High efficiency encoder

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a high-efficiency coding device that encodes input digital data by so-called high-efficiency coding.

【0002】

[Conventional technology]

There are various conventional methods for efficiently coding signals such as audio or voice, but for example, non-blocking that divides and encodes audio signals on the time axis into a plurality of frequency bands without blocking them. Band division coding (sub-band coding: SBC), which is a frequency band division method, or conversion of time axis signals to signals on the frequency axis (orthogonal conversion) and dividing into multiple frequency bands for each band Examples include a blocked frequency band division method in which each encoding is performed, that is, so-called conversion coding and the like. Further, a high-efficiency coding method that combines the above-mentioned band division coding and transform coding is also considered. In this case, for example, after band division is performed by the above band division coding, each of the above-mentioned methods. The signal for each band is orthogonally converted into a signal on the frequency axis, and coding is applied to each of the orthogonally converted bands.

【0003】

Here, for example, as a filter for performing the band division, for example, there is a QMF filter, and the QMF filter is described in, for example, 1976 RECrochiere Digitalcoding of speech in subbandsBell Syst.Tech. J. Vol.55, No. 8 1976. It is stated. Further, for example, ICASSP 83, BOSTON Polyphase Quadrature filters-Anew subband coding technique Joseph H. Rothweiler describes an equal bandwidth filtering method.

【0004】

Further, as the above-mentioned orthogonal transform, for example, an input audio signal is blocked in a predetermined unit time (frame), and fast Fourier transform (FFT), cosine transform (DCT), modified DCT transform (MDCT), etc. are performed for each block. There is an orthogonal transform that transforms the time axis into the frequency axis by doing so. MDCT is described in ICASSP 1987 Subband / Transform Coding Using Filter Bank DesignsBased on Time Domain Aliasing Cancellation J.P.Princen ABBradley Univ.of Surrey Royal Melbourne Inst.of Tech.

【0005】

Further, as the frequency division width for quantizing each frequency component divided into frequency bands, for example, the frequency division width by band division in consideration of human auditory characteristics is used. That is, the audio signal may be divided into a plurality of bands (for example, 25 bunts) with a bandwidth that is generally called a critical band (critical band) so that the higher the band, the wider the bandwidth. 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 process is encoded by the bit allocation, the allocated bits adaptive to the MDCT coefficient data for each band obtained by the MDCT process for each block. Coding will be done by number.

【0006】

The following two methods are known as the above-mentioned bit allocation method. For example, in IEEE Transactions of Accoustics, Speech, and Signal Processing, vol.ASSP-25, No.4, August 1977, bits are allocated based on the signal magnitude for each band. However, in this method, the quantization noise spectrum is flattened and the noise energy is minimized, but there is a drawback that the actual noise feeling is not optimal because the so-called masking effect is not used audibly.

【0007】

For example, ICASSP 1980 The critical band coder digital encoding of the perceptual requirements of the auditory system MAKransner MIT uses auditory masking to obtain the required signal-to-noise ratio for each band and perform fixed bit allocation. The method is described. However, this method has a drawback that the characteristic value is not so good because the bit allocation is fixed even when the characteristic is measured by the sine wave input.

【0008】

[Problems to be Solved by the Invention]

In order to solve the above-mentioned drawbacks in the above two bit allocation methods, for example, all the bits that can be used for bit allocation are the amount of the fixed bit allocation pattern predetermined for each small block and the signal size of each block. It is divided and used for the bit allocation that depends on the bit, and the division ratio depends on the signal related to the input signal, and the smoother the spectrum of the signal, the more the division ratio to the fixed bit allocation pattern. A high-efficiency coding device has been proposed that increases the value of.

【0009】

According to the bit allocation method in such a high-efficiency coding apparatus, when energy is concentrated in a specific spectrum such as a sine wave input, by allocating many bits to a block containing the spectrum, the whole is allocated. The signal-to-noise characteristics of can be significantly improved. In general, human hearing is extremely sensitive to a signal having a steep spectral component. Therefore, improving the signal-to-noise characteristic by using such a method simply improves the measured value. It is effective not only to make it sound but also to improve the sound quality in terms of hearing.

【0010】

However, if bit allocation depending on the input signal is performed on the basis of simply improving the signal-to-noise characteristic, a signal containing a large number of steep spectral components, such as a triangle sound, can be assigned at a low bit rate. When compression is attempted, sufficient bits are not allocated to the blocks corresponding to each spectrum, and sufficient sound quality cannot be obtained in terms of audibility.

【0011】

Therefore, the present invention has been proposed in view of the above circumstances, and even when a signal containing a large number of steep spectral components is compressed at a low bit rate, a high sound quality that is audibly good can be obtained. An object of the present invention is to provide an efficiency coding device.

【0012】

[Means for solving problems]

The high-efficiency coding device of the present invention has been proposed in order to achieve the above-mentioned object, and is a high-efficiency coding device that efficiently encodes input digital data by adaptive bit allocation, and is a bit. All bits that can be used for allocation are divided into a fixed bit allocation pattern that is predetermined for each small block subdivided in terms of time and frequency, and a bit allocation that depends on the size of the signal in each small block. It is provided with an adaptive bit allocation coding means for dividing and using and weighting bit allocation depending on the size of the signal in each of the small blocks according to the corresponding frequency band of the small block. is there.

【0013】

That is, in the high-efficiency coding device according to the present invention, all the bits that can be used for bit allocation depend on a predetermined fixed bit allocation pattern for any short time and the signal size of each block. In addition to the fixed bit allocation pattern, the bit allocation depending on the signal size of each block is also weighted according to the corresponding band of the block, in addition to the bit allocation. , It solves the above-mentioned problems.

【0014】

Here, as the above weighting, the fact that the noise on the high frequency side is harder to hear than the noise on the low frequency side due to the sensitivity of the human ear, and the noise on the high frequency side is easily masked by the signal on the low frequency side. Based on this, it is effective to allocate more bits to the block on the low frequency side.

【0015】

Therefore, the adaptive bit allocation coding means determines that the weighting of the bit allocation performed according to the corresponding frequency band of the small block is the weighting that allocates more bits to the low frequency side if the signal energy is the same. can do.

【0016】

Further, the division ratio between the fixedly assigned bits and the bits assigned depending on the input signal can be applied to the present invention with or without depending on the signal related to the input signal. , Even better sound quality can be obtained by relying on the input signal.

【0017】

Therefore, the adaptive bit allocation coding means uses all the bits that can be used for bit allocation as a predetermined fixed bit allocation pattern for each small block subdivided with respect to time and frequency, and a signal in each small block. It is also possible to perform bit allocation as the division ratio when the bit allocation depends on the size of the input signal.

【0018】

Furthermore, by preparing a plurality of the above weighting patterns in advance and switching them according to the input signal, or by gradually changing the weighting variable according to the input signal, it is possible to assign bits that are more audible and improve the sound quality. It can be improved.

【0019】

Therefore, the adaptive bit allocation coding means performs bit allocation depending on the size of the signal in the small block based on weighting according to the corresponding frequency band of the small block by a weighting coefficient that changes depending on the input signal. It can also be done.

【0020】

[Action]

According to the high-efficiency coding apparatus of the present invention, all the bits that can be used for bit allocation are set to a predetermined fixed bit allocation pattern for any short time and bits that depend on the signal size of each block. In addition to the fixed bit allocation pattern, the bit allocation that depends on the signal size of each block is also weighted according to the corresponding band of that block. For a signal having a plurality of isolated spectrum components, it is possible to easily realize efficient bit allocation suitable for hearing, and it is possible to encode a high-quality music signal at a lower bit rate.

【0021】

[Example]

Hereinafter, examples of the present invention will be described with reference to the drawings.

【0022】

As shown in FIG. 1, the high-efficiency coding device of this embodiment is a high-efficiency coding device that efficiently encodes the input digital data (digital audio data) supplied to the input terminal 10 by adaptive bit allocation. Therefore, all the bits that can be used for bit allocation are the bits that depend on the predetermined fixed bit allocation pattern for each small block subdivided with respect to time and frequency and the size of the signal in each small block. Adaptive bit allocation coding means 16, which is used separately for the allocation and the bit allocation depending on the size of the signal in each of the small blocks is weighted according to the corresponding frequency band of the small block. It has 17,18.

【0023】

Here, as the above weighting, the fact that the noise on the high frequency side is harder to hear than the noise on the low frequency side due to the sensitivity of the human ear, and the noise on the high frequency side is easily masked by the signal on the low frequency side. Based on this, it is effective to allocate more bits to the block on the low frequency side.

【0024】

Therefore, the adaptive bit allocation coding means 16, 17, 18 allocates more bits to the low frequency side if they have the same signal energy, by weighting the bit allocation performed according to the corresponding frequency band of the small block. It can be weighted.

【0025】

Further, the division ratio between the fixedly assigned bits and the bits assigned depending on the input signal can be applied to the present invention with or without depending on the signal related to the input signal. , Even better sound quality can be obtained by relying on the input signal.

【0026】

Therefore, the adaptive bit allocation coding means 16,17,18 uses all the bits that can be used for bit allocation as a predetermined fixed bit allocation pattern for each small block subdivided in terms of time and frequency. It is also possible to perform bit allocation as the division ratio when the bit is allocated depending on the size of the signal in the small block and the division ratio is used as the division ratio depending on the input signal.

【0027】

Furthermore, by preparing a plurality of the above weighting patterns in advance and switching them according to the input signal, or by gradually changing the weighting variable according to the input signal, it is possible to assign bits that are more audible and improve the sound quality. It can be improved.

【0028】

Therefore, the adaptive bit allocation coding means 16,17,18 performs bit allocation depending on the size of the signal in the small block based on the weighting according to the corresponding frequency band of the small block by the input signal. It can also be done by a changing weighting factor.

【0029】

As an embodiment of the present invention, an input digital signal such as an audio PCM signal is coded with high efficiency by using band division coding (SBC), adaptive transform coding (ATC), and adaptive bit allocation (APC-AB). This will be described with reference to FIG. 1 above, which is a configuration to be transformed.

【0030】

In the high-efficiency coding apparatus of this embodiment shown in FIG. 1, the input digital signal (input audio PCM signal) was divided into a plurality of frequency bands by a filter or the like, and orthogonal conversion was performed for each frequency band. The spectrum data of the frequency axis is encoded by adaptively allocating bits for each so-called critical bandwidth (critical band) in consideration of human auditory characteristics, which will be described later. Of course, the non-blocking frequency division width by a filter or the like may be an equal division width.

【0031】

Further, in the embodiment of the present invention, the block size (block length) is adaptively changed according to the input signal before the orthogonal conversion, and the critical bandwidth (critical band) is further subdivided in critical band units or in the high frequency range. Floating processing is performed on the converted blocks. The critical band is a frequency band divided in consideration of human auditory characteristics, and the noise of a pure tone when the pure tone is masked by a narrow band noise of the same intensity in the vicinity of the frequency of the pure tone. It is the band that it has. The bandwidth of this critical band becomes wider as the frequency increases. For example, the entire frequency band of 0 to 20 kHz is divided into, for example, 25 critical bands.

【0032】

That is, in FIG. 1, for example, an audio PCM signal of 0 to 20 kHz is supplied to the input terminal 10. This input signal is divided into a 0 to 10 kHz band and a 10 kHz to 20 kHz band by, for example, a band divided filter 11 composed of a so-called QMF filter or the like, and a signal in the 0 to 10 kHz band is also divided by a band divided filter 12 composed of a so-called QMF filter or the like. It is divided into a 0 to 5 kHz band and a 5 kHz to 10 kHz band.

【0033】

The 10kHz to 20kHz band signals from the band division filter 11 are sent to the MDCT (Modified Discrete Cosine Transform) circuit 13 and the block size determination circuit 19 which are examples of the orthogonal conversion circuit, and 5kHz to 10kHz from the band division filter 12. The band signal is sent to the MDCT circuit 14 and the block size determination circuit 20, and the 0 to 5 kHz band signal from the band division filter 12 is sent to the MDCT circuit 15 and the block size determination circuit 21. The block size determination circuits 19, 20 and 21 determine the block size during MDCT processing, and the MDCT circuits 13, 14 and 15 determine the block size determination circuit 19 for signals from the band division filters 11 and 12. MDCT processing is applied to each of the block sizes of, 20 and 21.

【0034】

Here, a specific example of the block size of each MDCT circuit 13, 14, 15 is shown in FIG. In the specific example of FIG. 2, the frequency band is widened and the time resolution is increased (the block length is shortened) toward the higher frequency side. That is, for a signal in the 0 to 5 kHz band on the low frequency side and a signal in the 5 kHz to 10 kHz band on the mid frequency band, b_L, b_MFor signals in the 10kHz to 20kHz band on the high frequency side, b_H1, b_H2MDCT is performed twice in total in the block.

【0035】

In this embodiment, while simplifying the device by making the number of orthogonal conversion block samples in each band the same in this way, the frequency resolution is improved on the low frequency side where the critical bandwidth is narrow, and for transient signals. The time resolution is improved on the high frequency side, which contains many dominant components. Further, in this embodiment, each band is allowed to be further divided into 1/2 and 1/4 adaptive blocks assuming that the signal changes significantly with time.

【0036】

Returning to FIG. 1 again, the spectrum data or MDCT coefficient data on the frequency axis obtained by MDCT processing in each MDCT circuit 13, 14, 15 is the so-called critical band (critical band) or the critical band in the high frequency band. Are grouped for each divided band and sent to the above-mentioned adaptive bit allocation coding circuits 16, 17, and 18.

【0037】

In the adaptive bit allocation coding circuits 16, 17, and 18, each spectral data (or MDCT coefficient) is assigned according to the number of bits allocated to each of the critical band (critical band) or the band further divided the critical band in the high frequency band. Data) is requantized. The specific configuration of the adaptive bit allocation coding circuits 16, 17, and 18 will be described later.

【0038】

The data encoded in this way is taken out via the output terminals 22, 24, 26. At this time, in the configuration of the latter stage, along with the above-coded data, floating information indicating what kind of signal magnitude was normalized and a bit indicating what kind of bit length was quantized. Long information is also sent at the same time.

【0039】

Here, a specific configuration of the adaptive bit allocation coding circuit will be described with reference to FIG.

【0040】

The outputs of the MDCT circuits 13, 14 and 15 in FIG. 1 are sent to the energy calculation circuit 303 that calculates the energy for each band via the input terminal 400 of the adaptive bit allocation coding circuit shown in FIG. In the energy calculation circuit 303 for each band, the energy for each band obtained by further dividing the critical band in the critical band or the high frequency band calculates, for example, the square root of the squared average of each amplitude value in the band. It is required by doing things. It is also possible to use the peak value, the average value, or the like of the amplitude value instead of the energy for each band.

【0041】

For example, in the critical band (critical band) as the output from the energy calculation circuit 303, or in the high frequency range, the spectrum of the total value for each band obtained by further dividing the critical band is, for example, the spectrum (bark spectrum) SB as shown in FIG. It becomes. However, in FIG. 4, in order to simplify the illustration, the number of bands in the critical band (critical band) or the band in which the critical band is further divided in the high frequency band is 12 bands (B).₁~ B₁₂).

【0042】

Here, assuming that the number of bits that can be used for transmission or recording by expressing the MDCT coefficient in this embodiment is, for example, 100 Kbps, in this embodiment, a fixed bit allocation pattern using 100 Kbps is created. The usable bit number of 100 Kbps is set by, for example, the total usable bit number output circuit 302. This total number of usable bits can also be input from the outside.

【0043】

Further, in this embodiment, a plurality of bit allocation patterns for the fixed bit allocation are prepared, and various selections can be made depending on the nature of the signal. In the configuration of FIG. 3, the fixed bit distribution circuit 305 has various patterns in which the bit amount of the block for a short time corresponding to the above 100 Kbps is distributed to each frequency.

【0044】

That is, in the fixed bit distribution circuit 305, in particular, a plurality of patterns having different bit distribution ratios in the mid-low range and the high range are prepared. Then, the smaller the signal size, the smaller the amount allocated to the high frequency band is selected. By doing so, it is possible to take advantage of the loudness effect in which the sensitivity in the high frequency range decreases as the signal becomes smaller. As the signal magnitude at this time, the signal magnitude of the entire band can be used, but for example, the output of a non-blocking frequency division circuit in which a filter or the like is used or the MDCT output can also be used. it can.

【0045】

Further, in the present embodiment, the energy-dependent bit allocation is weighted by multiplying the dB value of the energy of each small block by a predetermined coefficient for each small block, and the value obtained in this way. It is done in proportion to. Here, by setting the weighting coefficient so as to have a larger value with respect to the low frequency band, more bits are assigned to the low frequency band. The energy-dependent bit allocation is performed by the energy-dependent bit allocation circuit 304 to which the output of the energy calculation circuit 303 is supplied.

【0046】

That is, in the energy-dependent bit distribution circuit 304, a plurality of patterns of the weighting coefficients are prepared as in the case of the fixed bit distribution, and the plurality of patterns are switched by an input signal, or, for example, two weighting patterns are input signals. The energy-dependent bit allocation is calculated using the weighting pattern interpolated by. As described above, in this embodiment, by changing the weighting coefficient according to the input signal, bit allocation more suitable for the sense of hearing becomes possible, and sound quality can be improved.

【0047】

In FIG. 3, the division ratio between the allocation to the fixed bit allocation pattern as described above and the bit allocation depending on the bark spectrum (spectrum SB) is determined by an index representing the smoothness of the signal spectrum. That is, in this embodiment, the output of the energy calculation circuit 303 is sent to the spectrum smoothness calculation circuit 308, and in the spectrum smoothness calculation circuit 308, the sum of the absolute values of the differences between the adjacent values of the signal spectrum is the sum of the signal spectra. The value divided by the sum is calculated as an index, and this index is sent to the bit division rate determination circuit 309 for obtaining the division rate of the bit allocation.

【0048】

The division rate data from the bit division rate determination circuit 309 is supplied to the multiplier 402 to which the output of the fixed bit distribution circuit 305 is supplied and the multiplier 401 to which the output of the energy-dependent bit distribution circuit 304 is supplied, respectively. Sent. The outputs of these multipliers 401 and 402 are sent to the sum calculation circuit 306. That is, the sum of the fixed bit allocation and the critical band for each band (critical band) or the value of the bit allocation depending on the spectrum for each band obtained by further dividing the critical band in the high frequency band is calculated by the sum calculation circuit 306. This calculation result is sent from the output terminal (bit allocation amount output terminal of each band) 307 to the subsequent configuration and used for quantization.

【0049】

Further, as another method for obtaining the above-mentioned division ratio, for example, the total S1 of the value obtained by multiplying the dB value of the weighted energy by the index R having a value between 0 and 1 obtained from the above index and ( Obtain the total S2 of the value obtained by multiplying 1-R) by the fixed bit allocation pattern for each small block, and fix the ratio of the total S1 and S2 to the sum of these total S1 and S2 with the energy-dependent bit allocation. It is also possible to use a method such as the division rate of the bit allocation of the pattern.

【0050】

Here, FIG. 6 shows a state of bit allocation when a signal having the spectrum shown in FIG. 5, for example, is input to the configuration of this embodiment. However, in FIGS. 5 and 6, the number of bands for quantizing the spectrum is 12. In FIG. 6, the square in the shaded area in the figure represents the number of bits allocated based on the size of the signal component of each block, and the square wave other than the shaded area in the figure is assigned to each block based on a fixed pattern. The number of bits is represented, and the number of bits corresponding to the sum of these is assigned to each block. The numerical values in FIGS. 5 and 6 above are expressed so as to take real values instead of integer values, but this represents the calculation process in the middle, and finally these numerical values are used, for example. The number of bits allocated to each block may be obtained by rounding off.

【0051】

The input signal shown in FIG. 5 contains three signal components A, B, and C in the figure having substantially the same magnitude of isolated spectra. At this time, if the bits assigned based on the magnitude of the signal component of each block are distributed so as to maximize the signal noise characteristics as conventionally performed, for example, the block numbers 2,6,10 in the figure are used. In addition to the bits assigned based on a fixed pattern, approximately the same number of bits will be added to each block of. On the other hand, in the bit allocation method in the embodiment of the present invention, many bits are added in the order of block numbers 2, 6 and 10 in the figure. Therefore, according to the bit allocation method in the embodiment of the present invention, the signal noise characteristic on the high frequency side is deteriorated as compared with the conventional method, but the signal noise characteristic on the low frequency side is improved.

【0052】

Further, the high-frequency noise generated when the bit allocation method of the embodiment of the present invention is used is originally harder to hear than the low-frequency noise in terms of the dependence of the sensitivity of the human ear on the frequency. In addition, since it is masked by the low frequency signal, it does not pose a big problem in terms of hearing.

【0053】

Therefore, by using the bit allocation method of the present embodiment, it is possible to improve the audible sound quality by the amount that the noise on the low frequency side, which is more easily heard, can be suppressed.

【0054】

It should be noted here that, in the case of the bit allocation method of this embodiment, for example, the block number 6 in FIG. 5 is assigned a smaller number of bits than the block number 2, but for example, the block number 4 or the like. More bits are allocated. Such bit allocation cannot be obtained by simply applying a fixed bit allocation pattern that allocates more bits to the low frequencies, and as described above, the signal in each small block. This is possible because bit allocation depending on the size of is performed by weighting according to the corresponding band of the small block.

【0055】

Further, in this example, it is assumed that only a few spectra can be obtained as a result of MDCT in the low frequency range of 100 Hz or less. In such a case, since many signals corresponding to higher frequency frequencies are mixed in each spectrum on the low frequency side obtained by calculation, a sufficiently large number of bits are allocated to the low frequency side. There is a need. Therefore, approximately, the lower frequency side may be assigned more bits based on the magnitude of the signal component of each block.

【0056】

Further, if a high-efficiency coding device capable of obtaining a spectrum longer, for example, a spectrum of 100 Hz or less can be obtained densely enough, the sensitivity of the human ear is low, for example, for a spectrum corresponding to 50 Hz or less. It is also possible to make the bit allocation, which depends on the signal size, less than the bit allocation for signals in higher bands.

【0057】

FIG. 7 shows a configuration of a decoding device for re-decoding a signal encoded with high efficiency by the high-efficiency coding device of the present embodiment described above.

【0058】

That is, in FIG. 7, the quantized MDCT coefficient of each band is given to the decoding circuit input terminals 122,124,126, and the block size information used is given to the input terminals 123,125,127. The signal via these input terminals is sent to the decoding circuit (adaptive bit allocation decoding circuit) 116,117,118. In the decoding circuits 116,117,118, the bit allocation is canceled by using the adaptive bit allocation information.

【0059】

Next, the output of the decoding circuit 116,117,118 is sent to the IMDCT circuit 113,114,115. Further, block size information is sent to the IMDCT circuit 113,114,115 via the terminals 123,125,127. In these IMDCT circuits 113,114,115, the signal on the frequency axis is converted into the signal on the time axis. The partial band time-axis signals from the IMDCT circuits 113,114,115 are decoded into full-band signals by the IQMF circuits 112,111. This decoded signal is output from the output terminal 110 to the subsequent configuration.

【0060】

According to the decoding device of FIG. 7, the coded data from the high-efficiency coding device can be decoded with a small-scale configuration, and a decoding signal with good sound quality can be obtained.

【0061】

[Effect of the invention]

As is clear from the above description, according to the high-efficiency coding apparatus of the present invention, all the bits that can be used for bit allocation are divided into a predetermined fixed bit allocation pattern for any short time and each. In addition to the fixed bit allocation pattern, the bit allocation depending on the signal size of each block is also set to the corresponding band of the block. By weighting accordingly, it is complicated not only when the signal spectrum is flat or when there is only one isolated spectrum, but also when a signal is input in which there are many steep spectra. It is possible to allocate bits that are audibly desirable without performing various masking calculations, and it is possible to realize a high-efficiency coding device that is small in size and has good sound quality even at a lower bit rate.

[Simple explanation of drawings]

[Figure 1]

It is a block circuit diagram which shows the structural example of the high efficiency coding apparatus of this invention embodiment.

[Figure 2]

It is a figure for demonstrating the frequency and time division of the signal of the high efficiency coding apparatus of this invention embodiment.

[Fig. 3]

It is a figure which shows the structure (an example of the bit allocation algorithm) of the adaptive bit allocation coding circuit of the high efficiency coding apparatus of this invention embodiment.

[Fig. 4]

It is a figure which shows the bark spectrum.

[Fig. 5]

It is a figure which shows the example of the spectrum of the input signal in the high efficiency coding apparatus of this invention embodiment.

[Fig. 6]

It is a figure for demonstrating the bit allocation by the high efficiency coding apparatus of this Example with respect to an input signal.

[Fig. 7]

It is a block circuit diagram which shows the structural example of the high-efficiency decoding apparatus of this Example.

[Explanation of symbols]

10 ... Input terminal of high-efficiency coding device 11,12 Band division filter 13,14,15 MDCT circuit 16,17,18 Adaptive bit allocation coding circuit 19,20,21 Block size determination circuit 22,24,26 Coded output terminal 23,25,27 Block size information output terminal 122,124,126 Coded input terminal 123,125,127 Block size information input terminal 116,117,118 Adaptive bit allocation decoding circuit 113,114,115 IMDCT circuit 112,111 IQMF circuit 110 High-efficiency decoding device output terminal 302 Total number of usable bits Output circuit 303 Energy calculation circuit for each band 304 Energy-dependent bit distribution circuit 305 Fixed bit distribution circuit 306 Bit sum calculation circuit 307 Bit allocation amount output terminal for each band 308 Spectral smoothness calculation circuit 309 Bit division rate determination circuit