Method and apparatus for audio and video synchronizing in MPEG playback systems

A method for synchronizing and decoding/decompressing audio and video signals from an encoded data stream, the method comprising the steps of:

• in combined system and video system decoder, receiving the encoded data stream comprising at least audio data packets, video data packets, audio presentation time stamps and video presentation time stamps, and separating said encoded data stream into an encoded audio data stream and an encoded video data stream, which encoded audio data stream comprises at least audio data packets and said audio presentation time stamps and which encoded video data stream comprises at least said video data packets and said video presentation time stamps;
• detecting, in said combined system and video decoder the presence of an audio presentation time stamp in the encoded audio data stream;
• storing, in said combined system and video decoder, a detected audio presentation time stamp from the encoded audio data stream;
• in an audio decoder, coupled to the combined system and video decoder, receiving said audio data packets from the encoded audio data stream and decoding/decompressing said audio data packets;
• detecting, in said audio decoder, the presence of an audio presentation time stamp in the encoded audio data stream and outputting a flag when audio data packets corresponding to said audio presentation time stamp are decoded;
• setting, in said combined system and video decoder, a system time clock counter with a stored audio presentation time stamp as a start count when said flag is received and incrementing said start count according to a predetermined clock frequency and outputting a system time clock;
• decoding/decompressing said encoded video data stream in synchronization with said system time clock;
• storing, in a first audio data buffer in said combined system and video decoder, audio data packets and audio presentation time stamps from said encoded audio data stream;
• and
• receiving, in a second audio data buffer in said audio decoder, the encoded audio data stream from said first audio data buffer and storing audio data packets and audio presentation time stamps.

A multimedia system for reading, decoding, and decompressing encoded audio/video data into video data for display on a plurality of display types and into audio data for reproduction on a plurality of sound reproduction devices, the multimedia system comprising:

• a system decoder receiving the encoded data stream comprising at least audio data packets, video data packets, audio presentation time stamps and video presentation time stamps, and separating said encoded data stream into an encoded audio data stream and an encoded video data stream, which encoded audio data stream comprises at least audio data packets and said audio presentation time stamps and which encoded video data stream comprises at least said video data packets and said video presentation time stamps;
• a first audio data buffer, coupled to said system decoder, for receiving and storing audio data packets and audio presentation time stamps from said encoded audio data stream;
• a first audio presentation time stamp detector, coupled to said system decoder, for detecting the presence of an audio presentation time stamp in the encoded audio data stream;
• a latch, coupled to said first audio presentation time stamp detector, for storing a detected audio presentation time stamp from the encoded audio data stream;
• a system time clock counter, coupled to said first audio presentation time stamp detector, for receiving said audio presentation time stamp as a start count when a load signal is received, and incrementing said start count according to a predetermined clock frequency and outputting a system time clock;
• a video decoder, coupled to said system decoder and said system time clock counter, for receiving said system time clock and said encoded video data stream and decoding/decompressing said encoded video data stream in synchronization with said system time clock;
• an audio decoder, for receiving said audio data packets from the encoded audio data stream and decoding/decompressing said audio data packets, wherein said audio decoder further comprises a second audio data buffer for receiving the encoded audio data stream from said first audio data buffer and storing audio data packets and audio presentation time stamps;
• and
• a second audio presentation time stamp detector, coupled to said audio decoder, for detecting the presence of an audio presentation time stamp in the encoded audio data stream and outputting a load signal to said system time clock counter in said combined system and video decoder when audio data packets corresponding to said audio presentation time stamp are decoded.

An apparatus for receiving an encoded data stream comprising at least audio data packets, video data packets, audio presentation time stamps and video presentation time stamps and decoding said video data packets, said apparatus comprising:

• a system decoder for receiving the encoded data stream and separating said data stream into an encoded audio data stream and an encoded video data stream, which encoded audio data stream comprises at least audio data packets and audio presentation time stamps and which encoded video data stream comprises at least said video data packets and video presentation time stamps, and for outputting said audio data stream to an external audio decoder, wherein said system decoder further comprises a parser for separating the encoded data stream into an encoded audio data stream comprising audio data packets and audio presentation time stamps and an encoded video data stream comprising video data packets and video presentation time stamps and a memory having addressable storage, coupled to said parser, for addressing addressable storage to selectively store and read the encoded audio data, the encoded video data, or decoded video data to and from addressable storage;
• an audio presentation time stamp detector, coupled to said system decoder, for detecting the presence of an audio presentation time stamp in the encoded audio data stream;
• a system time clock counter, coupled to said audio presentation time stamp detector, for receiving said audio presentation time stamp as a start count when a signal is received from the external audio decoder indicating that audio data corresponding to an audio presentation time stamp has been decoded, incrementing said start count according to a predetermined clock frequency and outputting a system time clock;
• a video decoder, coupled to said system decoder and said system time clock counter, for receiving said system time clock and said encoded video data stream and decoding said encoded video data stream in synchronization with said system time clock;
• a latch, coupled to said audio presentation time stamp detector, for storing a detected audio presentation time stamp from the encoded audio data stream;
• and
• an audio data buffer, coupled to said system decoder, for receiving and storing audio data packets and audio presentation time stamps from said encoded audio data stream.