Abstract: A video signal-processing device that can improve the apparent contrast of the luminance signal at a television receiving set includes a quantity of black expansion computing section for computationally determining the quantity of black expansion when the luminance component of the input video signal is not higher than a first luminance level, a gain controller for regulating the quantity of black expansion as computationally determined by the quantity of black expansion computing section, a quantity of black expansion adding section for generating an output video signal by adding the quantity of black expansion regulated by the gain controller to the luminance component of the input video signal, and a vertical span adding block for integrating the luminance component of the output video signal not higher than a second luminance level for a field.

Abstract: A video signal-processing device that can improve the apparent contrast of the luminance signal at a television receiving set includes a quantity of black expansion computing section for computationally determining the quantity of black expansion when the luminance component of the input video signal is not higher than a first luminance level, a gain controller for regulating the quantity of black expansion as computationally determined by the quantity of black expansion computing section, a quantity of black expansion adding section for generating an output video signal by adding the quantity of black expansion regulated by the gain controller to the luminance component of the input video signals and a vertical span adding block for integrating the luminance component of the output video signal not higher than a second luminance level for a field.

Abstract: A dark level restoring circuit for a television receiver which receives a video signal, clamps a pedestal portion of the video signal to a reference pedestal level by a pedestal clamper, compares the output of the pedestal clamper with a reference dark level, and amplifies the compared result by a gain control amplifier. The output of the pedestal clamper and the amplified compared result are synthesized, the dark peak level is held, and the held dark peak level and the reference pedestal level are compared wherein the gain of the gain control amplifier is controlled by the compared result. A blanking signal is received, and a mute signal is generated which corresponds to a non-video signal portion when the effective raster size of the video signal is smaller than the size of a face plate of a cathode ray tube to which the video signal is supplied.

Abstract: A vertical synchronization processing circuit includes a counter for counting a clock signal synchronized with a horizontal sync. signal, a circuit for resetting the counter in response to a vertical synchronization signal within a predetermined limit prohibiting reset due to a non-standard signal, a memory for storing the data counted at the timing of reset, and a circuit for changing a predetermined limit prohibiting reset due to a non-standard signal according to the data from the memory. A circuit for discriminating an existence of a vertical synchronization interval can also be provided along with a second resetting circuit for resetting the counter if the discriminating circuit detects the existence of the vertical synchronization interval when the counter counts a predetermined number of clock signals in case there is not a vertical synchronization pulse within the predetermined limit.