Abstract: A component of color difference signal is detected from a video component signal, and its color saturation information is compared with a predetermined threshold level, then in response to the comparison result, information is generated in order to control phase modulation such as, when the information is smaller than the threshold level, phases of color burst signals are modulated during a specified period, and when the information is larger than the threshold level, the phase stays as standard. The generated information is added to the color video signal. These steps can avoid unpleasant striped color noises appeared on a conventional color TV receiver, the unpleasant striped color noises has been caused by a modified color burst signal without the above steps.

Abstract: A picture quality improving circuit for automatically obtaining a corrected image by capturing features of the input video signals. The circuit first compares an input luminance signal with a plurality of reference values, measures the results of the comparison by a plurality of counters and obtains a cumulative histogram within a predetermined period of time. Next, the cumulative histogram signals are stored in a latch circuit for a predetermined period of time, and an interpolation circuit determines and outputs a correction signal corresponding to the input luminance signal by interpolating the cumulative histogram. Accordingly, when a large number of dark signals exist in the input luminance signal, the cumulative histogram signals will describe an upwardly projecting graph, and the dark portions of the signal will be extended in a bright direction. Thereby, the picture quality can be improved.

Abstract: Input analog image signals are converted to digital image signals and applied to a demodulation circuit and a synchronous circuit. In the demodulation circuit, the digital image signals are demodulated and then compressed by a compression circuit. In the synchronous circuit, the digital image signals are synchronously processed so as to output horizontal pulses in accordance with a horizontal synchronizing signal contained in the digital image signals and so as to output phase difference information denoting a timing difference between the output of a horizontal pulse and an interpolated crossing of the horizontal synchronizing signal across a synchronizing threshold. A boundary at an image portion and a mask portion of an output image signal is corrected so that the boundary is substantially free of jitter using the horizontal pulses and the phase difference information output by the synchronous circuit.

Abstract: A comb filter serves to process an input digital video signal which is derived from an analog video signal by a analog-to-digital conversion including a sampling process responsive to a system clock signal. The comb filter includes a separating device for separating the input video signal into a plurality of video signals which are offset with each other in timing and which have a clock rate equal to 1/N times a clock rate of the system clock signal where N denotes a predetermined natural number greater than 1. A first delaying device serves to delay a first output signal of the separating device. A chroma signal processor separates a first chroma signal in response to the first output signal of the separating device and an output signal of the first delaying device. A first subtracter serves to subtract the first chroma signal from the output signal of the first delaying device. A second delaying device serves to delay a second output signal of the separating device.

Abstract: A video chroma signal processing circuit in which a composite video signal, formed of an analog luminance signal and an analog chrominance signal, is separated into Y and C components and converted into digital codes by AD converters and processed by processing circuits. The outputs of the processing circuits are converted into analog signals again with DA converters to produce a picture image; wherein, it is intended to obtain a wide band of a luminance signal by making efficient use of an AD converter for a chrominance signal and to improve horizontal resolution. The apparent sampling frequency is doubled by sampling the AD converter for a chrominance signal with a phase reverse to that of an AD converter for a luminance signal so as to improve the horizontal resolution of the luminance signal.

Abstract: A video signal processing circuit for providing a compressed picture insertion function in a television receiver, whereby a compressed-size picture expressed by one video signal is displayed as an insert within a full-size picture that is expressed by another video signal, by demodulating and combining the video signals, which can be of respectively different television standards, such as the PAL and MUSE standards. The circuit utilizes only one demodulator circuit for one video signal and two demodulator circuits for the other signal. When one of the video signals is in accordance with a broadcast standard such as the MUSE standard, which requires a large-scale demodulator circuit, a significant reduction in overall circuit scale is achieved by comparsion with the prior art, in which two demodulator circuits are required for each of the video signals.