Saturday 1 April 2017

programmable logic - AC-Coupling on Composite video


Many sources say that composite video input should be AC-coupled. Voltage levels for blank, black and white signal are also specified. How is it possible to detect these voltage levels after AC coupling (aka dc-blocking capacitor)?


Doesn't the DC-component (average) of the signal vary wildly depending if the content is all black (0V-0.3V) or all white (0V-1V)?




Answer



Yes, it does. That's why the next step is usually DC restoration, which clamps the sync peaks to a specific voltage. (The component following the blocking capacitor is a diode, rather than a resistor.) This then establishes the correct relative voltages for "black" and "white".


No comments:

Post a Comment

arduino - Can I use TI's cc2541 BLE as micro controller to perform operations/ processing instead of ATmega328P AU to save cost?

I am using arduino pro mini (which contains Atmega328p AU ) along with cc2541(HM-10) to process and transfer data over BLE to smartphone. I...