Patent ID: 6421466
Filing Date: 2002-07-16
Classification: H04N

Abstract:
A motion estimator for compressing digital-video images comprising:a memory for storing images containing digital pixels; a pixel averager, receiving a 2Ã—2 group of pixels, for outputting one pixel as an average of four pixels; a width reducer, receiving a full-width pixel, for outputting a reduced-width pixel having fewer digital bits than the full-width pixel; the memory temporarily storing: a first image input to the motion estimator, a reduced-width level-1 image, generated by the width reducer from the first image, the reduced-width level-1 image containing reduced-width pixels having fewer bits per pixel than full-width pixels in the first image; wherein the first image is deleted from the memory once the reduced-width level-1 image is generated; a level-2 image generated by the pixel averager, the level-2 image having one-quarter of a number of pixels of the first image, a reduced-width level-2 image, generated by the width reducer from the level-2 image, the reduced-width level-2 image containing reduced-width pixels; wherein the level-2 image is deleted from the memory once the reduced-width level-2 image is generated; a level-3 image generated by the pixel averager, the level-3 image having one-quarter of a number of pixels of the level-2 image, a reduced-width level-3 image, generated by the width reducer from the level-3 image, the reduced-width level-3 image containing reduced-width pixels; wherein the level-3 image is deleted from the memory once the reduced-width level-3 image is generated; a level-4 image generated by the pixel averager, the level-4 image having one-quarter of a number of pixels of the level-2 image, a reduced-width level-4 image, generated by the width reducer from the level-4 image, the reduced-width level-4 image containing reduced-width pixels; wherein the level-4 image is deleted from the memory once the reduced-width level-4 image is generated; a calculator, receiving the reduced-width level-4 image and an old reduced-width level-4 image, for finding a matching block of reduced-width pixels that most-closely matches a selected block of pixels in the old reduced-width level-4 image, the calculator generating a level-4 motion vector identifying the matching block; the calculator also receiving the reduced-width level-3 image and an old reduced-width level-3 image, for finding a matching block of reduced-width pixels within a search range determined by the level-4 motion vector, the matching block being a block within the search range that most-closely matches a selected block of pixels in the old reduced-width level-3 image, the calculator generating a level-3 motion vector identifying the matching block; the calculator also receiving the reduced-width level-2 image and an old reduced-width level-2 image, for finding a matching block of reduced-width pixels within a search range determined by the level-3 motion vector, the matching block being a block within the search range that most-closely matches a selected block of pixels in the old reduced-width level-2 image, the calculator generating a level-3 motion vector identifying the matching block; the calculator also receiving the reduced-width level-1 image and an old reduced-width level-1 image, for finding a matching block of reduced-width pixels within a search range determined by the level-2 motion vector, the matching block being a block within the search range that most-closely matches a selected block of pixels in the old reduced-width level-1 image, the calculator generating a level-1 motion vector identifying the matching block; and wherein the level-1 motion vector is output to an encoded video stream as a substitute for the selected block, whereby reduced-width pixels are stored for motion estimation.