JP3606454B2 - Audio signal transmission method and audio decoding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an audio signal transmission method for transmitting an audio signal obtained by predictive encoding and compressing an audio signal , and an audio decoding method for decoding the audio signal .
[0002]
[Prior art]
As a method for predictively encoding a speech signal, the present inventor has used a plurality of predictors having different characteristics for the original digital speech signal of one channel (channel) in the previous application (Japanese Patent Application No. 9-289159). Calculate multiple linear prediction values of the current signal from past signals in the region, calculate the prediction residual for each predictor from the original digital speech signal and the multiple linear prediction values, and select the minimum value of the prediction residual Proposed method to do.
[0003]
[Problems to be solved by the invention]
However, in the above method, a certain degree of compression effect can be obtained when the original digital audio signal has a sampling frequency = 96 kHz and the number of quantization bits = 20 bits. = 192 kHz) is used, and the number of quantization bits tends to be 24. Therefore, it is necessary to improve the compression rate.
[0004]
Accordingly, an object of the present invention is to provide an audio signal transmission method with an improved compression rate when an audio signal is predictively encoded, and an audio decoding method for decoding the audio signal .
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention comprises the following means 1) and 2) .
That is,
[0006]
1) A second multi-channel digital audio signal including at least five channels of left, center, right, surround left, and surround right having the same sampling frequency by a predetermined matrix operation and having a correlation with each other. Converting to a multi-channel audio signal;
The second multi-channel audio signal is obtained for each channel in response to the input audio signal, and a head sample value is obtained, and the linearity of the current signal from the past in the time domain is obtained by a plurality of linear prediction methods having different characteristics. Selecting a linear prediction method so that each prediction value is predicted, and a prediction residual obtained from the predicted linear prediction value and the speech signal is minimized;
A data structure including header information, user data including a compressed PCM private header and an audio compressed PCM data portion, and a head sample value, a prediction residual, and a linear prediction method of each channel selected in the above step. Including predictive coded data including the audio compressed PCM data portion, and placing the UPC / EAN-ISRC number and UPC / EAN-ISRC data of the audio signal in the compressed PCM private header. An audio signal transmission method for transmitting an audio signal encoded by an encoding method,
Predictive encoded data including the selected head sample value, prediction residual, and linear prediction method, and the UPC / EAN-ISRC number and UPC / EAN-ISRC data of the speech signal are packetized and transmitted via a communication line. An audio signal transmission method characterized by transmitting.
2) A second multi-channel digital audio signal including at least five channels of left, center, right, surround left, and surround right is correlated with the same sampling frequency by a predetermined matrix operation. Converting to a multi-channel audio signal;
The second multi-channel audio signal is obtained for each channel in response to the input audio signal, and a head sample value is obtained, and the linearity of the current signal from the past in the time domain is obtained by a plurality of linear prediction methods having different characteristics. Selecting a linear prediction method so that each prediction value is predicted, and a prediction residual obtained from the predicted linear prediction value and the speech signal is minimized;
A data structure including header information, user data including a compressed PCM private header and an audio compressed PCM data portion, and a head sample value, a prediction residual, and a linear prediction method of each channel selected in the above step. Including predictive coded data including the audio compressed PCM data portion, and placing the UPC / EAN-ISRC number and UPC / EAN-ISRC data of the audio signal in the compressed PCM private header. An audio decoding method for decoding an original audio signal from data encoded by an encoding method,
Calculating a prediction value from predictive encoded data including the selected first sample value, prediction residual, and linear prediction method;
Restoring the first plurality of channels of digital audio signals from the calculated predicted value;
A speech decoding method comprising:
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of a speech encoding apparatus to which the present invention is applied and a speech decoding apparatus corresponding thereto, FIG. 2 is a block diagram showing in detail the encoding unit of FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing a DVD pack format, FIG. 5 is an explanatory diagram showing a DVD audio pack format, and FIGS. 6 and 7 are flowcharts showing an audio transmission method. is there.
[0008]
Here, the following four systems are known as multi-channel systems.
(1) Dolby surround system, 3 channels for forward L, C, R + 1 channel for rear S, 4 channels in total (2) 4 channels of Dolby AC-3 system, forward L, C, R, SW + rear SL, SR 2 channels in total 6 channels (3) 6 channels (L, C, R, SW, SL, SR) in the same way as Dolby AC-3 method (3) DTS (Digital Theater System) method
(4) SDDS (Sony Dynamic Digital Sound) system 6 channels of forward L, LC, C, RC, R, SW + 2 channels of backward SL, SR in total 8 channels
The encoding-side five-channel (ch) correlation circuit 1 shown in FIG. 1 includes, as an example of a multi-channel signal, left (L), center (C), right (R), surround left (SL), and surround right (SR). The 5ch PCM data is converted into the following 5ch (L) and (D1) to (D4) based on the Lch and output to the encoding unit 2 shown in detail in FIG.
L = L (reference channel)
D1 = C- (L + R) / 2
D2 = RL
D3 = SL-a × L
D4 = SR−b × R
However, 0 ≦ a, b ≦ 1
[0010]
As shown in detail in FIG. 2, the encoding unit 2 predictively encodes the PCM data of each channel (L), (D1) to (D4), and transmits this to the decoding side via a recording medium or a communication medium. On the decoding side, the prediction encoded data of each channel (L), (D1) to (D4) is decoded by the decoding unit 3 shown in detail in FIG. 3, and then the original 5 channels are converted by the 5-channel correlation circuit 4 as follows. Restore.
R = (R−L) + L
C = C- (L + R) / 2 + L / 2 + R / 2
SL = SL-a * L + a * L
SR = SR-b * R + b * R
[0011]
The encoding unit 2 will be described in detail with reference to FIG. The PCM data of each channel (L), (D1) to (D4) is stored in one frame buffer 10 for each frame. Then, the sample data of each channel of one frame is applied to the prediction circuits 15L and 15D1 to 15D4, respectively, and the head sample data of one frame of each channel is applied to the formatting circuit 19. Each of the prediction circuits 15L and 15D1 to 15D4 uses a plurality of predictors (not shown) having different characteristics for the PCM data of each channel (L) and (D1) to (D4) from the past signal in the time domain to the present. A plurality of linear prediction values of the signal are calculated, and a prediction residual for each predictor is calculated from the original PCM data and the plurality of linear prediction values. The subsequent buffers / selectors 16L and 16D1 to 16D4 temporarily store the prediction residuals calculated by the prediction circuits 15L and 15D1 to 15D4, respectively, and predict prediction residuals for each subframe specified by the selection signal generator 17. Select the minimum value of.
[0012]
The selection signal generator 17 applies a bit number flag of the prediction residual to the packing circuit 18 and the formatting circuit 19, and also outputs a predictor selection flag indicating the predictor having the smallest prediction residual to the formatting circuit 19. Apply to. The packing circuit 18 packs the prediction errors for 5ch selected by the buffers / selectors 16L and 16D1 to 16D4 with the designated number of bits based on the bit number flag designated by the selection signal generator 17.
[0013]
The formatting circuit 19 that follows is for one frame, a frame header,
The first sample value of one frame of each ch (L), (D1) to (D4),
A predictor selection flag for each subframe of each channel (L), (D1) to (D4);
A bit number flag for each subframe of each channel (L), (D1) to (D4),
A prediction residual data string (number of variable bits) of each ch (L), (D1) to (D4),
Multiplex and output as a variable rate bitstream. According to such predictive coding, when the original signal is, for example, sampling frequency = 96 kHz, the number of quantization bits = 24 bits, and 5 channels, a compression rate of 71% can be realized.
[0014]
Next, the decoding unit 3 will be described with reference to FIG. The variable rate bit stream data in the above format is separated by the deformatting circuit 21 based on the frame header. Then, the head sample data and predictor selection flag of one frame of each ch (L), (D1) to (D4) are applied to the prediction circuits 23L and 23D1 to 23D4, respectively, and each ch (L), (D1) to The bit number flag (D4) and the prediction residual data string are applied to the unpacking circuit 22. Here, the plurality of predictors (not shown) in the prediction circuits 23L and 23D1 to 23D4 have the same characteristics as the plurality of predictors in the prediction circuits 15L and 15D1 to 15D4 on the encoding side, respectively, and are selected by the predictors. The same characteristic is selected by the flag.
[0015]
The unpacking circuit 22 separates the prediction residual data strings of the respective channels (L) and (D1) to (D4) based on the bit number flags and outputs them to the prediction circuits 23L and 23D1 to 23D4, respectively. In the prediction circuits 23L and 23D1 to 23D4, the prediction residual data of each of the channels (L) and (D1) to (D4) from the unpacking circuit 22 and a predictor selected from the plurality of internal predictors are respectively selected. The previous predicted value predicted by each one selected by the flag is added to calculate the current predicted value, and then the PCM data of each sample value is calculated based on the first sample value of one frame.
[0016]
Here, when the variable rate bit stream data predictively encoded by the encoding unit 2 shown in FIG. 2 is recorded on a DVD audio disk as an example of a recording medium, the audio (A) of the compressed PCM shown in FIG. Packed in a pack. This pack has 20 bytes of user data (A packet, V packet), 4 bytes of pack start information, 6 bytes of SCR (System Clock Reference) information, and 3 bytes of Mux rate ( rate) information and a 1-byte stuffing total 14-byte pack header are added (1 pack = total 2048 bytes). In this case, the time of the A pack in the same title can be managed by setting the SCR information as a time stamp as “1” in the first pack in the ACB unit and continuing in the same title.
[0017]
As shown in detail in FIG. 5, the compressed PCM A packet is composed of a 17, 9 or 14 byte packet header, a compressed PCM private header, and audio compressed PCM data of 1 to 2011 bytes in the format shown in FIG. ing. The compressed PCM private header is
A 1-byte substream ID,
2-byte UPC / EAN-ISRC (Universal Product Code / European Articial Number-International Standard Recording Code) number and UPC / EAN-ISRC data;
-1 byte private header length,
A 2-byte first access unit pointer;
・ 8 bytes of audio data information (ADI) ・ 0 to 7 bytes of stuffing bytes
It is made up of.
[0018]
Also, when the variable rate bit stream data predictively encoded by the encoding unit 2 shown in FIG. 2 is transmitted via a network, the encoding side packetizes it for transmission as shown in FIG. 6 (step S41). Then, a packet header is added (step S42), and then the packet is sent out on the network (step S43). As shown in FIG. 7, the decoding side removes the header (step S51), then restores the data (step S52), then stores this data in the memory and waits for decoding (step S53).
[0019]
Next, a second embodiment will be described with reference to FIGS. In the above-described embodiment, one type of correlation signal (L), (D1) to (D4) is configured to be predictively encoded. In the second embodiment, a plurality of types of correlation signals are used. It is configured to selectively predict and encode one type of signal. For this reason, the encoding unit shown in FIG. 8 includes first to n-th correlation circuits 1-1 to 1-n, and these n correlation circuits 1-1 to 1-n are, for example, 5ch (L, C , R, SL, SR) PCM data is converted into n types of 5ch signals having different correlations. The n-th correlation circuit 1-n performs conversion as follows, for example.
L = L (reference channel)
D1 = CL
D2 = RL
D3 = SL-L
D4 = SR-R
[0020]
Also, prediction circuits 15L and 15D1 to 15D4 and buffer / selectors 16L and 16D1 to 16D4 are provided for each of the correlation circuits 1-1 to 1-n, and the compression rate is based on the data amount of the minimum value of the prediction error for each group. Is selected by the correlation selection signal generator 17b. At this time, the selection flag (correlation circuit selection flag, correlation coefficients a and b of the correlation circuit) is added and multiplexed.
[0021]
Further, on the decoding side shown in FIG. 9, n correlation circuits 4-1 to 4-n (or coefficients a and b with which the coefficients a and b can be changed are different from the correlation circuits 1-1 to 1-n on the encoding side. Two correlation circuits 4) are provided. When the n groups of prediction circuits shown in FIG. 8 have the same configuration, the decoding device does not need to have n groups of prediction circuits as shown in FIG. Then, one of the correlation circuits 4-1 to 4-n is selected based on the selection flag transmitted from the encoding device, or the coefficients a and b are set and the original 5ch (L, C, R, SL, SR) is restored.
[0022]
In the first embodiment, the signals L and D1 to D4 having one type of correlation are configured to be predictively encoded. The group of the signals L and D1 to D4 and the original signal L, The group of C, R, SL, and SR may be predictively encoded, and the group with the higher compression rate may be selected.
[0023]
【The invention's effect】
As described above, according to the present invention, since a multi-channel audio signal is converted into a correlated second multi-channel audio signal and subjected to predictive encoding, the predictive encoding of the audio signal is performed. In addition, the compression rate can be improved, and the improved audio signal can be transmitted and decoded .
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of a speech encoding apparatus to which the present invention is applied and a speech decoding apparatus corresponding to the speech encoding apparatus.
FIG. 2 is a block diagram illustrating in detail an encoding unit in FIG. 1;
FIG. 3 is a block diagram illustrating in detail a decoding unit in FIG. 1;
FIG. 4 is an explanatory diagram showing a DVD pack format;
FIG. 5 is an explanatory diagram showing a format of a DVD audio pack;
FIG. 6 is a flowchart showing an audio transmission method.
FIG. 7 is a flowchart showing an audio transmission method.
FIG. 8 is a block diagram showing a speech encoding apparatus according to a second embodiment.
9 is a block diagram showing a speech decoding apparatus corresponding to FIG.
[Explanation of symbols]
1,1-1 to 1-n, 4,4-1 to 4-n correlation circuit (correlation means)
15L, 15D1 to 15D4 Prediction circuit (composed with the buffer / selectors 16L and 16D1 to 16D4 to form a predictive coding means)
16L, 16D1-16D4 Buffer / Selector

Claims (2)

A second plurality of channels having the same sampling frequency and having a correlation with a plurality of digital audio signals of the first plurality of channels including at least five channels of left, center, right, surround left and surround right by a predetermined matrix operation Converting to an audio signal of
The second multi-channel audio signal is obtained for each channel in response to the input audio signal, and a head sample value is obtained, and the linearity of the current signal from the past in the time domain is obtained by a plurality of linear prediction methods having different characteristics. Selecting a linear prediction method so that each prediction value is predicted, and a prediction residual obtained from the predicted linear prediction value and the speech signal is minimized;
A data structure including header information, user data including a compressed PCM private header and an audio compressed PCM data portion, and a head sample value, a prediction residual, and a linear prediction method of each channel selected in the above step. Including predictive coded data including the audio compressed PCM data portion, and placing the UPC / EAN-ISRC number and UPC / EAN-ISRC data of the audio signal in the compressed PCM private header. An audio signal transmission method for transmitting an audio signal encoded by an encoding method,
Predictive encoded data including the selected head sample value, prediction residual, and linear prediction method, and the UPC / EAN-ISRC number and UPC / EAN-ISRC data of the speech signal are packetized and transmitted via a communication line. An audio signal transmission method characterized by transmitting. A first plurality of channels of digital audio signals including at least five channels of left, center, right, surround left and surround right, and a plurality of correlated second channels having the same sampling frequency by a predetermined matrix operation Converting to an audio signal of
The second multi-channel audio signal is obtained for each channel in response to the input audio signal, and a leading sample value is obtained, and the linearity of the current signal from the past in the time domain is obtained by a plurality of linear prediction methods having different characteristics. Selecting a linear prediction method so that each prediction value is predicted, and a prediction residual obtained from the predicted linear prediction value and the speech signal is minimized;
A data structure including header information, user data including a compressed PCM private header and an audio compressed PCM data portion, and a head sample value, a prediction residual, and a linear prediction method of each channel selected in the above step. Including predictive coded data including the audio compressed PCM data portion, and placing the UPC / EAN-ISRC number and UPC / EAN-ISRC data of the audio signal in the compressed PCM private header. An audio decoding method for decoding an original audio signal from data encoded by an encoding method,
Calculating a prediction value from predictive encoded data including the selected first sample value, prediction residual, and linear prediction method;
Restoring the first plurality of channels of digital audio signals from the calculated predicted value;
A speech decoding method comprising:

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