Ram based yuv-rgb conversion

Abstract

Encoded color image data, stored in a first format such as YUV or YIQ, is converted to RGB format for output to a color display system. The conversion is carried out in real time synchronism with generation of the display, in order to minimize buffer storage requirements for the RGB output data. Present circuits use RAM (random access memory) storage arrays lookup tables for product functions defined in associated conversion equations. Each product function is a product of multiplication of a predetermined constant and data representing a U or V component of a source image pixel. Use of these tables effectively speeds up the conversion process, and has the added advantage of flexibility since the respective data is changeable to adjust to various image and display formats and conditions. In one embodiment, a RAM array used in the present format conversion process is also used (in a different display mode, with different stored data) as a conventional source of palette data. In the present conversion process, a cascaded network of adders receives product functions read out of one or more lookup table RAM arrays, adds certain of these functions together, and adds data representing Y components corresponding to the lookup table U and V arguments, to produce final output data representing red, green and blue (RGB) attributes of an instantly displayable pixel corresponding to a source pixel associated with respective source YUV components.