Design And Implement Of Decoding For ISDB-T System Tansport Stream

With the requirement of high quality Audio-Visual life, many countries have awaked to the importance of digital television technology ,jumped on the bandwagon of reseach and development, and have worked out the model digital television broadcast standards which are suitable to their own situation. The transmission standard ISDB-T for Japanese digital terrestrial television was approved as the official standard by ITU in Feb. 2002, became the 3^rd transmission standard for digital terrestrial television following ATSC for Amereica and DVB-T for Europe.In ISDB-T system, stream operations include the coordination of data retrieval off the channel, the adjustment of clocks, and the management of the buffers. On decoding, de-multiplexing is required to reconstitute elementary streams from the multiplexed Program Stream or Transport Stream. Stream_id codes in Program Stream packet headers and Packet ID codes in the Transport Stream make this possible. The adjustment of clocks is the display synchronization of video and audio, to recover system clock (STC) by reference, to decode and display according to the time indicated by decode time stamp (DTS) and the display time stamp (PTS).At the beginning, this paper describes the characters and protocol structsture of ISDB-T system. According to ISDB-T, one or more programs can be broadcasted, which are composed by television (picture and sound), audio and data separately or assembledly. Decoding of video and audio applies H.264 and AAC (advanced audio coding ) respectively. Then, this paper introduces the structure of Transport Stream and the key technologies of multiplexing, video compression and audio compression. Program Streams are formed by multiplexing elementary streams, and Transport Streams are formed by multiplexing elementary streams, Program Streams, or the contents of other Transport Streams. The key technologies of multiplexing includes the collection and remap of program specific information(PSI) and the renewal of system clock; the key technologies of video compression comprises intra prediction , inter prediction, quantization and so on; the key technologies of audio compression are composed of gain control ,subband filter, Huffman coding and so on. Thirdly, this paper describes in total how to parse Elementary Stream (ES in short) and section from received MPEG2 Transport Stream (TS in short) ,and how to deal with incorrect TS packet, also explays how to send Video ES and Audio ES to video decoder and audio decoder to decode and output, and how to compare time stamp with system clock (STC) in order to ensure synchronization of video and audio. At last but not least, this paper introduces the structure , function and work flow of demultiplexing module ,vedio decoding module and audio decoding module respectively .