KR19990060792A - Bitstream Transmission Method for Improving Audio and Video Output Synchronization - Google Patents

Abstract

According to the present invention, in a digital video decoder such as a digital satellite broadcast receiver or a digital television system, audio information is included in a user extention on a video syntax according to a video presentation time and transmitted. The present invention relates to a bitstream transmission method for improving audio and video output synchronization by eliminating a separate audio packet and allowing accurate audio / video synchronization.

The present invention is shown in Figure 2; Compressing and encoding video data into a presentation unit, compressing and encoding audio data during the video presentation unit time, encoding the encoded and encoded presentation unit time audio data into video data, and A bitstream transmission method for improving audio and video output synchronization, which is controlled by a process of transmitting video data, which does not process a PTS, thereby simplifying audio and video synchronization, and synchronizing audio and video using a PTS. This eliminates the need for skips and repetitive operations that occur when the device is hit, and prevents data loss on the video and audio timebases.

Description

Bitstream Transmission Method for Improving Audio and Video Output Synchronization

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bit stream transmission method for improving audio and video output synchronization. In particular, the present invention relates to video presentation of audio information in a digital video decoder such as a digital satellite broadcasting receiver or a digital television system. It is included in the user extention of video syntax in accordance with the video presentation time and transmitted so that no audio packet is required and audio / video synchronization can be precisely matched. The present invention relates to a bitstream transmission method for improving audio and video output synchronization.

Fig. 1 shows the structure of a transmitter on the transmitting side according to the conventional MPEG2 standard.

A conventional encoder is a video encoder 101 for converting and encoding an analog video input signal into a digital signal, and a PES packet for inserting and presenting a presentation time stamp (PTS) into the video data encoded by the video encoder 101. An audio encoder 103 for converting and encoding an analog audio input signal into a digital signal, and inserting a presentation time stamp (PTS) into the audio data encoded by the audio encoder 103 to packetize it. A PES packetizer 104, a timing controller 105 for processing the audio and video data, and a mixer for outputting the video and audio packet data output from the PES packetizers 102 and 104 as stream data. 106).

In the conventional encoder configured as described above, video and audio data are separated and transmitted independently, and a presentation time stamp (PTS) is inserted in each of them to be used for A / V synchronization. .

The video encoder 101 converts an input analog video signal into a digital signal and encodes the video data in conformity with the MPEG2 standard. The packetizer 102 inserts a PTS into the video data (ES: Elementary Stream) to form a packet stream ( Configure PES: Packetized Elementary Stream.

At this time, the PTS is inserted into the header of the PES to be periodically transmitted.

The audio encoder 103 also converts an analog audio signal into a digital signal and encodes the audio data according to the MPEG2 standard. The packetizer 104 inserts a PTS into the audio data ES to form a packet stream PES. The PTS is inserted into the header of the PES to periodically transmit audio data.

The packetized video data and audio data are mixed in the mixer 106 to form a program stream or a transport stream.

Here, the program stream is generated by mixing PES packets having a common time base into one stream, and the transport stream is generated by mixing several programs having a time base independently, where one program has several It consists of PES streams.

The operation of the transmitting encoder as described above is performed by a reference clock (system clock: STC) and drives a counter. The packet encoder periodically takes a sample of the counter and inserts it on the transport stream.

The sample value at this time is called a system clock reference (SCR) in the program stream and a program clock reference (PCR) in the transport stream.

As described above, the conventional encoder separately separates and transmits video and audio data, and inserts a presentation time stamp (PTS) into each of them to use for A / V synchronization. Since the decoder side first extracts the reference clock (PCR or SCR) value transmitted with the bitstream, the decoder clock is synchronized with the encoder clock.

That is, demultiplexing the desired video and audio PES streams from the program stream or the transport stream, extracting the PTS information inserted in each PES header, and the demultiplexed video stream is sent to the video decoder, and demultiplexed audio. The stream is sent to the audio decoder.

At this time, the correspondence between the PTS value and the presentation unit corresponding to the PTS value, that is, the video and the audio frame, is traced, and the PTS value and the current STC counter value are compared to present the decoded video and audio data. The timing of the presentation will be determined.

If the PTS value is different from the current STC counter value, it must be ignored or repeated.

Therefore, according to the conventional A / V synchronization method, since the transmitting side encodes video and audio data into separate packets, and transmits the mixed packets, the receiving side decodes the correlation at the time of receiving the video and audio data. It does not match the correlation at the point of actual presentation.

Therefore, in order to overcome this problem, a PTS (point to be presented) is inserted into video and audio data, respectively, so that their presentation points are aligned on a common timebase (PCR). Therefore, separate PTS processing for packet data is required. .

The present invention synchronizes audio and video outputs by inserting audio compression data of the required number of channels as user data (user_data) on the syntax so that corresponding audio data can be transmitted together for every picture which is a presentation unit of video. Provided are a bitstream transmission method for improvement.

In particular, in the present invention, the video data and audio data generated in the presentation unit time of the video in MPEG2 (that is, during the time corresponding to one picture) are mixed and configured in the transmission unit, and the time correlation between the received Corresponding to the correlation at the last presentation, the receiver provides a bitstream transmission method for improving audio and video output synchronization, which allows audio and video synchronization to be synchronized without any manipulation.

1 is a block diagram of a conventional transmitter encoder

Figure 2 is a data combining method for explaining the bitstream transmission method of the present invention

Figure 3 is a block diagram of a transmitter of the transmitting side according to the present invention

2 is a diagram illustrating a bitstream transmission method for improving audio and video output synchronization according to an embodiment of the present invention, which includes compressing and encoding video data in a presentation unit, and compressing and encoding audio data during a video presentation unit time. And transmitting the encoded audio and video data by combining the compressed and encoded presentation unit time audio data with the video data.

3 shows a configuration of an encoder to which the bitstream transmission method for improving audio and video output synchronization according to the present invention is applied, and a video encoder 301 for converting and compressing analog video input signals into digital signals. An audio encoder 302 for converting an analog audio input signal into a digital signal and compressing the encoded audio signal; a byte count calculator 303 for counting the audio compressed data during the video presentation unit time; and the data compressed and counted data. A mixer 305 for combining the timing controller 304 for control, the output video data of the video encoder 301 and the compressed coded audio data for a presentation unit time, and the mixer 305 of the mixer 305. PES packetizer 306 packetizes the output.

The bitstream transmission apparatus for improving audio and video output synchronization according to the present invention configured as described above performs a method of combining audio data corresponding to the unit time according to the video presentation unit time (picture) and transmitting the video data. It demonstrates in detail as follows.

The video encoder 301 compresses and encodes the video data before encoding as shown in (a) of FIG. 2 into a video presentation unit time (time corresponding to one picture) under the control of the timing controller 304 as shown in (b). .

The audio encoder 302 compresses and encodes the audio data before encoding as shown in (e) of FIG. 2 under the control of the timing controller 304 and inputs it to the byte count calculator 303 as shown in (d).

The byte count calculator 303 calculates the number of bytes of the encoded audio data (d in FIG. 2) of the audio encoder 302, and corresponds to the video presentation unit time (one picture) as shown in FIG. The coded audio data (d in FIG. 2) corresponding to the number of bytes of the length is added to the mixer 305.

Therefore, in the mixer 305, the encoded video data (b in FIG. 2) during one presentation unit time (one picture) shows the encoded audio data (d in FIG. 2) having a length corresponding to the unit time. Combining as shown in 2 (c), constitutes encoded video and audio data.

The encoded video and audio data are packetized by the PES packetizer 306 and transmitted in the transmission unit as shown in FIG.

When the transmission unit is configured and transmitted as described above, the receiving decoder receives both video and audio data generated within the same time interval and decodes the received data within the same time interval.

Therefore, no separate operation for audio and video output synchronization is required.

However, also in this case, it is necessary to synchronize the system clock of the receiving side protector with the transmitting side clock through PCR restoration.

When the present invention is applied to an MPEG2 bitstream, audio compressed data of the required number of channels can be inserted as user data (user_data) after Picture Coding Extension (PCE). Audio data corresponding to the audio data can be transmitted together.

On the other hand, if other data (closed caption, etc.) can also be transmitted in the same area as above, a flag for distinguishing them may be required.

However, this may be determined by the use of the user data area, and the audio packet may be combined and transmitted in the reserved area of the user extension on the video syntax.

By utilizing the user area in this way, compatibility with existing devices (synchronization method) is secured.

That is, since the form of combining the audio data that is lost during the video presentation unit time with the video data is the use of the user area, the existing receiver will ignore the data in this area, so there is no problem in compatibility with the existing receiver.

As described above, the bitstream transmission method and apparatus for improving the audio and video output synchronization according to the present invention do not process the PTS, so that the audio and video synchronization becomes simple and easy, and when the audio and video are synchronized using the PTS, This eliminates the need for skipping or repetitive operations that occur and prevents data loss on the video and audio time bases.

In addition, according to the present invention, a transmission unit for combining audio data with video data can be applied within a standard defined in MPEG as a user area, and can be applied as an additional function while maintaining compatibility with an existing system.

Claims (3)

Compressing and encoding video data into a presentation unit, compressing and encoding audio data during the video presentation unit time, encoding the encoded and encoded presentation unit time audio data into video data, and Bitstream transmission method for improving audio and video output synchronization, characterized in that the control by the process of transmitting video data. The method of claim 1, wherein the audio / video data is configured as one transmission unit combined by using a user area of a transmission standard. The audio and video output synchronization improvement of claim 1, wherein the audio data corresponding to the video presentation unit time is combined with the audio data corresponding to the video presentation unit time by calculating the number of bytes of the audio data. Bitstream transmission method for the.