Stream synchronization method and apparatus for MPEG playback system
First Claim
1. An apparatus for controlling playback of audio and video signals from an encoded data stream comprising at least audio data packets, video data packets, audio presentation time stamps and video presentation time stamps, said apparatus comprising:
- a system decoder for receiving the encoded data stream and separating said data stream into an encoded audio data stream comprising at least audio data packets and audio presentation time stamps and an encoded video data stream comprising at least said video data packets and video presentation time stamps;
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 system time clock counter for receiving a start count, 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;
an audio decoder for receiving said audio data packets from the encoded audio data stream and decoding said audio data packets;
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 when audio data packets corresponding to said audio presentation time stamp are decoded; and
a step controller, coupled to said system time clock counter, said first audio presentation time stamp detector, and said audio decoder, for receiving a step control signal and allowing input of a start count to said system time clock counter from an external source.
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Accused Products
Abstract
A multimedia system including an audio/video decoder/decompresser for decoding/decompressing a compressed encoded audio/video data stream to generate video images for display and audio signals for audible reproduction. The multimedia system includes an integrated system and video decoder with an audio/video synchronization circuit for substantially synchronizing the display of video images with audio playback. In addition, a step control is provided to allow for viewing of video images on a frame-by frame basis or to freeze or play video in slow motion. When step control is activated, audio output is muted. Audio data corresponding to displayed video is transmitted to the muted audio decoder. An internal system clock may be suppressed to the system clock counter. An external CPU may provide system clock start times corresponding to video frames to be displayed. The external CPU may increment the system clock counter by a an amount corresponding to the difference between a successive frame or number of frames. When nominal playback is resumes, the audio and video data streams are substantially in synchronization.
196 Citations
46 Claims
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1. An apparatus for controlling playback of audio and video signals from an encoded data stream comprising at least audio data packets, video data packets, audio presentation time stamps and video presentation time stamps, said apparatus comprising:
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a system decoder for receiving the encoded data stream and separating said data stream into an encoded audio data stream comprising at least audio data packets and audio presentation time stamps and an encoded video data stream comprising at least said video data packets and video presentation time stamps; 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 system time clock counter for receiving a start count, 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; an audio decoder for receiving said audio data packets from the encoded audio data stream and decoding said audio data packets; 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 when audio data packets corresponding to said audio presentation time stamp are decoded; and a step controller, coupled to said system time clock counter, said first audio presentation time stamp detector, and said audio decoder, for receiving a step control signal and allowing input of a start count to said system time clock counter from an external source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for controlling the playback of audio and video signals from an encoded data stream including step control, the method comprising the steps of:
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in a combined system and video 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 comprising at least audio data packets and said audio presentation time stamps and an encoded video data stream comprising 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; setting in said combined system and video decoder, a system time clock counter to a start count corresponding to the detected audio presentation time stamp and incrementing said start count according to a predetermined clock frequency and outputting a system time clock; and decoding/decompressing said encoded video data stream in synchronization with said system time clock, wherein said method of step control further comprises the steps of; receiving a step control signal; suppressing the reception of said audio presentation time stamp as a start count by said system time clock counter; allowing input of a start count to said system time clock counter from an external source; and selectively passing audio data corresponding to a start count in said system time clock counter to said audio decoder. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. 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 sounds reproduction devices, the multimedia system comprising:
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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 comprising at least audio data packets and said audio presentation time stamps and an encoded video data stream comprising at least said video data packets and said video presentation time stamps; 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 system time clock counter, coupled to said first audio presentation time stamp detector, for receiving a start count 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; 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 when audio data packets corresponding to said audio presentation time stamp are decoded; and a step controller, coupled to said system time clock counter, said first audio presentation time stamp detector, and said audio decoder, for receiving a step control signal and allowing input of a start count to said system time clock counter from an external source. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44)
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45. An apparatus for controlling playback of audio and video signals from an encoded data stream comprising at least audio data packets, video data packets, audio presentation time stamps and video presentation time stamps, said apparatus comprising:
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a system decoder for receiving the encoded data stream and separating said data stream into an encoded audio data stream comprising at least audio data packets and audio presentation time stamps and an encoded video data stream comprising at least said video data packets and video presentation time stamps; a system time clock counter for receiving a start count, 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; an audio decoder for receiving said audio data packets from the encoded audio data stream and decoding said audio data packets; an 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 when audio data packets corresponding to said audio presentation time stamp are decoded.
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46. A method for controlling the playback of audio and video signals from an encoded data stream including step control, the method comprising the steps of:
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in a combined system and video 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 comprising at least audio data packets and said audio presentation time stamps and an encoded video data stream comprising 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; receiving, in audio decoder, the encoded audio data stream and storing audio data packets and audio presentation time stamps; decoding/decompressing said audio data packets in said audio decoder; setting in said combined system and video decoder, a system time clock counter to a start count in response to a detected audio presentation time stamp and incrementing said start count according to a predetermined clock frequency and outputting a system time clock; and decoding/decompressing said encoded video data stream in synchronization with said system time clock.
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Specification