Entropy encoding and decoding scheme
First Claim
1. A method for decoding comprising:
- receiving, by a VLC decoder, a first portion of a bitstream;
reconstructing, by the VLC decoder, source symbols of a first subsequence of source symbols from codewords of the first portion of a bitstream;
receiving, by an arithmetic decoder, a second portion of a bitstream;
reconstructing, by the arithmetic decoder, source symbols of a second subsequence of source symbols from codewords of the second portion of a bitstream;
retrieving, by a composer, source symbols from the first subsequence and source symbols from the second subsequence; and
composing, by the composer, a sequence of syntax elements having a value range which is sub-divided into a sequence of partitions from the first subsequence of source symbols and the second subsequence of source symbols by individually composing each syntax element from a respective number of source symbols by, for at least a subgroup of the syntax elements, determining the respective number of source symbols based on a value of the respective syntax elements and a partition of the sequence of partitions, and by summing-up the values of the respective number of source symbols, as long as the value of at least one source symbol corresponds to a range of a corresponding partition, so as to obtain the value of the syntax element;
wherein the subgroup of the syntax elements comprises absolute transform coefficient levels of absolute transform coefficients of transform blocks of a picture with the absolute transform coefficient levels of a respective transform block being arranged within the sequence of syntax elements in accordance with a scan path leading through the absolute transform coefficients of the respective transform blocks and;
wherein the composer is configured to adapt at least one limit between the partitions during composing the absolute transform coefficient levels of the absolute transform coefficients of a respective transform block.
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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.
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Citations
30 Claims
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1. A method for decoding comprising:
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receiving, by a VLC decoder, a first portion of a bitstream; reconstructing, by the VLC decoder, source symbols of a first subsequence of source symbols from codewords of the first portion of a bitstream; receiving, by an arithmetic decoder, a second portion of a bitstream; reconstructing, by the arithmetic decoder, source symbols of a second subsequence of source symbols from codewords of the second portion of a bitstream; retrieving, by a composer, source symbols from the first subsequence and source symbols from the second subsequence; and composing, by the composer, a sequence of syntax elements having a value range which is sub-divided into a sequence of partitions from the first subsequence of source symbols and the second subsequence of source symbols by individually composing each syntax element from a respective number of source symbols by, for at least a subgroup of the syntax elements, determining the respective number of source symbols based on a value of the respective syntax elements and a partition of the sequence of partitions, and by summing-up the values of the respective number of source symbols, as long as the value of at least one source symbol corresponds to a range of a corresponding partition, so as to obtain the value of the syntax element; wherein the subgroup of the syntax elements comprises absolute transform coefficient levels of absolute transform coefficients of transform blocks of a picture with the absolute transform coefficient levels of a respective transform block being arranged within the sequence of syntax elements in accordance with a scan path leading through the absolute transform coefficients of the respective transform blocks and; wherein the composer is configured to adapt at least one limit between the partitions during composing the absolute transform coefficient levels of the absolute transform coefficients of a respective transform block. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 21)
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11. An apparatus for decoding comprising:
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a VLC decoder configured to; receive a first portion of a bitstream; and reconstruct source symbols of a first subsequence of source symbols from codewords of the first portion of a bitstream; an arithmetic decoder configured to; receive a second portion of a bitstream; and reconstruct a second subsequence of source symbols from codewords of the second portion of a bitstream; a composer configured to; retrieve all source symbols from the first subsequence and all source symbols from the second subsequence; and compose a sequence of syntax elements having a value range which is sub-divided into a sequence of partitions from the first subsequence of source symbols and the second subsequence of source symbols by individually composing each syntax element from a respective number of source symbols by, for at least a subgroup of the syntax elements, determining the respective number of source symbols based on a value of the respective syntax elements and a partition of the sequence of partitions, and by summing-up the values of the respective number of source symbols, as long as the value of at least one source symbol corresponds to a range of a corresponding partition, so as to obtain the value of the syntax element; wherein the subgroup of the syntax elements comprises absolute transform coefficient levels of absolute transform coefficients of transform blocks of a picture with the absolute transform coefficient levels of a respective transform block being arranged within the sequence of syntax elements in accordance with a scan path leading through the absolute transform coefficients of the respective transform blocks; wherein the composer is configured to adapt at least one limit between the partitions during composing the absolute transform coefficient levels of the absolute transform coefficients of a respective transform. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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22. A method for encoding comprising:
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receiving, by a decomposer, a sequence of syntax elements having a value range which is sub-divided into a sequence of partitions; converting, by the decomposer, the sequence of syntax elements into a sequence of source symbols by individually decomposing at least a subgroup of the syntax elements into a corresponding number of source symbols, based on a value of the respective syntax elements and a partition of the sequence of partitions, so that a sum of values of the source symbols yields the value of the respective syntax element, wherein, if the number of source symbols is greater than one, a value of at least one source symbol corresponds to a range of a corresponding partition; receiving, by a subdivider, the sequence of source symbols; subdivide, by the subdivider, the sequence of source symbols into a first subsequence of source symbols and a second subsequence of source symbols; receiving, by a VLC encoder, the source symbols of the first subsequence; encoding, by the VLC encoder, the source symbols of the first subsequence; receiving, by an arithmetic encoder, the source symbols of the second subsequence; and encoding, by the arithmetic encoder, the second subsequence of source symbols; wherein the subgroup of the syntax elements comprises absolute transform coefficient levels of absolute transform coefficients of transform blocks of a picture with the absolute transform coefficient levels of a respective transform block being arranged within the sequence of syntax elements in accordance with a scan path leading through the absolute transform coefficients of the respective transform blocks; wherein the decomposer is configured to adapt at least one limit between the partitions during decomposing the absolute transform coefficient levels of the absolute transform coefficients of a respective transform block based on at least one of already encoded absolute transform coefficient levels of absolute transform coefficients of the respective transform blocks preceding in a scan order, a position of the absolute transform coefficient level to be decomposed in the scan order, an evaluation of the already reconstructed absolute transform coefficient levels of transform coefficients neighboring spatially the position of the absolute transform coefficient level to be decomposed, and an evaluation of the already reconstructed absolute transform coefficient levels of transform coefficients neighboring in scan order the position of the absolute transform coefficient level to be decomposed. - View Dependent Claims (23, 24, 25, 26)
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27. An apparatus for encoding comprising:
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a decomposer configured to; receive a sequence of syntax elements having a value range which is sub-divided into a sequence of partitions; and convert the sequence of syntax elements into a sequence of source symbols by individually decomposing at least a subgroup of the syntax elements into a corresponding number of source symbols, based on a value of the respective syntax elements and a partition of the sequence of partitions, so that a sum of values of the source symbols yields the value of the respective syntax element, wherein, if the number of source symbols is greater than one, a value of at least one source symbol corresponds to a range of a corresponding partition; a subdivider configured to; receive the sequence of source symbols; and subdivide the sequence of source symbols into a first subsequence of source symbols and a second subsequence of source symbols; a VLC encoder configured to; receive the source symbols of the first subsequence; and encode the source symbols of the first subsequence; and an arithmetic encoder configured to; receive the source symbols of the second subsequence; and encode the second subsequence of source symbols; wherein the subgroup of the syntax elements comprises absolute transform coefficient levels of absolute transform coefficients of transform blocks of a picture with the absolute transform coefficient levels of a respective transform block being arranged within the sequence of syntax elements in accordance with a scan path leading through the absolute transform coefficients of the respective transform blocks; wherein the decomposer is configured to adapt at least one limit between the partitions during decomposing the absolute transform coefficient levels of the absolute transform coefficients of a respective. - View Dependent Claims (28, 29, 30)
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Specification