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4. Synchronization and clocks
The digitization of signals has led to the emergence of a very important problem in the transfer of signals between devices: synchronizing the clocks of each device. The AES3 standard elegantly solves this problem between transmitting and receiving equipment: the transmitter inserts its clock into the transmitted stream and allows the receiver to synchronize with it. But this is not enough when several devices need to work in parallel, or when the receiver's clock is imposed, for example by a video clock.
Synchronization requires two things. Firstly, sampling frequencies must be identical, guaranteeing the same number of samples every second. Secondly, audio frames must occur at the same instant, within tolerances. Sound engineers pay a great deal of attention to the quality of clock signals, as the quality of the restored analog signal depends on them.
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Synchronization and clocks
Inserting audio into video
Bibliography
General works
- WATKINSON (J.) - The Art of Digital Audio. - Focal Press (1991).
- BALLOU (G.M.) (éd.) - Handbook of Sound Engineers : The New Audio Cyclopedia. - Butterworth-Heinemann (1998).
In Engineering...
Norms, standards
- AES Recommended practice for digital audio engineering – Serial transmission format for two-channel linearly represented digital audio data - AES3-2003 -
- Specification of the digital audio interface (the AES/EBU interface) - EBU Tech. 3250-E - 2004
- Interface audionumérique pour les studios de radiodiffusion - UIT-R BS.647-2 - 03-92
- AES information document for digital audio engineering – Transmission...
Organizations
Audio Engineering Society (AES) http://www.aes.org
American National Standard Institute (ANSI) http://www.ansi.org
European Broadcasting Union (EBU)
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