Abstract: A data compression system uses sameness information, such as temporal sameness of corresponding pixels, in the coding process. Two sets of contexts are used, one set when a pixel is the same as a sameness pixel, and one set of contexts for residual coding of the pixel when it is not the same. The use of the sameness bit saves computation because, if in decoding the one "sameness" bit, a decompressor determines that the pixel is equal to the corresponding pixel in a previous frame, then no further decoding is needed for that pixel.

Abstract: Transforms such as the DCT are useful for image compression. One close relative of the DCT is preferred for its arithmetic simplicity. A method and apparatus is described whereby the image compression is done with no multiplications while still compatible with a JPEG (Joint Photographic Experts Group) Transform. Other enhancements are made to improve image quality.

Abstract: An apparatus and method for increasing the throughput of a data processing system such as an acoustic or image compression system. An addition or subtraction of two pluralities of numbers is accomplished in parallel by combining numbers into a pair of "doublevectors," adding or subtracting the pair of doublevectors, and separating the resultant doublevector to provide values representative of the results of the addition or subtraction on the original plurality of numbers. Similarly, a left-shift of a plurality of numbers is accomplished by combining the numbers into a single doublevector, left-shifting the doublevector, and extracting a plurality of output values representative of the left-shifted values of the original numbers. Using additions, subtractions and shifts a linear transform such as the Generalized Chen Transform may be performed using doublevectors to provide a substantial increase in computation speed.

Abstract: Transforms such as the DCT are useful for image compression. One close relative of the DCT is preferred for its arithmetic simplicity. A method and apparatus is described whereby the quantization operates with speeds comparable to 16 bit transforms yet the mean squared error is comparable to that of a 32 bit transform. The factorability of the transform into a relatively rapid set of additions and a set of multiplications permits an efficient pipelined data flow wherein the addition sections of the vertical and horizontal transforms are performed by the same hardware prior to a final multiplication.

Abstract: In an image compression system using a typical image compression scheme, a pointer array is provided to point to each of the many MCUs in a compressed image file. From all the blocks of an image, a subset of the blocks is selected as a virtual image. The virtual image is edited, and each edited block is compressed into an edited block. The edited block is compressed into an edited MCU and placed in an edited block region, and the pointer to the original MCU is changed to point to the new MCU. In this way, the pointer array can be modified to perform an Undo operation. An edge table is provided to hold values where each value, when combined with the differential value for a block on the edge of the virtual image, provides an absolute value for the block without reference to blocks beyond the edge of the virtual image. The entries in the edge table are determined from the compressed MCUs without the blocks being fully decompressed. More than one edge table can be provided.

Abstract: Transforms such as the DCT are useful for image compression. One close relative of the DCT is preferred for its arithmetic simplicity. A method and apparatus is described whereby the image compression is done with no multiplications while still compatible with a JPEG (Joint Photographic Experts Group) Transform. Other enhancements are made to improve image quality.