Video processing circuit

DETAILED DESCRIPTION A video input is received by the composite video to Y/C splitter which provides the luminance portion of the video signal to the luminance processing section and to the synchronizing signal (sync) separator, while also providing the chroma component to the chroma processor.
The luminance processor includes a back porch clamp to supply video with a constant back porch voltage to the sync splitter which splits the sync from the main video signal and directs it to a separate signal path for special processing.
The syncless video is applied to a potentiometer which serves as a video gain control whose output is applied to a white clipper which ensures that an excessive video signal cannot be outputted.
The video is then amplified and summed with the previously split off sync to form a normal video signal.
The split off sync signal is optionally amplified and clipped to output a standard amplitude over a range of input amplitudes.
Optionally sync can be taken from the sync separator or an external sync source.
The sync signal is then blanked to remove any residual, DC restored and supplied to the sync summer.
An electronic SPST switch selects between the luminance processor output and the output of the composite video to Y/C splitter to provide a user option of UNITY gain or no processing as well as a split screen function.
The switched luminance is then amplified to provide a standard video level to the luminance output connector.
The chroma processor receives its input from the chroma output of the composite video to Y/C splitter and is provided to three parallel paths--burst processing, active picture processing and unity, only one of which is active at any one time.
The three outputs of the three paths are summed in a chroma amplifier which provides the output signal to the chroma output connector.
The luminance and chroma signals are summed to provide a composite output to the composite output connector.
A sync separator receives video from luminance output of the composite video to Y/C splitter and provides horizontal and vertical sync as well as a burst pulse