Abstract: Color television signals obtained by scanning a still picture are converted into digital video signals and stored in video frame memory for delaying the signals. Undelayed and delayed digital video signals are added together to produce a luminance signal in which the color carrier is suppressed. A circuit for detecting a change of picture provides a start signal after which the first frame of a still picture is stored and is then recycled until there is another picture change. To reduce the effect of recycling, the continuously supplied picture signal is modified by a factor of 1-k, and the recycled picture is modified by the factor k, wherein k varies between 0 and 1 (or 100%) and is a gradually rising function whose rise time extends over a multiplicity, for example 2-4, video frame periods.

Abstract: The correction factor applied to a delayed television signal in a television noise reduction system and the complement of that factor applied to the undelayed television signal from which the delayed television signal is derived after averaging with the weighted delayed signal of an earlier of the preceding television frames, are modified in accordance with whether the source of the origninal television signals is or is not repeating at least one field of the television frames before going on to the next. The variation of the correction factor can also be made to depend on the number of repetitions of each frame. In an automatic system, operating in connection with a film scanner capable of scanning a motion picture film at different speeds (frames per second) to produce television signals in accordance with either the American or European television standard, the correction factor is set at the value 1 whenever a film frame is scanned for more than two half-frame television fields.

Abstract: An improved movement detector (8) for a television noise reduction system interposes a recursive filter (12) between the absolute value circuit (9) which signalizes the magnitude difference between delayed and undelayed television signals and the function generator (11) which forms the correction factor k which controls the degree of noise reduction. Especially for filtering changes in the vertical direction and the recursive filter involves a considerable saving in equipment.

Abstract: The amount of noise reduction of a television signal produced by averaging corresponding pixels from one frame to the next is reduced by a correction factor when motion in the picture is detected. In order to prevent very active motion from disturbing detection of the noise level, a noise level measurement signal is subjected to a hold of its value in a time briefly preceding a highly active motion in the picture until a time shortly after the end of such highly active motion. The motion signal is processed so as to provide such a hold only when motion is highly active in the picture, and that signal is prolonged in a further circuit so that it will have a duration long enough to cover build-up of that motion and its trailing off, when the noise measurement signal is delayed by about half of the prolongation, so that the noise measurement level that is held corresponds to the noise level prior to the buildup of the motion which shortly thereafter becomes highly active.

Abstract: In a system for noise reduction in a television signal utilizing a full frame picture store to enable averaging of corresponding signals of successful frames for noise reduction and having also a motion detector, the signal representing motion is passed through a combination of a low-pass filter and a threshold circuit of which, respectively, the cut-off frequency and the threshold value are controllable as a function of the noise amplitude. As a result, at low noise content of the input signal, no disturbing loss of sharpness of moving edges occurs, whereas at higher noise amplitudes, although noise reduction is at the cost of some loss of edge sharpness, the annoying effects of having noise reduction controlled by the noise itself, are avoided.

Abstract: A method and apparatus for representing the amplitude curve of a selected portion of a video signal upon the picture screen of a video display device, at least the selected portion being in digital form and not requiring conversion to analog form prior to such representation.This is achieved by using the line structure of the line raster produced on the picture screen of the video display device as a digital-analog converter. The range of possible digital values for the individual picture elements of the selected line of the video signal are allocated as reference values to respective lines of the line raster, and during each line period of the line raster the digital values of the elements are compared in succession with the appertaining reference value.

Abstract: The video signals are applied to a standard aperture correction circuit and also to a non-linear circuit. The output of the non-linear circuit and the output of the standard aperture correction circuit are applied to the two inputs of a modulator whose output is combined in a summing circuit with video signals delayed by a time delay corresponding to the time delay in the non-linear circuit and modulator. In a preferred embodiment the non-linear transfer function corresponds to A.sup.2 -A and is achieved by a double-balanced modulator the DC level at whose inputs is adjusted to yield the desired transfer function.

Abstract: Correction signals for aperture correction of video signals are generated in such a way that the peak values of the correction signal produced in an aperture corrector which are dependent upon the frequency of the video signal to be corrected are maintained constant.