EP0648056A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Audio/video synchronization in a digital transmission system
Assignee: Technicolor USA Inc
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Filing: 1994-09-28
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Granted: —
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Expires: 2014-09-28
Abstract
Abstract A receiver (FIGURE 2) for decoding associated compressed video and audio information components transmitted in mutually exclusive "frames" of data with respective time stamps PTS vid and PTS aud respectively, includes a controller (216) which is responsive to the respective received time stamps to provide coarse synchronization by delaying or skipping respective frames of one or the other of the components to approximately time align the two components. Fine synchronization is provided by adjusting the processing or clock frequency (215) of the audio signal processor (212) independent of the video processor(214). The control for the frequency adjustment is related to the difference between audio and video time stamps.
Inventors
- 👤 Douglas Edward Lankford
- 👤 Michael Scott Deiss
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 11:27
CPC Classifications
H; H04; H04N; H04N21/00; H04N21/40; H04N21/43; H04N21/4302; H04N21/4305; H04N21/41; H04N21/426; H04N21/4307; H04N21/43072; H04N21/434; H04N21/4341; H04N21/439; H04N21/4392; H04N21/80; H04N21/85; H04N21/854; H04N21/8547; H04N5/00; H04N5/04; H04N5/44; H04N5/60; H04N5/602; H04N7/00; H04N7/24; H04N7/52; H04N7/54; H04N7/56
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
221 words
Apparatus for providing synchronized, reproduced audio and video signals from recovered compressed audio and video signal, which audio and video signals include respective time stamps PTSaud and PTSvid determined at predetermined intervals and related to an encoder system clock, said apparatus characterized by: a source (200) of said recovered compressed audio and video signals, and a source (208, 37) of reference frequency; a counter (208, 36) responsive to said reference frequency for providing a sequence of values modulo N where N is an integer; decompression apparatus (214) responsive to said recovered compressed video signal for providing decompressed video signal and said time stamp PTSvid; decompression apparatus (212) responsive to said recovered compressed audio signal for providing decompressed audio signal and said time stamp PTSaud; means (222, 217) for capturing values (LVS) of said sequence at predetermined times related to the provision of said time stamps PTSvid and for generating the difference (Δ V-PTS) of said values LVS and corresponding time stamps PTSvid; and (220, 218) for capturing values (LAS) of said sequence at predetermined times related to the provision of said time stamps PTSaud and generating the difference (Δ A-PTS) of said values LAS and corresponding time stamps PTSaud; and means (219, 216, 215) responsive to said differences Δ V-PTS and Δ A-PTS for synchronizing the decompressed audio and video signals.
Claim 2
Dependent Claim
48 words
The apparatus set forth in claim 1 characterized in that said means for synchronizing the decompressed audio and video signals includes means (216, 212) for skipping/repeating predetermined intervals of decompressed audio signal responsive to the difference the between values Δ V-PTS and Δ A-PTS exceeding a predetermined value.
Claim 3
Dependent Claim
47 words
The apparatus set forth in claim 1 characterized in that said means for synchronizing the decompressed audio and video signals includes means (216,214) for skipping/repeating predetermined intervals of decompressed video signal responsive to the difference the between values Δ V-PTS and Δ A-PTS exceeding a predetermined value.
Claim 4
Dependent Claim
69 words
The apparatus set forth in claim 1 characterized in that said decompression apparatus (212) responsive to said recovered compressed audio signal provides decompressed audio signal at a rate determined by a processing (215) clock signal and said means for synchronizing the decompressed audio and video signals further includes means (216) responsive to the differences (Δ V-PTS) -(Δ A-PTS) , for variably adjusting the rate of said processing clock signal.
Claim 5
Dependent Claim
177 words
Apparatus for providing synchronized, reproduced audio and video signals from recovered compressed audio and video signal, which audio and video signals include respective time stamps PTSaud and PTSvid determined at predetermined intervals and related to an encoder system clock, said apparatus characterized by: a source (200) of said recovered compressed audio and video signals, and a source (208) of a local clock signal; decompression apparatus (214) responsive to said recovered compressed video signal for providing decompressed video signal and said time stamp PTSvid; decompression apparatus (212) responsive to said recovered compressed audio signal for providing decompressed audio signal and said time stamp PTSaud; means (217, 218, 220, 222) for determining, in cycles of said local clock signal, the time T between occurrences of corresponding time stamps PTSaud and PTSvid; means (219) for calculating the difference between values of corresponding time stamps PTSaud and PTSvid and comparing such difference with said time T to generate an A/V synchronization error signal; and means (215, 216)responsive to said A/V synchronization error signal for synchronizing the decompressed audio and video signals.
Claim 6
Dependent Claim
62 words
The apparatus set forth in claim 5 characterized in that said means for determining the time T comprises means including a counter for counting cycles of said local clock signal and providing a value representing said time T which is equal to the number of cycles of said clock signal occurring between the occurrences of said corresponding time stamps PTSaud and PTSvid.
Claim 7
Dependent Claim
85 words
The apparatus set forth in claim 6 characterized in that said means including a counter comprises: a counter responsive to said local clock signal for providing a sequence of count values modulo N where N is an integer; and means responsive to an occurrence of said time stamps PTSaud for capturing a first count value and responsive to the occurrence of a corresponding time stamp PTSvid for capturing a second count value; a subtractor for determining the difference between said first and second count values.
Claim 8
Dependent Claim
46 words
The apparatus set forth in claim 5 characterized in that said recovered compressed audio and video signal includes system clock references (SCR's), and said apparatus further includes means responsive to said system clock references for generating said local clock signal synchronous with said encoder system clock.
Claim 9
Dependent Claim
57 words
The apparatus set forth in claim 5 characterized in that said respective decompression apparatus provide decompressed video signals in predetermined intervals and decompressed audio signal in further predetermined intervals, and said means for synchronizing includes apparatus responsive to said A/V synchronization error signal for skipping or repeating ones of said predetermined intervals of said decompressed audio signals.
Claim 10
Dependent Claim
55 words
The apparatus set forth in claim 9 characterized in that said decompression apparatus for providing decompressed audio signal includes a source of a processing clock signal for operating said decompression apparatus and said means for synchronizing includes further apparatus responsive to said A/V synchronization error signal for varying the frequency of said processing clock signal.
Claim 11
Dependent Claim
26 words
The apparatus set forth in claim 10 characterized in that said apparatus for varying the frequency of said processing clock signal includes a binary rate multiplier.
Claim 12
Dependent Claim
57 words
The apparatus set forth in claim 7 characterized in that said respective decompression apparatus provide decompressed video signals in predetermined intervals and decompressed audio signal in further predetermined intervals, and said means for synchronizing includes apparatus responsive to said A/V synchronization error signal for skipping or repeating ones of said predetermined intervals of said decompressed audio signals.
Claim 13
Dependent Claim
55 words
The apparatus set forth in claim 12 characterized in that said decompression apparatus for providing decompressed audio signal includes a source of a processing clock signal for operating said decompression apparatus and said means for synchronizing includes further apparatus responsive to said A/V synchronization error signal for varying the frequency of said processing clock signal.
Claim 14
Dependent Claim
131 words
Apparatus for providing synchronized, reproduced audio and video signals from recovered compressed audio and video signal, which audio and video signals include respective time stamps PTSaud and PTSvid determined at predetermined intervals and related to an encoder system clock, said apparatus comprising respective decompression apparatus for decompressing said compressed audio and video signals and producing said time stamps PTSaud and PTSvid; and means responsive to the occurrence of said time stamps PTSaud and PTSvid for measuring the time between an occurrence of a PTSaud and the next occurring PTSvid and adjusting the decompression rate of at least one of said decompression apparatus such that the time between an occurrence of a PTSaud and the next occurring PTSvid substantially equals the difference in values of said PTSaud and the next occurring PTSvid.
References Cited (Backward Citations)
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