Methods and apparatus for comparing blocks of pixels

摘要

Techniques for comparing blocks of pixels in digital image encoding. The techniques apply a pattern of elements containing contiguous pixels to the blocks being compared, and only the pixels in the elements are compared. The pixels are contiguous in the horizontal dimension of the digital image, which ensures that the block matching process is sensitive to small-scale vertical features of the image. A version of the technique which is particularly advantageous for use with DSPs that can process the pixels in a word in parallel uses checkerboard patterns in which each element is a word. Variations on the patterns take into account the fact that the block of pixels being compared may be word-aligned, misaligned by one pixel, misaligned by two pixels, and misaligned by three pixels. Misalignment may be dealt with by not comparing pixels that do not belong to the blocks being compared or by using an aligned pattern which does not completely cover the block and adding elements in the portion covered by the pattern to compensate for the elements that are not covered.