Abstract: A hierarchial search for moving image encoding determines a motion vector by comparing a target block to sets of blocks selected according to the results of previous comparisons. Typically, each set of blocks includes a central block and four blocks offset on x and y axes. Blocks most similar to the target block provide co-ordinates of a center block in a next stage of the search. The hierarchial search searches regions indicated by previous comparisons to be similar to the target block and thereby reduces the number of comparisons and the search time required to find a motion vector. A motion estimation circuit for the hierarchial search includes: five processing elements which compare the target block to five blocks; a first memory that asserts a target block pixel value to the processing elements; a second memory that asserts five search window pixel values to the processing elements.

Abstract: A video compression system in accordance with the present invention may use a frame buffer which is only a fraction of the size of a full frame buffer. A subsampler connected to an input of the frame buffer performs 4 to 1 subsampling on the video data to be stored in the frame buffer. This allows the frame buffer to be one-fourth the size of a full frame buffer. The subsampling may even be 9 to 1, 16 to 1, or another ratio, for a concomitant decrease in frame buffer size. An upsampler is connected to the output of the frame buffer for providing interpolated and filtered values between the subsamples. Novel methods of filtering and interpolating performed by the upsampler are described. A new motion estimation technique is also described herein which directly detects the number of bits required to be transmitted to convey the difference between the predicted video data and the current video data, where a fewer number of bits used to convey the difference corresponds to better motion estimation.

Abstract: A new motion estimation technique is described herein which directly detects the number of bits required to be transmitted to convey the difference between the predicted video data and the current video data, where a fewer number of bits used to convey the difference corresponds to better motion estimation. The search criterion for the best estimate of movement of a block is the minimum number of bits for conveying this difference instead of minimizing the mean squared error (MSE) or mean average difference (MAD). Thus, complex calculations involving MSD or MAD are avoided. The motion estimator of the preferred embodiment uses a look-up table to convert motion compensated difference signals for a block of pels into the number of bits required to be transmitted to convey the difference signals.

Abstract: A video compression system in accordance with the present invention may use a frame buffer which is only a fraction of the size of a full frame buffer. A subsampler connected to an input of the frame buffer performs 4 to 1 subsampling on the video data to be stored in the frame buffer. This allows the frame buffer to be one-fourth the size of a full frame buffer. The subsampling may even be 9 to 1, 16 to 1, or another ratio, for a concomitant decrease in frame buffer size. An upsampler is connected to the output of the frame buffer for providing interpolated and filtered values between the subsamples. Novel methods of filtering and interpolating performed by the upsampler are described. A new motion estimation technique is also described herein which directly detects the number of bits required to be transmitted to convey the difference between the predicted video data and the current video data, where a fewer number of bits used to convey the difference corresponds to better motion estimation.

Abstract: A video image frame consisting of a two-dimensional array of picture elements (pixels) is decomposed into a set of rectangular image portions (tiles). Within each tile, variance between pixel intensity values is less than a predetermined value. A tile is encoded by a value set identifying the tile and including a single intensity value for all pixels in the tile. Frame-to-frame variation of the video image is encoded by inter-frame tile comparison and encoding of sub-tiles representative of change from a previous frame to a current frame.