There is an increasing awareness, both in broadcasting engineering circles and in the viewing audience, that audio-video synchronization errors in broadcasting, usually seen as problems with lip-sync, are occurring more frequently than they used to and often with greater magnitude. The Society of Motion Picture and Television Engineers S22 Committee on Television Systems Technology has formed an Ad Hoc Group on Lip Sync Issues to review all aspects of this problem and make recommendations for solutions.
SMPTE is therefore issuing this Request for Information from interested companies or individuals, particularly relating to the following areas:
-Sources of differential audio-video delay in television production, post-production, and distribution.
-Audio-video delay issues through professional MPEG encoding and decoding systems.
-Differential audio-video delay arising in consumer receiver, decoding, and display devices.
-Out-of-service methods of measuring differential audio-video delay.
-In-service (during program) methods of measuring differential audio-video delay.
-Devices for correcting differential audio-video delay at different points in the broadcast chain.
It is noted that there is an ATSC Implementation Subcommittee Finding: "Relative Timing of Sound and Vision for Broadcast Operations" (see www.atsc.org/standards/is_191.pdf). There is also an ITU recommendation: ITU-R BT.1359-1, "Relative Timing of Sound and Vision for Broadcasting" (available from www.itu.int/publications/bookshop/index.html). These references are provided for information only and it is noted that some broadcasters have adopted target tolerances for synchronization errors that are smaller than those indicated by the ATSC and ITU.
SMPTE is particularly interested to hear from manufacturers with practical solutions or proposals for measurement and correction of audio-video synchronization errors, and those willing to participate in development of related standards.
Responses should be sent in the first instance, and as soon as possible, to the ad hoc group chair, Graham Jones of NAB at gjones@nab.org.
NAB Science and Technology www.nab.org/scitech
ATSC www.atsc.org
SMPTE www.smpte.org
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