Method and apparatus for switching between data compression modes
First Claim
1. A method for switching between lossless data compression modes, from the one of said modes which is presently used for preceding binary format input data (present mode) to the other of said modes (other mode) for present binary format input data, said switching indicated by at least one multibit mode switch character having a number of bits, comprising the steps of:
- receiving said present binary format input data;
FIFO determining compression efficiency of said present input data under each of said modes on an ongoing basis;
FIFO comparing said compression efficiencies for said present input data under each of said modes; and
switching from said present mode to said other mode for compressing said present input data for which said compression efficiency is determined in said FIFO determining step only upon said FIFO comparing step indicating said compression efficiency of said present mode being less than said compression efficiency of said other mode by a threshold value, said threshold value directly related to said number of bits in said multibit mode switch character.
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Accused Products
Abstract
Disclosed are a method and apparatus for switching between lossless data compression modes, and the switching indicated by at least one multibit mode switch character. The binary format input data is received and a FIFO determination of the compression efficiency of the input data under each mode is made on an ongoing basis. The ongoing basis may be for each compressed code word or more. A FIFO comparison of the compression efficiencies under each mode are made, and the modes for compressing the input data are switched only upon the comparison, or accumulated comparisons, indicating the compression efficiency of the present mode is less than the compression efficiency of the other mode by a threshold value, the threshold value directly related to the number of bits in the multibit mode switch character. One or both of the data compression modes may comprise a Lempel-Ziv compression, such as ALDC (LZ-1 derivative) or DCLZ (LZ-2 derivative), for compressing the input data into variable sized tokens, and the FIFO compression efficiency may be determined based on the bit length of each variable sized token.
90 Citations
24 Claims
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1. A method for switching between lossless data compression modes, from the one of said modes which is presently used for preceding binary format input data (present mode) to the other of said modes (other mode) for present binary format input data, said switching indicated by at least one multibit mode switch character having a number of bits, comprising the steps of:
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receiving said present binary format input data; FIFO determining compression efficiency of said present input data under each of said modes on an ongoing basis; FIFO comparing said compression efficiencies for said present input data under each of said modes; and switching from said present mode to said other mode for compressing said present input data for which said compression efficiency is determined in said FIFO determining step only upon said FIFO comparing step indicating said compression efficiency of said present mode being less than said compression efficiency of said other mode by a threshold value, said threshold value directly related to said number of bits in said multibit mode switch character. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A data compression apparatus for switching between lossless data compression modes, from the one of said modes which is presently used on preceding binary format input data (present compression mode) to the other of said modes (other compression mode) for present binary format input data, indicating said switching with at least one multibit mode switch character having a number of bits, comprising:
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an input for receiving said present binary format input data; a first lossless data compressor coupled to said input for providing a first data compression of said present input data according to a first compression mode and providing an output of said present input data in said first compression mode; a second lossless data compressor coupled to said input for providing a second data, compression of said input data according to a second compression mode and providing an output of said present input data in said second compression mode; comparison logic coupled to said first and said second compressors, said comparison logic compares on an ongoing FIFO basis compression efficiency between said first and said second lossless data compressors in compressing said present input data, providing an efficiency comparison output, and wherein said comparison logic additionally compares said efficiency comparison output between said present compression mode and said other compression mode with a threshold value, said threshold value directly related to said number of bits in said multibit mode switch character, and wherein said comparison logic additionally providing a signal upon said efficiency comparisons exceeding said threshold value; and a compression output selector coupled to said comparison logic and said first and said second compressors for selecting said output from one of said first and said second compressors at a time, and, upon said comparison logic providing said signal, switching between the one of said first and said second compressors in said present compression mode to the one of said first and said second compressors of said other compression mode, for said output of said present input data for which said comparison was made, and signaling said switch between said first and said second compressors by outputting said at least one multibit mode switch character. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification