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lip sync

Lip synchronization (lip sync) is the matching of lip movement with speech. The problem of lip sync occurs in movies, videos, and on television; especially in digital video and digital TV. It can be due to video production, signal processing or transmission.

In high-definition television( HDTV), the incoming video signal is processed through complex digital image processing. This includes de-interlacing, which means converting the interlaced video back to one with progressive scan, format conversion, noise reduction, and several other processes. This image processing takes a certain amount of time to execute and must be synchronized with the audio signal so that there is no time delay between the image and the audio. Such a time delay leads to asynchrony with lip movement in speech. Most HDTV sets have appropriate compensation circuits that delay the sound relative to the picture so that the lip movement is synchronous with the speech.

During transmission, lip synchronization can be impaired by different transmission paths, for example, when the picture is transmitted via satellite and the sound via terrestrial networks and both are recombined on the transmitter side.

Informations:
Englisch: lip sync
Updated at: 08.04.2010
#Words: 182
Links: synchronization (SYN), speech, television (TV), digital video (DV), television (TV)
Translations: DE
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