KR960003455B1 - Ms stereo digital audio coder and decoder with bit assortment - Google Patents

Abstract

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Description

MS stereo digital audio encoding and decoding apparatus for adaptively allocating bits to each channel for encoding and decoding

1 is a block diagram showing an MS side stereo digital audio encoding apparatus of the present invention.

2 is a diagram showing bit allocation states for mutual similarity values in the MS stereo digital audio encoding apparatus of the present invention.

3 is a block diagram showing an MS stereo digital audio decoding apparatus of the present invention.

* Explanation of symbols for main parts of the drawings

110: MS matrix unit 120: mutual similarity calculation unit

130: adaptive bit allocation unit 140, 150: first and second encoders

160: multiplexer 310: demultiplexer

320, 330: first and second decoder 340: MS matrix unit

350: bit allocation government extractor

The present invention relates to an apparatus for adaptive channel bit allocation middle-side stereo digital audio encoding and decoding. In particular, the present invention relates to first and second (or left (L) and right ( R)) The present invention relates to an adaptive channel bit allocation MS stereo digital audio encoding and decoding apparatus that increases encoding and decoding efficiency by adaptively encoding and decoding according to mutual similarity values of audio signals input to a channel.

Currently, high definition television (HDTV) information transmission systems, which are being developed for the purpose of reproducing sound quality signals such as compact discs (CDs) and digital audio tape recorders (DATs), which are in practical use, are relatively narrow. As video and audio signals must be transmitted through both 6MHZ transmission lines, an efficient signal compression technique has been required for audio signals as well as video signals.

To this end, it is a high-quality digital audio signal processing technology for HDTV that uses the adaptive trasform coding technique that reflects the human auditory characteristics to reproduce the sound quality of the digital audio device level even with a relatively simple receiver at a low data rate. It is actively researched for possible algorithm and hardware implementation.

With the above-described adaptive transform coding scheme, the prior art stereo device uses a sum and a difference signal of two channel signals, namely middle and side, to transmit stereo audio signals of the first and second two channels. ), There is an MS stereo system that reproduces the first and second two channel signals after the signal is transmitted in a reverse process.

In the above-described conventional MS stereo encoding apparatus, it is common to encode digital audio signals input to the first and second channels by allocating the same bits to each channel. This approach is sometimes efficient because it takes advantage of the mutual similarity of the two channels. However, when the amount of information for each of the M channel and the S channel is different from each other, there is a problem in that the encoding and decoding efficiency decreases when the above-described method is used.

Accordingly, an object of the present invention is to solve the above-described problems, and an object of the present invention is to adaptively encode and perform an MS signal performing an MS metric in response to mutual similarity values of audio signals input to first and second channels. The present invention provides an apparatus for adaptive channel bit allocation MS stereo digital audio encoding and decoding for increasing encoding and decoding efficiency by decoding.

According to an embodiment of the present invention, an audio signal of a middle (M) channel obtained by adding and multiplying an audio signal for a first channel and a second channel, which are digitally converted and inputted at a predetermined sampling frequency, and multiplied by a predetermined value, A middle side (MS) matrix unit which generates an audio signal of a side (S) channel obtained by subtracting two audio signals and multiplying the audio signal by a predetermined value; A mutual similarity calculating unit configured to input audio signals for the first and second channels to calculate mutual similarity values of the audio signals for the two channels, and generate index information of predetermined intervals corresponding to the values; Wow ; An encoder for encoding the audio signal for the M channel and the audio signal for the S channel provided by the MSM matrix unit into bits corresponding to predetermined index information provided from the mutual similarity calculator; An adaptive bit allocation unit for extracting predetermined bit allocation information (BM, BS) and providing the bit information to the encoder in response to the index information provided from the mutual similarity calculating unit; And a multiplexer which multiplexes the encoded audio signals of the M and S channels provided by the encoder and the bit allocation information provided by the similarity calculator to generate a bit stream suitable for channel characteristics.

According to another embodiment of the present invention, a demultiplexer for inputting a bit stream received through compression encoding and demultiplexing to restore an audio signal for M channel and an audio signal for S channel and bit information allocated in the encoding; ; A decoder for decoding an audio signal for M and S channels provided by the demultiplexer; A bit allocation information extracting unit extracting bit information allocated to each of the M and channel channels as bit information allocated during encoding provided by the demultiplexing unit and providing the bit information to the decoder; And an MS matrix unit for converting audio signals of the decoded M and S channels provided by the decoder into audio signals of original first and second channels.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention;

1 is a block diagram illustrating an adaptive channel bit allocation MS stereo encoding apparatus according to the present invention. The encoding apparatus includes an MS matrix unit 110, a mutual similarity calculating unit 120, an adaptive bit allocation unit 130, The first and second encoders 140 and 150 and the multiplexer 160 are included.

The MS matrix unit 310 inputs and adds 111 the digitalized audio signals x (n) and y (n) for the first and second channels, multiplies 112 by a predetermined value, and then first audio signal. Outputs a second audio signal (S (n)) by outputting (M (n)) and subtracting (113) the audio signal of two channels and multiplying it to a predetermined value by a predetermined value. Second encoders 140 and 150. The mutual similarity calculator 120 uses a similarity value for the audio input signals x (n) and y (n) for the first and second channels. (Index) is calculated and transmitted to the adaptive bit allocation unit 130, which will be described later.

For example, the mutual similarity calculation first calculates the mutual similarity of an input signal in units of frames consisting of N samples (where N is a positive integer) for each of the first and second channels, and x (for N samples). n), assuming that the average of y (n) is 0, the mutual similarity (C) value can be obtained by the following equation (1).

Here, E {·} is an expected value and means a probabilistic average. The calculation of the expected value E {·} in Equation (1) can be approximated by using an arithmetic mean using finite number of data.

The method of calculating the mutual similarity of Equation (1) using N pieces of data is shown in Equation (2).

In the general case where the mean is not zero for N samples, the mutual similarity (C) value is obtained by the following equation (3).

Here, mean (*) represents an arithmetic mean, and is shown by following formula (4).

If the average of x (n) and the average of y (n) are M _x and M _y , respectively, the mutual similarity (C) of the above-described formula (3) can be expressed as the following formula (5).

The mutual similarity (C) in Eq. (5) represents the magnitude of the mutual similarity (or correlation) of the two channels x (n) and y (n), depending on the value of bits in each channel M (n) and S (n). The weighting method for the allocation is as described later.

Referring to FIG. 2, bit allocation is performed for each channel, for example, classified into three sections in response to the mutual similarity (C) calculated by Equation (5). That is, in the adaptive bit allocation unit 130, as shown in the drawing, the C value obtained through the above equation (5) is between I ₂ and 0.5, and if the C value is -0.5 or less, I ₁ and 0.5 or more. In this case, an index of I ₃ is output, and the bit allocation corresponding to the index is shown in Table 1 below.

TABLE 1

That is, Table 1 is an example of encoding at an average rate of 128 Kbps per channel. The present invention sets the BM and BS allocated in correspondence with the indices I ₁ , I ₂ and I _{3 as} shown in Table 1, and outputs them in the above-described mutual similarity calculator 120 to output the first and second encoders ( 140) 150 and the multiplexer 160, respectively.

The first and second encoders 140 and 150 encode the bit allocation information provided from the adaptive bit allocation unit 130 by using a known encoding method, respectively, and provide the encoded bit allocation information to the multiplexer 370. The multiplexing unit 370 inputs the encoded digital audio signal provided by the first and second encoders 350 and 360 and the bit allocation information provided by the adaptive bit allocation unit 130 to fit the channel characteristics. Multiplex the output bit stream.

3 is a block diagram illustrating an adaptive channel bit allocation MS stereo decoding apparatus according to the present invention, which includes a demultiplexer 310, first and second decoders 320 and 330, an MS matrix unit 340, and bits. The allocation information extractor 350 is included. The demultiplexer 410 inputs a bit stream transmitted through compression encoding by the encoding apparatus, demultiplexes the bit allocation information corresponding to the index, and the audio signals of the M and S channels encoded by the encoding apparatus. The second decoders 320 and 330 and the bit allocation information extracting unit 350 are provided respectively. The first and second decoders 320 and 330 decode the encoded stereo audio signal provided by the demultiplexer 310 by using a known decoding method (M '(n), S' (n)) to form an MS matrix. Provided at 340.

The MS matrix unit 340 inputs the decoded M and S channels of the digital audio signals provided by the first and second decoders 320 and 330 to perform the same operation as the above-described encoding apparatus, thereby performing the final audio signal (x). outputs '(n), y' (n))

As described above, according to the adaptive channel bit allocation MS stereo encoding and decoding apparatus according to the present invention, an audio signal inputted with addition and difference signals for two channels on which the MS metric is performed is input to the first and second two channels. There is a great advantage to increase the encoding and decoding efficiency by adaptively encoding and decoding in response to the mutual similarity value of.

Claims (6)

The audio signal of the middle (M) channel, which is digitally converted to a predetermined sampling frequency and input to the first and second channels, is multiplied by a predetermined value, and the audio signal of the two channels is subtracted. A middle side (MS) matrix unit for generating an audio signal of a side (S) channel multiplied by a predetermined value; A mutual similarity calculating unit configured to input audio signals for the first and second channels to calculate mutual similarity values of the audio signals for the two channels, and generate index information of predetermined intervals corresponding to the values; ; An encoder for encoding the audio signal for the M channel and the audio signal for the S channel provided by the MS matrix unit into bits corresponding to predetermined index information provided from the mutual similarity calculator; An adaptive bit allocation unit for extracting predetermined bit allocation information (BM, BS) and providing the bit information to the encoder in response to the index information provided from the mutual similarity calculating unit; And a multiplexer for multiplexing the encoded audio signals of the M and S channels provided by the encoder and the bit allocation information provided by the similarity calculator to generate a bit stream suitable for channel characteristics. MS stereo digital audio encoding apparatus for assigning and encoding. The method of claim 1, wherein the mutual similarity calculation unit determines the mutual similarity value (C) in the following equation, Here, M ₂ and M _y represent an average value of the input signals x (n) and y (n), and x ₁ and y ₁ represent values for sequentially adding to the digital audio input signal. Stereo digital audio coding device. The MS stereo digital audio encoding apparatus of claim 1, wherein the index information provided from the mutual similarity calculator is set to three intervals (I ₁ , I ₂ , I ₃ ). The method of claim 3, wherein in the index information representing the three sections, I ₁ is the case where the mutual similarity value is -0.5 or less, I ₂ is the case where the similarity value is -0.5 to 0.5, and I ₃ is 0.5 An MS stereo digital audio encoding apparatus characterized by the above-mentioned case. The bit allocation information (BM, BS) of the M and S channels provided to the encoder by the adaptive bit allocation unit corresponds to the three index information (I ₁ , I ₂ , I ₃ ), respectively. In the case of I ₁ , the BM is set to 96 Kbps, the BS is set to 160 Kbps. In the case of I ₂ , the BM is set to 128 Kbps and the BS is set to 128 Kbps. In the case of I ₃ , the BM is set to 160 Kbps and the BS is set to 96 Kbps. MS stereo digital audio encoding apparatus characterized in that. A demultiplexer for inputting a bit stream received through compression encoding and demultiplexing to recover an audio signal for M channel and an audio signal for S channel and bit information allocated in the encoding; A decoder for decoding an audio signal for M and S channels provided by the demultiplexer; A bit allocation information extracting unit which extracts bit information allocated to the M and S channels as bit information allocated during encoding provided from the demultiplexer and provides the bit information to the decoder; MS stereo unit for converting the audio signal for the decoded N and S channels provided by the decoder to the audio signal of the original first and second channels.