Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code

Introduced: January 1985

Full Title

Full titles differ between systems:

IPC:

Conversion of a code where information is represented by a given sequence or number of digits to a code where the same information is represented by a different sequence or number of digits > Compression; Expansion; Suppression of unnecessary data, e.g. redundancy reduction > Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code

CPC:

Conversion of a code where information is represented by a given sequence or number of digits to a code where the same information is represented by a different sequence or number of digits > Compression (speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N); Expansion; Suppression of unnecessary data, e.g. redundancy reduction > Conversion to or from variable length codes, e.g. Shannon-Fano code, Huffman code, Morse code

CPC subdivides this area 3x more granularly than IPC with 4 additional codes.

4 codes are CPC-only extensions, 1 exist only in IPC.

IPC defines codes here since 1985.

Child Classifications

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H03M 7/4006 +1 CPC CPC only CPC only
H03M 7/4025 CPC only CPC only
H03M 7/4031 +1 CPC CPC only CPC only
H03M 7/4093 CPC only CPC only
H03M 7/42 using table look-up for the coding or decoding process, e.g. using read-only memory since 1985 +1 CPC IPC+CPC Available in IPC and CPC
H03M 7/44 Suppression of irrelevant zeroes since 1985 IPC only IPC only