Anyone who has read my "Technology Corner" column in TV Technology is aware that the topic of audio-video synchronization and lip sync has been dealt with there more than once. As the world of television production, post production, distribution, and broadcast has become increasingly digitized, the differential audio and video processing and throughput delays characteristic of digital video and audio systems have multiplied the potential for audio-video synchronization errors to develop and worsen as the signals propagate through the system.
In order to address the lip sync issue, the SMPTE Committee on Television Systems Technology, S22, has formed an Ad Hoc Group on Lip Sync Issues. Its charter is to review all aspects of this problem and to recommend solutions. To this end, the ad hoc group is requesting information from interested companies and individuals. It is specifically requesting information relating to the following areas (quoted from the SMPTE RFI):
- 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
Responses to this SMPTE request are to be conveyed to ad hoc group chair Graham Jones of NAB. He may be reached by telephone at NAB headquarters, or via e-mail at .
Lip sync errors are ubiquitous in today's television world. Some in the industry believe that a delay of a given duration is more noticeable, and therefore worse, in HD than in SD. We urge anyone who has input for the SMPTE ad hoc group to contact Graham as soon as possible.