Entropy encoding and decoding scheme

Abstract

Decomposing a value range of the respective syntax elements into a sequence of n partitions with coding the components of z laying within the respective partitions separately with at least one by VLC coding and with at least one by PIPE or entropy coding is used to greatly increase the compression efficiency at a moderate coding overhead since the coding scheme used may be better adapted to the syntax element statistics. Accordingly, syntax elements are decomposed into a respective number n of source symbols si with i=1 . . . n, the respective number n of source symbols depending on as to which of a sequence of n partitions into which a value range of the respective syntax elements is sub-divided, a value z of the respective syntax elements falls into, so that a sum of values of the respective number of source symbols si yields z, and, if n>1, for all i=1 . . . n−1, the value of si corresponds to a range of the ith partition.

1 - 20 . (canceled) 
     
     
         21 . An apparatus for decoding comprising:
 a symbol decoder configured to obtain, based on codewords from a data stream, a first sequence of source symbols and a second sequence of source symbols, wherein source symbols of the first and second sequences are related to level values of transform coefficients of a transform coefficient block, wherein the level values of transform coefficients are encoded into the data stream according to a scan order; and   a composer configured to:   compose a sequence of syntax elements having a value range which is sub-divided into a plurality of disjoint portions including at least three portions by, for each syntax element:
 obtaining a set of source symbols from the first and second sequences based on a portion of the plurality of disjoint portions associated with the syntax element, and 
 combining values of the source symbols of the set to determine the value of the syntax element; and 
   adapt one or more limits between the plurality of disjoint portions.   
     
     
         22 . The apparatus of  claim 21 , wherein the symbol decoder comprises:
 a first decoder configured to: receive a first portion of the data stream, and reconstruct source symbols of the first sequence of source symbols from codewords of the first portion of the data stream; and   a second decoder configured to: receive a second portion of the data stream, and reconstruct source symbols of the second sequence of source symbols from codewords of the second portion of the data stream.   
     
     
         23 . The apparatus of  claim 21 , wherein a source symbol in the second sequence of source symbols corresponds to a first-ordered portion in the plurality of disjoint portions, and the plurality of disjoint portions is arranged such that a first portion covers higher values of the value range than a second portion. 
     
     
         24 . The apparatus of  claim 21 , wherein the source symbols from the first sequence and the source symbols from the second sequence correspond to different portions. 
     
     
         25 . The apparatus of  claim 21 , wherein source symbols of the first and second sequences are related to absolute level values of transform coefficients of a transform coefficient block. 
     
     
         26 . The apparatus of  claim 21 , wherein the apparatus is at least a portion of a programmable logic device, a programmable gate array, a microprocessor, a computer or an electronic circuit. 
     
     
         27 . The apparatus of  claim 22 , wherein one of the first decoder and the second decoder is configured to use arithmetic coding to reconstruct the source symbols, and the other of the first decoder and the second decoder is configured to use Golomb-Rice coding to reconstruct the source symbols. 
     
     
         28 . The apparatus of  claim 21 , the composer is configured to adapt at least one limit between the plurality of disjoint portions during composing absolute transform coefficient levels of the transform coefficients of the transform coefficient block based on at least one of:
 a previously reconstructed absolute transform coefficient level of a transform coefficient preceding in a scan order,   a position of a current absolute transform coefficient level to be composed in the scan order,   an evaluation of previously reconstructed absolute transform coefficient levels of transform coefficients spatially neighboring the position of the current absolute transform coefficient level to be composed, and   an evaluation of previously reconstructed absolute transform coefficient levels of transform coefficients neighboring according to the scan order the position of the current absolute transform coefficient level to be composed.   
     
     
         29 . An apparatus for encoding comprising:
 a decomposer configured to:   receive a sequence of syntax elements having a value range which is sub-divided into a plurality of disjoint portions including at least three portions, wherein the syntax elements of the sequence are related to level values of transform coefficients of a transform coefficient block, wherein the level values of transform coefficients are encoded according to a scan order, and obtain a sequence of source symbols based on the sequence of syntax elements by decomposing each syntax element into a corresponding set of source symbols based on a portion of the plurality of disjoint portions associated with the syntax element, such that a combination of values of the source symbols of the set yields the value of the syntax element; and   a sub-divider configured to:   receive the sequence of source symbols, and   sub-divide the sequence of source symbols into a first sequence of source symbols and a second sequence of source symbols, and   wherein the decomposer is configured to adapt one or more limits between the plurality of disjoint portions.   
     
     
         30 . The apparatus of  claim 29 , further comprising: a first encoder configured to encode the source symbols of the first sequence; and a second encoder configured to encode the source symbols of the second sequence. 
     
     
         31 . The apparatus of  claim 29 , wherein a source symbol in the second sequence of source symbols corresponds to a first-ordered portion in the plurality of disjoint portions, and the plurality of disjoint portions is arranged such that a first portion covers higher values of the value range than a second portion. 
     
     
         32 . The apparatus of  claim 30 , wherein the first encoder or the second encoder is further configured to encode a scaling factor. 
     
     
         33 . The apparatus of  claim 29 , wherein the source symbols from the first sequence and the source symbols from the second sequence correspond to different portions of the plurality of disjoint portions. 
     
     
         34 . The apparatus of  claim 30 , wherein one of the first encoder and the second encoder is configured to use arithmetic coding to encode the source symbols, and the other of the first encoder and the second encoder is configured to use Golomb-Rice coding to encode the source symbols. 
     
     
         35 . The apparatus of  claim 29 , wherein the apparatus is at least a portion of a programmable logic device, a programmable gate array, a microprocessor, a computer or an electronic circuit. 
     
     
         36 . A non-transitory computer-readable medium for storing video data, comprising:
 a data stream stored in the non-transitory computer-readable medium and comprising data associated with a first sequence of source symbols and a second sequence of source symbols, wherein the source symbols of the first and second sequences are related to level values of transform coefficients of a transform coefficient block, the level values of transform coefficients being encoded into the data stream according to a scan order, and the source symbols are obtained based on a sequence of syntax elements having a value range which is sub-divided into a plurality of disjoint portions including at least three portions by executing operations using a processor, the operations including:   decomposing each syntax element into a corresponding set of source symbols based on a portion of the plurality of disjoint portions associated with the syntax element, such that a combination of values of the source symbols of the set yields the value of the syntax element, and   adapting one or more limits between the plurality of disjoint portions.   
     
     
         37 . The non-transitory computer-readable medium of  claim 36 , the operations further comprising: encoding the source symbols of the first sequence using a first encoder; and encoding the source symbols of the second sequence using a second encoder. 
     
     
         38 . The non-transitory computer-readable medium of  claim 37 , wherein the first encoder or the second encoder is configured to encode a scaling factor. 
     
     
         39 . The non-transitory computer-readable medium of  claim 36 , wherein a source symbol in the second sequence of source symbols corresponds to a first-ordered portion in the plurality of disjoint portions, and the plurality of disjoint portions is arranged such that a first portion covers higher values of the value range than a second portion. 
     
     
         40 . The non-transitory computer-readable medium of  claim 36 , wherein source symbols of the first and second sequences are related to absolute level values of transform coefficients of a transform coefficient block.