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Abstract

Apparatus for quantizing compressed viedo data arranged in macroblocks calculates a quantizing parameter independently for each macroblock. The apparatus determines the relative coding complexity of respective macroblocks, and then determines which of the more complex macroblocks can withstand relatively severe quantization without significantly affecting image quality. This determination is made on the basis of the relative amount of codewords in blocks associated with respective macroblocks. In general, the data required to encode each one of the associated blocks is compared to find the block with the minimum data associated with each macroblock. A scale factor is then generated which is a function of the amount of data in the minimum block associated with a macroblock and the average of the data for all the minimum blocks in an image frame. The scale factor is utilized to scale a global quantization value applied to at least a portion of a frame of compressed video data.

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First Claim