Abstract: A video signal processing circuit includes a level shifter for shifting the dc level of an input luminance signal; a gain adjuster for increasing the gain for the luminance signal when the luminance signal has a low luminance level and for decreasing the gain for the luminance signal when the luminance signal has a high luminance level; and a shifting amount setting unit for setting the amount for shifting the dc level on the basis of the frequency distribution of the luminance signal and the rate of modulation of the luminance signal.

Abstract: In digital VTR's, a change in levels and frequency response in the VTR analog circuits or analog transmission paths causes a problem of deterioration in the video picture quality due to quantization distortion when dubbing is repeated based on an analog video signal. In order to solve this problem, according to the present invention, a level reference signal is superposed as a predetermined digital value on an output video signal of the reproducer, then based on the reference signal, the level and the frequency response of the analog transmission path are corrected in the recorder. Thus, dubbing can be achieved by using digital VTR's without any influence of quantization distortion.

Abstract: A broadcasting signal detecting circuit of a SECAM system can easily determine whether the received broadcasting is from a PAL or SECAM system in accordance with the existence of a color burst at the position of a delayed burst gate pulse, using the fact that within the back porch of the horizontal sync signal, the color burst loading period is different.