Abstract: A video signal processing system improves the image quality displayed in a CRT or printed by a video printer. In order to produce natural and fine video signals, pixel data corresponding to an intermediate position between two neighboring pixels, are produced from pixel data of the neighboring two pixels. The pixel data corresponding to the intermediate position is produced by a convolution operation with respect to the pixel data of the two neighboring pixels and a quantized value of an impulse response signal.

Abstract: A signal modification circuit receives an input signal and produces an output having a modified characteristic. When the signal modification circuit is embodied in an audio circuit receiving an analog audio signal having a first variant level at its input, the audio circuit produces an output signal having a second variant level in which a frequency characteristic in a high frequency range is modified so that the second variant level decreases in accordance with a function of l/fm (f being frequency and m being an integer determined depending upon the nature of the audio signal) relative to the first variant level while being trapped in selected discrete frequencies. For this purpose a combination of a low-pass filter and a plurality of trap filters connected in series with one another, or a combination of a low-pass filter and a plurality of band-pass filters connected in parallel to one another.

Abstract: A data generator generates digital data at a sampling time interval .sub..DELTA. T (sampling frequency f.sub.s =1/.DELTA.T), and the three latest items of digital data V.sub.-1, V.sub.0, V.sub.+1 are repeatedly latched successively in three latch circuits every 3.multidot..sub..DELTA. T. A pulse response signal generator outputs unit pulse response signals of period 3.multidot..sub..DELTA. T at the time interval .multidot..sub..DELTA. T, and three multiplying-type DA converters multiply these three unit pulse response signals .phi..sub.0 (t+.sub..DELTA. T), .phi..sub.0 (t), .phi..sub.0 (t-.sub..DELTA. T) by the digital data V.sub.-1, V.sub.0, V.sub.+1, respectively, at a speed of a.multidot.f.sub.s (a times in time .sub..DELTA. T). The outputs of these multiplying-type DA converters are combined into an analog signal S.sub.A, which is delivered as an output.

Abstract: A digital analog converter which is especially suitable for use in converting a digital audio signal into an analog audio signal includes a unit pulse response signal generator for successively generating unit pulse response signals at a predetermined time interval, a digital data generator for generating digital data at the predetermined time interval, a multiplier for multiplying a unit pulse response signal generated at a certain time by a predetermined item of the digital data, and a mixer for producing an analog signal output by combining the unit pulse response signals that have been multiplied by the digital data.