Importance

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Abstract

A method for ensuring synchronization of MPEG-1 data is carried in an MPEG-2 transport stream for decoding by an MPEG-1 decoder. The method includes searching the MPEG-2 transport stream for a packet start code prefix indicating the start of a PES packet and storing the data associated with the PES packet into a buffer. If the PES packet is a video PES packet, the packet header is examined to determine if a PTS is present. If a PTS is present, the video data in the PES packet are examined during storage to the buffer to locate the first occurrence of a picture start code in the data. Once the first occurrence of a picture start code is located, a flag is set indicating the correspondence between the PTS and the identified picture start code. The video data remaining in the video PES packet is then stored to the buffer without further examination. The PES packet data are stored without examination if a PTS is not present. In either instance, the stored data are transmitted from the buffer to the video decoder in known lengths. If the PES packet is an audio PES packet, a current value of a system time clock is subtracted from a value of a first PTS contained in an audio PES packet to calculate an audio delay. The audio delay is then adjusted to account for audio decoding, audio transmission, and video decoding times. Audio data stored in the buffer are not enabled for delivery to an audio decoder until after the audio delay has elapsed.

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First Claim