MPEG2 ts Summary (4)

TS supports multiplexing, so it can be used to transmit multi-layer programs after reuse. In the process of multiplexing, we should note the time reference and synchronization problems that need to be faced during decoding. Because the de-multiplexing requires synchronization of various information, during the multiplexing process, you need to insert the relevant time information: pts, DTS, and PCR.

During ts formation, PTS and DTS inject the clock information into the PES package according to the STC reference when ES is packaged into PES, And then when PES is cut into ts, then, the PID and PCR information are injected into the TS package. When multiple Ts are reused, the PCR of each ts will be extracted and analyzed, then, according to the unified STC reference, the new PCR is generated and injected into ts. Finally, because the original Pat table information is not applicable, the new Pat table needs to be generated again, and attach it to the new TS stream. After this multi-layer multiplexing, the new TS stream can enter the modulation and transmission stages. For the process, see:

The decoding process is faced with the following problems: demultiplexing, video and audio synchronization, and the decoding cache never overflows. Demultiplexing separates the Programs transmitted by ts in different time sequences in the same channel. The video/audio synchronization is completed by DTs, PTS, and PCR, and PCR is the absolute time scale for rebuilding the system time benchmark, DTS and PTS are the relative time points for decoding and reproduction. To solve the problem that the decoder cache is overwhelming, it must be implemented through the system target Decoder (STD) model, the basic idea is as follows:

1. After the TS Stream enters the decoder, it first splits various es streams (including PSI information stream) by the commutator according to a certain time sequence ).
2. After the decomposition, the es stream enters its own transmission cache, and its PES stream enters its primary storage. Note that the PSI information stream enters the system cache, it also reaches the primary storage.
3. Finally, the decoder extracts the media or system information from each primary storage based on the DTs information for decoding, and displays the media content based on the PTS information.

For the process, see: