Entropy encoding and decoding scheme

摘要

In PIPE coding, where alphabet symbols are distributed among a plurality of specialized entropy en/decoders according to their probability distribution estimate, a categorizing stage is provided where source symbols to be encoded are sub-divided into a first substream which is subject to VLC coding, and a second substream which is subject to PIPE coding. By this measure, source symbols having an appropriate symbol probability distribution, i.e. a probability distribution suitable for being efficiently coded by means of VLC coding without the deficiencies outlined above in the introductory portion of the specification of the present application, may be categorized as VLC coded symbols whereas other symbols may be treated as PIPE coded symbols and subject to PIPE coding, the coding complexity of which is higher than VLC coding, but at a better compression efficiency.

主权项

1. An entropy encoding apparatus comprising:
a subdivider configured to subdivide a sequence of source symbols into a first subsequence of source symbols and a second subsequence of source symbols; a VLC encoder configured to symbol-wisely convert the source symbols of the first subsequence into codewords forming a first bit stream; a PIPE encoder configured to encode the second subsequence of source symbols, represented in form of a sequence of alphabet symbols, the PIPE encoder comprising:
an assigner configured to assign a measure for an estimate of a probability distribution among the possible values the respective alphabet symbols may assume, to each alphabet symbol of the sequence of alphabet symbols based on information comprised within previous alphabet symbols of the sequence of alphabet symbols;a plurality of entropy encoders each of which is configured to convert the alphabet symbols forwarded to the respective entropy encoder into a respective second bit stream; anda selector configured to forward each alphabet symbol to a selected one of the plurality of entropy encoders, the selection depending on the measure assigned to the respective alphabet symbol; and a decomposer configured to convert a sequence of syntax elements into the sequence of source symbols by individually decomposing at least a subgroup of the syntax elements into a respective integer number of source symbols such that a mathematical function common for the subgroup, applied upon the integer number of source symbols of the respective syntax element, yields the respective syntax element, wherein the subdivider is configured such that one of the source symbols of the integer number of source symbols of the respective syntax elements belongs to the first subsequence of source symbols and another one of the source symbols of the integer number of source symbols of the respective syntax elements belongs to the second subsequence of source symbols.