The luminance signal record circuit and its manner null when regenerating between the image systems of difference containment compatibility

摘要

An improved adaptive folding circuit for a video signal recording/reproducing system. The improved adaptive folding circuit has an adaptive emphasis circuit and an adaptive deemphasis circuit for receiving a luminance signal. The adaptive emphasis circuit includes a horizontal high pass filter for filtering the luminance signal and a horizontal low pass filter for filtering the luminance signal. A level detector is provided to receive the output of the horizontal high pass filter, the output of the level detector being provided to a look-up-table. A soft switch is controlled by the output of the look-up-table to provide for output of a proper mixture of the outputs of the horizontal high pass filter and/or the horizontal low pass filter. The adaptive deemphasis circuit attenuates the high frequency luminance level and outputs an adaptively deemphasized luminance signal to a modulator for modulation according to a modulation frequency Ff. An adder receives the outputs of the soft switch and the modulator and provides an improved adaptively folded luminance signal for output through a low pass filter and digital-to-analog converter.