Robust method for recovering a program time base in MPEG-2 transport streams and achieving audio/video sychronization

摘要

An internal system time clock within an MPEG-2 decoder is synchronized in frequency and optionally in phase, but not in value, to program clock reference time stamps within a received MPEG-2 transport stream. A demultiplexer separating audio and video packets from the transport stream modifies the decoding and presentation time stamps within such packets by at least an offset between the program clock reference time stamp values and the internal system time clock time before forwarding the packets to the audio and video decoders. Discontinuities in the program clock reference time stamp sequence automatically result in a change in the offset, such that the internal system time clock continues to increase monotonically and decoding and presentation time stamps within the packets are not suddenly invalidated.