Recently,I'm studing something about synchronize between video and audio stream in VLC. Through reading the source code, I found that every time when demux was finished, a function call "es_out_Control(p_demux,ES_OUT_SET_PCR,...)" will be invoked. Having read inner contents of es_out_Control, I feel its work is set the PCR which could mean "Program Clock Reference " (don't know whether it's right). Then,it might be a system wide refence clock, didn't it?

Here comes the problem: In the next step ,that is decoder module, I haven't found anything about this "pcr",why? how did synchronize work in this part?
