Abstract: For a possibly flexible use of an arrangement (1) for mixing and/or processing one or more video signals, the arrangement (1) includes video hardware components (2) which are implemented for a dedicated purpose and, within the arrangement (1), are exclusively usable for said dedicated purpose, in that the arrangement (1) also includes video computers (3, 4) which can alternatively perform a plurality of functions and are thus usable within the arrangement (1) for different purposes, dependent on their need, the video hardware components (2) being implemented for uses which are computer-intensive and/or require a large bandwidth, the video computers (3, 4) being provided for uses which can be processed in real time by the video computers (3, 4), the arrangement (1) accommodating a control circuit (6) which assigns tasks to the video computers (3, 4), dependent on their need.

Abstract: A test pattern generator for digital television signals produces a zone plate pattern on an orthogonal pixel raster generated by pixel and line counters. The counter outputs are supplied to respective ROMs each storing a parabolic function. Their outputs are added to define zone plate circles on the basis of the circle equation x.sup.2 =y.sup.2 =r.sup.2. Circular patterns of evenly spaced color bars are produced by interposing a square root extracting ROM ahead of another ROM which converts the phase values into amplitude values. The optional interposition of a square root function after the addition and before the conversion into amplitude values provides a different circular test pattern. It can be readily modified in various ways under control of a microprocessor or EPROM.