Black and burst

The sub carrier 'burst' seen from waveform monitor

Black and burst also known as bi-level sync and black burst is an analogue signal used in broadcasting. It consists of a video signal with a blacked-out picture.[1] It is used to synchronise video signals together to put them on the same timing plane. It provides vertical timing that allows synchronous switching between two video signals.

Black and burst also locks the colour phase between signals. The burst section of the waveform allows the phase relationship of the two signals to be timed together by sending pulses to the internal oscillators of the equipment.

History

PAL is a broadcast transmission standard for Europe, and from this standard the black and burst analogue reference was created. Black and burst became common when the PAL video format became standard in Europe, then became the most commonly used reference signal.

Black and burst is now a predecessor to tri-level sync.

Waveform

Its natural waveform is a negative pulse of -40 IRE followed by 10 cycles of the colour sub carrier of video. For PAL video, the frequency of the sub carrier is 4.43361875MHZ.[2]

See also

References

  1. ↑ Michael Talbot-Smith (1 January 1994). Audio Engineer's Reference Book. Focal Press. ISBN 978-0-7506-0386-7.
  2. ↑ TV and Video Engineers Handbook, Third Edition - Eugene Trundle. Page 14. 1999 ISBN 0-7506-4194-0 Newnes Press


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