Abstract: An electrical network emulates the transmission characteristics of a video signal cable, allowing tests to be made as to the length to which the cable may be extended before video signal degradation occurs. The preferred embodiment emulates a Beldon.RTM. 8281 coaxial cable, used for the transmission of serial digital video signals, and comprises four sections. The sections are arranged to emulate cable lengths of 25 meters, 50 meters and 200 meters.

Abstract: A method and an apparatus for sampling a reference signal so as to generate an error signal indicative of a phase error between an actual sampling phase and a desired sampling phase. The desired sampling phase is displaceable from an optimum sampling phase, so as to facilitate the sampling of an NTSC color burst signal or to effect hue control during sampling of the modulated chroma sub-carrier. The reference signal is sampled at the frequency of said signal and a plurality of said samples are accumulated. After said samples have been accumulated, said accumulation is multiplied by the sine or by the cosine of the phase displacement angle between the optimum sampling phase and the derived sampling phase.

Abstract: A system for creating video images by `drawing` on a touch tablet with a stylus. Addresses designated by the stylus are translated by a computer (16) into addresses in a frame delay store (13). The operator may choose an artists implement, the effect of which is simulated in the image by brush stamp signals representing the distribution power of the implement. Brush stamp signals are provided for a patch of signals round a designated address. During a frame period the brush stamp signals are processed to produce signals representing the effect of overlapping brush stamps for a portion of a line drawn in that period. The store is a frame delay store where the stored signals are continuously recycled. During a cycle of the store signals corresponding to the addresses covered by the brush stamps are sequentially up-dated by combining with incoming video signals in proportions determined by the brush signals. This produces the effect on a screen of a line drawn with the chosen implement.

Abstract: A system for producing output print-dot data suitable for hard copy printing devices (10). A first framestore (11) stores first intensity-related pixel data at a first resolution, which is converted to first higher resolution print-dot data by a print-dot generator (17,18). A control store (19) stores one-bit control data at the said higher resolution and the output print data is selected from the first print-dot data or from a second source of print dot data in response to the control data. Both sources of print-dot data may be derived from intensity related pixel data generated on an electronic graphic system such as a PAINTBOX (Registered Trade Mark). The high resolution data may also be generated by the system and displayed electronically with full color graphics.

Abstract: A processing circuit which is arranged to operate in three modes. The first mode is to act as a brush processor in video graphics creation combining incoming video signals with stored video signals to produce a graphic signal. The second mode allows an image to be composed from two or more input pictures using stencil signals. The third mode is useful in still picture applications where one frame is to be viewed and the next previewed. Stencil signals allow the operator to cut or fade from one frame to the other.

Abstract: A video movement detector suitable for detecting picture movement and/or noise on a video signal. A first detector detects differences frame by frame on a portion of picture having a plurality of picture points from more than one line. A second detector detects differences frame by frame from a portion of picture having a plurality of picture points from the same line, and a third detector detects differences frame by frame from a portion of a picture comprising a single picture point. Movement is determined to have taken place when the differences measured by the respective detectors exceed predetermined thresholds. The selected thresholds are typically of different values to provide the capability of distinguishing between noise and movement in varying conditions. The movement detection arrangement can be used to control picture manipulation during processing such as in a noise reduction system, standards conversion or picture size change arrangements.