encoding is performed so as to have a factor and a word length of each frequency component.

As described above, in the apparatus of this embodiment,
By selectively switching the coding by the first noise component coding circuit 641 and the coding by the second noise component coding circuit 642,
It becomes possible to achieve highly efficient coding with a higher degree of compression.

The first noise component encoding circuit 641
Alternatively, the signal obtained by the encoding by the second noise component encoding circuit 642 is the tone component encoding circuit 60.
It is sent to the code string generation circuit 605 together with the tonal component coded by 3, and is converted into a code string here. The code string generation circuit 605 is also supplied with the number of tone component information and the position information of the tone component from the signal component separation circuit 602, and these are also added to the above code sequence.

The code string generated by the code string generating circuit 605 is sent to the ECC encoder 606. In the ECC encoder 606, the code string generation circuit 6
An error correction code is added to the code string from 05. The output from the ECC encoder 606 is subjected to so-called 8-14 modulation by the EFM circuit 607 and supplied to the recording head 608. The recording head 608 records the code string output from the EFM circuit 607 on the disk 609. The disc 609
Can be, for example, a magneto-optical disk or a phase change disk. An IC card or the like may be used instead of the disc 609.

Next, FIG. 2 shows a schematic configuration of a signal decoding apparatus of an embodiment to which the signal decoding method of the present invention for decoding the signal encoded by the encoding apparatus of FIG. 1 is applied. .

That is, in FIG. 2, the signal decoding apparatus according to the embodiment of the present invention includes a tone component decoding circuit 702 which is a first decoding means for decoding a signal obtained by encoding a tone component, and a tone component. Other than the noise component, the function as a separating means for separating the encoded noise component in the encoding unit and the signal encoding only the scale factor (or maximum value or average value) in the encoding unit Code string decomposing circuit 701 also having
A first noise component decoding circuit 731 which is a frequency component coded signal decoding means for decoding the coded noise component separated by 01, and a pseudo signal generation circuit 734 which generates a predetermined pseudo signal. , The encoded scale factor (or maximum value or average value) separated by the code string decomposition circuit 701 is decoded, and the pseudo signal is standardized by the decoded scale factor (or maximum value or average value). And a second noise component decoding circuit 734 which is a standardized information coded signal decoding means for converting into a frequency component in the coding unit.

In FIG. 2, the code string reproduced from the disk 609 via the reproducing head 708 is supplied to the EFM demodulation circuit 709. The EFM demodulation circuit 709 demodulates the input code string. The demodulated code string is supplied to the ECC decoder 710, where error correction is performed.

The code string decomposition circuit 701 recognizes which part of the code string is the tone characteristic component code based on the number of tone characteristic component information and the position information in the error-corrected code sequence, and is inputted. The code sequence is separated into a tone component code and a noise component code, the tone component code is encoded by the tone component decoding circuit 702, and the noise component is further encoded by the first noise component encoding. Circuit 641
Signal and the signal coded by the second noise component coding circuit 642, respectively, and the corresponding first noise component decoding circuit 731 and second noise component decoding respectively. Supply to the circuit 732. Also,
The code string separation circuit 701 also separates the position information of the tone component from the input code string and outputs it to the combining circuit 704 in the subsequent stage. The tone component code separated by the code string decomposition circuit 701 and sent to the tone component decoding circuit 702 is subjected to dequantization and denormalization here to be decoded, and the synthesis circuit in the subsequent stage. Sent to 704.

On the other hand, the signal supplied to the first noise component decoding circuit 731 is subjected to dequantization and denormalization using the scale factor and the word length of each frequency, and noise is removed. It is decoded into the sex component. The signal sent to the first noise component decoding circuit 731 is stored in the memory 733 so that it can be used in the decoding process of the next frame. This memory 73
The signal read from No. 3 is sent to the pseudo signal generating circuit 734.

In the pseudo signal generating circuit 734, as shown in FIG. 3, the frame F _{n-1 immediately} before the frame (for example, the frame F _n ) to be decoded by the second noise component decoding circuit 732 is used. Signal, that is, the signal stored in the memory 733, the second noise component decoding circuit 7
There is a signal of the coding unit b _m of the noise component of the frame F _n-1 of the preceding frame F _n-1 corresponding to the coding unit b _m of the noise component of the frame F _n to be decoded in 32. Stored in 733), the signal of the encoding unit b _m of the frame F _n−1 is output to the second noise component decoding circuit 732. Further, the pseudo signal generating circuit 734 is arranged so that the frame F to be decoded by the second noise component decoding circuit 732.
corresponding to the encoding unit b _m of _n noise component of not the previous frame F _n-1 of the noise characteristic component signal encoding units b _m of present (not stored in the memory 733) In this case, a random signal corresponding to the coding unit b _m is generated and output to the second noise component decoding circuit 732. Since the example of FIG. 3 shows the example corresponding to FIG. 9 described above, _m of the encoding unit b m is 4 (that is, the fourth encoding unit b ₄ ).

The second noise component decoding circuit 732
In the above, while decoding the coded scale factor (or maximum value or average value) corresponding to the coding unit b _m of the frame F _n to be decoded supplied from the code string decomposition circuit 701, The decoded scale factor (or maximum value) of the signal or the random signal obtained by decoding the signal of the coding unit b _m of the noise component of the frame F _{n-1 one} frame before, which is supplied from the pseudo signal generation circuit 734. Alternatively, the noise component nc of the encoding unit b _m is standardized by the average value).

The first noise component decoding circuit 731
The decoded frequency component from the second noise component decoding circuit 732 and each decoded frequency component from the tone component decoding circuit 702 are processed by the noise component selection circuit 640 shown in FIG. Circuit 704 for performing the synthesis corresponding to the separation of the signal components and the signal component separation circuit 602 of FIG.
Is supplied to. The synthesis circuit 704 is also supplied with the positional information of the tone component from the code string separation circuit 701. In the synthesis circuit 704, the first noise component decoding circuit 731 and the second noise component decoding circuit 7
By combining the frequency component from 32 and using the position information of the tone component, the decoded tone component is added to a predetermined position of the synthesized noise component to obtain the noise component. And tonal components are synthesized on the frequency axis.

That is, the signals obtained by the respective constituent elements up to the synthesis circuit 704 after the code string decomposition circuit 701 will be described by taking the above-mentioned FIG. 3 as an example. In the system from the noisy component decoding circuit 731 to the synthesizing circuit 704 of 1, the noisy component of the scale factor and the word length is used for each coding unit such as frames F _n-1 and F _{n + 1} . Decoding and decoding of tonal components,
And their synthesis. On the other hand, the tone component decoding circuit 702, the second noise component decoding circuit 732, the memory 733, and the pseudo signal generating circuit 7 are included.
In the system from 34 to synthesis circuit 704, frame F
For each coding unit, except the _n noise component encoding units b ₄ of the decoding and tone using the scale factor and word length for the frame F _n-1 and F _{n + 1} Likewise units of coding Decoding and combining of the sex component are performed, and the coding unit b ₄ of the frame F _n is
For the noisy component of, the process of normalizing the noisy component of the coding unit b ₄ of the immediately preceding frame F _{n-1 by} the scale factor (or the maximum value or the average value) to obtain the noisy component nc And then synthesizing them.

The decoded signal synthesized by the synthesizing circuit 704 is subjected to conversion processing by an inverse transforming circuit 705 which performs an inverse transform corresponding to the transforming in the transforming circuit 601 of FIG. 1, and the original signal is converted from the signal on the frequency axis. It is returned to the waveform signal on the time axis. The output waveform signal from the inverse conversion circuit 705 is output from the terminal 705. The details of the inverse conversion circuit 705 will be described later.

Here, in FIG. 4, from the code string decomposition circuit 701 to the second noise component decoding circuit 732, the memory 733 and the pseudo signal generation circuit 7 of the signal decoding apparatus of FIG.
34 shows the flow of processing performed in the system up to 34. In FIG. 4, I indicates the number of coding units and N indicates the total number of coding units in a frame.

That is, in FIG. 4, first, in step S1, 0 is substituted into the variable I indicating the number of the coding unit b of an arbitrary frame F _n . In the next step S2, is the coded signal of the I-th coding unit b _{I in} the code string decomposition circuit 701 a signal coded by the second noise component coding circuit 642 in FIG. It is determined whether or not, and if the result is NO, the process proceeds to step S8, which will be described later, and if the result is YES, the process proceeds to step S3.

In step S3, the scale factor (or maximum value or average value) of the I-th encoding unit b _I is decoded.

In the next step S4, the frame F _n
Corresponding encoding unit b of the frame F _{n-1 immediately} before
_It is determined whether _I has a frequency component. If YES is determined, the process proceeds to step S5. If NO is determined, the process proceeds to step S6.

In step S5, the previous frame
F_n-1Corresponding encoding unit b of _IFrequency component of
Scaled component) is decoded in step S3.
Standardized by the factor (or maximum value or average value)
Then, it progresses to step S8.

On the other hand, in step S6, the pseudo signal generating circuit 734 generates random data. In the next step S7, the random data is standardized by the decoded scale factor (or maximum value or average value), and then the process proceeds to step S8.

In step S8, it is judged whether or not the variable I indicating the number of the coding unit is equal to the total number N of the coding units of the frame F _n . If the judgment is YES, the process is terminated, If no is determined, the process proceeds to step S9. In the step S9, the variable I indicating the number of the encoding unit is incremented by 1 and the step S2
Return to.

Next, the structure of the conversion circuit 601 shown in FIG. 1 will be described with reference to FIG. In FIG. 5, the signal supplied through the terminal 200 (the signal through the terminal 600 in FIG. 1) is a band division filter 201 to which the polyphase quadrature filter or the like is applied.
Is divided into four bands by. The signals of each band divided into four bands by the band division filter 201 are made into spectrum signal components by the forward spectrum conversion circuits 211 to 214 which respectively perform spectrum conversion such as MDCT. That is, each forward spectrum conversion circuit 2
The bandwidth of the signals to 11 to 224 is ¼ of the bandwidth of the signal supplied to the terminal 200.
The signal from is thinned to 1/4. The outputs of these forward spectrum conversion circuits 211 to 214 are transmitted through terminals 221 to 224 to the signal component separation circuit 6 of FIG.
Sent to 02.

Of course, the conversion circuit 601 shown in FIG. 1 can be considered in many ways other than this embodiment. For example, the input signal may be directly converted into a spectrum signal by MDCT, or DFT or DCT may be used instead of MDCT. You may convert by. It is also possible to divide the signal into band components by a band splitting filter such as a so-called QMF, but since the method of the present invention works particularly effectively when energy is concentrated at a specific frequency, a large number of frequency components It is convenient to adopt the method of converting into the frequency component by the above-mentioned spectrum conversion which is obtained with a relatively small amount of calculation.

Next, FIG. 6 shows a basic configuration of a circuit for encoding the tone component and the noise component in the configuration of FIG. 1 described above. In FIG. 6, the signal of the frequency component supplied to the terminal 300 is the normalization circuit 3
After being normalized by 01 for each predetermined band, it is sent to the quantization circuit 303. The signal supplied to the terminal 300 is also sent to the quantization accuracy determination circuit 302. The quantization circuit 303 quantizes the signal from the normalization circuit 301 based on the quantization accuracy calculated by the quantization accuracy determination circuit 303 from the signal through the terminal 300. The output from the quantization circuit 303 is output from the terminal 304 and sent to the code string generation circuit 605 in FIG. The output signal from the terminal 304 includes, in addition to the signal component quantized by the quantization circuit 303, normalization coefficient information in the normalization circuit 301 and quantization precision information in the quantization precision determination circuit 302. Is also included.

Next, a specific structure of the inverse conversion circuit 705 of FIG. 2 corresponding to the conversion circuit 601 of FIG. 5 will be described with reference to FIG. In FIG. 7, the signals supplied from the combining circuit 704 via the terminals 501 to 504 are converted by the inverse spectrum converting circuits 511 to 514 which perform the inverse spectrum converting corresponding to the forward spectrum converting in FIG. 5, respectively. These inverse spectrum conversion circuits 511
The signals of the respective bands obtained by ˜514 are combined by the band combining filter 515 which performs the combining process corresponding to the division by the band dividing filter 201 of FIG. The output of the band synthesis filter 515 comes to be output from the terminal 521.

Although the above description has been centered on the example in which the method of the embodiment of the present invention is applied to an acoustic signal, the method of the embodiment of the present invention can be applied to general waveform signal encoding. Is possible. However, in the case of an acoustic signal, the tone component information has a particularly significant auditory sense, and the method of the embodiment of the present invention can be applied particularly effectively.

[0072]

As is apparent from the above description, in the signal coding method and apparatus of the present invention, the frequency component in the coding unit is coded when the second signal is coded. The frequency component encoding process and the standardized information encoding process for encoding only the standardized information based on the frequency component in the encoding unit are selectively switched for each encoding unit. In this case, the total number of allocated bits required is not insufficient, the transmission buffer memory does not overflow, and the amount of information to be transmitted or recorded does not increase. It becomes possible to compress.

In the recording medium of the present invention, the second
Since only the frequency component in the coding unit of the signal of and the standardization information based on the frequency component in the coding unit are selectively switched and coded for each coding unit, the recorded information increases. Therefore, the capacity of the recording medium can be effectively used.

Further, in the signal decoding method and apparatus of the present invention, when decoding the second coded signal of the coding unit, the standardized information coded signal is decoded and the decoded standard is decoded. Since the predetermined pseudo signal is standardized by the encoding information to be the decoded frequency components in this encoding unit, even if the encoding units that did not include the frequency components are alternately supplied, they will be decoded. Since the pseudo signal exists as a frequency component in the encoding unit, the reproduction signal is not modulated by the encoding unit that does not include the frequency component. Therefore, in the signal decoding method and apparatus of the present invention, even if the bit is not allocated to the noise component of the coding unit at the time of coding, the sound obtained by decoding is No audible adverse effect (sound fluctuation) occurs.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a schematic configuration of a signal encoding device according to an embodiment of the present invention.

FIG. 2 is a block circuit diagram showing a schematic configuration of a signal decoding device according to an embodiment of the present invention.

FIG. 3 is a diagram for explaining a decoding operation of the signal decoding device according to the embodiment of the present invention.

FIG. 4 is a flowchart showing a flow of a decoding operation of a main part of the signal decoding device according to the present embodiment.

FIG. 5 is a block circuit diagram deer showing a specific configuration of a conversion circuit of the signal encoding device according to the present embodiment.

FIG. 6 is a block circuit diagram showing a basic configuration of an encoding circuit of the signal encoding device according to the present embodiment.

FIG. 7 is a block circuit diagram showing a specific configuration of an inverse conversion circuit of the signal decoding device according to the present embodiment.

FIG. 8 is a diagram for explaining a conventional encoding operation.

FIG. 9 is a diagram for explaining a drawback of conventional decoding.

[Explanation of symbols]

 601 Conversion circuit 602 Signal component separation circuit 603 Tone component encoding circuit 605 Code string generation circuit 606 ECC encoder 607 EFM circuit 608 Recording head 609 Disk 640 Noise component selection circuit 641 First noise component encoding circuit 642 Second Noise component encoding circuit 701 code string decomposition circuit 702 tone component decoding circuit 704 synthesis circuit 705 inverse conversion circuit 708 reproducing head 709 EFM demodulation circuit 710 ECC decoder 731 first noise component decoding circuit 732 second Noise component decoding circuit 733 Memory 734 Pseudo signal generation circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiya Tsutsui 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (31)

[Claims] 1. An input signal is converted into a frequency component, the frequency component is separated into a first signal composed of a tone component and a second signal composed of other components, and the first signal and the second signal are composed. In the signal coding method of coding each signal, a frequency component coding process of coding a frequency component in the coding unit and a frequency component in the coding unit at the time of coding the second signal And a standardized information coding process for coding only standardized information based on the above-mentioned, a signal coding method characterized by selectively switching each coding unit. 2. The signal coding method according to claim 1, wherein a scale factor and a word length of a coding unit are used in the frequency component coding process in the coding of the second signal. 3. The signal coding method according to claim 1, wherein the standardization information is a scale factor of a coding unit. 4. The signal coding method according to claim 1, wherein the standardization information is a maximum value of frequency components in a coding unit. 5. The signal coding method according to claim 1, wherein the standardization information is an average value of frequency components in a coding unit. 6. A conversion means for converting an input signal into a frequency component, a separation means for separating the frequency component into a first signal composed of a tone component and a second signal composed of other components, and the first component. And a second encoding means for encoding the second signal, wherein the second encoding means is included in an encoding unit. Frequency component coding means for coding the frequency component, standardization information coding means for coding only the standardization information based on the frequency component in the coding unit, and the second signal selectively for each coding unit. And a switching means for switching to the frequency component coding means or the standardization information coding means. 7. The signal coding apparatus according to claim 6, wherein the frequency component coding means of the second coding means uses a scale factor and a word length of a coding unit. 8. The signal coding apparatus according to claim 6, wherein said standardized information coding means codes the scale factor of the coding unit as standardized information. 9. The signal coding apparatus according to claim 6, wherein the standardization information coding means codes the maximum value of the frequency components in the coding unit as standardization information. 10. The signal coding apparatus according to claim 6, wherein the standardization information coding means codes the average value of the frequency components in the coding unit as standardization information. 11. A recording medium on which an encoded signal is recorded, wherein an input signal is converted into a frequency component, and the frequency component is a first signal composed of a tone component and a second signal composed of other components. And the first signal is encoded, and only the frequency component in the encoding unit of the second signal and the standardization information based on the frequency component in the encoding unit are selectively selected for each encoding unit. A recording medium, wherein the recording medium is characterized by being switched to and encoded, and recording the encoded first signal and second signal. 12. The recording medium according to claim 11, wherein the encoded frequency component of the second signal has a scale factor and a word length of an encoding unit. 13. The recording medium according to claim 11, wherein the standardized information is a scale factor of an encoding unit. 14. The standardized information is a maximum value of frequency components in a coding unit.
The recording medium according to 1. 15. The standardized information is an average value of frequency components in a coding unit.
The recording medium according to 1. 16. A first encoded signal obtained by encoding a first signal having a tone characteristic frequency component and a frequency component in an encoding unit of a second signal having a frequency component having a tone characteristic other than Decoding the encoded frequency component encoded signal and the second encoded signal obtained by selectively switching the standardized information encoded signal in which only the standardized information based on the frequency component in the encoding unit is encoded. A signal decoding method, wherein the decoding of the second coded signal of the coding unit comprises:
A signal decoding method characterized by decoding the standardized information coded signal, and standardizing a predetermined pseudo signal by the decoded standardized information to obtain a frequency component in the coding unit. 17. The signal decoding method according to claim 16, wherein the frequency component coded signal before a predetermined time is used as the predetermined pseudo signal at the current time. 18. The signal decoding method according to claim 17, wherein the predetermined time corresponds to one unit time for converting a time axis signal into a frequency axis frequency component at the time of encoding. 19. The signal decoding method according to claim 16, wherein a random sequence signal is generated and the random sequence signal is used as the predetermined pseudo signal. 20. The signal decoding method according to claim 16, wherein the signal obtained by decoding the frequency component coded signal has a scale factor and a word length of the coding unit. 21. The signal decoding method according to claim 16, wherein the standardization information is a scale factor of a coding unit. 22. The standardized information is a maximum value of frequency components in a coding unit.
6. The signal decoding method according to item 6. 23. The standardized information is an average value of frequency components in a coding unit.
6. The signal decoding method according to item 6. 24. First decoding means for decoding a first coded signal obtained by coding a first signal composed of a tone characteristic frequency component, and a second signal composed of a frequency component other than the tone characteristic. Separation for selectively separating a frequency component encoded signal obtained by encoding the frequency component in the encoding unit and a standardized information encoded signal obtained by encoding only the standardization information based on the frequency component in the encoding unit Means, frequency component coded signal decoding means for decoding the frequency component coded signal separated by the separating means, pseudo signal generating means for generating a predetermined pseudo signal, and standardization information separated by the separating means. And a standardized information coded signal decoding means for decoding the coded signal and standardizing the pseudo signal with the decoded standardized information to obtain a frequency component in the coding unit. Signal decoding apparatus according to claim. 25. The signal decoding apparatus according to claim 24, wherein the pseudo signal generating means outputs the frequency component coded signal of a predetermined time before as the predetermined pseudo signal of the current time. 26. The signal decoding apparatus according to claim 24, wherein the predetermined time corresponds to one unit time for converting a time axis signal into a frequency axis frequency component at the time of encoding. 27. The signal decoding apparatus according to claim 24, wherein said pseudo signal generating means outputs a random sequence signal as said predetermined pseudo signal. 28. The signal decoding apparatus according to claim 24, wherein the signal obtained by decoding the frequency component coded signal has a scale factor and a word length of the coding unit. 29. The signal decoding apparatus according to claim 24, wherein the standardization information is a scale factor of a coding unit. 30. The standardized information is a maximum value of frequency components in a coding unit.
4. The signal decoding device according to 4. 31. The standardized information is an average value of frequency components in a coding unit.
4. The signal decoding device according to 4.