KR20010055541A - Apparatus for controlling input buffer in audio decoder - Google Patents

Abstract

PURPOSE: A controller for an input buffer is provided to control an input data buffer of PES and ES inputted from GA type HDTV receiver to an audio decoder. CONSTITUTION: A muxing unit(51) decides input of serial audio bit stream or input of SPDIF format data. A control unit(52) receives an STC for a time stamp count for synchronization of video data and audio data. Then, difference in the signals is calculated. A buffer control unit(54) detects a frame synchronization for an AC-3 data according to an ES input bit stream data as an AC-3 encoded data. Then, frames are checked for storing data by 32-bit unit. In case of an ES input bit stream data as an MPEG(Moving Picture Experts Group) encoded data, the buffer control unit parses a header portion of an MPEG frame data to check synchronization, bit rate, sampling frequency, and layer field. Then, bit rate, ID, layer, sampling frequency field are added to the synchronization field for detecting synchronization.

Description

Apparatus for controlling input buffer in audio decoder

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to digital audio signal processing of multimedia. In particular, a packetized elementary stream (PES) and an elementary (ES) input to an audio decoder from a High Definition TeleVision (HDTV) receiver of a Grand Alliance (GA) method An input decoder control apparatus of an audio decoder, which is adapted to control an input data buffer of a stream.

In general, audio signal processing methods commonly used in multimedia systems include AC-3, MPEG-1, 2, Pro-Logic methods, and a large amount of data processing functions are required for processing such audio signals. In order to process audio data in real time, a certain amount of buffer and control thereof are required.

Conventionally, dedicated processors such as memory and DSP have been used for input buffer control capable of processing such various audio data.

However, in order to process audio data of AC-3, MPEG, Pro-Logic, synchronization signal detection, error detection, frame size detection, and AV synchronization correction according to each mode should be performed, which requires a lot of control. As in the prior art, when a series of functions are handled by a dedicated processor, hardware resources are significantly increased.

Accordingly, the present invention has been proposed to solve the above-mentioned general problems, and an object of the present invention is to provide an audio decoder capable of controlling input data buffers of PES and ES input to an audio decoder in a GA type HDTV receiver. An input buffer control device is provided.

In order to achieve the above object, the input buffer control apparatus of an audio decoder according to the present invention,

A muxing unit which allocates and processes a serial input bitstream inputted in a system demux input format and an SPDIF format; A calculator configured to calculate a difference between an audio signal and a video signal using a system reference clock received from a system demux; A PES parser connected to the muxing unit and the calculation unit and detecting an ES stream which is pure audio data by parsing PES header information after detecting PES synchronization from a PES packet; A buffer control unit connected to the muxing unit and the PES parsing unit to perform synchronization detection, CRC detection, and frame size check of each frame for AC-3, MPEG, and Pro-Logic audio data, and write the data to the input buffer in units of frames. It consists of the technical configuration features.

1 is a block diagram of an audio decoder to which the present invention is applied;

2 is a block diagram of an input buffer control apparatus of an audio decoder according to an embodiment of the present invention;

3 is a block diagram showing input and output signals of the input buffer control device of FIG.

FIG. 4 is a diagram showing an example of data processing of the calculator in FIG.

5 is an input / output waveform diagram of a calculation unit in FIG.

6 is a bit stream structure diagram of a general MPEG-1 audio layer 1;

FIG. 7 is a view showing an example of processing of the buffer control unit in FIG. 2;

FIG. 8 is a diagram illustrating an input / output signal in FIG. 3.

9 is a timing diagram of an input / output signal with a demux in FIG. 1;

FIG. 10 is a timing diagram of input / output signals with the SPDIF in FIG. 1;

11 is a block diagram of an audio synchronization signal detection apparatus.

<Explanation of symbols for main parts of the drawings>

50: input buffer control unit 51: muxing unit

52: calculator 53: PES parser

54: buffer control unit

Hereinafter, an embodiment according to the technical spirit of the input buffer control apparatus of the present invention audio decoder as described above is as follows.

First, the present invention is a design of an input buffer control unit used in an audio decoder ASIC (Applicable Specific Integrated Circuit) for an HDTV receiver. In order to reduce the size of an ASIC chip, an apparatus capable of reducing hardware size than a dedicated processor has been developed. Audio data input accepts PES and ES data for each mode through the system demux input format and the Sony Philips Digital Interface (SPDIF) format for AC-3, MPEG, and Pro-Logic encoded data. It includes many functions such as synchronization for audio input data, cyclic redundancy check (CRC), frame size check, and AV synchronization.

1 is a block diagram of an audio decoder to which the present invention is applied.

As shown in the drawing, a general audio decoder includes a demux 10, an SPDIF 20, a main controller 30, a host 40, and the like, and an input buffer controller 50 is added according to the present invention.

2 is a block diagram of an input buffer control apparatus of an audio decoder according to an embodiment of the present invention.

As shown in the figure, a muxing unit 51 for byte-allocating and processing the serial input bitstream input in the system demux input format and the SPDIF format; A calculation unit 52 for calculating a difference between an audio signal and a video signal using a system reference clock received from the demux 10 of the system; A PES parser 53, connected to the muxing unit 51 and the calculating unit 52, for detecting PES synchronization from a PES packet and parsing PES header information to detect an ES stream which is pure audio data; It is connected to the muxing unit 51 and the PES parsing unit 53 and performs frame detection on the input buffer by performing synchronization detection, CRC detection, and frame size check of each frame for audio data of AC-3, MPEG, Pro-Logic. A buffer control unit 54 writes in units.

In the above, the muxing unit 51 determines whether to receive the serial audio bitstream from the demux 10 as input or the data of the SPDIF format as input, and the audio decoder decodes the decoding mode and the non-decoding. In non-decoding mode, the start signal of the frame is selected according to each mode.

The calculation unit 52 receives an STC for a time stamp count (STC) for synchronization of video and audio data, performs a count, calculates an AV synchronization difference, and calculates a difference between an audio signal and a video signal. Calculate

When the ES input bitstream data is AC-3 encoded data, the buffer controller 54 detects frame sync (0x0b77) for AC-3 data, checks frames CRC1 and CRC2, and checks the input buffer. It is stored in 32-bit units, and it is determined that synchronization detection for AC-3 data is valid only when two consecutive synchronization detections are performed.

When the ES input bitstream data is MPEG encoded data, the buffer controller 54 performs synchronization check by parsing the header portion of the MPEG frame data, and checks the bit rate, sampling frequency, and even the layer field. The sync is detected by adding the bitrate, ID, layer, and sampling frequency fields to the sync field.

The operation of the input buffer control apparatus for the audio decoder according to the present invention configured as described above will be described in detail with reference to the accompanying drawings.

First, the present invention is to control the input data (AC-3, MPEG, Pro-Logic encoded data) of the audio decoder, by allocating a serial input bit stream to detect the PES synchronization from the PES packet and then parse the PES header information Delay / Advanced of audio and video for AV synchronization is calculated. In addition, the ES stream, which is pure audio data, is detected through header information of the PES packet, synchronization detection of audio data, CRC check, frame size calculation, and the like are stored in the input buffer. After the decoding start signal is transmitted to the main control unit 30 of the audio decoder, the next audio data frame is received, and the operation of repeating synchronization detection, CRC check, and frame size calculation is then repeated.

The format of the input data input to the audio decoder supports both the format input from the demux 10 of the system and the format input from the SPDIF 20. Therefore, the input buffer control unit 50 requires a muxing unit 51 for selecting data of the system demux input format and the SPDIF format.

The submodule of the input buffer controller 50 is largely configured as follows.

* Muxing unit 51: performs the data selection function of the system demux input format and SPDIF format

* Calculation unit 52: performing the delay / improvement calculation function between the data to synchronize the audio / video data

* PES parser 53: Parsing the PES packet

* Buffer control unit 54: As the core of the input buffer control unit 50, it performs functions such as frame detection and error detection according to the format of input data such as AC-3, MPEG, Pro-Logic, etc.

FIG. 3 is a block diagram showing input and output signals of the input buffer control device of FIG.

Therefore, the serial input data consists of ADATA, ADEN, ADREQ, and ADCLK. The input data format is selected by the system demux format (SPDIF = Low) and the SPDIF format (SPDIF = High) according to the SPDIF selection.

In addition, when the input data format is a system demux, an ES stream (ES = High) in which the input data includes only pure audio data, and a PES stream (ES = Low) including audio data and video data are selected according to the ES. When the input data is a PES stream, the STC [32: 0] for time stamp counts is received and counted at 90 Hz for synchronization of video and audio data. This value is received as an input from the main control unit 30 of the audio decoder and used to synchronize AV.

Referring to the operation of the present invention in more detail as follows.

First, the muxing unit 51 is a module for determining whether to receive a serial audio bitstream from the system demux 10 as input or input data of an SPDIF format as an input to the input data of the audio decoder. In addition, when the audio decoder is in a decoding mode and a non-decoding mode, START_FLAG, which is a start signal of a frame, is selected according to each mode.

The calculator 52 is a module for audio / video synchronization, and calculates a difference between an audio signal and a video signal using a system reference clock received from the system demux 10. The calculation procedure for AV synchronization is as follows.

4 is a diagram illustrating an example of data processing of the calculator in FIG. 2, and FIG. 5 is an input / output waveform diagram of the calculator in FIG. 2.

According to the international standard MPEG-2 system ISO / IEC 13818-1, the main buffer size of the audio ES is 3584.

According to the AC-3 specification, the audio bitstream has a minimum bit rate of 32 Kbps.

Therefore, the maximum time difference of audio / video is as follows.

3584 / (32/8) = 0.875 sec

The STC 33-bit counter in PCR (Program Clock Reference) counts 90K per second. That is 90 / msec.

The AC-3's audio block size is 5.3msec.

From these results, 1sec / 5.3msec ?? 200, that is, 8 bits are required to represent the time difference between the PTS and STC, and a total of 9 bits are required because a flag is needed to indicate whether the audio is faster or slower than the video. Can be.

STC also receives PCR [32..0] from the i ² C bus interface.

On the other hand, the PES parser 53 checks the syntax through a 32-bit shift register.

On the other hand, the buffer controller 54 performs almost all the functions of the input buffer controller 50 as the core of the audio decoder.

Therefore, when the PES packet bitstream including the audio / video data is received and the PES parser 53 exports the ES stream, which is pure audio data, is passed to the buffer controller 54, the buffer controller 54 receives each frame therefrom. It performs synchronization detection, frame size check, CRC check and stores in 32-bit unit in input buffer. In addition, the function of the buffer controller 54 varies slightly depending on the type of the ES input bitstream data.

First, when ES input bitstream data is AC-3 encoded data, it detects frame sync (0x0b77) for AC-3 data, checks frames CRC1 and CRC2, and stores them in 32-bit units in the input buffer. Perform. At this time, it is determined that the synchronization detection for AC-3 data is valid only when two consecutive synchronization detections are performed.

If the ES input bitstream data is MPEG encoded data, the CRC check is not performed, but the header part of the MPEG frame data is parsed to check not only the synchronization but also the bit rate, sampling frequency, and layer field. In addition, in the MPEG frame data, the synchronization (11111111: 12 "1") values are not specified, and thus the synchronization detection probability is low, thereby increasing the synchronization detection probability by adding a bit rate, ID, layer, and sampling frequency field to the synchronization field. . The bitstream format of the MPEG frame data and the synchronization detection scheme are the same as those of the bitstream structure of the general MPEG-1 audio layer 1 of FIG.

FIG. 7 is a diagram showing an example of the processing of the buffer control unit in FIG.

Thus, the 4-bit bitrate index follows the example of FIG.

8 is a view illustrating the input / output signal in FIG. 3, FIG. 9 is a timing diagram of the input / output signal with the demux in FIG. 1, FIG. 10 is a timing diagram of the input / output signal with the SPDIF in FIG. 1, and FIG. 11. Is a block diagram of an audio synchronization signal detection apparatus.

Thus, data transmission is performed between the upper system Demux 10, the SPDIF 20, the main control unit 30, and the host 40.

As such, the present invention controls the input data buffers of the PES and the ES input to the audio decoder from the GA type HDTV receiver.

Although the preferred embodiment of the present invention has been described above, the present invention may use various changes, modifications, and equivalents. It is clear that the present invention can be applied in the same manner by appropriately modifying the above embodiments. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

As described above, the input buffer control apparatus of the audio decoder according to the present invention may provide an input buffer control unit, and may further include a counter for detecting a synchronization signal and a PES for a KR mode such as AC-3, MPEG, Pro-Logic, etc. By sharing a lot of hardware resources, such as a parser, it is possible to reduce the hardware size.

Claims (5)

In the audio decoder, A muxing unit which allocates and processes a serial input bitstream inputted in a system demux input format and an SPDIF format; A calculator configured to calculate a difference between an audio signal and a video signal using a system reference clock received from a system demux; A PES parser connected to the muxing unit and the calculation unit and detecting an ES stream which is pure audio data by parsing PES header information after detecting PES synchronization from a PES packet; A buffer control unit connected to the muxing unit and the PES parsing unit to perform synchronization detection, CRC detection, and frame size check of each frame for AC-3, MPEG, and Pro-Logic audio data, and write the data to the input buffer in units of frames. Input buffer control device of an audio decoder, characterized in that consisting of. According to claim 1, The muxing unit, Determines whether to receive serial audio bitstream as input or data in SPDIF format from demux and select start signal of frame according to each mode when audio decoder is in decoding mode and non-decoding mode. Input buffer control device of an audio decoder. The method of claim 1, wherein the calculation unit, And an STC for a time stamp count for synchronizing video and audio data, performing a count to calculate an AV synchronization difference, and calculating an audio signal and a video signal difference. The method of claim 1, wherein the buffer control unit, If the ES input bitstream data is AC-3 encoded data, after detecting frame synchronization with AC-3 data, check frames CRC1 and CRC2 and store them in 32-bit units in the input buffer. The input buffer control apparatus of the audio decoder, characterized in that it is determined that the synchronization detection is effective only after two consecutive synchronization detections. The method of claim 1, wherein the buffer control unit, If the ES input bitstream data is MPEG encoded data, the header part of the MPEG frame data is parsed to perform a synchronization check, and the bitrate, sampling frequency, and layer fields are also checked. And a sampling frequency field to detect synchronization.