JP3465697B2 - Signal recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention encodes and transmits input digital data by so-called high efficiency encoding.
A signal recording medium used for a signal encoding or decoding device to which information encoding or decoding of digital data or the like is applied, in which a reproduced signal is obtained by recording, reproducing, and decoding, and the encoded signal is recorded. It is about.

[0002]

2. Description of the Related Art Conventionally, there are various techniques for high-efficiency coding of audio or voice signals. For example, audio signals on the time axis are not blocked in a certain unit time and are divided into a plurality of frequency bands. Band division coding, which is a non-blocking frequency band division method of dividing and encoding
Band coding: SBC), or the time axis signal is divided into blocks in a certain unit time, and each block is converted into a signal on the frequency axis (spectral conversion), divided into multiple frequency bands, and coded for each band There is a so-called transform coding, which is a block frequency band division method for converting into a block. 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, The signal for each band is spectrally converted into a signal on the frequency axis, and coding is performed for each spectrally converted band.

Here, as a band-splitting filter used in the above-described band-splitting coding or the above-described combination high-efficiency coding method, for example, there is a so-called QMF filter, which is, for example, the 1976 RECrochiere Digital co
ding of speech in subbands Bell Syst.Tech. J. Vol.5
5, No. 8 1976. Also, for example, ICASSP83,
BOSTON Polyphase Quadrature filters-A new subband
Coding technique Joseph H. Rothweiler describes a technique for partitioning filters of equal bandwidth.

Further, as the above-mentioned spectrum conversion,
For example, an input audio signal is divided into blocks in a predetermined unit time (frame), and a discrete Fourier transform (DFT), a cosine transform (DCT), a modified DCT transform (MDCT), etc. are performed for each block to set a time axis as a frequency axis. There is a spectral transformation that transforms. Regarding the above MDCT, ICASSP 1987, Subband / Transfo
rm Coding Using FilterBank Designs Based on Time D
omain Aliasing Cancellation, JPPrincen, ABBrad
ley, Univ. of Surrey Royal Melbourne Inst. of Tec
h.

As described above, by quantizing the signal divided into each band by the filter or spectrum conversion, the band in which the quantization noise is generated can be controlled,
By utilizing the properties such as the masking effect, it is possible to perform more efficient audio coding. Further, if the normalization is performed for each band, for example, with the maximum value of the absolute value of the signal component in that band before the quantization is performed here, more efficient encoding can be performed.

Further, as a frequency division width for quantizing each frequency component divided into frequency bands, for example, band division considering human auditory characteristics is performed. That is, an audio signal may be divided into a plurality of bands (for example, 25 bands) with a bandwidth such that a higher band generally called a critical band has a wider bandwidth. Further, at the time of encoding the data for each band at this time, encoding is performed by predetermined bit allocation for each band or 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, adaptive allocation bits are assigned to the MDCT coefficient data for each band obtained by the MDCT processing for each block. The encoding will be performed by numbers.

The following two methods are known as the above-mentioned bit allocation method. That is, for example, IEEE Trans
actions of Accoustics, Speech, and Signal Processi
In ng, 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 is flattened and the noise energy is minimized, but the actual noise feeling is not optimal because the masking effect is not used auditorily. Also, for example, ICASSP 1980, The criticalband code
r --digital encoding of the perceptual requiremen
In ts of the auditory system, MA Kransner, MIT, a method for obtaining a necessary signal-to-noise ratio for each band and performing fixed bit allocation by using auditory masking is described. However, in this method, even when the characteristic is measured with a sine wave input, the characteristic value is not so good because the bit allocation is fixed.

In order to solve these problems, all bits that can be used for bit allocation have a fixed bit allocation pattern predetermined for each small block and a bit allocation depending on the signal size of each block. A high-efficiency coding device that is used by dividing into parts to be performed, makes the division ratio dependent on the signal related to the input signal, and increases the division ratio to the fixed bit allocation pattern portion as the spectrum of the signal becomes smoother, EUROPEAN PATENT APPLICATION, Publication
number 0 525 809 A2, Datte of publication of appl
ication 03.02.93 Proposed in Bulletin 93/05.

According to this method, when energy is concentrated on a specific spectrum such as a sine wave input, a large number of bits are allocated to a block including the spectrum, thereby significantly improving the overall signal-to-noise characteristic. can do. In general, human hearing is extremely sensitive to a signal having a steep spectrum component. Therefore, improving the signal-to-noise characteristic by using such a method does not only improve the numerical value in measurement. Not only that, it is effective in improving the sound quality in terms of hearing.

Many other methods have been proposed for the bit allocation method. Further, if the model relating to hearing is further refined and the coding apparatus is improved, it is possible to realize more efficient coding in terms of hearing. It will be possible.

Here, a conventional signal coding apparatus will be described with reference to FIGS.

In FIG. 18, an acoustic signal waveform supplied through a terminal 100 is converted into a signal frequency component by a conversion circuit 101, and then a signal component encoding circuit 102.
Each component is encoded by, the code string generation circuit 103 generates a code string, and the code string is output from the terminal 104.

FIG. 19 shows a specific structure of the conversion circuit 101 shown in 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 via the terminal 200 is decimated to 1/2, and in the band division filter 202, the band division filter 201 outputs 1
One of the signals decimated to / 2 is further decimated to ½ (the signal at the terminal 200 is decimated to ¼). That is, the bandwidth of the two signals from the band split filter 202 is 1 / the bandwidth of the signal from the terminal 200.
It is 4.

The signals of the respective bands divided into the three bands by the band dividing filters 201 and 202 as described above are converted into spectrum signal components by forward spectrum conversion circuits 203, 204 and 205 for performing spectrum conversion such as MDCT. Done. The outputs of these forward spectrum conversion circuits 203, 204, 205 are sent to the signal component coding circuit 102 of FIG.

FIG. 20 shows a specific configuration of the signal component coding circuit 102 of FIG.

In FIG. 20, the output from the signal component encoding circuit 102 supplied to the terminal 300 is normalized by the normalizing circuit 301 for each predetermined band and then sent to the quantizing circuit 303. To be In addition, the terminal 30
The signal supplied to 0 is also sent to the quantization precision determination circuit 302.

In the quantizing circuit 303, the terminal 30
Based on the quantization precision calculated by the quantization precision determination circuit 302 from the signal passing through 0, the normalization circuit 20
The signal from 1 is quantized. The output from the quantization circuit 303 is output from the terminal 304, and
Is sent to the code string generation circuit 103. In addition, this terminal 3
In addition to the signal component quantized by the quantization circuit 303, the output signal from the
Normalization coefficient information and the quantization accuracy determination circuit 30
The quantization accuracy information in 2 is also included.

FIG. 21 shows a schematic configuration of a decoding device which decodes and outputs an acoustic signal from a code string generated by the encoding device having the configuration of FIG.

In FIG. 21, the code string decomposition circuit 401 extracts the code of each signal component from the code string generated through the configuration of FIG. 18 supplied through the terminal 400. From these codes, each signal component is restored by the signal component decoding circuit 402, and then the inverse transform circuit 403 performs inverse transform corresponding to the transform of the transform circuit 101 in FIG. 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 shown in FIG.

The configuration of FIG. 21 corresponds to the configuration example of the conversion circuit shown in FIG. 19 and includes terminals 501, 502,
The signals supplied from the signal component decoding circuit 402 via 503 are converted by inverse spectrum conversion circuits 504, 505, 506 which perform inverse spectrum conversion corresponding to the forward spectrum conversion in FIG. The signals of the respective bands obtained by the inverse spectrum conversion circuits 504, 505, 506 are combined by the two-stage band combining filter.

That is, the outputs of the inverse spectrum converting circuits 505 and 506 are sent to the band synthesizing filter 507 to be combined, and the output of the band synthesizing filter 507 and the output of the inverse spectrum converting circuit 504 are combined with the band synthesizing filter 5.
It is synthesized at 08. The output of the band synthesis filter 508 comes to be output from the terminal 509 (terminal 404 in FIG. 21).

Next, FIG. 23 is a diagram for explaining a conventional coding method in the coding apparatus shown in FIG. In the example of FIG. 23, the spectrum signal is obtained by the conversion circuit of FIG. 19, and FIG. 23 shows the absolute value level of the spectrum 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 is grouped into five predetermined bands shown by b1 to b5 in FIG. Will be referred to herein as a coding unit) and the normalization and quantization will be performed. Here, the bandwidth of each coding unit is narrow on the low frequency side and wide on the high frequency side, and it is possible to control the generation of quantization noise according to the auditory characteristics.

[0025]

However, in the above-mentioned conventional method, the band for quantizing the frequency component is fixed. So, for example, if the spectrum is concentrated around some particular frequencies, then trying to quantize those spectral components with sufficient accuracy will result in a large number of spectra belonging to the same band as those spectral components. Therefore, many bits must be allocated.

That is, as is clear from FIG. 23, when the normalization is performed collectively for each predetermined band, for example, in the band b3 in FIG. Numerical values will be normalized based on a large normalization coefficient value determined by the tone component.

At this time, generally, the noise contained in the tone-like acoustic signal in which the energy of the spectrum is concentrated at a specific frequency is much higher than the noise added to the acoustic signal in which the energy is gently distributed over a wide frequency band. It is easy to hear, which 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 synthesized with the preceding and following blocks, the Distortion becomes large (a large connection distortion occurs when synthesized with waveform signals of adjacent time blocks), which also causes a great audible obstacle. Therefore, quantization must be performed with a sufficient number of bits for encoding the tone component, but if the quantization precision is determined for each predetermined band as described above, the tone component is included. Since it is necessary to allocate many bits to many spectra in a coding unit and perform quantization, the coding efficiency becomes poor. Therefore, conventionally, it has been difficult to improve the coding efficiency without deteriorating the sound quality especially for a tone-like acoustic signal.

Therefore, according to the present invention, a signal processed by a signal coding apparatus, a signal coding method, or the like, which makes it possible to increase the coding efficiency without deteriorating the sound quality, especially for a tone-like acoustic signal. It is intended to provide a signal recording medium on which is recorded.

[0029]

A signal recording medium according to the present invention is a signal recording medium in which an encoded signal is recorded, in which an input signal is converted into a frequency component, and the frequency component is composed of a tone component. The signal is separated into a second signal composed of the first signal and other components, the first signal is encoded together with position information on the frequency axis of the tone component, and the signal based on the second signal is encoded. It is formed by recording the encoded and encoded first and second signals and the encoded position information.

Here, in the signal recording medium of the present invention,
The above-mentioned conversion is a spectrum conversion, and the position information on the frequency axis of the tone component is encoded and the encoded position information is recorded. Further, the number information of the tone component within a predetermined range is encoded, and the encoded number information is recorded. The signal based on the second signal is a signal in which the encoded binary signal including the main part of the tone component of the first signal of the frequency component is zero. The signal based on the second signal is a signal in which the first signal of the frequency component and its neighboring frequency components are set to zero. The separating step encodes the tone component, decodes the encoded tone component, and subtracts the decoded tone component from the frequency component of the input signal to generate a difference signal. And the second signal is the difference signal. At least the step of encoding the signal based on the second signal of the steps of encoding the first signal and the step of encoding the signal based on the second signal encodes the input signal. Normalizing every two bits and quantizing the normalized signal.
At least the step of encoding the signal based on the second signal among the steps of encoding the first signal and the step of encoding the signal based on the second signal is performed on the input signal. The step of performing variable length coding is included.
The separating step separates the first signal from only the high frequency band of the frequency component. In the conversion step, conversion is performed so that the frequency resolution on the low frequency side becomes higher than the frequency resolution on the high frequency side. The input signal is a voice signal. The position information includes information indicating a difference between the position information of the current block and the position information of another time block. First above
The number of frequency components set to 0 for each frequency component of the signal is higher 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 of the first signal is asymmetric on the high frequency side and the low frequency side around the one frequency component of the first signal. Is. The separating step encodes the tone component of the difference signal, decodes the encoded tone component, and subtracts the decoded tone component from the difference signal to generate a new difference signal. And including at least one step of setting the new difference signal as the difference signal,
Signal is a new differential signal described above.

Further, the signal recording medium on which the coded signal according to the present invention is recorded has the tone characteristic component information regarding the tone characteristic component and the noise characteristic component information regarding the noise characteristic component recorded separately.

Here, in the signal recording medium of the present invention,
The tone component information includes position information of the tone component on the frequency axis, or number information of the tone and other components within a predetermined range. At least the noise component information of the tone component information and the noise component information includes normalization coefficient information and quantization accuracy information.

[0033]

According to the signal recording medium of the present invention, an input acoustic signal, for example, is separated into a signal component in which energy is concentrated at a specific frequency and a component in which energy is gently distributed over a wide band and is encoded. By recording the applied signal, high coding efficiency can be realized and the recording capacity can be effectively used.

[0034]

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 to which a signal coding method for obtaining a signal recording medium according to an embodiment of the present invention is applied.

In FIG. 1, an acoustic waveform signal is supplied to the terminal 600. This acoustic signal waveform has a conversion circuit 601.
After being converted into a signal frequency component by, the signal is 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 separated into a tone component having a steep spectrum distribution and a signal component other than that, that is, a noise component having a flat spectrum distribution. Of these separated frequency components, the tone component having the steep spectrum distribution is processed by the tone component coding circuit 603, and the noise component which is the other signal frequency component is processed by the noise component coding circuit 604. , Respectively, respectively. These tone component coding circuit 603 and noise component coding circuit 60
A code string is generated by the code string generation circuit 605, and the output from 4 is output. ECC encoder 606
An error correction code is added to the code string from the code string generation circuit 605. ECC encoder 606
The output from is modulated by the EFM circuit 607 and supplied to the recording head 608. The recording head 608 is E
The code string output from the FM circuit 607 is stored in the disk 609.
To record. The disk 609 can be, for example, a magneto-optical disk or a phase change disk. Also, disk 6
An IC card or the like may be used instead of 09.

It should be noted that the conversion circuit 601 has the above-mentioned configuration shown in FIG.
A configuration similar to can be used. Of course, Figure 1
As a specific configuration of the conversion circuit 601 of FIG. 6, many other configurations than the configuration of FIG. 19 can be considered. For example, the input signal may be directly converted into a spectrum signal by MDCT, or the spectrum conversion may be performed by DFT instead of MDCT. And DC
It is also possible to use T or the like.

Further, as described above, it is possible to divide the signal into band components by a band division filter.
Since the method of the present invention works particularly effectively when the energy is concentrated on the characteristic frequency, it is convenient to adopt a method of converting the frequency component into the frequency component by the above-described spectrum conversion in which a large number of frequency components are obtained with a relatively small amount of calculation. Is good.

Further, the tone characteristic component encoding circuit 603 and the noise characteristic component encoding circuit 604 can also be basically realized by the same configuration as that shown in FIG.

On the other hand, 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 coded by the coding apparatus of FIG. 1 is applied.

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 component code based on the number of tone component information in the error-corrected code string, and determines the input code string as the tone component. The code and the noise component code are separated. 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 combining 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 to perform decoding. To be done. After that, the decoded signals from the tone component decoding circuit 702 and the noise component decoding circuit 703 are supplied to a synthesizing circuit 704 that performs synthesis corresponding to the separation in the signal component separating circuit 602 of FIG. . Synthesis circuit 704
Is a decoded signal of the tone 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 by adding them to the predetermined position of the decoded signal of the noise component. Further, the combined decoded signal is subjected to conversion processing by an inverse conversion circuit 705 which performs inverse conversion corresponding to the conversion in the conversion circuit 601 of FIG. 1, and the signal on the frequency axis is converted to the original waveform signal on the time axis. Returned to. This inverse conversion circuit 7
The output waveform signal from 05 is output from the terminal 707.

The processing order of the inverse conversion and the composition may be reversed, and in this case, the composition inverse conversion unit 711 in FIG. 2 has the configuration shown in FIG. In FIG. 3, the inverse conversion circuit 712 is
Converts the decoded signal of the noise component on the frequency axis from the noise component decoding circuit 703 into a noise component signal on the time axis. The inverse conversion circuit 713 arranges the decoded signal of the tone component from the tone component decoding circuit 702 at the position on the frequency axis indicated by the position information of the tone component supplied from the code string separation circuit 701. This is inversely transformed to generate a tone component signal on the time axis. The synthesizing circuit 714 synthesizes the noise component signal on the time axis from the inverse transform circuit 712 and the tone component signal on the time axis from the inverse transform circuit 713 to generate the original waveform signal.

The inverse conversion circuits 705, 712, 7
The same configuration as that of FIG. 22 described above can be used for 13.

Here, FIG. 4 shows the flow of a specific process for separating the tone component in the signal component separation circuit 602 of the encoding apparatus of FIG.

In FIG. 4, I is the spectrum signal number, N is the total number of spectrum signals, and P and R are predetermined coefficients. Further, in the tone component, the absolute value of a certain spectrum signal is larger than other spectrum components when viewed locally, and it is the maximum of the absolute value of the spectrum signal in that time block (block at the time of spectrum conversion). Is greater than or equal to a given size compared to the value,
Further, when the sum of the energies of the spectrum and neighboring spectrums (for example, the spectrums on both sides) indicates a predetermined ratio or more with respect to the energy within a predetermined band including those spectra, the spectrum signal and, for example, The spectral signals on both sides are considered to be tonal components. Here, the predetermined band for comparing the ratios of the energy distributions can be set to be narrow in the low range and wide in the high range, for example, in accordance with the critical bandwidth in consideration of the nature of hearing.

That is, in FIG. 4, first, the maximum spectrum absolute value is substituted into the variable A0 in step S1, and the spectrum signal number I is set to 1 in step S2. In step S3, a certain spectrum absolute value within a certain time block is substituted into the variable A.

In step S4, it is judged whether or not the above-mentioned spectrum absolute value is a maximum absolute value spectrum which is locally larger than other spectrum components. If it is not the maximum absolute value spectrum (No), the process proceeds to step S10. , If it is the maximum absolute value spectrum (Yes), step S5
Proceed to.

In step S5, the ratio between the variable A of the maximum absolute spectrum and the variable A0 of the maximum absolute spectrum in the time block containing the maximum absolute spectrum, and the coefficient P indicating a predetermined magnitude are compared. Comparison (A /
A0> P) and A / A0 is larger than P (Ye
s), in step S6, if A / A0 is P or less (N
In step o), the process proceeds to step S10.

In step S6, the energy value of a spectrum adjacent to the spectrum of the spectrum absolute value (maximum absolute value spectrum) (for example, the sum of the energies of the adjacent spectrums) is substituted for the variable X, and in the next step S7, the maximum value. The energy value within a predetermined band including the absolute value spectrum and its neighboring spectrum is substituted for the variable Y.

In the next step S8, the ratio between the variable X of the energy value and the variable Y of the energy value within the predetermined band and the coefficient R indicating a predetermined ratio are compared (X / Y> R). , X / Y is greater than R (Yes), step S9 is performed. If X / Y is less than or equal to R (No), step S9 is performed.
Go to 10.

In step S9, when the energies of the maximum absolute value spectrum and its neighboring spectrum show a predetermined ratio or more with respect to the energy within a predetermined band including those spectra, the maximum absolute value of the maximum absolute value spectrum. The spectrum signal and, for example, the spectrum signals on both sides of the spectrum signal are considered to be tone components, and the fact is registered.

In the next step S10, the above step S
It is judged whether or not the number I of the spectrum signal registered in 9 and the total number N of spectrum signals are equal (I = N). If they are equal (Yes), the processing is terminated, and if they are not equal (No), Proceeds to step S11. In this step S11, I = I + 1 is set and the number of the spectrum signal is incremented by 1, and the process returns to step S3 to repeat the above-mentioned processing.

The signal component separation circuit 602 supplies to the tone component encoding circuit 603 the frequency component determined to be the tone component by the above processing, and the other frequency components as the noise component and the noise component. Encoding circuit 6
Supply to 04. Further, the signal component separation circuit 602 supplies the code string generation circuit 605 with the number of pieces of frequency information determined to be a tone component and information of the position thereof.

FIG. 5 shows an example of how the tone component is separated from the frequency component as described above.

In the example shown in FIG. 5, TCA and TC in the figure
Four tone components indicated by B, TCC and TCD are extracted. Here, since the tone component is concentrated and distributed in a small number of spectrum signals as in the example of FIG. 5, even if these components are quantized accurately, the total number of bits is too large. Not necessary. In addition, the efficiency of encoding can be improved by first normalizing and then quantizing the tone component, but since the number of spectrum signals that compose the tone component is relatively small, normalization and requantization processing is performed. May be omitted to simplify the device.

Further, FIG. 6 shows an example in which the noise component is obtained by removing the tone component from the original spectrum signal.

As shown in FIG. 6, each of the bands b1 to b5
In the above, since the tone component is removed from the original spectrum signal as described above, the normalization coefficient in each coding unit has a small value, and therefore, the quantization noise generated with a small number of bits should be small. You can

Here, if the nature of hearing is utilized, the coding of the noise component can be performed more efficiently. That is, the masking effect works effectively in the vicinity of the tone-like signal on the frequency axis. Therefore, even if encoding is performed assuming that the extracted noise component in the vicinity (noise component in the vicinity of the tone component) is 0, the audio signal decoded later is perceived as the original sound and the 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.

In FIG. 7, the noise component of the coding unit in which the main part of the tone component (TCA, TCB, TCC, TCD) exists is set to zero. Therefore, of the noise components in each band, only the coding unit in band b5 is actually coded. This method can perform compression in a very simple way, such as when the coding unit is referenced to a critical bandwidth.

Further, another concrete example of the encoding method utilizing such a property will be described with reference to FIG.

In FIG. 8, the noise component of the coding unit is not set to 0, but each tone component (T
CA, TCB, TCC, TCD) have a predetermined number of spectral components in the vicinity thereof set to zero. This predetermined number can be changed in accordance with the frequency of the tonal component based on the nature of hearing, so that it is small in the low range and large in the high range. Further, in this specific example, as a result, all the noise components of the coding unit in the band b4 become 0,
The noise component of band b4 is not actually encoded. Also according to the method of this specific example, it is possible to perform aurally effective efficient compression by a relatively simple means. Since the masking by the tone component works strongly on the high frequency side, the range in which the noise component is 0 may be asymmetric.

Further, the noise component is converted into the code string generation circuit 60.
5, for example, DAHuffman: A Method for Const
ruction of Minimum Redundancy Codes, Proc.IRE,
40, p.1098 (1952), the so-called variable length code may be used for encoding. In such an encoding method, the coding efficiency 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, coding efficiency can be improved by assigning a code with a short length to 0.

As described above, the tone characteristic component is separated, the tone characteristic component and the signal in the vicinity thereof are set to 0, and then the noise characteristic component is coded. It is also possible to adopt a method of encoding a component and subtracting a decoded signal, and then encoding.

A signal coding apparatus according to this method will be described with reference to FIG. For the same configuration as in FIG.
The same number is given and the explanation is omitted.

The spectrum 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 determines the tone component by the processing of FIG. 4 described above, and supplies only the determined tone component to the tone component encoding circuit 603. Further, the tone component extraction circuit 802 determines the number of tone component information and the center position information thereof by the coded sequence generation circuit 6
Output to 05. The tone component encoding circuit 603 normalizes and quantizes the input tone component, and supplies the normalized and quantized tone component to the encoded string generation circuit 605 and the local decoder 804. .
The local decoder 804 de-quantizes and denormalizes the normalized and quantized tone component, and decodes the original tone component signal. However, at this time,
The decoded signal will include quantization noise. The output from the local decoder 804 is supplied to the adder 805 as the first decoded signal. The adder 805 is still supplied with the original spectrum signal from the conversion circuit 601 via the switch 806 controlled by the switch control circuit 808. The adder 805 subtracts the first decoded signal from the original spectrum signal and outputs the first difference signal. When the extraction, the encoding, the decoding, and the difference processing of the tone component are completed once, the difference signal of the first time is used as the noise component and the switch control circuit 80.
8 is supplied to the noise component encoding circuit 604 through the switch 807 controlled by the switch 8. When repeating the extraction, encoding, decoding, and difference processing of tone components,
The first difference signal is supplied to the tone component extraction circuit 802 via the switch 801. The tone component extraction circuit 802, tone component encoding circuit 603, and local decoder 804 perform the same processing as described above, and the obtained second decoded signal is supplied to the adder 805. Further, the first difference signal is supplied to the adder 805 via the switch 806. The adder 805 outputs the second difference signal by subtracting the second-time decoded signal from the first-time difference signal. When the extraction, the encoding, the decoding, and the differential processing of the tone component are finished twice, this second difference signal is a noise component, and the noise component encoding circuit 604 passes through the switch 807. Is supplied to. When the extraction, encoding, decoding, and difference processing of the tone component are further repeated, the same process as described above is performed.
02, tone characteristic component encoding circuit 603, local decoder 804, and adder 805. The switch control circuit 808 keeps a threshold value for the number of tonal component information, and extracts the tonal component when the number of tonal component information obtained from the tonal component extraction circuit exceeds this threshold.
The switch 807 is controlled to end the encoding / decoding processing. Further, when the tone component is no longer extracted in the tone component encoding circuit 603, the tone component extraction, encoding, decoding, and difference processing can be terminated.

FIGS. 10 and 11 show an example of the case where encoding is performed by such a method. FIG. 11 shows a signal obtained by encoding and decoding one tone component from the spectrum signal of FIG. It has been deducted.

Further, by further extracting the component shown by the broken line in the drawing as a tone component from the spectrum signal of FIG. 11 and encoding it, the encoding accuracy of the spectrum signal can be improved, and this is repeated. As a result, highly accurate encoding can be performed. When this method is used, the encoding accuracy can be sufficiently high even if the upper limit of the number of bits for quantizing the tone component is set low. Therefore, the number of bits for recording the quantization bit number is recorded. There is also an advantage that can be made smaller. In addition, the method of extracting the tonal component in multiple stages in this way is not limited to the case of subtracting a signal equivalent to the one obtained by encoding and decoding the tonal component from the original spectrum signal, and extracting it. The present invention is also applicable to the case where the spectral signal of the generated tone component is set to 0, and the expression "a signal separated from the tone component" and the like in the description of the present invention include both of them.

Next, FIG. 12 shows a concrete example in which the extraction of the tone component is performed only in the high 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 range, and this is realized by a small-scale device. Is difficult. Further, in order to encode the tone component, it is necessary to encode the position information and the normalization information of the tone component. However, if there are many tone components with poor separation in the low frequency range, it is necessary to encode them. It is disadvantageous to increase the efficiency of encoding by recording the information of (1) as many as the number of extracted tone components. Therefore, when the frequency resolution cannot be sufficiently obtained on the low frequency side, the tone component may be separated and encoded only on the high frequency side as in the example of FIG.

Further, in order to secure a sufficient frequency resolution in the low range, the frequency resolution in the low range and the high range may be changed. For example, in the above-described conversion circuit of FIG. 19 applied to the conversion circuit 601 of FIG. 1 of the present embodiment, the rates of the output signals of the two bands of the band division filter 202 are the forward spectrum conversion circuit 203 of the band division filter 201. Although it is decimated to half of the rate of the signal sent to, the forward spectrum conversion circuits 203, 204, 205 can perform forward spectrum conversion on the same number of input signals. The frequency resolution of the spectrum signal can be made twice as high as the resolution of the spectrum signal from the forward spectrum conversion circuit 203.

FIG. 13 shows a concrete example of a code string (code string recorded on a recording medium) when the spectrum signal of FIG. 8 is coded 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 the tone component TCA, TCB, TCC, of FIG.
Tone component information tcA, tcB, t corresponding to TCD
cC, tcD and the noise component information nc1, nc2, nc3, nc4, nc corresponding to the bands b1 to b5 of FIG.
Records are recorded in order of 5.

Here, the tone characteristic component information includes the center position information CP indicating the position of the center spectrum of the tone characteristic component (for example, in the case of the tone characteristic component TCB, for example, 1).
5) and quantization precision information indicating the number of bits for quantization (for example, 6 in the case of the tone component TCB),
The normalized coefficient information is recorded on the recording medium together with the normalized and quantized signal component information (for example, information SC1, SC2, SC3). Note that, for example, when the quantization precision is fixedly determined by the frequency, it is not necessary to record the quantization precision information.

In the above embodiment, the position of the center spectrum of each tone component is used as the position information of the tone component. However, the position of the lowest spectrum of each tone component (for example, In the case of the tone component TCB, 14) may be recorded.

Regarding the noise component information,
The quantization accuracy information and the normalized coefficient information are normalized and quantized signal component information (for example, information SC1 and SC).
2, ..., SC8) will be recorded on the recording medium. When the quantization accuracy information is 0 (see FIG. 13).
The noise component information nc4) indicates that encoding is not actually performed in the encoding unit. Also in this case, if the quantization precision is fixedly determined by the band, the quantization precision information does not need to be recorded, but at this time, for example, encoding is actually performed like the band b4. It becomes impossible to specify a coding unit that does not exist. In such a case, for example, 1-bit flag information indicating whether or not encoding is actually performed in each encoding 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 is possible to efficiently record by such a method.

FIGS. 14 and 15 show the states of spectrum signals in adjacent time blocks.
14 represents the spectrum signal of the next time block in FIG.

In FIGS. 14 and 15, for example,
The spectrum 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 almost the same as in the previous block, and the diagram of FIG. Middle TCA, TC
15 corresponds to the tone components of B, TCC and TCD.
In the figure, the tone components of TCE, TCF, TCG, and TCH appear. Therefore, it is possible to efficiently record the center position information of the tone component in the relative position with the center position information of the tone component of the previous time block. Specific examples thereof are shown in FIGS. 16 and 17. is there.

In FIG. 16, the tone component information in the time block of FIG. 14 is tcA, tcB, tcC, t.
It shall be recorded in the order of cd. Here, for example, in the spectrum signal in the time block of FIG. 15, as the center position information CP of the tone component information tcF of TCF in the diagram of FIG. 15, the center position difference information CP with the tone component of TCB is shown in FIG. The center position information CP1 encoded with 2 bits as shown can be recorded as shown in FIG. As described above, the center position information CP of many tone-like components can be represented by a short code by corresponding to the tone-like components in other time blocks, for example, immediately preceding time blocks, and efficient encoding is possible. Becomes However, the tone characteristic component of TCH is a variation of the tone characteristic component of TCD, but this cannot be represented by the center position difference information of FIG.
Center position information CP2 by invalidating the tone component information of D
Is used to record the information of the tone component of TCF.
The symbols shown in FIG. 17 are of course an example,
For example, the number of tonality component information tcn1 can be omitted because it is known from the information of the previous time block.

Although the above description has been focused on an example in which the method of the present invention is applied to an acoustic signal, the method of the present invention can also be applied to general waveform signal coding. 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.

[0083]

As is clear from the above description, the signal recorded on the signal recording medium according to the present invention separates the tone component of the input signal from the other components at the time of encoding. Therefore, it is possible to efficiently code. In particular, when the present invention is used for encoding an audio signal, a tone component that is important for hearing is encoded with sufficiently high accuracy, and a noise component that is not so important for hearing is encoded with minimum accuracy. Is possible, and extremely efficient signal compression becomes possible. Therefore, if this compressed signal is recorded in a recording medium, the recording capacity can be effectively used, and further, by decoding the signal obtained by reproducing this recording medium, a good acoustic signal can be obtained. Will be available.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a schematic configuration of an encoding device for obtaining a signal recording medium of an embodiment of the present invention.

FIG. 2 is a block circuit diagram showing a schematic configuration of a decoding device for decoding the signal recording medium of the embodiment of the present invention.

FIG. 3 is a block circuit diagram showing a configuration of a synthetic inverse conversion unit.

FIG. 4 is a flowchart showing a processing flow in a signal component separation circuit of the encoding device for obtaining the signal recording medium of the embodiment of the present invention.

FIG. 5 is a diagram for explaining a tone component in the signal coding according to the present embodiment.

FIG. 6 is a diagram for explaining a noise component in the signal coding according to the present embodiment.

FIG. 7 is a diagram showing separated tone components in the signal coding according to the present embodiment.

FIG. 8 is a diagram for explaining another example of signal coding according to the present embodiment.

FIG. 9 is a block circuit diagram showing a schematic configuration of a signal encoding device for explaining the signal encoding method of the present embodiment.

FIG. 10 is a diagram for explaining a method for encoding a signal obtained by encoding a tone component and subtracting a decoded signal from the original spectrum signal in the signal encoding of the present embodiment.

FIG. 11 is a diagram showing a state in which a signal obtained by encoding and decoding a tone component is subtracted from the original spectrum signal in the signal encoding of the present embodiment.

[Fig. 12] Fig. 12 is a diagram for explaining a case where the extraction of the tone component is performed only in the high frequency band in the signal coding according to the present embodiment.

FIG. 13 is a diagram for explaining recording of a code string obtained by being coded by the signal coding according to the present embodiment.

FIG. 14 is a diagram showing a state of a spectrum signal in a certain time block in the signal coding according to the present embodiment.

FIG. 15 is a diagram showing a state of a spectrum signal in a time block adjacent to a time block in the signal coding according to the present embodiment.

FIG. 16 is a diagram for explaining an example in which the center position information of the tone component information of the spectrum signal in the time block of the present 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 encoding device.

FIG. 19 is a block circuit diagram showing a specific configuration of a conversion circuit of this embodiment and a conventional encoding device.

FIG. 20 is a block circuit diagram showing a specific configuration of a signal component encoding circuit of the present embodiment and a conventional encoding 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 the inverse conversion circuit of the present embodiment and the conventional decoding device.

[Fig. 23] Fig. 23 is a diagram for describing a conventional encoding method.

[Explanation of symbols]

601 conversion circuit, 602 signal component separation circuit, 6
03 tone component coding circuit, 604 noise component coding circuit, 605 code string generation circuit, 701 code string decomposing circuit, 702 tone component decoding circuit,
703 noise component decoding circuit, 704 combining circuit, 705 inverse conversion circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H03M 7/30 G10L 11/00 G10L 19/00

Claims (19)

(57) [Claims] 1. A signal recording medium on which an encoded signal is recorded, wherein an input signal is converted into a frequency component, and the frequency component is converted into a first signal composed of a tone component and a second signal composed of other components. And separating the first signal into the signal on the frequency axis of the tone component.
Position information, coded a signal based on the second signal, coded the first and second signals , and coded
A signal recording medium formed by recording the position information . 2. The signal recording medium according to claim 1, wherein the conversion is a spectrum conversion. 3. The signal recording medium according to claim 1, wherein the signal recording medium is formed by encoding number information of the tone component within a predetermined range and recording the encoded number information. 4. The signal based on the second signal is a signal in which the signal of the encoding unit including the main part of the tone component of the first signal of the frequency component is set to 0. Item 1. The signal recording medium according to item 1. 5. The signal recording medium according to claim 1, wherein the signal based on the second signal is a signal in which the first signal of the frequency component and the frequency components in the vicinity thereof are set to 0. . 6. The separating step encodes the tone component, decodes the encoded tone component, and subtracts the decoded tone component from the frequency component of the input signal to obtain a difference. The signal recording medium according to claim 1, further comprising a step of generating a signal, wherein the second signal is the differential signal. 7. An input signal is converted into a frequency component, and the frequency component is converted into a first signal composed of a tone component.
Is separated into a second signal composed of other components, and the first signal is separated by the position of the tone component on the frequency axis.
Position information, coded a signal based on the second signal, coded the first and second signals, and coded
A signal record formed by recording the above position information.
In the recording medium, the separating step encodes the tonal component to obtain the encoded tone.
And decode the above tone component.
Generate a differential signal by subtracting from the frequency component of the input signal
And the second signal is the difference signal .
Signal recording medium. 8. At least the step of encoding a signal based on the second signal of the steps of encoding the first signal and the step of encoding a signal based on the second signal is input. The signal recording medium according to claim 1, further comprising the step of: normalizing the generated signal for each coding unit, and quantizing the normalized signal. 9. At least the step of encoding a signal based on the second signal among the steps of encoding the first signal and the step of encoding a signal based on the second signal is input. The signal recording medium according to claim 1, further comprising a step of performing variable length coding on the generated signal. 10. The signal recording medium according to claim 1, wherein the separating step separates the first signal from only the high frequency band of the frequency component. 11. The signal recording medium according to claim 1, wherein in the converting step, conversion is performed such that the frequency resolution on the low frequency side is higher than the frequency resolution on the high frequency side. 12. The signal recording medium according to claim 1, wherein the input signal is an audio signal. 13. The location information signal recording medium according to claim 1, wherein the includes information indicating a difference between the position information of the position information and other time blocks of the current block. 14. The signal according to claim 5 , wherein the number of frequency components set to 0 for each frequency component of the first signal is higher on the high frequency side than on the low frequency side. recoding media. 15. The number of frequency components zeroed for one frequency component of the first signal is equal to the first frequency component.
6. The signal recording medium according to claim 5, wherein one of the signals in the signal is asymmetric with respect to the high frequency side and the low frequency side. 16. The separating step encodes a tone component of the differential signal, decodes the encoded tone component, subtracts the decoded tone component from the difference signal, and newly adds 7. The signal according to claim 6 , further comprising the step of generating at least one different differential signal and using the new differential signal as the differential signal, wherein the second signal is the new differential signal. recoding media. 17. A signal recording medium in which an encoded signal is recorded, wherein tone characteristic information relating to a tone characteristic component including position information on a frequency axis of a tone characteristic component and a noise characteristic component relating to a noise characteristic component. A signal recording medium characterized in that information and information are recorded separately. 18. The signal recording medium according to claim 17, wherein the tone component information includes number information of the tone component within a predetermined range. 19. The signal recording according to claim 17, wherein at least the noise component information of the tone component information and the noise component information includes normalization coefficient information and quantization accuracy information. Medium.