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WO1999052298A1 - Ameliorations en synchronisation audio-video - Google Patents

Ameliorations en synchronisation audio-video Download PDF

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Publication number
WO1999052298A1
WO1999052298A1 PCT/GB1999/001041 GB9901041W WO9952298A1 WO 1999052298 A1 WO1999052298 A1 WO 1999052298A1 GB 9901041 W GB9901041 W GB 9901041W WO 9952298 A1 WO9952298 A1 WO 9952298A1
Authority
WO
WIPO (PCT)
Prior art keywords
audio
video
synchronisation
delay
time
Prior art date
Application number
PCT/GB1999/001041
Other languages
English (en)
Inventor
Barry Flannaghan
Original Assignee
Snell & Wilcox Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Snell & Wilcox Limited filed Critical Snell & Wilcox Limited
Priority to EP99914665A priority Critical patent/EP1068737A1/fr
Priority to AU33394/99A priority patent/AU3339499A/en
Publication of WO1999052298A1 publication Critical patent/WO1999052298A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/4302—Content synchronisation processes, e.g. decoder synchronisation
    • H04N21/4307—Synchronising the rendering of multiple content streams or additional data on devices, e.g. synchronisation of audio on a mobile phone with the video output on the TV screen
    • H04N21/43072—Synchronising the rendering of multiple content streams or additional data on devices, e.g. synchronisation of audio on a mobile phone with the video output on the TV screen of multiple content streams on the same device

Definitions

  • This invention relates to the processing of audio and video signals.
  • a common problem in the broadcast environment is the difference in delay experienced by the audio and video processes. With many new digital video processes in the signal chain and the consequential need for re- synchronisation, the delay of the video may often differ significantly from that of the audio. This causes the well known lip-sync error problem.
  • a video synchroniser operates by re-timing and, where necessary, either dropping or inserting fields.
  • Each video synchroniser may therefore add up to 40ms of video delay in a 50 field per second system such as PAL or 34ms in NTSC or other 60Hz systems. The precise delay will depend on often arbitrary system clocks. In new installations the audio is often "embedded" in the video channel and so when passing through the synchroniser it will experience the same delay as the video.
  • the present invention consists in one aspect in a digital video synchronisation process in which digital video and audio signals are delayed by the same varying amount to ensure synchronisation with a timing reference and, on dropping or repeating of a video field, the audio signal is time compressed or expanded to recover audio/video synchronisation over a time period governed by the maximum acceptable pitch change or other 2 degradation, characterised in that the trend in delay is monitored to enable prediction of the dropping or repeating of a video field and in that said time compression or expansion is initiated a selected time interval in advance thereof.
  • this time interval is selected to minimise the perceived loss of audio/video synchronisation. That is to say, regard is had to the asymmetry in the thresholds for perceived loss of synchronisation for advanced and retarded audio.
  • the video synchroniser shown in the drawing receives a digital video input signal with embedded audio and provides as an output synchronised with an externally generated timing reference, a digital video signal, again with embedded audio.
  • Digital video first passes into block 10; this extracts the audio data and the timing signals.
  • Video passes to the main memory 12 to be delayed until it is co-timed with the output timing signal extracted by block 14 from the reference input.
  • Block 16 measures the delay between the input and output timing signals and passes this figure to a microprocessor 18. The calculated delay is passed to the audio data memory 20.
  • the audio data and video data memories now give an identical delay.
  • a re-sampling digital filter 22 alters the audio data sampling rate to match the outgoing video in order that the audio data can be synchronously inserted by block 24 into the outgoing video data stream.
  • a synchroniser such as this when its input and output timing references are of a different frequency, as is usual, will occasionally drop or repeat a video frame. In effect, it gains or loses 40ms (at 50Hz). Whereas the resulting picture disturbance is often imperceptible, the same is not true for audio - it is not possible to cut or add 40ms of audio without major disturbance.
  • a typical implementation will compensate by re-sampling the audio to a higher or lower frequency.
  • the microprocessor 18 will initiate a process of reading extra audio samples from the audio memory 20.
  • a pitch change results, but if this is kept to less than 1%, it is unlikely to be noticed.
  • the audio will initially be adrift by a noticeable 40ms.
  • 8 seconds assuming 0.5% pitch change
  • the audio and video will once again be co-timed.
  • the microprocessor 18 will continually monitor the video delay and calculate the rate of change of delay over time.
  • the processor will initiate an increase in the audio delay to give a 0.5% pitch change.
  • the audio will be 30ms (at 50Hz) delayed with respect to the video. If the above discussed thresholds for perception of an audio delay are correct, this loss in synchronisation is imperceptible. Immediately after the frame loss the audio will be 10ms early. If the above- discussed thresholds for perception of an audio advance are correct, this loss in synchronisation is similarly imperceptible.
  • the audio and video will be co-timed.
  • the pitch change and the balance between worst case advance and delay may be controlled by the user.
  • Use of the invention has in this example and on the assumed perception thresholds, replaced a synchronisation error which is perceptible for up to 6 seconds, by a synchronisation error which is not perceptible at all.
  • rate conversion is only one example of a technique for time compression or expansion of the audio signal.
  • Numerous alternative techniques, such as silence compression, will be known to the skilled reader and fall within the scope of the claimed invention.

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Television Systems (AREA)

Abstract

En synchronisation de vidéo numérique, la tendance au décalage est contrôlée pour avoir la possibilité de prévoir la répétition ou l'abandon d'un champ vidéo. A un intervalle de temps choisi avant l'abandon ou la répétition du champ vidéo, on initie la compression ou l'expansion de temps audio. De cette manière, la perte de synchronisation audio demeure en dessous des seuils de perception.
PCT/GB1999/001041 1998-04-03 1999-04-06 Ameliorations en synchronisation audio-video WO1999052298A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP99914665A EP1068737A1 (fr) 1998-04-03 1999-04-06 Ameliorations en synchronisation audio-video
AU33394/99A AU3339499A (en) 1998-04-03 1999-04-06 Improvements relating to audio-video delay

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9807295.2A GB9807295D0 (en) 1998-04-03 1998-04-03 Improvements relating to audio-video delay
GB9807295.2 1998-04-03

Publications (1)

Publication Number Publication Date
WO1999052298A1 true WO1999052298A1 (fr) 1999-10-14

Family

ID=10829887

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1999/001041 WO1999052298A1 (fr) 1998-04-03 1999-04-06 Ameliorations en synchronisation audio-video

Country Status (4)

Country Link
EP (1) EP1068737A1 (fr)
AU (1) AU3339499A (fr)
GB (1) GB9807295D0 (fr)
WO (1) WO1999052298A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000041400A3 (fr) * 1999-01-06 2001-02-01 Koninkl Philips Electronics Nv Systeme de transmission d'un signal multimedia
WO2002001878A1 (fr) * 2000-06-28 2002-01-03 Grundig Ag Procede et dispositif de transmission synchrone de signaux
EP1414247A3 (fr) * 2002-10-22 2004-05-19 Broadcom Corporation Méthode et système de contrôle du débit de données pour un décodeur audio/vidéo
EP1289305A3 (fr) * 2001-08-07 2005-10-05 Hitachi Ltd. Appareil de traitement de signal numérique, décodeur de vidéo numérique, appareil d'enregistrement avec décodeur de vidéo numérique et méthode de traitement de signal
CN109906613A (zh) * 2016-09-14 2019-06-18 Dts有限责任公司 音频和视频的多模式同步渲染

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994029979A1 (fr) * 1993-06-09 1994-12-22 Intelligence At Large, Inc. Procede et appareil pour systeme de communication numerique multimedia
EP0648056A2 (fr) * 1993-09-30 1995-04-12 Thomson Consumer Electronics, Inc. Synchronisation audio/vidéo dans un système de transmission numérique
US5603016A (en) * 1994-08-03 1997-02-11 Intel Corporation Method for synchronizing playback of an audio track to a video track

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994029979A1 (fr) * 1993-06-09 1994-12-22 Intelligence At Large, Inc. Procede et appareil pour systeme de communication numerique multimedia
EP0648056A2 (fr) * 1993-09-30 1995-04-12 Thomson Consumer Electronics, Inc. Synchronisation audio/vidéo dans un système de transmission numérique
US5603016A (en) * 1994-08-03 1997-02-11 Intel Corporation Method for synchronizing playback of an audio track to a video track

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
"METHOD FOR SYNCHRONIZING AN AUDIO DIGITAL DATA STREAM WITH ANOTHER INFORMATION STREAM", IBM TECHNICAL DISCLOSURE BULLETIN, vol. 38, no. 4, 1 April 1995 (1995-04-01), pages 141, XP000516100, ISSN: 0018-8689 *
KAWAHARA K ET AL: "A SINGLE CHIP MPEG1 DECODER", 1995 SYMPOSIUM ON VLSI CIRCUITS, KYOTO, JUNE 8 - 10, 1995, 8 June 1995 (1995-06-08), INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS, pages 65/66, XP000557803, ISBN: 0-7803-2600-8 *
KIRBY D G ET AL: "A NEW TECHNIQUE TO MAINTAIN SOUND AND PICTURE SYNCHRONISATION", EBU REVIEW- TECHNICAL, no. 264, 1 January 1995 (1995-01-01), pages 13 - 21, XP000670474, ISSN: 0251-0936 *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000041400A3 (fr) * 1999-01-06 2001-02-01 Koninkl Philips Electronics Nv Systeme de transmission d'un signal multimedia
WO2002001878A1 (fr) * 2000-06-28 2002-01-03 Grundig Ag Procede et dispositif de transmission synchrone de signaux
US7418012B2 (en) 2000-06-28 2008-08-26 Grundig Multimedia B.V. Method and device for time-synchronized relaying of signals
EP1289305A3 (fr) * 2001-08-07 2005-10-05 Hitachi Ltd. Appareil de traitement de signal numérique, décodeur de vidéo numérique, appareil d'enregistrement avec décodeur de vidéo numérique et méthode de traitement de signal
EP1414247A3 (fr) * 2002-10-22 2004-05-19 Broadcom Corporation Méthode et système de contrôle du débit de données pour un décodeur audio/vidéo
US7466362B2 (en) 2002-10-22 2008-12-16 Broadcom Corporation Data rate management system and method for A/V decoder
CN109906613A (zh) * 2016-09-14 2019-06-18 Dts有限责任公司 音频和视频的多模式同步渲染
CN109906613B (zh) * 2016-09-14 2022-09-13 Dts有限责任公司 音频和视频的多模式同步渲染

Also Published As

Publication number Publication date
GB9807295D0 (en) 1998-06-03
EP1068737A1 (fr) 2001-01-17
AU3339499A (en) 1999-10-25

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