Sunday, 4 May 2014

Composite Video Signal

Composite Video Signal: The composite video signal is the video signal into which blanking and synchronizing pulses are inserted at proper timings.

Composite video signal consists of a camera signal corresponds to desired picture information, blanking pulses to make the retraces invisible and synchronizing pulses to synchronize the transmitter and receiver scanning.

Video signal of the composite video signal varies in between 10 % to 72 % levels. The 10 % level of the signal corresponds the peak white level while the 72 % level of the signal corresponds to peak dark level. Gray shades are represented by the signals with the amplitude level varying in between 10 % and 72 % levels.

Blanking pulses are placed from 72 % level to 75 % level. Sync pulses are placed from 75 % level to 100 % level (both vertical & horizontal during the blanking periods).

Peak White level: 10 to 12 % level is called peak white level because when video signal is having this amplitude a peak white spot is produced on the picture tube.

Peak Black level: 72% level is called black level. This level produces blackness on the raster.

Blanking level: 75 % level is called blanking level because the blanking pulses are inserted at this level.

Pedestal Height: The difference between blanking level and average brightness level is called pedestal height.


DC level or average brightness level: This level corresponds to the average value of the complete frame. 

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