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AssigneeCisco Technology, Inc.
InventorsWen-hsiung Chen, Fang Wu, Gregory Pelton
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A method and an apparatus to encode a series of quantized coefficients of a transform of a block of image data. The transform is such that 0 is the most likely coefficient amplitude and 1 is the next most likely coefficient amplitude. The method includes forming symbols (called events) from the series of quantized transform coefficients. An event is a run of none or more zero-valued coefficients followed by a run of one of a predefined set of sequences, each sequence in the set being either a single coefficient of amplitude greater than one, or a sequence of 1's and 0's starting with a coefficient of amplitude 1. The method includes forming a codeword for each formed event. Relatively short codewords are formed to represent events that are relatively more likely to occur, and relatively long codewords are formed to represent events that are relatively less likely to occur. In one implementation, each event is a run of none or more zero-valued coefficients followed by one of a predefined set of sequences, each sequence in the set being either a single coefficient of amplitude greater than one, or a sequence of l's and 0's starting with a coefficient of amplitude 1. In another implementation, an event is a run of none or more zero-valued coefficients followed by a run of one or more non-zero-amplitude coefficients. In a variation, The events include runs of none or more zero-valued coefficients followed by a subset of all possible runlengths of non-zero-amplitude coefficients. In one implementation, the subset includes no runs of length 2 or more of coefficients of amplitude 3 or more.
A method for processing a series of digital signals that each have an amplitude from the amplitude set consisting a first subset of values and a second subset of values, the first subset of values including the most common amplitude and at least one other amplitude, the processing to reduce the amount of data used to represent the digital signals and to form codewords such that the more frequently occurring sequences of values of digital signals are represented by relatively short codewords and the less frequently occurring sequences of values of digital signals are represented by relatively long codewords, the method comprising,
A memory to store a data structure that provides a codeword for an event of a set of events formed from a series of quantized transform coefficients of a block of image data,
A memory to store a data structure that provides the event for a set of codewords, each event describing a quantized transform coefficients of a block of image data, the codewords obtained from a bitstream representing compressed image data,
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