Abstract: A lossless image compression encoder/decoder system having a context determination circuit and a code generator. The image compressor uses the context of a pixel to be encoded to predict the value of the pixel and determines a prediction error and maps the prediction error to a mapped value having a distribution suitable for Golomb encoding. The image compressor contains a context quantizer that quantizes the context of pixels. The image compressor determines a Golomb parameter based on the context and historical information gathered during the coding of an image. To avoid systematic prediction biases in an image, the image compressor adjusts the distribution of prediction residuals to a distribution suitable for Golomb coding. As it encodes a particular pixel, the encoder uses the Golomb parameter to determine a Golomb code for the prediction error and encodes that value. To decompress an image, the decompressor determines and quantizes the context of each pixel being decoded.

Abstract: An error correction system reduces redundancy of a two-dimensional product code array by eliminating an excess redundancy in prior product codes that provides detection of more corrupted rows than can be corrected. The product code array is formed utilizing a row coding, a column coding, and an intermediate coding, which may each be Reed-Solomon codes. The product code array has a total redundancy of n.sub.1 r.sub.2 +r.sub.1 r.sub.2 symbols, where r.sub.1 is the redundancy of the row coding, r.sub.2 is the redundancy of the column coding, and raw data symbols fill a k.sub.1 by k.sub.2 and a r.sub.1 by (k.sub.2 -r.sub.2) symbol portions of the product code array. A decoder for the product code array is capable of detecting and correcting up to r.sub.2 corrupted rows of the product code array.

Abstract: A lossless image compression encoder/decoder system having a context determination circuit and a code table generator. The image compressor uses the context of a pixel to be encoded to predict the value of the pixel and determines a prediction error. The image compressor contains a context quantizer that quantizes the context of pixels. The image compressor counts the error values for each quantized context and uses these counts to generate context-specific coding tables for each quantized context. As it encodes a particular pixel, the encoder looks up the prediction error in the context-specific coding table for the context of the pixel and encodes that value. To decompress an image, the decompressor determines and quantizes the context of each pixel being decoded. The decompressor uses the same pixels as the compressor to determine the context. The decompressor retrieves from the context-specific coding table the error value corresponding to the coded pixel.

Abstract: A scheme for compression of large sets of short blocks of data for storage in a storage medium, such as a read-only memory. Applications of the scheme include compression of fonts for printers, ROM disks in portable PCs, and others. These applications require random access to individual blocks, and fast, real-time decompression. The scheme applies an asymmetrical three-stage methodology in which a first stage provides training and optimization for a set of data blocks; a second stage effects data compression; and a third stage effects data decompression.

Abstract: A class of lossless data compression algorithms use a memory-based dictionary of finite size to facilitate the compression and decompression of data. To reduce the loss in data compression caused by dictionary resets, a standby dictionary is used to store a subset of encoded data entries previously stored in a current dictionary. In a second aspect of the invention, data is compressed/decompressed according to the address location of data entries contained within a dictionary built in a content addressable memory (CAM). In a third aspect of the invention, the minimum memory/high compression capacity of the standby dictionary scheme is combined with the fast single-cycle per character encoding/decoding capacity of the CAM circuit. In a fourth aspect of the invention, a selective overwrite dictionary swapping technique is used to allow all data entries to be used at all times for encoding character strings.

Abstract: The invention is a dictionary initialization scheme adaptive to changes in the type and structure of input data. The compression ratio is increased by minimizing the number of data entries used to represent single characters in the input data. By using fewer codes than what is normally used to represent characters in an array of input data, the dictionary can have fewer entries than the alphabet size. A further aspect of the invention implements a type of run-length encoding in the LZ methodology which exploits the redundant structure existing in the compressed stream in the presence of a long run. Some of the codewords in the compressed stream are deleted but can be recovered at the decompression site. The foregoing LZE method is used alone, or used in combination with other methods to form a compression scheme that is especially useful for transmitting network packets.

Abstract: A novel memory hashing system is disclosed. The system converts an address into a hashed address of the form (B,C) where B is a module number in a multi-module memory system and C is an offset in the module. The system can be shown to have no pathological cases for any stride value less than some predetermined value. An apparatus according to the present invention is conveniently implemented in a pipelined architecture which allows one address value to be calculated each memory cycle. The present invention utilizes a special matrix calculated from a primitive polynomial for calculating the hashed addresses. The conversion of any given address requires one row of the matrix. The entries of the matrix may be stored in ROM. Alternatively, the required row of the matrix may be calculated in response to receiving the address which is to be convened to the hashed address.

Abstract: A class of lossless data compression algorithms use a memory-based dictionary of finite size to facilitate the compression and decompression of data. To reduce the loss in data compression caused by dictionary resets, a standby dictionary is used to store a subset of encoded data entries previously stored in a current dictionary. In a second aspect of the invention, data is compressed/decompressed according to the address location of data entries contained within a dictionary built in a content addressable memory (CAM). In a third aspect of the invention, the minimum memory/high compression capacity of the standby dictionary scheme is combined with the fast single-cycle per character encoding/decoding capacity of the CAM circuit. The circuit uses multiple dictionaries within the storage locations of a CAM to reduce the amount of memory required to provide a high data compression ratio.

Abstract: A class of lossless data compression algorithms use a memory-based dictionary of finite size to facilitate the compression and decompression of data. When the current dictionary (CD) fills up with encoded character strings, it is reset thereby losing the compression information previously contained in the dictionary. To reduce the loss in data compression caused by dictionary resets, a second, standby dictionary (SD) is used to simultaneously store a subset of the encoded data entries stored in the first dictionary. The data entries in the second dictionary represent the data entries of the first dictionary that compress the greatest amount of input data. When the first dictionary is ready to be reset, the first dictionary is replaced with the second dictionary, maintaining high data compression and freeing up memory space for new encoded data strings.

Abstract: A method of transforming a multi-beam ultrasonic image in which a plurality of ultrasonic beams are simultaneously transmitted into an object along a plurality of lines and across a plurality of arcs. The reflected signals are sensed along each line and sampled thereby creating an image matrix of sampled values taken from the intersection of each line and arc. For each image value, a linear combination of surrounding values is formed to create a transformed image value which reduces the effect of interbeam interference.

Abstract: A Reed-Solomon decoder is implemented in systolic arrays wherein clock and control information propagate serially with the data. Progressive loss of coherence in such arrays is compensated by a folded array structure symmetrized in clock control whereby coherence is progressively re-established at the output of each such array.

Abstract: A systematic systolic array of R Cauchy cells receives a message stream of K symbols, systolically computes R check symbols therefrom and appends them to the end of the meassage stream to form a codeword of N=K+R symbols. The Cauchy cells operate independently, there being no feedback as is usually required, so that only adjacent cells need operate synchronously, a clock signal being systolically passed from cell to cell and the systolic array as a whole being asynchronous. As a result, the encoder may operate at much higher data rates and is easily reconfigurable in real time to adjust for any changes in the number of message symbols (K) or the number of check symbols (R).