Data decoding method and apparatus

A device for decoding unaligned variable-length code words comprising:

• (a) input means for receiving input data words;
• said input data words containing adjacently arranged variable-length code words;
• (b) means for selecting at least one fixed length data token from said input data words;
• said token containing at least a portion of a current code word;
• said token optionally containing at least a portion of an adjacent code word;
• (c) decoding means for receiving said fixed length data token and for producing responsive thereto a source symbol corresponding to said current code word and a residual prefix word carrying information about the length and content of said portion of said adjacent code word if such adjacent code word is present;
• and
• (d) means for storing unaltered at least one residual prefix word produced previously by said decoding means;
• wherein said decoding means is further responsive to said stored but otherwise unaltered residual prefix word.

A device for decoding unaligned variable-length code words comprising:

• (a) means for defining a plurality of sequential operational cycles including a current cycle and at least one previously occurring cycle and at least one subsequently occurring cycle;
• (b) input means for receiving input data words;
• said input data words containing adjacently arranged variable-length code words;
• (c) means for selecting at least one fixed length data token from said input data words;
• said token containing at least a portion of a current code word to be decoded in said current cycle;
• said token optionally containing at least a portion of a subsequent code word to be decoded in said subsequent cycle;
• (d) decoding means for receiving said token and for producing responsive thereto a source symbol corresponding to said current code word and a residual prefix word carrying information about the length and content of said portion of said subsequent code word if such portion of said subsequent code word is present;
• and
• (e) means for storing unaltered at least one residual prefix word produced by said decoding means in said previous cycle;
• wherein said decoding means is further responsive to said stored but otherwise unaltered residual prefix word.

A device for decoding unaligned variable-length code words comprising:

• (a) means for receiving in sequence a plurality of fixed-length data tokens;
• said plurality of tokens collectively forming a data stream including a plurality of adjacently arranged variable-length code words;
• and
• (b) decoding means for decoding each of said variable-length code words into a corresponding source symbol;
• said decoding means comprising:
• (i) means for selecting one of said tokens;
• said token containing at least a portion of a current code word;
• said token optionally containing at least a portion of an adjacent code word;
• (ii) code translation means responsive to said portion of said current code word and to a previously generated residual word for producing the source symbol corresponding to said current code word;
• and
• (iii) means for generating a residual word responsive at least to said portion of said adjacent code word, said residual word being representative of, but not identical to, said portion of said adjacent code word.

A device for decoding unaligned variable-length code words comprising:

• (a) means for defining a plurality of sequential operational cycles including a current cycle and at least one previously occurring cycle and at least one subsequently occurring cycle;
• (b) input means for receiving a plurality of fixed length data words, each data word comprising at least two adjacently arranged fixed length data tokens;
• (c) means for selecting at least one of said data tokens for processing during said current cycle;
• (d) storage means for storing in an unaltered form at least one prefix word produced in said previous cycle;
• and
• (e) code table memory means connected for receiving said data token from said selecting means and for receiving said stored prefix word from said storage means in an unaltered form;
• said code table memory being responsive to said data token and said stored prefix word for producing a source symbol corresponding to a first portion of said data token;
• said code table memory being further responsive to said data token and said stored prefix word for producing a new prefix word for use during said subsequent cycle in processing an optional remaining portion of said data token;
• said prefix word containing information as to the length and contents of a code word associated with said optional remaining portion of said data token.