Apparatus and method for coding or decoding signals, and recording medium

Description: TECHNICAL FIELD [Detailed description of the invention]

Technical field The present invention encodes input digital data by so-called high-efficiency coding, transmits, records, reproduces, and decodes to obtain a reproduced signal. Information coding or decoding of digital data or the like is applied to signal coding. Alternatively, the present invention relates to a decoding device, a signal coding or decoding method, and a recording medium on which the encoded signal is recorded. Background technology Conventionally, there are various methods for highly efficient coding of signals such as audio and audio. For example, an audio signal on the time axis is not blocked in a certain unit time but is divided into a plurality of frequency bands for coding. Band division coding (sub-band coding: SBC), which is a non-blocking frequency band division method, and blocks the time axis signal in a certain unit time and converts each block into a signal on the frequency axis (spectrum). (Conversion) is performed to divide into a plurality of frequency bands, and each band is encoded. Examples thereof include so-called conversion coding, which is a blocked frequency band division method. Further, a high-efficiency coding method that combines the above-mentioned band division coding and conversion coding is also considered. In this case, for example, after performing band division by the above-mentioned band division coding, each of the above-mentioned methods. The signal for each band is spectrally converted into a signal on the frequency axis, and each of the spectrum-converted bands is encoded. Here, as a filter for band division used in the band division coding and the high efficiency coding method of the combination, for example, there is a filter such as so-called QMF, which is, for example, 1976 RECrochiere Digital coding of speech. in subbands Bell Syst.Tech.J.Vol.55, No.8 1976. Also, for example, ICASSP 83, BOSTON Polyphase Quadrature filters-A new subband coding technique Joseph H. Rothweiler describes an equal bandwidth filtering technique. Further, as the above-mentioned spectrum transform, later, the input audio signal is blocked in a predetermined unit time (frame), and the discrete Fourier transform (DFT), cosine transform (DCT), modified DCT transform (MDCT), etc. are performed for each block. There is a spectrum transform that transforms the time axis into the frequency axis by performing. Regarding the above MDCT, ICASSP 1987 Subband / Transform Coding Using Filter Bank Designs Based on Time Domain Aliasing Cancellation JPPrincen ABBradley Univ.of Surrey Royal Melbourne Described in the Inst.of Tech. In this way, by quantizing the signal divided for each band by a filter or spectral conversion, it is possible to control the band in which quantization noise is generated, and it is audibly higher by utilizing properties such as the masking effect. Efficient coding can be performed. Further, if the normalization is performed for each band by, for example, the maximum value of the absolute value of the signal component in that band before the quantization is performed here, more efficient coding can be performed. Further, as the frequency division width for quantizing each frequency component divided into frequency bands, for example, band division is performed in consideration of human auditory characteristics. That is, the audio signal may be divided into a plurality of bands (for example, 25 bands) with a bandwidth that is generally called a critical band (critical band) so that the higher the band, the wider the bandwidth. Further, when coding the data for each band at this time, coding is performed by a predetermined bit allocation for each band or an 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 allocation bits adaptive to the MDCT coefficient data for each band obtained by the MDCT processing for each block. Coding will be done by number. Here, the following two methods are known as the above-mentioned bit allocation methods. That is, for example, IEEE Transactions of Accoustics, Speech, and Signal Processing, vol.ASSP-25, No.4, August In 1977, bit allocation is performed based on the signal magnitude of each band. In this method, the quantization noise spectrum is flattened and the noise energy is minimized, but the actual noise feeling is not optimal because the masking effect is not used audibly. For example, in ICASSP 1980 The critical band coder --digital encoding of the perceptual requirements of the auditory system MAKransner MIT, by using auditory masking, the required signal-to-noise ratio for each band is obtained and fixed bit allocation is obtained. The method of doing this is described. However, in this method, even when the characteristic is measured by the sine wave input, the characteristic value is not so good because the bit allocation is fixed. In order to solve these problems, all the bits that can be used for bit allocation are divided into a fixed bit allocation pattern predetermined for each small block and a bit allocation depending on the signal size of each block. EUROPEAN PATENT APPLICATION, a high-efficiency coding device that is used for division and makes the division ratio dependent on the signal related to the input signal, and increases the division ratio to the fixed bit allocation pattern as the spectrum of the signal becomes smoother. Proposed in Publication number 0 525 809 A 2, Date of publication of application 03.02.93 Bulletin 93/05. According to this method, when energy is concentrated in a specific spectrum such as a sine wave input, the overall signal-to-noise characteristic can be significantly improved by allocating many bits to the block containing the spectrum. it can. In general, human hearing is extremely sensitive to signals with steep spectral components, so improving the signal-to-noise ratio by using such a method merely improves the measured values. However, it is effective in improving the sound quality in terms of hearing. Many other methods have been proposed for bit allocation, and if the model related to hearing is refined and the capacity of the coding device is improved, more efficient coding can be performed auditorily. .. Here, the conventional signal coding apparatus will be described with reference to each figure after FIG. In FIG. 18, the acoustic signal waveform supplied via the terminal 100 is converted into a signal frequency component by the conversion circuit 101, and then each component is encoded by the signal component coding circuit 102 and then coded by the code sequence generation circuit 103. A code string is generated and output from terminal 104. FIG. 19 shows a specific configuration of the conversion circuit 101 of FIG. In FIG. 19, the signal supplied via the terminal 200 (the signal via the terminal 100 in FIG. 18) is divided into three bands by the two-stage band division filters 201 and 202. In the band division filter 201, the signal passing through the terminal 200 is thinned to 1/2, and in the band division filter 202, one signal thinned to 1/2 by the band division filter 201 is further thinned to 1/2. (The signal of terminal 200 will be thinned out to 1/4). That is, the bandwidth of the two signals from the band division filter 202 is 1/4 of the bandwidth of the signal from the terminal 200. The signals of each band divided into three bands as described above by these band division filters 201 and 202 are made into spectral signal components by forward spectrum conversion circuits 203, 204, 205 that perform spectral conversion such as MDCT, respectively. The outputs of these forward spectrum conversion circuits 203, 204, 205 are sent to the signal component coding circuit 102 of FIG. 18 above. FIG. 20 shows a specific configuration of the signal component coding circuit 102 of FIG. In FIG. 20, the output from the signal component coding circuit 102 supplied to the terminal 300 is normalized for each predetermined band by the normalization circuit 301, and then sent to the quantization circuit 303. The signal supplied to the terminal 300 is also sent to the quantization accuracy determination circuit 302. In the quantization circuit 303, the signal from the normalization circuit 301 is quantized based on the quantization accuracy calculated by the quantization accuracy determination circuit 302 from the signal via the terminal 300. The output from the quantization circuit 303 is output from the terminal 304 and sent to the code sequence generation circuit 103 of FIG. In addition to the signal components quantized by the quantization circuit 303, the output signal from the terminal 304 includes normalization coefficient information in the normalization circuit 301 and quantization accuracy information in the quantization accuracy determination circuit 302. Is also included. FIG. 21 shows a schematic configuration of a decoding device that decodes and outputs an acoustic signal from a code string generated by the coding device having the configuration of FIG. In FIG. 21, the code of each signal component is extracted from the code string generated by the configuration of FIG. 18 supplied via the terminal 400 by the code string decomposition circuit 401. From those codes, each signal component is restored by the signal component decoding circuit 402, and then the reverse conversion corresponding to the conversion of the conversion circuit 101 of FIG. 18 is performed by the reverse conversion circuit 403. As a result, an acoustic waveform signal is obtained, and this acoustic waveform signal is output from the terminal 404. FIG. 22 shows a specific configuration of the inverse conversion circuit 403 of FIG. The configuration of FIG. 21 corresponds to the configuration example of the conversion circuit shown in FIG. 19, and the signals supplied from the signal component decoding circuit 402 via the terminals 501, 502, and 503 correspond to the forward spectrum conversion in FIG. 19, respectively. The conversion is performed by the inverse spectrum conversion circuits 504, 505, 506 that perform the inverse spectrum conversion. The signals of each band obtained by these inverse spectrum conversion circuits 504, 505, 506 are synthesized by a two-stage band synthesis filter. That is, the outputs of the inverse spectrum conversion circuits 505 and 506 are sent to the band synthesis filter 507 and synthesized, and the output of the band synthesis filter 507 and the output of the inverse spectrum conversion circuit 504 are combined by the band synthesis filter 508. .. The output of the band synthesis filter 508 will be output from the terminal 509 (terminal 404 in FIG. 21). Next, FIG. 23 is a diagram for explaining a conventionally performed coding method in the coding apparatus shown in FIG. In the example of FIG. 23, the spectral signal was obtained by the conversion circuit of FIG. 19, and FIG. 23 shows the absolute value level of the spectral signal by MDCT converted into a dB value. In FIG. 23, the input signal is converted into 64 spectral signals for each predetermined time block, which are grouped in each of the five predetermined bands shown in b1 to b5 in the figure of FIG. 23 (this is referred to here as this). Normalization and quantization are performed collectively in (referred to as a coding unit). Here, the bandwidth of each coding unit is narrow on the low frequency side and wide on the high frequency side, so that the generation of quantization noise can be controlled according to the nature of hearing. However, in the conventionally used method described above, the band for quantizing the frequency component is fixed. Therefore, for example, when the spectra are concentrated in the vicinity of some specific frequencies, if an attempt is made to quantize those spectral components with sufficient accuracy, for a large number of spectra belonging to the same band as those spectral components. Many bits must be allocated. That is, as is clear from FIG. 23, when normalization is performed collectively for each predetermined band, for example, in the band b3 in the figure in which the signal contains a tone component, the normalization coefficient value is toned. It will be normalized based on a large normalization coefficient value determined by the sex component. At this time, in general, the noise contained in the toned acoustic signal in which the energy of the spectrum is concentrated on a specific frequency is very audible as compared with the noise added to the acoustic signal in which the energy is gently distributed over a wide frequency band. It is easy to hear and is a major obstacle to hearing. Furthermore, if the spectral components with large energy, that is, the tonal 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 previous and next blocks, the inter-blocks The distortion becomes large (a large connection distortion occurs when combined with the waveform signal of the adjacent time block), which also causes a large audible impairment. Therefore, it is necessary to perform quantization with a sufficient number of bits for coding the tone component, but if the quantization accuracy is determined for each predetermined band as described above, the tone component is included. It is necessary to allocate a large number of bits to a large number of spectra in the coding unit for quantization, which deteriorates the coding efficiency. Therefore, conventionally, it has been difficult to improve the coding efficiency of a toned acoustic signal without deteriorating the sound quality. Therefore, the present invention relates to a signal coding device or a signal coding method capable of increasing the coding efficiency of an acoustic signal having a tone property without deteriorating the sound quality, and further, these signal coding devices and the like. An object of the present invention is to provide a recording medium on which a signal processed in (1) is recorded, and a signal decoding device or a signal decoding method for decoding a coded signal reproduced from the recording medium or transmitted from the signal coding device. Is to be. Disclosure of invention In the signal coding method of the input signal according to the present invention, the 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 above is described. It is characterized in that the first signal is encoded together with the position information of the tone component on the frequency axis, and the signal based on the second signal is encoded. Here, in the signal coding method of the present invention, the conversion is a spectral conversion, and the numerical information within a predetermined range of the tone component is encoded. Further, the signal based on the second signal is a signal obtained by setting the signal of the coding unit including the main part of the tone component of the first signal of the frequency component to 0, or the first signal of the frequency component. It is a signal in which the frequency component of the signal and its vicinity is set to 0. Further, in the separation step, the tone component is encoded, the encoded tone component is decoded, and the decoded tone component is subtracted from the frequency component of the input signal to generate a difference signal. The second signal is the difference signal. Of the first signal coding step and the signal coding step based on the second signal, at least the signal coding step based on the second signal encodes the input signal. It includes the steps of normalizing each unit and quantizing the normalized signal. Of the first signal coding step and the signal coding step based on the second signal, at least the signal coding step based on the second signal is performed on the input signal. Includes steps to perform variable length coding. The separation step separates the first signal only from the high frequencies of the frequency components. In the above conversion step, conversion is performed so that the frequency resolution on the low frequency side is higher than the frequency resolution on the high frequency side. The input signal is an audio signal. Further, the above-mentioned position information includes information indicating a difference between the position information of the current block and the position information of another time block. The number of frequency components set to 0 for each frequency component of the first signal is larger on the high frequency side than on the low frequency side. The number of frequency components set to 0 with respect to one frequency component in the first signal is asymmetrical on the high frequency side and the low frequency side with respect to one frequency component in the first signal. Is. In the separation step, the tone component of the difference signal is encoded, the encoded tone component is decoded, and the decoded tone component is different from the difference signal. Next, the coding device for encoding the input signal of the present invention has a means for converting the input signal into a frequency component, and a second signal having the frequency component composed of a tone component and a second component composed of other components. A means for separating into a signal, a first coding means for encoding the first signal together with position information of the tone component on the frequency axis, and a second for encoding a signal based on the second signal. It is characterized by having two coding means. Here, in the signal coding apparatus of the present invention, the conversion is a spectral conversion, and has a coding means for coding numerical information within a predetermined range of the tone component. The signal based on the second signal is a signal obtained by setting the signal of the coding unit including the main part of the tone component of the first signal of the frequency component to 0, or the first signal of the frequency component and the first signal of the frequency component. It is a signal in which the frequency component in the vicinity is set to 0. The separation means includes a coding means for encoding the tone component, a decoding means for decoding the encoded tone component, and a frequency component of the input signal with the decoded tone component. The second signal is the difference signal, including means for generating a difference signal by subtracting from. At least the second coding means among the first coding means and the second coding means is a normalization means that normalizes the input signal for each coding unit and is normalized. Includes a quantization means that quantizes the signal. At least the second coding means among the first coding means and the second coding means includes a variable length coding means that performs variable length coding on the input signal. The separation means separates the first signal only from the high frequencies of the frequency components. The conversion means performs conversion so that the frequency resolution on the low frequency side is higher than the frequency resolution of the high frequency example. The input signal is an audio signal. The above-mentioned position information includes information indicating a difference between the position information of the current block and the position information of another time block. The number of frequency components set to 0 for each frequency component of the first signal is larger on the high frequency side than on the low frequency side. The number of frequency components set to 0 with respect to one frequency component in the first signal is asymmetrical on the high frequency side and the low frequency side with respect to one frequency component in the first signal. Is. The separation means includes a coding means for encoding the tone component of the difference signal, a decoding means for decoding the encoded tone component, and the difference signal for decoding the decoded tone component. A means for generating a new difference signal by subtracting from the above new difference signal and outputting the new difference signal as the difference signal. Therefore, according to the present invention, an input, for example, an acoustic signal is separated into a signal component in which energy is concentrated in a specific frequency and a component in which energy is gently distributed in a wide band and coded to obtain a high code. It is possible to realize the efficiency of conversion. A brief description of the drawing FIG. 1 is a block circuit diagram showing a schematic configuration of a coding device according to an embodiment of the present invention. FIG. 2 is a block circuit diagram showing a schematic configuration of a decoding device according to an embodiment of the present invention. FIG. 3 is a block circuit diagram showing the configuration of the synthetic inverse conversion unit. FIG. 4 is a flowchart showing a processing flow in the signal component separation circuit according to the embodiment of the present invention. FIG. 5 is a diagram for explaining a tone component in the signal coding of this embodiment. FIG. 6 is a diagram for explaining a noise component in the signal coding of this embodiment. FIG. 7 is a diagram showing separated tone components in the signal coding of this embodiment. FIG. 8 is a diagram for explaining another example of signal coding in this embodiment. FIG. 9 is a block circuit diagram showing a schematic configuration of a signal coding device for explaining the signal coding method of this embodiment. FIG. 10 is a diagram for explaining a method of coding a signal obtained by subtracting a decoded signal by coding a tone component from the original spectral signal in the signal coding of the present embodiment. FIG. 11 is a diagram showing a state in which a signal obtained by coding and decoding a tone component is subtracted from the original spectral signal in the signal coding of this embodiment. FIG. 12 is a diagram for explaining a case where the band for extracting the tone component is performed only in the high frequency band in the signal coding of this embodiment. FIG. 13 is a diagram for explaining the recording of the code string obtained by coding by the signal coding of this embodiment. FIG. 14 is a diagram showing a state of a spectral signal in a certain time block in the signal coding of this embodiment. FIG. 15 is a diagram showing a state of a spectral signal in a time block adjacent to a certain time block in the signal coding of this embodiment. FIG. 16 is a diagram for explaining an example in which the center position information of the tone component information in the spectral signal in the time block of this embodiment is encoded by 2 bits. FIG. 17 is a diagram for explaining a recording state when the center position information of this embodiment is recorded on a recording medium. FIG. 18 is a block circuit diagram showing a schematic configuration of a conventional coding device. FIG. 19 is a block circuit diagram showing a specific configuration of a conversion circuit of this embodiment and a conventional coding device. FIG. 20 is a block circuit diagram showing a specific configuration of a signal component coding circuit of this embodiment and a conventional coding device. FIG. 21 is a block circuit diagram showing a schematic configuration of a conventional decoding device. FIG. 22 is a block circuit diagram showing a specific configuration of an inverse conversion circuit of this embodiment and a conventional decoding device. FIG. 23 is a diagram for explaining a coding method according to the prior art. The best mode for carrying out the invention Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a signal coding apparatus according to an embodiment of the present invention to which the signal coding method of the present invention is applied. 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. In the signal component separation circuit 602, the signal frequency component obtained by the conversion circuit 601 is divided into a tone component having a steep spectral distribution and a noise component having another signal frequency component, that is, a flat spectral distribution. Be separated. Of these separated frequency components, the tone component having the steep spectral distribution is the tone component coding circuit 603, and the noise component which is the other signal frequency component is the noise component coding circuit 604. , Each encoded. The output from the tone component coding circuit 603 and the noise component coding circuit 604 is output after a code string is generated by the code string generation circuit 605. The ECC encoder 606 adds an error collection code to the code string from the code string generation circuit 605. The output from the ECC encoder 606 is modulated 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 disk 609 can be, for example, a magneto-optical disk or a phase change disk. Further, an IC card or the like can be used instead of the disk 609. The conversion circuit 601 can have the same configuration as that of FIG. 19 described above. Of course, as a specific configuration of the conversion circuit 601 of FIG. 1, many can be considered in addition to the configuration of FIG. 19, for example, the input signal may be directly converted into a spectral signal by MDCT, or the spectral conversion may be performed. It is also possible to use DFT or DCT instead of MDCT. Further, as described above, it is possible to divide the signal into band components by a band division filter, but since the method of the present invention works particularly effectively when energy is concentrated on a specific frequency, a large number of frequencies are used. It is convenient to adopt the method of converting into a frequency component by the above-mentioned spectral conversion obtained by obtaining a component with a relatively small amount of calculation. Further, the tone component coding circuit 603 and the noise component coding circuit 604 can also be realized with basically the same configuration as in FIG. 20 described above. On the other hand, FIG. 2 shows a schematic configuration of a signal decoding device of an embodiment to which the signal decoding method of the present invention for decoding a signal encoded by the coding device of FIG. 1 is applied. In FIG. 2, the code string reproduced from the disk 609 via the reproduction 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 component code based on the number of tone component information in the error-corrected code string, and uses the input code string as the tone component. Separate into a code and a noise component code. Further, the code string separation circuit 701 separates the position information of the tone component from the input code string and outputs it to the synthesis circuit 704 in the subsequent stage. The tone component code is sent to the tone component decoding circuit 702, and the noise component code is sent to the noise component decoding circuit 703, where dequantization and denormalization are performed and decoding is performed, respectively. Will be done. After that, the decoding signals from the tone component decoding circuit 702 and the noise component decoding circuit 703 are supplied to the synthesis circuit 704 that performs the synthesis corresponding to the separation in the signal component separation circuit 602 of FIG. .. The synthesis circuit 704 adds the decoding signal of the tone component to a predetermined position of the decoding signal of the noise component based on the position information of the tone component supplied from the code string separation circuit 701. The noise component and the tone component are combined on the frequency axis. Further, the synthesized decoded signal is converted by the inverse conversion circuit 705 that performs the inverse conversion corresponding to the conversion in the conversion circuit 601 of FIG. 1, and the waveform signal on the original time axis is converted from the signal on the frequency axis. Returned to. The output waveform signal from the inverse conversion circuit 705 is output from the terminal 707. The processing order of the inverse conversion and the synthesis may be reversed. In this case, the synthetic inverse conversion unit 711 in FIG. 2 has the configuration shown in FIG. In FIG. 3, the inverse conversion circuit 712 reverse-converts the decoding signal of the noise component on the frequency axis from the noise component decoding circuit 703 into the noise component signal on the time axis. The inverse conversion circuit 713 arranges the decoding signal of the tone component from the tone component decoding circuit 702 at a position on the frequency axis indicated by the position information of the tone component supplied from the code sequence separation circuit 701. This is inversely converted to generate a tone component signal on the time axis. The synthesis circuit 714 synthesizes the noise component signal on the time axis from the inverse conversion circuit 712 and the tone component signal on the time axis from the inverse conversion circuit 713 to generate the original waveform signal. The same configuration as in FIG. 22 described above can be used for the inverse conversion circuits 705,712,713. Here, FIG. 4 shows a specific flow of processing for separating the tone component in the signal component separation circuit 602 of the coding device of FIG. In FIG. 4, I indicates the number of the spectral signal, N indicates the total number of spectral signals, and P and R indicate predetermined coefficients. Further, in the above tone component, the absolute value of a certain spectral signal is locally larger than that of other spectral components, and it is the maximum of the absolute value of the spectral signal in the time block (block at the time of spectral conversion). It is greater than or equal to a predetermined magnitude compared to the value, and the sum of the energies of that spectrum and neighboring spectra (eg, adjacent spectra) is greater than or equal to a predetermined ratio of the energies in a predetermined band containing those spectra. When is shown, the spectral signal and, for example, the spectral signals on both sides of the spectral signal are considered to be tone components. Here, as a predetermined band for comparing the ratio of the energy distribution, in consideration of the nature of hearing, for example, it can be narrow in the low range and wide in the high range according to the critical bandwidth. That is, in FIG. 4, first, in step S1, the maximum spectral absolute value is assigned to the variable A0, and in step S2, the number I of the spectral signal is set to 1. In step S3, a certain spectral absolute value in a certain time block is assigned to the variable A. In step S4, it is determined whether or not the absolute value of the spectrum is a maximum absolute value spectrum that is larger than other spectral components when viewed locally, and if it is not a maximum absolute value spectrum (No), the process proceeds to step S10 and the maximum absolute value is obtained. If it is a value spectrum (Yes), the process proceeds to step S5. In step S5, the ratio of the variable A of the maximum absolute value spectrum to the variable A0 of the maximum spectrum absolute value in the time block including the maximum absolute value spectrum is compared with the coefficient P indicating a predetermined magnitude (A). / A0> P) is performed, and if A / A0 is larger than P (Yes), the process proceeds to step S6, and if A / A0 is P or less (No), the process proceeds to step S10. In step S6, the energy value of the spectrum in the vicinity of the spectrum of the absolute value of the spectrum (maximum absolute value spectrum) (for example, the sum of the energies of the spectra on both sides) is assigned to the variable X, and in the next step S7, the maximum absolute value spectrum is obtained. The energy value in a predetermined band including the spectrum of and its vicinity is assigned to the variable Y. In the next step S8, the magnitude comparison (X / Y> R) between the ratio of the variable X of the energy value and the variable Y of the energy value in the predetermined band and the coefficient R indicating the predetermined ratio is performed, and X / When Y is greater than R (Yes), the process proceeds to step S9, and when X / Y is less than or equal to R (No), the process proceeds to step S10. In step S9, when the energy in the maximum absolute value spectrum and its neighboring spectra shows a predetermined ratio or more with respect to the energy in a predetermined band including those spectra, the signal of the maximum absolute value spectrum is shown. And, for example, the signals of the spectra on both sides of the signal are regarded as the tone component, and that fact is registered. In the next step S10, it is determined whether or not the number I of the spectral signals registered in step S9 above and the total number N of the spectral signals N are equal (I = N), and if they are equal (Yes), the process ends. If they are not equal, the process proceeds to step S11. In this step S11, the number of the spectral signal is increased one by one with I = I + 1, and the process returns to step S3, and the above processing is repeated. The signal component separation circuit 602 supplies a frequency component determined to be a tone component by the above processing to the tone component coding circuit 603, and uses the other frequency components as noise components to be a noise component coding circuit. Supply to 604. Further, the signal component separation circuit 602 supplies the code string generation circuit 605 with information on the number of frequency information determined to be the tone component and its position. FIG. 5 shows an example in which the tone component is separated from the frequency component as described above. In the example shown in FIG. 5, the four tonic components indicated by TC A, TC B, TC C, and TC D in the figure are extracted. Here, since the tonic components are concentrated and distributed in a small number of spectral signals as in the example of FIG. 5, even if these components are quantized with high accuracy, the number of bits as a whole is too large. Not needed. Further, the coding efficiency can be improved by once normalizing the tone component and then quantizing it, but since the spectral signals constituting the tone component are relatively small, the normalization and requantization processing can be performed. May be omitted to simplify the device. Further, FIG. 6 shows an example showing a noise component obtained by removing the tone component from the original spectral signal. As shown in FIG. 6, since the tone component is removed from the original spectral signal in each band b1 to b5 as described above, the normalization coefficient in each coding unit is a small value, and therefore, The quantization noise generated even with a small number of bits can be reduced. Here, by utilizing the property of hearing, the coding of the noise component can be performed more efficiently. That is, the masking effect works effectively in the vicinity of the toned signal on the frequency axis. Therefore, even if the extracted noise component in the vicinity (the noise component in the vicinity of the tone component) is coded as 0, the acoustic signal decoded later is the original sound and audibility. , I don't feel a big difference. A specific example of the coding method in the noise component coding circuit 604 utilizing such a property will be described with reference to FIG. 7. In FIG. 7, the noise component of the coding unit in which the main parts of the tone components (TC A, TC B, TC C, TC D) are present is set to 0. Therefore, of the noise components in each band, only the coding unit in band b5 is actually coded. This method can perform compression by a very simple method, such as when the coding unit is based on the critical bandwidth. In addition, another specific example of a coding method utilizing such a property will be described with reference to FIG. In FIG. 8, instead of setting the noise component of the coding unit to 0, the spectral component of a predetermined number in the vicinity of each tone component (TC A, TC B, TC C, TC D) is set to 0. ing. This predetermined number can be changed according to the frequency of the tone component based on the nature of hearing so that it is small in the low frequency range and high in the high frequency range. Further, in this specific example, as a result, all the noise components of the coding unit in the band b4 become 0, and the noise components in the band b4 are not actually encoded. Even by the method of this specific example, efficient compression that is audibly effective can be performed by a relatively simple means. Since masking by the tone component works strongly on the high frequency side, the range in which the noise component is set to 0 may be asymmetric. Further, the noise component is encoded in the code sequence generation circuit 605 by, for example, the so-called variable length code described in DAHuffman: A Method for Construction of Minimum Redundancy Codes, Proc.IRE, 40, p.1098 (1952). You may. In such a coding method, the efficiency of coding is improved by assigning a short code length to a pattern with a high frequency, but when such a code is used, the noise component is set to 0 as described above. The method of keeping works effectively. That is, since many 0 components appear, the coding efficiency can be improved by assigning a code having a short length to 0. The method of this embodiment in which the tone component is separated, the tone component and the signal in the vicinity thereof are set to 0, and then the noise component is encoded has been described above. However, the tone component is coded from the original spectral signal. It is also possible to take a method of encoding the signal obtained by subtracting the decrypted signal. A signal coding device according to this method will be described with reference to FIG. The same configuration as in FIG. 1 is given the same number, and the description thereof will be omitted. The spectral signal obtained by the conversion circuit 601 is supplied to the tone component extraction circuit 802 via the switch 801 controlled by the control circuit 808. The tone component extraction circuit 802 discriminates the tone component by the process of FIG. 4 described above, and supplies only the discriminated tone component to the tone component coding circuit 603. Further, the tone component extraction circuit 802 outputs the number of tone component information and the center position information thereof to the coded sequence generation circuit 605. The tone component coding circuit 603 normalizes and quantizes the input tone component, and supplies the normalized and quantized tone component to the coded sequence generation circuit 605 and the local decoder 804. .. The local decoder 804 dequantizes and denormalizes the normalized and quantized toned components, and decodes the signal of the original toned components. However, at this time, the decoded signal includes quantization noise. The output from the local decoder 804 is supplied to the adder 805 as the first decoding signal. Further, the adder 805 is supplied with the original spectral signal from the conversion circuit 601 via the switch 806 controlled by the switch control circuit 808. The adder 805 subtracts the first decoding signal from the original spectral signal and outputs the first difference signal. When the extraction, coding, decoding, and differentiation processing of the tone component is completed in one time, this first difference signal is used as a noise component via the switch 807 controlled by the switch control circuit 808. It is supplied to the noise component coding circuit 604. When the extraction, coding, decoding, and differentiation processing of the tone component is repeated, the first difference signal is supplied to the tone component extraction circuit 802 via the switch 801. The tone component extraction circuit 802, the tone component coding circuit 603, and the local decoder 804 perform the same processing as described above, and the obtained second decoding signal is supplied to the adder 805. Further, the adder 805 is supplied with the first difference signal via the switch 806. Adder 805 is the first The second difference signal is output by subtracting the second decode signal from the difference signal. When the extraction, coding, decoding, and differentiation processing of the tone component is completed in two times, this second difference signal is used as the noise component via the switch 807, and the noise component coding circuit 604. Is supplied to. When the extraction, coding, decoding, and differentiation processing of the tone component is further repeated, the same processing as described above is performed by the tone component extraction circuit 802, the tone component coding circuit 603, the local decoder 804, and the adder 805. Is done by. The switch control circuit 808 holds a threshold value for the number of tone component information, and extracts, encodes, and decodes the tone component when the number of tone component information obtained from the tone component extraction circuit exceeds this threshold. Control switch 807 to end the conversion process. Further, in the tone component coding circuit 603, the extraction, coding, decoding, and differentiation processing of the tone component can be terminated when the tone component is no longer extracted. 10 and 11 show an example of coding by such a method, and FIG. 11 shows the spectral signal of FIG. 10 minus a signal obtained by encoding and decoding one tone component. Is. Further, the coding accuracy of the spectral signal can be improved by further extracting the component shown by the broken line in the figure from the spectral signal of FIG. 11 as a tone component and coding it, and by repeating this, the accuracy Can be highly coded. When this method is used, the coding accuracy can be sufficiently high even if the upper limit of the number of bits for quantizing the tone component is set low, and therefore, the number of bits for recording the number of quantization bits. There is also an advantage that can be made smaller. In addition, the method of extracting the tone component in multiple stages in this way is not limited to the case where the signal equivalent to the coded and decoded signal of the tone component is subtracted from the original spectral signal, but also extracted. It is also applicable when the spectral signal of the toned component is set to 0, and expressions such as "a signal in which the toned component is separated" include both of them in the description of the present invention. Next, FIG. 12 shows a specific example in which the band for extracting the tone component is set only in the high frequency range. Here, in general, when spectrum conversion is performed, the conversion section length of the spectrum conversion must be extremely long in order to obtain sufficient frequency resolution in the low frequency range, and it is difficult to realize this with a small-scale device. Is. Further, in order to encode the tone component, it is necessary to encode the position information and the normalization information of the tone component, but when there are many tone components with poor separation in the low frequency range, these are required. It is disadvantageous to record the number of extracted tone components in order to improve the coding efficiency. Therefore, when the frequency resolution cannot be sufficiently obtained on the low frequency side, the tone component may be separated and coded only on the high frequency side as in the example of FIG. Further, in order to secure sufficient frequency resolution in the low frequency band, the frequency resolution in the low frequency band and the high frequency band may be changed. For example, in the conversion circuit of FIG. 19 described above applied to the conversion circuit 601 of FIG. 1 of this embodiment, the rate of the output signals of the two bands of the band division filter 202 is the forward spectrum conversion circuit 203 of the band division filter 201. Although it is thinned to half the rate of the signal sent to, if the forward spectrum conversion is performed on the same number of input signals by the forward spectrum conversion circuit 203,204,205, the frequency resolution of the spectral signal from the forward spectrum conversion circuit 204,205 will be. It can be twice as high as the resolution of the spectral signal from the forward spectrum conversion circuit 203. FIG. 13 shows a specific example of a code string (code string recorded on a recording medium) when the spectrum signal of FIG. 8 is encoded by the method of the embodiment of the present invention. In FIG. 13, first, the number of tone component information tcn (4 in the example of FIG. 8) is recorded on the recording medium, and then on the tone component TC A, TC B, TC C, TC D of FIG. The corresponding tone component information tcA, tcB, tcC, tcD and the noise component information nc1, nc2, nc3, nc4, nc5 corresponding to each band b1 to b5 in FIG. 8 are recorded in this order. Here, the tone component information includes the center position information CP (for example, 15 in the case of the tone component TC B) representing the position of the center spectrum of the tone component and the number of bits for quantization. The represented quantization accuracy information (for example, 6 in the case of the tone component TC B) and the normalization coefficient information are recorded together with the normalized and quantized signal component information (for example, information SC1, SC2, SC3). It will be recorded on the medium. Of course, it is not necessary to record the quantization accuracy information when the quantization accuracy is fixedly determined by the frequency, for example. Further, in the above-described embodiment, the position of the central spectrum of each tone component is used as the position information of the tone component, but the position of the lowest spectrum of each tone component (for example, the tone component). In the case of TC B, 14) may be recorded. Regarding the noise component information, the quantization accuracy information and the normalization coefficient information are recorded together with the normalized and quantized signal component information (for example, information SC1, SC2, ..., SC8). Will be recorded in. When the quantization accuracy information is 0 (noise component information nc4 in FIG. 13), it is shown that the coding unit does not actually perform coding. In this case as well, if the quantization accuracy is fixedly determined by the band, it is not necessary to record the quantization accuracy information, but at this time, the coding is actually performed as in the band b4, for example. It becomes impossible to specify no coding unit. In such a case, for example, 1-bit flag information indicating whether or not coding is actually performed in each coding unit may be added. As described above, in order to record the tone component information on the recording medium by the method of the embodiment of the present invention, it is necessary to record the position of the tone component by some method. It can be recorded efficiently by the method. 14 and 15 show the state of the spectral signals in the adjacent time blocks, and the spectral signals in FIG. 15 show the ones in the next time block of FIG. In FIGS. 14 and 15, for example, the spectral signal obtained by the MDCT changes from block to block due to slight fluctuations in the phase and waveform signal in the time block, but the position of the tone component is in the previous block. It is almost the same as, and corresponds to the tone component of TC A, TC B, TC C, TC D in the figure of FIG. 14, and the tone property of TC E, TC F, TC G, TC H in the figure of FIG. Ingredients are appearing. Therefore, the center position information of the tone component can be efficiently recorded at a position relative to the center position information of the tone component in the previous time block, and specific examples thereof are shown in FIGS. 16 and 17. is there. In FIG. 16, it is assumed that the tone component information in the time block of FIG. 14 is recorded in the order of tcA, tcB, tcC, and tcD. Here, for example, among the spectral signals in the time block of FIG. 15, the center position difference information CP with the tone component of TC B is shown as the center position information CP of the tone component information tc F of TCF in the figure of FIG. The 2-bit coded center position information CP1 as shown in 16 can be recorded as shown in FIG. In this way, the center position information CP of many tone components can be represented by a short code by corresponding to the tone component in another time block, for example, the immediately preceding time block, and efficient coding is possible. It becomes. However, the tone component of TC H is a change of the tone component of TC D, but since this cannot be expressed by the center position difference information in FIG. 16, the tone component information of TC D is once invalidated and centered. Information on the tone component of TCH is recorded using the position information CP2. Note that the reference numerals shown in FIG. 17 are of course an example, and for example, the tone component information number tcn1 may be omitted because it can be understood from the information of the previous time block. In the above description, the method of applying the method of the embodiment of the present invention to the acoustic signal has been mainly described, but the method of the embodiment of the present invention can also be applied to the coding of a general waveform signal. is there. However, in the case of an acoustic signal, the tone component information has a particularly important auditory meaning, and the method of the embodiment of the present invention can be applied particularly effectively. As is clear from the above description, if the signal coding or decoding device, the signal coding or decoding method according to the present invention is used, the tone component of the input signal is efficiently separated from the other components. It becomes possible to encode. In particular, when the present invention is used for coding an acoustic signal, the tone component that is important for hearing is encoded with sufficiently high accuracy, and the noise component that is not so important for hearing is encoded with minimum accuracy. It is possible to achieve extremely efficient signal compression. Therefore, if this compressed signal is recorded on a recording medium, the recording capacity can be effectively used, and further, a good acoustic signal can be obtained by decoding the signal obtained by reproducing this recording medium. Will be able to.