Error detection and recovery for high rate isochronous data in mpeg-2

Abstract

Error recovery is provided for isochronous data ('isodata') obtained from a data stream. Isodata transport packets are monitored to locate isodata presentation time stamps (PTSs). The presentation of isodata from a buffer is synchronized to a system time clock (STC) using timing information derived from the PTSs. Discontinuity errors between said isodata transport packets are identified and, if a discontinuity of no more than one packet is identified, a write pointer of the buffer is advanced by a suitable number of bits to compensate for the discontinuity, while maintaining the synchronization of the presentation with respect to the STC. Additional error detection and recovery techniques are disclosed, including the maintenance of a presentation unit counter, the use of a PTE extension and PTS offset to verify output timing, the provision of a pair of PTS pointers verifying correct output data timing, the use of a packet elementary stream (PES) count to detect lost data in the transport stream, and the detection and discarding of packets designated as encrypted after any decryption should have already been completed.