KR980013417A - Method and apparatus for transmitting audio data - Google Patents

Abstract

The present invention relates to an audio data transmission method and apparatus suitable for transmitting PCM data and AC-3 data. The present invention extracts audio data and information data from an audio data source generating unit (10) Buffer 20 and the information data is processed by the microcomputer 30 so that the data inputted from the audio data source in the microcomputer 30 is PCNM or AC-3, The data transmission unit 40 and the AC-3 decoder 50 can support various sampling rates by transmitting PCNI data and AC-3 data and can support various transmission formats.

Description

Method and apparatus for transmitting audio data

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for transmitting audio data, and more particularly, to a method and apparatus for transmitting audio data suitable for transmitting PCM data and AC-3 data.

In this regard, in response to the enhancement of MPEG2 video quality, MPEG2 audio has also been standardized with the aim of improving the quality of multi-channel. Thus, MPEG2 audio was approved as IS (International Standard, International Standard) 13818-3 in November 1994 and standardization was completed.

MPEG2 audio is based on MPEG1 audio and several new techniques are being introduced to increase compression efficiency. Compared to MPEG1 audio, MPEG2 audio includes the following features in particular.

First, it is multi-channeled. The stereo function of MPEG1 audio has been expanded to 6 channels in MPEG2 audio, so you can enjoy stereo sound in the movie theater as it is. Looking at the components of the six channels (ie, the positions of the speakers), we can see that five broadband signals (20 KHz), C (Center), L (Left), R (Right), LS (Left Surround) (Low Frequency Enhancement) signal which provides only a separate signal (120 kHz). This is usually referred to as 5.1 channel, and it has a much more stereoscopic effect than the existing Dolby Surround stereo sound with four channels of L, R, LS, and RS.

In addition, Multi Iingual has been enhanced. As can be seen from satellite broadcasts in various regions such as Asia and Europe, the global village is gradually becoming one with the fullness of multimedia and information and communication technologies. In response to this, MPEG2 audio has a function to send additional voice to 7 languages in 5.1 channels separately.

MPEG2 audio also allows sampling frequencies of 16KHz, 22.05KHz, and 24KHz, which is half of the sampling frequency used in MPEG1 audio. This is because it is advantageous to reduce the sampling frequency when the bandwidth of the input signal is narrow in order to effectively compress a large amount of data of multi-channel and multi-ring at a limited bit rate.

Another consideration is the backward compatibility with MPEG1 audio. This means that the MPEG2 audio bit stream can be limitedly reproduced in the MPEG1 audio receiver. Concretely, 5.1-channel MPEG2 audio is reproduced in stereo in the MPEG1 audio receiver. For example, in the case of digital broadcasting using Mugungwha's satellite, MPEG2 is a standard, and a low-end model equipped with an MPEG1 audio decoder also receives MPEG2 bit stream and reproduces stereo sound. This is the same concept that color TV broadcasts are received in monochrome on black and white TVs and FM stereo broadcasts are received mono in mono receivers.

This backward compatibility for audio contrasts with the forward compatibility that MPEG2 video receivers in video can receive MPEG1 video bit streams. More precisely, when designing an MPEG2 audio decoder, audio is generally designed to be able to decode an MPEG1 audio bit stream, so that bidirectional compatibility is maintained in practice.

For this compatibility, MPEG2 audio includes a stereo component in an audio data portion in a bit string of MPEG1 audio, and an additional component of MPEG2 audio in a subsequent additional data portion. When there is not enough bit space and it is insufficient, the format (syntax) of the bit string is expanded and the remaining data is loaded here. As a result, the bitstream format of MPEG2 audio becomes very inefficient, which is one of the factors that deteriorates the performance of MPEG2 audio.

In order to compensate for this, the MPEG2 standard is being improved in the NBC (Non Backward Compatible) mode, instead of backward compatibility with MPEG1. NBC is expected to complete the international standard in 1997. Dolby's AC-3, which has been adopted as a standard in the US HDTV and movie industry and is likely to be adopted in recent digital video discs, is also becoming a candidate.

Accordingly, an object of the present invention is to provide an audio data transmission method and apparatus capable of supporting various sampling rates by transmitting PCM data and AC-3 data, and supporting various transmission formats.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating an audio data transmission apparatus according to an embodiment of the present invention. Referring to FIG. 1, there is shown an audio data transmission apparatus according to an embodiment of the present invention. The audio data source generation unit 10 generates an audio data source, A buffer 20 for receiving and temporarily storing audio data from the data source generating unit 10 and outputting the received audio data to the audio data generating unit 10; A microcomputer 30 for outputting a sampling rate and a type of audio data and a sampling rate from the microcomputer 30 to generate a serial clock and frame synchronization according to the mode, The audio data is received from the buffer 20 by selecting the PCM data or the AC-3 data, converts the data into serial data, And a transmission unit 40, is made to receive the serial clock and the frame synchronization, the serial data from the audio data transfer section 40 is transferred to the S / P DIF format (Format) or include AC- decoder 50.

2 is a block diagram showing an embodiment of the audio data transmitting unit 40 of FIG. 1. The audio data transmitting unit 40 selects an oscillator corresponding to the sampling rate from the microcomputer 30, A counter 42 for counting the frame synchronization from the serial clock generator 42 in accordance with the S / P DIF format and outputting a block count signal, 44 and the microcomputer 30 to convert the audio data received from the buffer 20 into serial data and to supply frame synchronization and serial clock from the serial clock generator 42 3 decoder 50, and receives a block count signal from the counter 44 to receive a frame count, a serial number, By generating a count start signal to match it comprises a counter 44, a reset (Reset) audio data load unit (46) for. The AC-3 decoder 50 may be replaced with an SPDIF transmitter or a digital / analog converter.

Hereinafter, the present invention will be described with reference to FIGS.

First, the audio data source generating unit 10 generates an audio data source constituting a predetermined bit stream. The buffer 20 comprises a first-in first-out (FIFO) Receives audio data from the generating unit 10, temporarily stores the audio data, and outputs the audio data.

Next, the microcomputer 30 receives the information according to the audio data from the audio data source generating unit 10, and outputs the type, the sampling rate, and the transmission enable signal of the audio data. 30 and generates a serial clock and a frame synchronizing signal in accordance with the mode, and then selects whether the audio data is PCM data or AC-3 data, And converts the audio data into serial data and outputs the serial data. The AC-3 decoder 50 receives and decodes the serial clock, frame synchronization, and serial data from the audio data transmission unit 40.

At this time, the serial clock generating unit 42 of the audio data transmitting unit 40 selects an oscillator corresponding to the sampling rate from the microcomputer 30, and generates frame synchronization and a serial clock according to the input source mode.

Next, the counter 44 counts the pre-sync from the serial call generator 42 to conform to the S / P DIF format and outputs a block count signal. The audio data load unit 46 receives the count signal from the microcomputer 30 Audio data from the buffer 20 in accordance with the selection source mode according to the type of the audio data, converts the audio data into serial data, receives the frame synchronization and the serial clock from the serial clock generation unit 42, 3 decoder 50 in accordance with a transmission enable signal from the microcomputer 30 and receives a block count signal from the counter 44 and generates a count start signal in accordance with the type of data to be transmitted And the counter 44 is reset.

In the S / P DIF format according to the present invention, the basic unit of transmission data is a sub-frame and transmits 16 bits of digital data per sub-frame.

At this time, two sub-frames constitute one frame. As shown in FIG. 3, 32 time slots constitute one sub-frame, and each time slot has contents. Also, as shown in FIG. 4, two sub-frames form one frame and 192 frames form a block.

Next, an AC-3 data stream according to the S / P DIF format will be described as follows.

- Additional information when transmitting

The following burst preamble is attached to one AC-3 sync frame.

OX F872 16-bit Sync word A

OX 4EIF 16-bit Sync Word B

OX 0001 Burst information (AC-3 data)

OX 3000 Length code (number of data bits)

-AC-3 Data 1 Since the sync frame consists of two blocks, and AC-3 data is compressed by 4 times, two blocks are transmitted to fill the bit rate and six blocks fill the empty data.

Also, it can be seen that there are many formatted formats in each of the serial data transmission modes as shown in FIGS. 6 and 10.

That is, in order to support sampling rates of 44.1 KHz, 48 KHz, and 96 KHz, the audio data transmitting unit 40 selects an oscillator corresponding to a sampling rate selected from oscillators having 32 times the sampling rate, and outputs the selected oscillator in the above format.

FIG. 11 is a flowchart illustrating an audio data transmission method according to an embodiment of the present invention.

First, it is determined whether the audio data to be transmitted is PCM or AC-3 data (100).

If the count is 192 and the count is 192 and the transmission enable is "0 ", the count is again set to" 1 " 1 "is repeated (110,120,130,140).

Next, when the AC-3 data is determined in step 100, the count is set to "1 ", and when the count is less than 3, the burst preamble is loaded and the frame synchronization and the serial clock edge are detected, , And repeats the process of determining whether the count is less than 3 (150, 160, 170, 180, 190).

If the count is not less than 3 in step 160, if the count is less than 386, the audio data is read and the step 180 is performed (200, 210).

If the count is not 1536 and the count is 1536 and the transmission enable is "0 ", the above-described step 150 is performed (step < RTI ID = 0.0 > 220, 230, 240).

As described above, according to the present invention, audio data and alarm data are extracted from an audio data source generator 10, audio data is stored in a buffer 20, information data is processed by a microcomputer 30, An audio data transfer unit 40 and an AC-3 decoder 50 for converting and decoding data input from an audio data source to conform to each format according to whether the data input from the audio data source is PCM or AC-3, Data can be transmitted to support various sampling rates, and various transmission formats can be supported.

FIG. 1 is a block diagram showing an embodiment of an audio data transmission apparatus according to the present invention.

FIG. 2 is a block diagram illustrating an embodiment of an audio data transmitting unit of FIG. 1

Figure 3 is a diagram showing the contents of each time slice in the SPDIF format

4 is a schematic diagram showing the block configuration of the SPDIF format

5 is a schematic diagram showing eight blocks for explaining the structure of transmission in the burst format of AC-3 data;

FIGS. 6 and 10 are timing diagrams showing five different formats according to the serial data transmission mode

FIG. 11 is a flow chart showing steps of an embodiment of the audio data transmission method according to the present invention;

DESCRIPTION OF THE REFERENCE NUMERALS

The present invention relates to an audio data transmission apparatus and a data transmission method therefor. More particularly, the present invention relates to an audio data transmission apparatus.

Claims (3)

An audio data source generating unit generating an audio data source; A buffer for receiving and temporarily storing audio data from the audio data source generating unit and outputting the audio data; A microcomputer receiving the information data according to the audio data from the audio data source generating unit and outputting the type and the sampling rate of the audio data; Receives a type of audio data and a sampling rate from the microcomputer, generates a serial clock and frame synchronization according to the mode, selects audio data to be PCN I data or AC-3 data, An audio data transfer unit for receiving and outputting serial data; And an AC-3 decoder receiving the serial clock, preliminary sync, and serial data from the audio data transmitting unit and transmitting the serial clock in the S / P DIF format. The apparatus of claim 1, wherein the audio data transmission unit comprises: a serial clock generator for selecting an oscillator corresponding to a sampling rate from the microcomputer and generating frame synchronization and a serial clock according to the input mode; A counter for counting the frame synchronization from the serial clock generator in accordance with the S / P DIF format and outputting a block count signal; Receiving audio data from the buffer in accordance with a mode selected according to a type of audio data from the microcomputer, converting the received audio data into serial data, receiving frame synchronization and a serial clock from the serial clock generation unit and receiving frame synchronization, a serial clock, And an audio data loading unit for receiving a block count signal from the counter and generating a count start signal in accordance with a type of data to be transmitted, thereby resetting the counter. Determining (100) whether the audio data to be transmitted is PCM or AC-3 data; If the PCM data is determined to be PCM data in step 100, the count is set to "1 ", and if the count is not 192, the serial data is transmitted. If the count is 192 and the transmission enable is & (110, 120, 130, 140); When the AC-3 data is determined to be AC-3 data, the count is set to " 1 ", and if the count is less than 3, the burst preamble is loaded. After the frame synchronization and the serial call detection are detected to transmit the serial data, And repeating the process of determining whether the number of times is less than 3 (160, 170, 180, 190); If the count is less than 3 in step 160, reading audio data if the count is less than 386 and performing step 180; If the count is not less than 386 in step 200, "OX 0000" is transmitted if the count is not 1536, and if the count is 1536 and the transmission enable is & And transmitting the audio data. ※ Note: It is disclosed by the contents of the first application.