JPH09102741A - Encoding method and device, decoding method and device and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To encode the multichannel signals with high compression. SOLUTION: A common processing analyzer 102 decides a combination of common frequency bands or channels based on the audio data supplied through the input terminals 101a to 101e. The common data extractors 103a to 103e extract the data on the common frequency bands, and other data are supplied to the encoders 105a to 105e. A common data producer 104 produces the common, data on the common frequency bands. The outputs of the extractors 103a to 103e and the output of the producer 104 are encoded by the encoders 105a to 105e. These encoded outputs are turned into a bit stream by a multiplexer 106 and outputted through an output terminal 107.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an encoding method and apparatus, a decoding method and apparatus, and a recording medium,
For example, a stereo such as a video tape recorder, a video disc player, or a so-called multi-sound acoustic system, which is suitable for use in compressing and encoding a multi-channel digital signal, an encoding method and apparatus, a decoding method and apparatus, and Recording medium

[0002]

2. Description of the Related Art Conventionally, there are various techniques and apparatuses for high-efficiency coding of audio or voice signals. For example, an audio signal in the time domain is divided into unit time blocks and the time of each block is divided into blocks. Axis frequency signal is converted into a signal on the frequency axis (orthogonal conversion), divided into a plurality of frequency bands, and a block frequency band division method that encodes each band, so-called transform coding (transform coding), An example is band division coding (subband coding: SBC), which is a non-blocking frequency band division method in which a time domain audio signal or the like is not divided into blocks for each unit time and is divided into a plurality of frequency bands for encoding. be able to.

Further, a high-efficiency coding method and apparatus combining the above-described band-division coding and transform coding has been considered. In this case, for example, band-division is performed by band-division coding. After that, the divided signal for each band is orthogonally transformed into a signal in the frequency domain, and the orthogonally transformed signal is encoded for each region.

Here, as the band division filter used in the above band division encoding, for example, QMF is used.
There is a filter such as (Quadrature Mirror Filter), and this QMF filter is referred to as "Digital coding of speech in subbands" R.
E. Crochiere, BellSyst.Tech. J., Vol.55, No.8 1976)
It is described in. This QMF filter divides the band into two equal bandwidths, and this filter is characterized in that so-called aliasing does not occur when the divided bands are combined later.

In addition, the document "Polyphase Quadrature Filters-New Band Division Coding Technique"("Poly
phase Quadrature filters -A newsubband coding tech
nique ", oseph H. Rothweiler ICASSP 83, BOSTON) describes a method for dividing equal-bandwidth filters. In this polyphase quadrature filter, the signal is divided into multiple bands of equal bandwidth. The feature is that it can be divided at one time.

Further, as the spectrum transformation of the above-mentioned orthogonal transformation, for example, an input audio signal is divided into blocks in a predetermined unit time (frame), and discrete Fourier transform (DFT), discrete cosine transform (DCT), or modified for each block. There is one that transforms a time axis into a frequency axis by performing discrete cosine transform (MDCT) or the like. Regarding the MDCT, reference is made to the document "Subband / Transform Coding Using Filter Bank Design Based on Time Domain Aliasing Cancellation"("Subband / Transform
Coding Using Filter Bank Designs Basedon Time Doma
in Aliasing Cancellation ", JPPrincen ABBradla
y, Univ.of Surrey Royal Melbourne Inst.of Tech. IC
ASSP 1987).

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

Here, as the frequency division width in the case of quantizing each frequency component divided into frequency bands, for example, a bandwidth considering human auditory characteristics is often used. That is, the audio signal may be divided into a plurality of bands (for example, 25 bands) with a bandwidth generally called a critical band in which the higher the band, the wider the 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, the MDC
When the coefficient data obtained by the T processing is encoded by the bit allocation, the number of adaptive allocation bits (adaptation to the MDCT coefficient data for each band obtained by the MDCT processing for each block) The encoding is performed with the number of distributed bits).

The following two methods are known as the bit allocation method (bit allocation method).

For example, the document "Adaptive Transform Coding of Speech Signals",
IEEE Transactions of Acoustics, Speech, and Signa
Processing, vol.ASSP-25, No.4, August 1977), bit allocation is performed based on the signal size of each band.

In addition, for example, the document "Critical band encoder-
Digital Encoding of Perceptual Requirements of the Auditory System "(" The critical band coder --digital encodi
ng of the perceptual requirements of the auditory
system ", MA Kransner MIT, ICASSP 1980) describes a method that uses auditory masking to obtain a necessary signal-to-noise ratio for each band and perform fixed bit allocation.

[0012]

By the way, for example, in the high-efficiency compression encoding system for audio signals using the above-mentioned sub-band coding or the like, the human auditory characteristic is utilized to convert the audio data into about 1 A method of compressing to / 5 has already been put into practical use. As a high-efficiency encoding method for compressing the audio data to about 1/5, for example, ATRAC (a trademark of Sony Corporation, Adaptive, which is used in MD (a trademark of Sony Corporation, Mini Disc) standard).
There is a method called TRansform Acoustic Coding).

Further, not only in the case of ordinary audio equipment, but also in stereo or multi-sound sound systems such as movie film projection systems, high-definition televisions, video tape recorders, video disc players, etc., for example, 4 to 8 channels, etc. Are handling audio or voice signals of multiple channels of
Even in this case, it is desired to perform high efficiency coding that reduces the bit rate.

Therefore, as shown in FIG. 13, a multi-channel coding apparatus that performs compression coding for each channel can be considered.

The encoder shown in FIG. 13 has an input terminal 1
Encoders 105a to 105e for respectively encoding the signals input from 01a to 101e, a multiplexer 106 for outputting the encoded signals from the encoders 105a to 105e as a bit stream, and a bit stream from the multiplexer 106. Output terminal 107.

Center (C) channel, left (L) channel, right (R) channel, left surround (SL) supplied via the input terminals 101a to 101e.
Each audio data of the channel and the right surround (SR) channel is encoded by the single channel encoder 10.
5a to 105e, respectively. In these encoders 105a to 105e, the input signal is encoded, and the encoded data is supplied to the multiplexer 106. The multiplexer 106 converts the encoded data of each channel into one bit stream, and the bit stream is output from the output terminal 107.

Further, a multi-channel decoding device which carries out decoding for each channel can be considered.

The decoding device shown in FIG. 14 has an input terminal 1
Demultiplexer 132 that divides the bit stream input from 31 into encoded data of each channel, decoders 133a to 133e that respectively decode encoded data corresponding to each channel from demultiplexer 132,
And output terminals 136a to 136e for outputting the signals decoded by the decoders 133a to 133e.

The encoded bit stream data supplied via the input terminal 131 is the demultiplexer 1
At 32, the data is divided into encoded data corresponding to each channel and is supplied to each of the decoders 133a to 133e. The encoded data supplied to the decoders 133a to 133e are decoded by the decoders 133a to 133e, and the decoded audio data is output to the output terminal 1
36a to 136e respectively output.

However, in the encoding device and the decoding device having the configurations shown in FIGS. 13 and 14, the high-efficiency encoding method for compressing the digital audio data to about ⅕ is for a single channel. This is an encoding method, and when encoding multi-channel audio data using this, an effective data code that uses elements such as data dependency between channels, data characteristics of each channel, and format characteristics. It cannot be processed. That is, it is impossible to use an element that the audio data of the C channel and the audio data of the L channel are similar to each other, or the audio data of the left and right surround channels are similar in terms of format.

Further, by utilizing the tendency that human sense of hearing has an uncertain sense of direction with respect to sounds in a high frequency band, data is shared between channels and coded in the high frequency band,
There is a method of reducing the recording area. However, the sense of direction is uncertain, but the level difference can be sensed, and therefore, when the sound is reproduced in multi-channels, the sound field often changes, especially when the correlation between the channels is weak.

The present invention has been made in view of such a situation, and in the compression encoding of multi-channel signals, high compression suitable for the degree of correlation of digital data between multi-channels has been existing. It can be realized by using an encoder and a decoder.

[0023]

According to a first aspect of the present invention, an encoding method sets a frequency band of a digital signal to be shared in accordance with the frequency characteristic of the digital signal and the reproduction environment of the digital signal, A feature is that a part or all of frequency bands of digital signals of a plurality of channels are made common to at least one common digital signal and the common digital signal is encoded.

According to a second aspect of the present invention, there is provided an encoding device which sets a frequency band of a digital signal to be shared in accordance with frequency characteristics of the digital signal and a reproduction environment of the digital signal, and a plurality of channels. It is characterized by comprising a commonizing means for commonizing at least one common digital signal in a frequency band of a part or the whole of the digital signal, and an encoding means for encoding the common digital signal.

According to a ninth aspect of the present invention, there is provided a decoding method for decoding a common digital signal on the basis of common information and decoding the common digital signal corresponding to a frequency band in which the digital signal is common. Is distributed to the corresponding channel and the digital signal corresponding to the channel is restored.

According to a tenth aspect of the present invention, there is provided a decoding device for decoding a common digital signal on the basis of the common information and a decoding unit corresponding to a frequency band in which the digital signal is common. Distribution means for distributing the common digital signal decoded by the means to channels,
Restoration means for restoring the digital signal corresponding to the channel.

It is possible to further provide adjusting means for adjusting the common digital signal in accordance with the recommended reproduction environment of the decoded digital signal.

According to a seventeenth aspect of the present invention, the combination of channels to be shared is set in accordance with the characteristics of the digital signal and the reproduction environment, and part or all of the digital signals of the channels to be shared are set. The frequency band is set, the signal in the frequency band of the digital signal of the common channel is made common to at least one common digital signal, the common digital signal is coded, and the common digital signal It is characterized in that reproduction information for reproducing the original digital signal of each channel is created for each frame.

According to the eighteenth aspect of the present invention, the encoding device sets a combination of channels to be used in common in accordance with the characteristics of the digital signal and the reproduction environment, and frequency of part or all of the digital signals of the channels to be used in common. Setting means for setting the band, commonizing means for commonizing the frequency band signal of the digital signal of the channel set by the setting means to at least one common digital signal, and commonizing commonalized by the commonizing means For each frame, reproduction information for reproducing the original digital signal of each channel before being standardized from the coding means for coding the standardized digital signal and the standardized digital signal standardized by the standardizing means. And reproduction information creating means for creating.

A decoding method according to a twenty-seventh aspect of the invention is to decode a common digital signal based on the common information, and to decode the common common signal based on predetermined reproduction information of a digital signal of a predetermined channel. The digitalized digital signal is adjusted, and the original digital signal of the predetermined one of the channels is restored based on the common digital signal and the digital signal of the predetermined one of the channel.

A decoding device according to a twenty-eighth aspect of the invention is based on a decoding means for decoding the common digital signal based on the common information and predetermined reproduction information of the digital signal of a predetermined channel, And adjusting means for adjusting the decoded common digital signal; common digital signals; and restoring means for restoring the original digital signal of the predetermined one of the channels based on the digital signal of the predetermined one of the channels. Is characterized by.

In the recording medium according to the thirty-third aspect, a part or all of the frequency bands of digital signals of a plurality of frames of a plurality of channels are made common to at least one common digital signal, and the frequency characteristics and reproduction of the digital signal are reproduced. Information related to the coding method for the signal in which the frequency band for commonization is changed according to the environment and the coded common digital signal and the coded digital signal excluding the common digital signal It is recorded together with.

In the recording medium according to the thirty-fourth aspect, a part or all of frequency bands of digital signals of a plurality of frames of a plurality of channels are made common to at least one common digital signal, and frequency characteristics and reproduction of the digital signal. Corresponding to the environment, the combination of channels for commonization and the frequency band are changed, and predetermined reproduction information for returning the commonized digital signal to the original digital signal before commonization is created for each frame, It is characterized in that a signal obtained by encoding the common digital signal and the encoded signal in which the reproduction information is included in the common information regarding the encoding of the common digital signal are recorded.

In the encoding method according to claim 1,
The frequency band of the digital signal to be shared is set according to the frequency characteristics of the digital signal and the reproduction environment of the digital signal, and at least one of all or some of the frequency bands of the digital signals of multiple channels is shared. The digital signal is standardized, and the standardized digital signal is encoded. Therefore, the digital signals of a predetermined frequency band of the digital signals of a plurality of channels can be shared.

In the encoding device according to the second aspect,
The setting means sets the frequency band of the digital signal to be shared according to the frequency characteristics of the digital signal and the reproduction environment of the digital signal, and the commonizing means sets a part or all of the digital signals of a plurality of channels. The frequency band is made common to at least one common digital signal, and the common digital signal is encoded by the encoding means. Therefore, the digital signals of a predetermined frequency band of the digital signals of a plurality of channels can be shared.

In the decoding method according to claim 9,
The common digital signal is decoded on the basis of the common information, and the decoded common digital signal is distributed to the corresponding channel corresponding to the frequency band in which the digital signal is common, and is distributed to this channel. The corresponding digital signal is restored. Therefore, the original digital signal of at least one channel can be restored from the common digital signal.

In the decoding apparatus according to the tenth aspect, the decoding means decodes the common digital signal based on the common information, and the distributing means converts the digital signal into a common frequency band. Correspondingly, the common digital signal decoded by the decoding means is
The signal is distributed to the corresponding channel, and the digital signal corresponding to this channel is restored by the restoring means. Therefore, the original digital signal of at least one channel can be restored from the common digital signal.

In the encoding method according to the seventeenth aspect, in accordance with the characteristics of the digital signal and the reproduction environment,
A combination of channels to be shared is set, and part or all of frequency bands of digital signals of channels to be shared are set, and signals in a frequency band of digital signals of channels to be shared are at least one shared. The digitalized signal is standardized, the standardized digital signal is encoded, and reproduction information for reproducing the original digital signal of each channel before being standardized is created for each frame from the standardized digital signal. . Therefore,
A digital signal in a predetermined frequency band of digital signals of a plurality of predetermined channels can be made common and a signal for returning it to the original digital signal can be output.

In the encoding apparatus according to the eighteenth aspect, the setting means sets the combination of channels to be shared in accordance with the characteristics of the digital signal and the reproduction environment, and the digital signal of the channels to be shared is set. A part or all of the frequency band of the digital signal is set by the commonizing means, and the signal of the frequency band of the digital signal of the channel set by the setting means is made common to at least one common digital signal, and by the encoding means. , The commonalized digital signal commonalized by the commonalizing means is encoded, and the reproduction information creating means converts the commonalized digital signal, which is commonalized by the commonalizing means, from the original of each channel before commonalization. Reproduction information for reproducing the digital signal is created for each frame. Therefore, it is possible to standardize the digital signals of the predetermined frequency band of the digital signals of the predetermined plural channels and output the reproduction information for returning the digital signals to the original digital signals.

In the decoding method according to the twenty-seventh aspect, the common digital signal is decoded, and the decoded common digital signal is generated based on predetermined reproduction information of the digital signal of a predetermined channel. The original digital signal of the predetermined one of the channels is restored based on the adjusted and common digital signal and the digital signal of the predetermined one of the channel. Therefore, the original digital signal can be restored based on the reproduction information.

In the decoding device according to the twenty-eighth aspect, the commonizing digital signal is decoded by the decoding means, and the adjusting means, based on the predetermined reproduction information of the digital signal of the predetermined one of the channels, The decoded common digital signal is adjusted, and the restoration means restores the original digital signal of the predetermined one of the channels based on the common digital signal and the digital signal of the predetermined one of the channel. Therefore, the original digital signal can be restored based on the reproduction information.

In the recording medium according to claim 33,
A frequency band of a part or all of digital signals of a plurality of frames of a plurality of channels is made common to at least one common digital signal, and a frequency band to be made common corresponds to a frequency characteristic of the digital signal and a reproduction environment. The modified and encoded common signal digital signal and the encoded digital signal excluding the common digital signal are recorded together with information about the encoding method. Therefore, it is possible to record a signal in which digital signals of a plurality of channels are made common and a digital signal of each channel excluding it as a high-efficiency compression-coded signal and reproduce it.

In the recording medium according to claim 34,
A combination of channels in which a part or all of the frequency bands of digital signals of a plurality of frames of a plurality of channels are made common to at least one common digital signal, and commonization is performed according to the frequency characteristics of the digital signal and the reproduction environment , And the frequency band is changed, predetermined reproduction information for returning the common digital signal to the original digital signal before commonization is created for each frame, and the common digital signal is common with the coded signal. The encoded signal is recorded by including the reproduction information in the commonized information regarding the encoding of the encoded digital signal. Therefore, the information for reproduction can be recorded, and a more stable sound field can be reproduced based on the information.

[0044]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of an encoding device to which the encoding method of the present invention is applied.
As shown in the figure, the encoding apparatus of the present invention is a single-channel compression encoder (for example, the so-called A described above).
A plurality of TRAC encoders are used to realize multi-channel compression encoding.

That is, the encoding apparatus shown in FIG. 1 is an apparatus for encoding digital audio signals of a plurality of channels and outputting encoding parameter information together with the encoded digital audio signals. Some or all of the signals are treated as one or more common signals, and the common frequency band is changed according to the frequency characteristics of this digital audio signal and the target playback environment. The encoded signal is encoded.

Common processing analyzer 1 constituting an encoding device
02 (setting means) performs analysis for selecting an effective common frequency band between channels from audio data of each channel input from the input terminals 101a to 101e. Common data extractors 103a to 103e
According to the analysis result of the common processing analyzer 102, the common part is extracted from the audio data of each channel input from the input terminals 101a to 101e, and the remaining part is output.

Common data generator 104 (common means)
Creates common data from the audio data input from the input terminals 101a to 101e and outputs it. The encoders 105a to 105e (encoding means) encode the data extracted from the common data supplied from the common data extractors 103a to 103e. Encoder 10
5f to 105g are adapted to encode the common data supplied from the common data generator 104.

In this embodiment, 5-channel audio data of a center (C) channel, a left (L) channel, a right (R) channel, a left surround (SL) channel, and a right surround (SR) channel is used. explain.

In the embodiment shown in FIG. 1, the input terminal 1
Center (C) supplied via 01a to 101e,
Left (L), Right (R), Left Surround (S
The audio data of each channel of L) and right surround (SR) is first input to the commonization processing analyzer 102. Here, an analysis for selecting an effective common frequency band between the channels described later is performed, and the analysis result is output to the common data extractors 103a to 103e and the common data generator 104.

Common data extractors 103a to 103e
, The common part is extracted from the audio data of each channel supplied via the input terminals 101a to 101e based on the analysis result from the common processing analyzer 102, and only the remaining part is the encoder. 105a to 105e. Note that these encoders 105a
To 105e are basically encoders 10 shown in FIG.
5a to 105e.

On the other hand, the output of the common processing analyzer 102 is
It is also supplied to the common data generator 104 as described above. In the common data generator 104, the input terminal 1
The data of each channel supplied via 01a to 101e are put together based on the analysis result supplied from the commonization processing analyzer 102, and one or a plurality of commonized data are created and output.

In the encoders 105a to 105e,
The input signals from the common data extractors 103a to 103e are encoded, and the encoders 105f to 105g are encoded.
In, the one or more common data output from the common data generator 104 are encoded respectively.

From these encoders 105a to 105g, encoded data as an encoded result and common information (common parameter information) used for encoding are output and supplied to the multiplexer 106. In the multiplexer 106, the output of each of the encoders 105a to 105g is made into one bit stream and is output from the output terminal 107.

FIG. 2 shows the common processing analyzer 1 shown in FIG.
2 is a block diagram showing an internal configuration of 02. FIG. In FIG. 2, audio data of each channel of center (C), left (L), right (R), left surround (SL), and right surround (SR) supplied via input terminals 101a to 101e. Are transmitted to the orthogonal transformers 121a to 121e, respectively, converted into frequency components and output.

In the frequency characteristic evaluators 122a to 122e, the human auditory characteristic such as a so-called minimum audible curve or masking threshold is calculated based on the frequency component data of each channel obtained from the orthogonal transformers 121a to 121e. The parameters are determined and output with the audio data.

In the commonization processing selector 123, the commonization is performed on the basis of the encoding target bit rate and the data regarding the commonization (audio data and viewing characteristic parameters) obtained from the frequency characteristic evaluators 122a to 122e. The frequency band is selected such that the absolute level of the quantization noise generated by is less than the minimum audible curve. As a result, the noise generated by the commonization cannot be heard. The selection result (common frequency band) is output from the output terminal 124, and the common data extractors 103a to 103e and the common data generator 104 shown in FIG.
Supplied to It should be noted that the data regarding commonization (common parameter information) output from the output terminal 124 is output in units of a predetermined frame (for example, sound frame).

As described above, in the above-described embodiment, by selecting the common frequency using the characteristics of the data, it is possible to reduce the discomfort caused by the common.

Further, the method of commonizing the frequency band and the channel selected by the commonizing processing selector 123 can be changed between the sound frames as the predetermined frames. This makes it possible to suppress the change in the sound field due to the commonization by selecting the most suitable common frequency band between the sound frames.

Further, in FIG. 2, it is possible to make a plurality of common frequency bands, combinations of channels, etc. exist in the same sound frame. For example, in the case where the frequency band below the minimum audible curve is expanded by independently encoding one or a plurality of channels in a specific frequency band, the channels shared by a plurality of frequency bands By performing the commonization processing in which the combination of is changed, more effective commonization becomes possible.

Alternatively, it is possible to allow a plurality of common combinations to simultaneously exist in a specific frequency band. For example, the front side (C, L, R) channels and the rear side (S
For example, in the case of data in which it is effective to share L, SR) channels separately, by creating a plurality of common channels having the same or different frequency bands to be shared, effective data characteristics can be obtained. Commonality is possible.

FIG. 3 shows an example of the structure of a decoding device to which the decoding method of the present invention is applied. That is, the decoding device shown in the figure is a device that realizes multi-channel decoding by using a plurality of single-channel decoders (for example, decoders corresponding to the so-called ATRAC system described above).

That is, the decoding apparatus shown in FIG. 3 treats a part or all of digital audio signals of a plurality of channels as one or a plurality of common signals, and determines the frequency characteristics and the purpose of the digital audio signals. Is a decoding device that decodes encoded digital audio signals of a plurality of channels including signals whose frequency bands are changed according to the reproduction environment, using the encoding parameter information. The generalized signal is decoded, the commonized signal decoded according to the common frequency band is distributed to a plurality of channels, and a digital audio signal of a plurality of channels is restored.

The demultiplexer 132 has the input terminal 13
1 is divided into encoded data and common parameter information used for encoding, and the decoder 1
33a to 133g (decoding means). The decoders 133a to 133e decode the unshared coded data supplied from the demultiplexer 132. The decoders 133f to 133g decode the common data and the common parameter information supplied from the demultiplexer 132 and output them.

The common data distributor 134 (sorting means) creates data for each channel from one or a plurality of common data based on the common parameter information supplied from the decoders 133f to 133g. Distribute to the corresponding channels. The common data synthesizers 135a to 135e (restoring means) are decoders 133a to 133e.
And the output from the common data distributor 134 are combined and output via the output terminals 136a to 136e.

In the embodiment shown in FIG. 3, the bit stream supplied via the input terminal 131 is first supplied to the demultiplexer 132. Since data (common parameter information) indicating a common channel is included in the bitstream together with the data of each channel, the demultiplexer 132 uses the coded data and the commonization used for coding. The parameter information and the channel information are divided for each channel and supplied to the decoders 133a to 133g.

Decoder 13 corresponding to the shared channel
3f to 133g are the same as the number of common channels,
The decrypted common data and common parameter information are output and sent to the common data distributor 134. The common data distributor 134 uses this common parameter information to create data for each channel from one or a plurality of common data, and distributes the data to the corresponding channels.

Common data synthesizers 135a to 135e
Is a combination of the outputs from the decoders 133a to 133e of each channel and the output from the common data distributor 134,
The decoded data corresponding to each channel is output from the output terminals 136a to 136e.

As described above, in the decoding apparatus shown in FIG. 3, the common data distributor 134 allows the common data corresponding to one or a plurality of common channels according to the frequency band or channel to be common. Are created, distributed to the corresponding channels, and combined by the common data combiner 135 with non-common data. Thereby, digital signals of a plurality of channels can be decoded from at least one or more common data. Even when there are plural types of common channels, there are plural common processing methods, or when data of a predetermined channel is encoded as common data of plural common channels, the common data distributor Decoding becomes possible by handling the distribution of the common data by the unit of 134.

Next, in the case where the multi-channel data is shared, the data shared by the state of the encoded data and the data not shared without deviating from the single-channel encoding method used in the embodiment. FIG. 4 shows an example of the configuration of a decoding device in the case where the above can be combined.

The decoding apparatus shown in FIG. 4 is a demultiplexer 13 for dividing the data of each channel and the data of a common channel from the input bit stream.
2. A common data distributor 137 that creates and distributes data for each channel from the common data based on the common parameter information, the common data supplied from the common data distributor 137, and the demultiplexer 132. It is composed of common coded data synthesizers 138a to 138e for synthesizing the data of the respective supplied channels and decoders 133a to 133e for decoding the output signals from the common coded data synthesizers 138a to 138e, respectively.

In the decoding device having the above-mentioned configuration, the demultiplexer 132 outputs the data of each channel and the data of the common channel from the bit stream supplied to the demultiplexer 132 via the input terminal 131. The divided data of each channel is sent to the common coded data synthesizers 138a to 138e, and the common channel data is divided into the common data distributor 137.
Supplied to

In the common data distributor 137, data for each channel is created from one or a plurality of common data based on the common parameter information, and the common coded data synthesizers 138a to 138a of the corresponding channel are generated. Thirteen
8e, respectively.

Common coded data synthesizers 138a to 138
In 8e, the data from the common data distributor 137 and the data from the demultiplexer 132 are combined as coded data and output.

In the decoders 133a to 133e at the next stage, the outputs from the corresponding common coded data synthesizers 138a to 138e are decoded respectively. Decoder 1
The outputs from 33a to 133e are output as the data of the respective channels from the output terminals 136a to 136e of the corresponding channels.

As described above, in the decoding apparatus shown in FIG. 4, the common data distributor 137 and the common coded data synthesizers 138a to 138e are provided before the decoders 133a to 133e. The number of decoders can be reduced, and the scale of the decoding device can be reduced.

Further, in the above-described embodiment, the following method using the channel reproduction environment can be used as a method for enabling reproduction that does not cause a feeling of strangeness in hearing.

First, it is possible to use a method of changing the processing method handled as common data according to the reproduction environment recommended for audio data.

That is, for example, when the center (C), the left (L), the right (R), the left surround (SL), and the right surround (SR) channels are unified into one channel, C: L: R: SL: SR = 1.0000: 0.7071: 0.7071:
Level conversion is performed at a ratio of 0.5000: 0.5000, and then the signals are combined and reproduced from one channel at the time of reproduction or distributed to all channels at the same ratio. This enables effective sharing.

Further, there are three channels of center (C), left (L) and left surround (SL), or center (C), right (R) and right surround (S).
When the three channels of R) are shared, for example, effective commonization is possible by using a ratio of C: L: SL = 0.7071: 1.00000: 0.7071 C: R: SR = 0.7071: 1.0000: 0.7071.

When two channels of left (C) and left surround (SL) or two channels of right (R) and right surround (SR) are shared, for example, L: SL = 1.0000: 0.7071 R: Using a ratio of SR = 1.0000: 0.7071 enables effective sharing.

When three channels of left (L), center (C), and right (R) or two channels of left surround (SL) and right surround (SR) are shared, for example, C: L : R = 1.0000: 0.7071: 0.7071 SL: SR = 0.7071: 0.7071 It becomes possible to use the ratio effectively.

Further, the left (L) and the center (C) 2
When the channels or the two channels of the right (R) and the center (C) are shared, for example, effective commonization is possible by using a ratio of C: L = 0.7071: 1.0000 C: R = 0.7071: 1.0000. Become.

In addition to the common parameter information, there is a coding method in which information for returning to the data before the common is included in the code. As a result, it is possible to perform reproduction without feeling uncomfortable in hearing.

FIG. 5 shows an example of the configuration of an encoding device for extracting parameters for reproducing the data used for commonization of each channel from the commonized data. The embodiment shown in FIG. 5 is obtained by adding common parameter extractors 108a to 108e (reproduction information creating means) to FIG. Detailed configurations and operations of the common parameter extractors 108a to 108e will be described later with reference to FIG.

FIG. 7 shows an example of the structure of a decoding device for realizing a method of adjusting common data by using parameters included in a code. The embodiment shown in FIG. 7 is obtained by adding common data adjusters 139a to 139e (adjusting means) to FIG.

In FIGS. 5 and 7, constituent elements corresponding to those in FIGS. 1 and 3 are designated by the same reference numerals, and description thereof will be omitted as appropriate.

First, in FIG. 5, the data of the corresponding channels are supplied to the input terminals 101a to 101e, respectively. The data output from the commonization processing analyzer 102 and input to the commonalization data extractors 103a to 103e and the commonalization data creator 104 is information regarding data used for commonization (commonization parameter information).
And there are as many channels as the sound source data. If the data of the corresponding channel is not used for commonization at all,
Information is provided that no data is used. On the other hand, the multiplexer 1 outputs the data from the common data generator 104.
The data supplied to 06 are the commonized data and its information, and there are the same number of common channels. The number of common channels is determined by the common processing analyzer 1
It changes depending on the commonization method such as the frequency band to be shared and the combination of channels selected by 02.

As shown in FIG. 5, in the configuration of FIG. 1, common parameter extractors 108a to 108e can be added to each channel. The common parameter extractors 108a to 108e are input with data used for commonization of each channel and common parameter information thereof, and all common data and common parameter information thereof. Common parameter extractor 108
a to 108e are based on these data and information,
The dependence between the common data in each common channel and the data of the channels corresponding to the common parameter extractors 108a to 108e and the method for returning to the data before the common are analyzed, for example, in encoding. A scale parameter of the channel in a frequency band unit to be used, or a unit of a plurality of bands, and a scale parameter ratio between frequency bands in the channel are obtained. These are sent to the multiplexer 106 and included in the code.

FIG. 6 shows an example of the structure of the common parameter extracting unit 108a shown in FIG. In the common parameter extractor 108a shown in FIG. 6, the common method analyzer 202 is supplied with the audio data of the channel through the input terminal 201a, and the common processing analyzer 102 through the input terminal 201b. Output signal is supplied. Further, all the common data and the common parameter information thereof are supplied from the common data generator 104 via the input terminals 201c to 201d.

In the common method analyzer 202, the common method used in each common channel (combination of common channels, etc.) and the common frequency band are analyzed, and the common frequency band is set. For each (e.g., critical band), data shared with the input data (common data) and its common parameter information are output.

Parameter analyzers 204a and 204b
Is for each frequency band for which a common parameter is set, and is a parameter effective for restoring the data of the channel from the common data by comparing the data of the channel and the common data (for example, The scale factor) is analyzed and output. Since the analysis result in the frame before that is used for this analysis, the output is the parameter recording memories 203a to 203 for storing the analysis result.
3b, the parameter analyzers 204a to 204a
For b, the analysis results recorded here are used as appropriate for analysis.

The common parameter formatter 205 is
The outputs of the parameter analyzers 204a and 204b are combined into one as a common parameter for the channel and output from the output terminal 206.

Common parameter extractors 108b to 10b
The configuration and operation of 8e are basically the same as the case of the above-described common parameter extractor 108a, and therefore illustration and description thereof will be omitted.

As described above, by referring to the parameter of the previous frame and setting the appropriate parameter value and accuracy for each frequency band, it is possible to reduce the discomfort caused by the commonization.

Further, in FIG. 7, in the configuration of FIG. 3, common data adjusters 139a to 139a are provided for each channel.
39e is added. Common data adjuster 139a
To 139e, the common data of the corresponding channel output from the common data distributor 134 and the common parameter information thereof, and the common parameter information of the corresponding channel output from the demultiplexer 132 are input. In the common data adjusters 139a to 139e, based on these, the common data in each common channel and the common data adjusters 139a to 139e.
Of the common data distributed to each channel by using the dependency between the data of each corresponding channel and the method (for example, scale parameter ratio) for returning to the data before common. Adjusted and changed respectively.

These common data are supplied to the common data combiners 135a to 135e, respectively, and combined with the non-common data supplied from the decoders 133a to 133e, and output from the output terminals 136a to 136e, respectively. To be done. As a result, it is possible to reproduce a sound field closer to the original signal data of the channel as compared with the decoding device of FIG.

As described above, in the above-described embodiment, the common data distributor 134 is used to adjust the common data to 1
The common data of one or a plurality of common channels are shared by the common data adjusters 139a to 139 of the corresponding channels.
9e are distributed and adjusted respectively. The adjusted common data is used as the common data synthesizers 135a to 135e.
By this, it is combined with data that is not shared. Thereby, digital signals of a plurality of channels can be decoded from at least one or more common data. Even if there are multiple types of common channels, there are multiple common processing methods, and even if the data of a specific channel is encoded in multiple common channels, the common data Decoding can be performed by performing distribution by the distributor 134 alone.

Further, as described above, before the common data is combined with the data of each channel, the common data adjuster 1
Since the common data is adjusted for each channel by 39a to 139e, it is possible to suppress the change in the sound field caused by the common data.

This system can be used as an independent system regardless of the reproduction environment of the channel. However, when the reproduction environment is specified, the dependence of the data can be predicted, so that the data and the reproduction environment can be predicted. It is possible to create a more effective common parameter by analyzing the common parameter using.

Further, there is an encoding method that uses time change information between sound frames to select a common channel or a common processing method in order to enable reproduction that does not cause a feeling of strangeness in hearing.

Here, the sound frame indicates a processing unit of audio data when encoding and decoding, and in the so-called ATRAC system used in this embodiment, 512 samples are taken at a sampling frequency of 44.1 kHz. is there.

By the way, the coding method and apparatus of this embodiment can change the common frequency band or the selection of the common processing method for each sound frame.
If you select the best frequency band and processing method to obtain playback that does not feel unnatural within each sound frame, the frequency band and processing method will change for each sound frame, resulting in discomfort due to sound frame switching. It may occur.

Therefore, in frequency band selection, the transition of selection is monitored in each sound frame, and, for example, a method of preventing repetition of a large band change, or a frequency band change in a steady state where input data changes little. By adopting the limiting method, it is possible to prevent the generation of a sense of discomfort due to a change in the common frequency band.

In selecting the common processing method,
The difference in sound quality due to the difference in processing method is larger than the difference in sound quality due to frequency band change, and frequent switching in sound frame units is not suitable. It is appropriate to switch at a frequency of at least several sound frames.

Next, another embodiment of the present invention will be described. The channel selections in the above-described embodiments are center (C), left (L), right (R), left surround (S).
L) and 5 channels of right surround (SR) are described, but 7 channels in which a left center (LC) channel and a right center (RC) channel are added to this, and conversely the center (C) Even in the case of four channels without channels, it is possible to encode digital signals of a plurality of channels.

The subwoofer (SW) is used in the above embodiment.
Although it is conceivable that channels are added to make six channels, since this subwoofer (SW) channel is a channel for reproducing low frequencies, the frequency band is narrow and there is little advantage in sharing. Therefore, it is possible to easily add it to the encoding and decoding device without adding it to the common processing.

Next, the above-mentioned encoders 105a to 105
The specific configuration and operation of e will be described with reference to FIGS. 8 to 11. Note that FIG. 8 shows a configuration example of the encoder 105a for one channel. The encoder 10
The configurations and operations of 5b to 105e are similar to those of the encoder 105a.
Since it is basically the same as the case, the description thereof is omitted here.

The signal band division filter 401 divides the signal input through the input terminal 424 into three frequency bands. Low frequency MDCT (Modified D
The iscrete Cosine Transform (improved discrete cosine transform) circuit 402L is 0 supplied from the band division filter 401.
MDCT for low frequency signals from kHz to 5.5 kHz
Perform the operation. The mid-range MDCT circuit 402M has 5.5 kHz to 11 kHz supplied from the band division filter 401.
MDCT operation is performed on the signal in the middle band of z. High range MD
The CT circuit 402H is configured to perform MDCT calculation on a high frequency signal of 11 kHz or higher (11 kHz to 22 kHz) supplied from the band division filter 401.

The block size evaluator 403 determines a time block length described later. Normalization circuits 404L to 4
04H divides the audio signal consisting of low, mid, and high frequencies into a total of 52 block floating units of low, mid, and high frequencies, and normalizes (normalizes) each unit. Has been done.

The bit allocator 405 obtains allocation bit number information, which will be described later, and supplies it to the requantizer 406. The requantizer 406 is adapted to perform requantization based on the distributed bit number information supplied from the bit distributor 405. The formatter 407 is adapted to convert the output signal from the requantizer 406 into a bitstream.

In FIG. 8, the input terminal 424 is connected to the input terminal 424 shown in FIG.
The common data extractor 103a shown in (1) supplies the remaining audio data (sampled and quantized audio data) obtained by extracting the common part from the original audio data. The data supplied to the input terminal 424 is the data of the band division filter 4 first.
01 depending on 0 to 5.5 kHz low range and 5.5 kHz
z to 11 kHz mid-range and 11 kHz or higher (11 kHz
Z to 22 kHz).

Of the signals of these three frequency bands, the low frequency signal from the band division filter 401 is input to the MDCT circuit 402L which performs MDCT operation, and the low frequency signal is M.
The MDCT circuit 402M that performs the DCT operation and the high-frequency signal are sent to the MDCT circuit 402H.
Each of the T circuits 402L to 402H is decomposed into frequency components. At this time, the time block length when performing the MDCT process is variable for each frequency band, and the time block length is shortened in the portion where the signal changes abruptly to improve the time resolution, and the signal is steady. In the part, the time block length is increased to control the effective transmission of signal components and the quantization noise.

This time block length is determined by the block size evaluator 403. That is, the signals of the three frequency bands from the band division filter 401 are also sent to the block size evaluator 403, and the block size evaluator 4
03 determines the time block length of MDCT processing, and the information indicating the determined time block length is MDCT circuit 402L.
To 402H.

Of the two types of time block lengths in MDCT processing, the long time block length is called the long mode and corresponds to a time of 11.6 ms, for example. The short time block length is called a short mode. For example, up to 1.45 ms in the high range (11 kHz or more), low range (5.5 kHz or less) and middle range (5.5 kHz to 1).
At 1 kHz), the time resolution is increased up to 2.9 ms.

In this way, the two-dimensional region of time and frequency (this is a block floating unit: Block Fl
The audio signal decomposed into the above signal components is divided into a total of 52 block floating units in the low band, the middle band, and the high band by the normalization circuits 404L to 404H, and standardized for each unit. Is normalized (normalized) (scale factor is determined).

Further, in the bit allocator 405, the characteristics of the audio signal are analyzed by utilizing the characteristics of human hearing. The analysis result is supplied to the requantizer 406 to which the signals for each unit from the normalization circuits 404L to 404H are supplied.

In the requantizer 406, the degree of accuracy with which each unit is to be encoded is determined based on the above analysis result, parameterized (word length is determined), and re-quantized. Quantization is performed.

Finally, in the formatter 407,
The parameter information for each unit and the requantized spectrum signal are assembled into a bit stream in one channel supplied to the multiplexer 106 shown in FIG. 1 according to a predetermined format. The output of the formatter 407 is output from the output terminal 425.

Here, the above-described encoding operation is performed in units of sound frames.

Further, the bit allocator 405 has a concrete structure as shown in FIG. That is, the energy calculation circuit 522 is configured to calculate energy for each critical band of the signal input from the input terminal 521. Convolution filter circuit 523
Performs a convolution process of multiplying an output signal from the energy calculation circuit 522 by a predetermined weighting function and adding the product.

The (n-ai) function generating circuit 525 generates and outputs an allowance function (n-ai). Subtractor 524
From the output of the convolutional filter circuit 523, (n−a
i) The output from the function generating circuit 525 is subtracted, and the result of the subtraction is supplied to the divider 526. The divider 526 is adapted to perform inverse convolution processing on the input signal to obtain a masking threshold.

The minimum audible curve generating circuit 532 supplies the data indicating the minimum audible curve to the synthesizing circuit 527. The synthesizing circuit 527 and the data indicating the minimum audible curve output from the minimum audible curve generating circuit 532 and the divider 526.
The masking threshold output from the above is synthesized and output. The subtractor 528 subtracts the output signal from the synthesis circuit 527 and the output from the energy calculation circuit 522 supplied via the delay circuit 529, and outputs the result.

The correction information output circuit 533 outputs data corresponding to a predetermined equal loudness curve. The permissible noise correction circuit 530 corrects the permissible noise level of the output signal from the subtractor 528 based on the output signal from the correction information output circuit 533, and outputs it via the output terminal 531.

In FIG. 9, the MD is connected to the input terminal 521.
The spectrum data in the frequency domain from the CT circuits 402L, 402M, and 402H is supplied.

This frequency domain data is sent to the energy calculation circuit 522 for each band, and the energy for each critical band (critical band) is, for example, the square of each amplitude value within the band (for example, the peak of the amplitude value). It can be obtained by calculating the sum of the squares of the values. Instead of the energy for each band, a peak value, an average value, etc. of the amplitude value may be used. The spectrum of the total sum value of each band as the output from the energy calculation circuit 522 is generally called a Bark spectrum (SB).
FIG. 10 shows such a Bark spectrum for each critical band. However, in FIG. 10, the number of critical bands is set to 1 in order to simplify the illustration.
It is represented by two bands (band B1 to band B12).

Here, in order to take into account the influence of the above-described Bark spectrum on so-called masking, a convolution processing is performed such that the Bark spectrum is multiplied by a predetermined weighting function and added. For this reason,
The output of the energy calculation circuit 522 for each band, that is, each value of the Bark spectrum is calculated by the convolution filter circuit 523.
Supplied to The convolution filter circuit 523 is, for example,
A plurality of delay elements that sequentially delay input data, and a plurality of multipliers that multiply outputs from these delay elements by a filter coefficient (weighting function) (for example, 25 corresponding to each band).
Number of multipliers), and a sum adder that sums the outputs of the multipliers.

The above-mentioned masking means a phenomenon in which one signal is masked by another signal and becomes inaudible due to human auditory characteristics. The masking effect is due to the time domain audio signal. There are an axial masking effect and a simultaneous time masking effect by a signal in the frequency domain. Due to these masking effects, even if there is noise in the masked portion, this noise will not be heard. For this reason, in an actual audio signal, noise within the masked range is regarded as acceptable noise.

Here, a specific example of the multiplication coefficient (filter coefficient) of each multiplier of the convolution filter circuit 523 will be described. When the coefficient of the multiplier M corresponding to an arbitrary band is 1, the multiplier M-1 gives a coefficient of 0.15, multiplier M-2 gives a coefficient of 0.0019, and multiplier M-3 gives a coefficient of 0.0000.
086, multiplier M + 1 gives a coefficient of 0.4, multiplier M + 2
By multiplying the output of each delay element by a coefficient of 0.06 with a coefficient of 0.007 by a multiplier M + 3, the convolution processing of the Bark spectrum is performed. However, M is 1 to 2
It is an arbitrary integer of 5.

Next, the output of the convolution filter circuit 523 is supplied to the subtractor 524. The subtractor 524 calculates a level α corresponding to an allowable noise level (allowable noise level) described later in the convoluted area. It should be noted that the level α corresponding to this allowable noise level is a level that becomes an allowable noise level for each band of the critical band by performing inverse convolution processing, as described later. here,
The subtractor 524 is supplied with an allowance function (function expressing a masking level) for obtaining the level α. The level α is controlled by increasing or decreasing this allowance function. The allowance function is supplied from the (n-ai) function generating circuit 525 as described below.

That is, the level α corresponding to the allowable noise level can be obtained by the following equation, where i is the number given in order from the low band of the critical band.

Α = S- (n-ai)

In this equation, n and a are constants, and a
> 0 and S are the intensities of the bark spectrum subjected to the convolution processing, and (n-ai) in the formula is the tolerance function. N as an example
= 38, a = -0.5 can be used.

In this way, the level α is obtained, and this data is supplied to the divider 526. The divider 526 is for deconvoluting the level α in the convolved region. Therefore, by performing this inverse convolution processing, the masking threshold can be obtained from the level α.
That is, this masking threshold becomes the allowable noise spectrum. Although the inverse convolution processing requires a complicated calculation, the inverse convolution is performed using the simplified divider 526 in this embodiment.

Next, the masking threshold is supplied to the subtractor 528 via the synthesizing circuit 527. Here, the output from the energy detection circuit 522 for each band, that is, the above-described Bark spectrum (SB) is supplied to the subtractor 528 via the delay circuit 529. Therefore, the subtractor 528 performs a subtraction operation on the masking threshold and the Bark spectrum, so that the Bark spectrum is equal to or lower than the level indicated by the level of the masking threshold (MS) as shown in FIG. Will be masked. The delay circuit 529 is provided to delay the Bark spectrum from the energy calculation circuit 522 in consideration of the delay amount in each circuit before the combining circuit 527.

The output from the subtractor 528 is taken out via the allowable noise correction circuit 530 and further via the output terminal 531. For example, RO in which the distribution bit number information is stored in advance.
It is supplied to M and the like (not shown). This ROM or the like outputs the energy obtained from the subtraction circuit 528 through the allowable noise correction circuit 530 (the energy of each band and the synthesis circuit 5).
The distribution bit number information for each band is output according to the level of the difference from the output of 27).

The distribution bit number information thus obtained is supplied to the requantizer 406 shown in FIG. 8, whereby the MDCT circuit 404 in the requantizer 406.
Each spectrum data in the frequency domain from L, 404M, and 404H is requantized with the number of bits assigned to each band.

That is, in summary, the requantizer 406
Then, in each band band (critical band) of the critical band or in the high band, depending on the level of the difference between the energy or peak value of the band obtained by further dividing the critical band into a plurality of bands and the output of the synthesizing circuit 527. The spectrum data for each band is quantized with the allocated number of bits.

By the way, at the time of synthesizing by the above-mentioned synthesizing circuit 527, data indicating a so-called minimum audible curve (RC) which is the human auditory characteristic as shown in FIG. And the masking threshold (MS) can be combined. In this minimum audible curve, if the absolute noise level is below the minimum audible curve, no noise will be heard.

Even if the coding (coding method) is the same, the minimum audible curve is different due to the difference in the reproduction volume at the time of reproduction. Since there is not much difference in how to go, for example 4kH
If the quantization noise in the most audible frequency band around z is not heard, it is considered that the quantization noise below the level of this minimum audible curve is not heard in other frequency bands.

Therefore, assuming that the system is used in such a manner that noise around the 4 kHz dynamic range of the system cannot be heard, the minimum audible curve (R
If the allowable noise level is obtained by synthesizing C) and the masking threshold (MS) together, the allowable noise level in this case can be up to the shaded portion in FIG. Become. In this embodiment, the level of 4 kHz of the minimum audible curve is set to the minimum level equivalent to 20 bits, for example. Also,
The signal spectrum (SS) is also shown in FIG.

In the allowable noise correction circuit 530,
The allowable noise level in the output from the subtractor 528 is corrected based on the information of the equal loudness curve sent from the correction information output circuit 533, for example. Here, the equal loudness curve is a characteristic curve relating to human auditory characteristics, for example, a curve obtained by obtaining the sound pressure of sound at each frequency that sounds the same as a pure tone of 1 kHz, and connecting the curves. It is also called the sensitivity curve (equal loudness curve). Further, this equal loudness curve draws a curve substantially the same as the minimum audible curve (RC) shown in FIG.

In this equal loudness curve, for example, in the vicinity of 4 kHz, the sound pressure is 8 to 1 at 1 kHz.
Even if it drops by 0 dB, it sounds the same as 1 kHz. Conversely, the sound pressure around 50 Hz is about 15 dB lower than the sound pressure at 1 kHz.
If it is not high, it will not sound the same size. For this reason, noise that exceeds the level of the minimum audible curve (allowable noise level)
It is understood that it is better to have a frequency characteristic given by a curve corresponding to the equal loudness curve. From this, it can be seen that correcting the allowable noise level in consideration of the equal loudness curve is suitable for human auditory characteristics.

Next, FIG. 12 shows a concrete configuration example of the decoder 133a of FIG. 4 corresponding to the encoder 105a of FIG. Since the configurations and operations of the decoders 133b to 133e are basically the same as those of the decoder 133a, the description thereof will be omitted here.

That is, the decoder shown in FIG. 12 decodes, for example, a coded signal for one of the channels read by a magnetic head or an optical head from a movie film. .

In FIG. 12, the input terminal 601 has the configuration shown in FIG.
The encoded data is supplied from the demultiplexer 132 shown in (3) to the deformatter 602. The deformatter 602 performs a process reverse to the process executed by the formatter 407 shown in FIG. 8, and each parameter information of each unit and the requantized spectrum signal (that is, quantized MDC).
T coefficient) is obtained.

The quantized MDCT coefficients for each unit from the deformatter 602 are supplied to the low frequency decoding circuit 603L, the middle frequency decoding circuit 603M, and the high frequency decoding circuit 603H, respectively. Supplied. Also,
These decoding circuits 603L, 603M, and 603H
Is also given parameter information from the deformatter 602. Each decoding circuit 603L, 603M, and 60
3H uses this parameter information to cancel bit allocation and perform decoding.

The outputs of these decoding circuits 603L to 603H are supplied to the corresponding IMDCT (inverse MDCT) circuits 604L to 604H. Also, each IMD
The parameter information is also sent to the CT circuits 604L to 604H, where the frequency domain signal is converted into the time domain signal. The time domain signals of these partial bands are decoded into full band signals by the band synthesis circuit 605 and output from the output terminal 606.

Data coded by the coding device as shown in FIGS. 1 and 5 is a DVD (Digital Video Disc) or a CD-ROM.
(Compact Disc Read Only Memor
y) or a recording medium such as MD (Mini Disc). Therefore, it is possible to record the data highly compressed and encoded by the encoding device on a recording medium such as a DVD and reproduce it by a decoding device such as a video disc player.

The above-described encoding method and decoding method of the present invention can be applied not only to the so-called ATRAC method used in the embodiments but also to other encoding methods. In particular, the effect is high in a coding method in which frequency information is converted by orthogonal conversion.

In the above embodiment, the case of encoding or decoding audio data of a plurality of channels has been described, but the present invention is not limited to audio data.

[0152]

According to the encoding method of the first aspect and the encoding apparatus of the second aspect, the commonization is performed in accordance with the frequency characteristics of the digital signal and the reproduction environment of the digital signal. Since the frequency band of the digital signal is set, part or all of the frequency bands of the digital signals of the plurality of channels are made common to at least one common digital signal, and the common digital signal is coded, Digital signals in a predetermined frequency band of digital signals of a plurality of channels can be shared. Therefore, it is possible to increase the compression ratio, and it is possible to suppress the change in the reproduced sound field due to the commonization by changing the common frequency band in accordance with the reproduction environment.

According to the decoding method of the ninth aspect and the decoding device of the tenth aspect, the common digital signal is decoded based on the common information, and the digital signal is standardized. Since the decoded common digital signal is distributed to the corresponding channel and the digital signal corresponding to this channel is restored in correspondence with the frequency band, at least one of the common digital signals is restored. The original digital signal of the channel can be recovered. Therefore, it is possible to suppress the change in the reproduced sound field due to the commonization by changing the method of restoring the commonized digital signal according to the reproduction environment.

According to the encoding method of the seventeenth aspect and the encoding apparatus of the eighteenth aspect, a combination of channels to be shared is set in accordance with the characteristics of the digital signal and the reproduction environment. A part or all of the frequency bands of the digital signals of the common channel are set, and the signals of the frequency band of the digital signal of the common channel are common to at least one common digital signal, and the common digital signal Is encoded, and reproduction information for reproducing the original digital signal of each channel before being shared is created for each frame from the common digital signal. Commonize the digital signals in the predetermined frequency band of the signals and output the signal to restore it to the original digital signal. Door can be. Therefore, it is possible to increase the compression rate, and by changing the reproduction information of the common digital signal according to the reproduction environment, it is possible to suppress the change in the reproduced sound field due to the commonization.

According to the decoding method of the twenty-seventh aspect and the decoding device of the twenty-eighth aspect, the common digital signal is decoded on the basis of the common information and the digital signal of the predetermined one of the channels is decoded. The decoded common digital signal is adjusted based on predetermined reproduction information,
Since the original digital signal of the predetermined channel is restored based on the common digital signal and the digital signal of the predetermined channel, it is possible to restore the original digital signal based on the reproduction information. it can. Therefore, it is possible to suppress the change in the reproduced sound field by changing the reproduction information according to the reproduction environment.

According to the recording medium of the thirty-third aspect, a part or all of the frequency bands of the digital signals of the plurality of frames of the plurality of channels are made common to at least one common digital signal, and the frequency characteristic of the digital signal is obtained. And, in accordance with the playback environment, the frequency band for commonization is changed, and the common digital signal is encoded,
Since the signals obtained by encoding the digital signals excluding the common digital signal are recorded together with the information on the encoding method, the signals obtained by commonizing the digital signals of the multiple channels and the signals of the respective channels excluding it are recorded. The digital signal can be recorded as a high-efficiency compression-encoded signal and reproduced. Therefore, it is possible to provide a more stable reproduced sound field.

According to the recording medium of the thirty-fourth aspect, some or all of the frequency bands of the digital signals of the plurality of frames of the plurality of channels are made common to at least one common digital signal, and the frequency characteristic of the digital signal is obtained. Depending on the playback environment, the combination of channels to be used for commonization and the frequency band are changed, and predetermined reproduction information for returning the commonized digital signal to the original digital signal before commonization is created for each frame. Since the reproduction information is included in the signal in which the common digital signal is encoded and the common information regarding the encoding of the common digital signal, the reproduction information is recorded. Can be recorded, and based on that, a more stable sound field can be reproduced. Therefore, it is possible to provide a more stable reproduced sound field.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of an encoding device of the present invention.

FIG. 2 is a block diagram showing a configuration example of a common processing analyzer of FIG.

FIG. 3 is a block diagram showing the configuration of an embodiment of a decoding device of the present invention.

FIG. 4 is a block diagram showing the configuration of another embodiment of the decoding device of the present invention.

FIG. 5 is a block diagram showing the configuration of another embodiment of the encoding device of the present invention.

6 is a block diagram showing a configuration example of a common parameter extractor of FIG.

FIG. 7 is a block diagram showing the configuration of still another embodiment of the decoding device of the present invention.

FIG. 8 is a block diagram showing a configuration example of the encoder of FIG. 1.

9 is a block diagram illustrating a configuration example of a bit allocator of the encoder of FIG.

FIG. 10 is a diagram for explaining a Bark spectrum (SB) and a masking threshold level (MS).

FIG. 11: Signal level (SS), minimum audible curve (R
It is a figure showing C) and a masking threshold (MS).

12 is a block diagram showing a configuration example of the decoder of FIG.

[Fig. 13] Fig. 13 is a block diagram illustrating a configuration example of a multi-channel audio encoding device when the present invention is not used.

FIG. 14 is a block diagram showing a configuration example of a multi-channel audio decoding device when the present invention is not used.

[Explanation of symbols]

 101 Input Terminal 102 Common Processing Analyzer 103 Common Data Extractor 104 Common Data Generator 105 Encoder 106 Multiplexer 107 Output Terminal 108 Common Parameter Extractor 121 Orthogonal Transformer 122 Frequency Characteristic Evaluator 123 Common Processing Selector 124 output terminal 131 input terminal 132 demultiplexer 133 decoders 134, 137 common data distributor 135 common data synthesizer 136 output terminal 138 common coded data synthesizer 139 common data adjuster 201 input terminal 202 common method analysis Device 203 Parameter recording memory 204 Parameter analyzer 205 Common parameter formatter 206 Output terminal 401 Band division filter 402L Low band MDCT circuit 402M Mid band MDCT circuit 402H High band MDCT times 403 Block size evaluator 404L, 404M, 404H Normalization circuit 405 Bit distributor 406 Requantizer 407 Formatter 424 Input terminal 425 Output terminal 521 Input terminal 522 Energy calculation circuit for each band 523 Convolution filter circuit 524 Subtractor 525 (N-ai) Function generation circuit 526 Divider 527 Synthesis circuit 528 Subtractor 529 Delay circuit 530 Allowable noise correction circuit 531 Output terminal 532 Minimum audible curve generation circuit 533 Correction information output circuit 601 Input terminal 602 Deformer 603L, 603M, 603H Decoding circuit 604L, 604M, 604H IMDCT circuit 605 Band combining circuit 606 Output terminal

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04N 7/24 H04N 7/13 Z

Claims (34)

[Claims] 1. A coding method in which digital signals of a plurality of frames of a plurality of channels are coded, wherein the digital signal is shared according to the frequency characteristics of the digital signal and the reproduction environment of the digital signal. Encoding the common digital signal by setting a frequency band of the common digital signal to at least one common digital signal for all or part of the frequency bands of the digital signals of a plurality of channels. Method. 2. An encoding device for encoding digital signals of a plurality of frames of a plurality of channels, wherein the digital signals to be commonized corresponding to the frequency characteristics of the digital signal and the reproduction environment of the digital signal. Setting means for setting a frequency band; commonizing means for making a part or all of the frequency bands of the digital signals of a plurality of channels common to at least one common digital signal; and encoding the common digital signal. An encoding device comprising: an encoding unit. 3. The encoding apparatus according to claim 2, wherein the setting unit sets the frequency band in which the digital signals of a plurality of channels are commonly used for each frame. 4. A signal of a predetermined frequency band of a digital signal of a predetermined one of the channels is divided and arranged in a plurality of common channels.
An encoding device according to claim 1. 5. The encoding device according to claim 2, wherein the digital signals in the same frame are shared in a plurality of frequency bands. 6. The information for reproducing a signal before commonization is analyzed for a part or all of the digital signals of a plurality of channels to be commonized, and the information is encoded. 2. The encoding device according to 2. 7. The encoding device according to claim 2, wherein the digital signal is a digital audio signal. 8. The encoding apparatus according to claim 2, wherein the digital signal is a frequency component obtained by converting a time axis into a frequency axis. 9. A frequency band of a part or all of digital signals of a plurality of channels is made common to at least one common digital signal, and common to correspond to frequency characteristics of the digital signal and reproduction environment of the digital signal. A decoding method in which the frequency band of the digital signal to be encoded is changed, and the digital signals of a plurality of channels encoded based on predetermined common information are decoded, wherein the common information is used. The common digital signal is decoded, the decoded common digital signal is distributed to the corresponding channel corresponding to the frequency band in which the digital signal is common, and the common digital signal corresponding to the channel is distributed. A decoding method characterized by restoring a digital signal. 10. A part or all of frequency bands of digital signals of a plurality of channels are made common to at least one common digital signal, and corresponding to frequency characteristics of the digital signal and reproduction environment of the digital signal,
A decoding device in which the frequency band of the digital signal to be made common is changed, and the digital signals of a plurality of channels encoded based on predetermined common information are decoded, wherein the common information is Based on the decoding means for decoding the common digital signal, the common digital signal decoded by the decoding means corresponding to the frequency band in which the digital signal is common, A decoding device, comprising: a distribution unit that allocates to a channel, and a restoration unit that restores the digital signal corresponding to the channel. 11. The decoding apparatus according to claim 10, further comprising adjusting means for adjusting the commonized digital signal in accordance with a recommended reproduction environment of the decoded digital signal. 12. The decoding device according to claim 10, wherein the decoding unit decodes the common digital signal in which the digital signals in a predetermined same frame are common in a plurality of frequency bands. Decryption device. 13. The decoding means decodes a coded signal in a predetermined frequency band of the digital signal of a predetermined one of a plurality of channels, which is arranged by being divided into a plurality of common digital signals. 11. The method according to claim 10,
3. The decoding device according to claim 1. 14. The adjusting means adjusts the common digital signal using predetermined information included in the common information for reproducing a signal before commonization. Decoding device according to. 15. The decoding device according to claim 10, wherein the digital signal is a digital audio signal. 16. The decoding device according to claim 10, wherein the digital signal is a frequency component obtained by converting a time axis into a frequency axis. 17. A coding method in which digital signals of a plurality of frames of a plurality of channels are coded, wherein the characteristics of the digital signals and the reproduction environment are satisfied,
Setting a combination of the channels to be shared, setting a part or all of the frequency bands of the digital signals of the channels to be shared, and a signal of the frequency band of the digital signals of the channels to be shared, At least one common digital signal is shared, the common digital signal is encoded, and reproduction information for reproducing the original digital signal of each channel before commonization from the common digital signal is provided. An encoding method characterized by being created for each frame. 18. An encoding device for encoding digital signals of a plurality of frames of a plurality of channels, wherein: in accordance with characteristics of the digital signals and reproduction environment,
Setting means for setting a combination of the channels to be shared and setting a frequency band of a part or all of the digital signals of the channels to be shared; and the digital signal of the digital signals of the channels set by the setting means. Commonizing means for commonizing a signal in a frequency band to at least one commonizing digital signal; coding means for coding the commonizing digital signal commonized by the commonizing means; and the commonizing means. Reproduction information creating means for creating, for each frame, reproduction information for reproducing the original digital signal of each channel before being made common from the commonized digital signal. Characteristic encoding device. 19. The reproduction information creating means corresponds to the characteristic of the digital signal and the reproduction environment,
19. The information for reproduction is changed.
An encoding device according to claim 1. 20. The reproduction information creating means corresponds to the characteristic of the digital signal and the reproduction environment,
The encoding device according to claim 18, wherein the accuracy of the reproduction information is changed. 21. The reproduction information creating means creates the reproduction information for at least one frequency band for each channel corresponding to the digital signal before being made common. The encoding device according to claim 18. 22. The reproduction information creating means sets the reproduction information of the digital signal of a predetermined one of the frames based on the characteristics of the digital signals of the frame before or after the frame, or both of the frames before and after the frame. The encoding device according to claim 18, wherein the encoding device is changed. 23. The encoding apparatus according to claim 18, wherein the characteristic of the digital signal is a frequency characteristic. 24. The encoding device according to claim 18, wherein the characteristic of the digital signal is an amplitude characteristic. 25. The encoding device according to claim 18, wherein the digital signal is a digital audio signal. 26. The encoding apparatus according to claim 18, wherein the digital signal is a frequency component obtained by converting a time axis into a frequency axis. 27. A frequency band of a part or all of digital signals of a plurality of frames of a plurality of channels is made common to at least one common digital signal, and a frequency characteristic of the digital signal and a reproduction environment of the digital signal are provided. Correspondingly, the combination of the channels corresponding to the digital signal to be shared, and the frequency band of the digital signal to be shared are changed, and the commonization is coded based on predetermined commonization information. A decoding method for decoding a digital signal, comprising: decoding the common digital signal based on the common information; and decoding based on predetermined reproduction information of the digital signal of a predetermined one of the channels. Adjusting the commonized digital signal that has been made common, and A decoding method, characterized in that, based on the digital signal of a predetermined one, the original digital signal of the predetermined one of the channel is restored. 28. Part or all of the frequency bands of digital signals of a plurality of frames of a plurality of channels are made common to at least one common digital signal, and the frequency characteristic of the digital signal and the reproduction environment of the digital signal are set. Correspondingly, the combination of the channels corresponding to the digital signal to be shared, and the frequency band of the digital signal to be shared are changed, and the commonization is coded based on predetermined commonization information. A decoding device for decoding a digital signal, comprising decoding means for decoding the common digital signal based on the common information, and predetermined reproduction information of the digital signal of a predetermined one of the channels. Adjusting means for adjusting the decoded common digital signal based on A decoding device comprising: a digital signal and a restoring means for restoring the original digital signal of the predetermined one of the channels based on the digital signal of the predetermined one of the channels. 29. The decoding apparatus according to claim 28, wherein the reproduction information is set for at least one frequency band of the channel. 30. The decoding device according to claim 28, wherein the reproduction information is changed in units of the frame. 31. The decoding device according to claim 28, wherein the digital signal is a digital audio signal. 32. The decoding apparatus according to claim 28, wherein the digital signal is a frequency component obtained by converting a time axis into a frequency axis. 33. A part or all of frequency bands of digital signals of a plurality of frames of a plurality of channels are made common to at least one common digital signal, and common to correspond to frequency characteristics and reproduction environment of the digital signal. The frequency band for performing the encoding is changed, and the signal obtained by encoding the common digital signal and the signal obtained by encoding the digital signal excluding the common digital signal are recorded together with information about the encoding method. A recording medium characterized by the following. 34. A part or all of frequency bands of digital signals of a plurality of frames of a plurality of channels are made common to at least one common digital signal, and common to correspond to frequency characteristics and reproduction environment of the digital signal. The combination of the channels to be standardized and the frequency band are changed, and predetermined reproduction information for returning the common digital signal to the original digital signal before commonization is created for each frame. A recording medium characterized in that a signal obtained by encoding a digital signal and an encoded signal in which the reproduction information is included in common information regarding the encoding of the common digital signal are recorded.