Abstract: A multiprocessor data processing system is described wherein the processors communicate to each other via a shared memory. Each of the processors comprises an administration unit (18a) and a computational unit. The administration unit of a writing processor maintains information defining a section in the memory which is free for storing data objects for readout by the reading processor. The administration unit of the reading processor maintains information defining a section in the memory in which the writing processor has written completed data for the data objects. The processors are arranged to signal a message to another processor via a processor synchronization channel for updating the information in the administration unit of said other processor.

Abstract: In a method of mixing a graphics signal and a video signal in a ratio alpha:(1-alpha), where the graphics signal is obtained by addressing a color look-up table (CLUT) in which color values (R, G, B) are stored, the number of color values stored for each mixing ratio depends on the mixing ratio so as to obtain an optimum filling of the color look-up table.

Abstract: An image rendering system renders a color image in which each pixel is associated with a respective aim color value. A quantizer selecta a respective quantized value indicating a color from a palette of colors for each pixel, in dependence on the aim color value associated with that pixel. The pixels are rendered with the colors indicated by the respective quantized values. The palette consists of a proper subset of the set of all colors that the aim color values can represent, and contains at least one palette color which does not lie on an RGB boundary, and is perceptually closer than any other of the palette color values to an RGB boundary color belonging to said set. For pixels for which the aim color value represents said RGB boundary color the quantizer means selects a quantized value indicating a further palette color, that lies on the RGB boundary.