Unwanted noise components in a derived composite video signal are processed in a novel noise processing circuit to effectively minimize the otherwise deleterious effects on the operation of associated electronic apparatus, such as a television receiver or the like. The circuit arrangement is such that a control signal of a selectably fixed amplitude is developed in response to each such unwanted noise component above a set, predetermined amplitude. The derived control signals are then substituted in place of such undesired noise components, on a one for one basis. A feature of the invention is that the derived control signals replacing the noise components are effected at an intermediate, or gray level, with respect to the video information being displayed and thereby minimizes the overall visual impact that would otherwise be evident.
A noise processing system is described for use in protecting a television receiver's sync processing path and its video processing path from impulse noise. To protect the video processing path, a first noise canceller receives a composite video signal, detects each noise pulse therein which exceeds a video noise threshold, and replaces each such noise pulse with a selected voltage level. The resultant noise processed video may then be applied to the receiver's video processing path. To protect the sync processing path, another noise canceller receives the composite video signal, detects noise pulses therein which exceed a sync noise threshold, generates a detection pulse for each such noise pulse, and combines the detection pulses with composite video so as to cancel the noise pulses. Thus, another noise processed video signal is developed for application to the receiver's sync processing path.
Apparatus for treatment of luminance and/or color data included in information representative of an image to be displayed in a visual display system, comprising a comparator for comparing the data with at least one reference datum defined upon a scale of level possible variations and a device for switching the levels of the data according to the positioning in relation to each reference datum to lead to a precise analysis of the displayed image.
A white level clipping circuit has an impedance element through which a video signal is supplied from an input terminal to an output terminal, the emitter of a PNP-type transistor is connected to the output side of the impedance element and the collector thereof is grounded while the base of the transistor is supplied with a constant bias voltage to effect white level clipping of the video signal derived at the output terminal. This clipping circuit carries out positive clipping operation with no frequency characteristics and hence avoids possible overmodulation when the clipped video signal is frequency-modulated for the recording thereof.
