Data compression system for successively applying at least two data compression methods to an input data stream
First Claim
1. A method of compressing an input character stream comprising the steps of:
- replacing a sequential repetition of a single character in said input character stream with said character and a repeat count indicative of the number of sequential repetitions of said character in said input character stream to form a once compressed character stream; and
encoding said once compressed character stream using textual substitution.
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Abstract
The improved data compression system concurrently processes both strings of repeated characters and textual substitution of input character strings. In this system, the performance of data compression techniques based on textual substitution are improved by the use of a compact representation for identifying instances in which a character in the input data stream is repeated. This is accomplished by nesting a run length encoding system in the textual substitution system. This structure adds the recognition of runs of a repeated character before the processor performs the textual substituted data compression operation. A further performance improvement is obtained by expanding the alphabet of symbols stored in the compressor'"'"'s dictionary to include both the characters of the input data stream and repeat counts which indicate the repetition of a character. The handling of these repeat counts by the textual substitution based compression technique is no different than the handling of characters, or certain modifications are made in the handling of repeat counts.
208 Citations
21 Claims
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1. A method of compressing an input character stream comprising the steps of:
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replacing a sequential repetition of a single character in said input character stream with said character and a repeat count indicative of the number of sequential repetitions of said character in said input character stream to form a once compressed character stream; and encoding said once compressed character stream using textual substitution. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for compressing an input character stream comprising:
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means for replacing, in response to the presence of a sequential repetition of a single character in said input character stream, said sequential repetition of a single character with said character and a repeat count indicative of the number of sequential repetitions of said character in said input character stream to form a once compressed input character stream; means for encoding said once compressed input character stream using textual substitution. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method of compressing an input character stream comprising the steps of:
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substituting the sequential repetition of a single character in said input character stream with said character and a repeat count indicative of the number of sequential repetitions of said character in said input character stream to form a once compressed input character stream; encoding said once compressed input character stream into reference values representative of strings, consisting of characters in combination with repeat counts, including the steps of; replacing each string, consisting of characters in combination with repeat counts, that has been previously encountered with a reference value that had been previously assigned to said previously encountered string, generating new reference values for strings, consisting of characters in combination with repeat counts, that have not been previously entered into a dictionary.
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16. A method of compressing an input character stream comprising the steps of:
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replacing a sequential repetition of a single character in said input character stream with said character and a repeat count indicative of the number of sequential repetitions of said character in said input character stream to form a once compressed input character stream; and compressing said once compressed input character stream using textual substitution. - View Dependent Claims (17, 18, 19, 20, 21)
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Specification