Browse Prior Art Database

DATACLOCK COMPRESSED

IP.com Disclosure Number: IPCOM000023960D
Original Publication Date: 1979-Jun-30
Included in the Prior Art Database: 2004-Apr-01
Document File: 2 page(s) / 381K

Publishing Venue

Xerox Disclosure Journal

Abstract

As shown in the figure, a non-branching decoder for decoding tree-type (e.g., Huffman) run length message codes, without conducting a bit-by-bitcode validating tree search, comprises a serial input/parallel output shift register 11 for addressing a programmable read only memory (PROM) 12. The PROM 12 is addressed in response to each code bit shifted into the shift register 11 but the only storage locations containing meaningful (non-zero) information are those which are

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XEROX DISCLOSURE JOURNAL

DATA DECOMPRESSION Proposed~ran Classification

U.S. Cl. 179/15,55 mt. Cl. H04b 1/66

As shown in the figure, a non~branching decoder for decoding tree-~type (e.g., Huffman) run length message codes, without conducting a bit~by~bitcode validating tree search, comprises a serial input/parallel output shift register 11 for addressing a programmable read only memory (PROM) 12. The PROM 12 is addressed in response to each code bit shifted into the shift register 11 but the only storage locations containing meaningful (non~zero) information are those which are

addressed by one or the other of the valid codes. Each of those storage locations or addresses contains a high ("1") logic level marker bit in the most significant bit position, a two bit identifier (to indicate whether the code is a "residue" code, a "block length" code or an "end of line" code), followed by a binary count representing the number of picture elements involved in the run length represented by the run length code by which the particular location is addressed. A run length counter 13 is loaded with the run length representing binary count in response to

the marker bit, and the shift register 11 is then reset or cleared after a suitable period of time as determined by a delay circuit 14. It is important to note that the run count is equal to the length of the "white" run only. The "black" terminaton of the "white" run is implied. Consequently, the shift register 15 receives on...