Audio entropy encoder/decoder for coding contexts with different frequency resolutions and transform lengths
First Claim
1. An audio encoding apparatus for encoding a sequence of segments of coefficients, the segments being subsequent to each other in time, the audio encoding apparatus comprisinga provider for providing the sequence of segments of coefficients from an audio stream representing a sampled audio signal by using different transform lengths such that segments of coefficients for which different transform lengths are used, spectrally represent the sampled audio signal at different frequency resolutions and comprise different numbers of coefficients;
- a processor for deriving an entropy coding context for a currently encoded coefficient of a current segment based on a previously encoded coefficient of a previous segment; and
an entropy encoder for entropy encoding the current coefficient based on the entropy coding context to acquire an encoded audio stream,wherein the processor is configured to compute the entropy coding context for the current coefficient byselecting a set of coefficients of the previous segment in a manner so that in case the number of coefficients of the previous segment and the number of coefficients of the current segment are different, a number of coefficients in the set of coefficients is a first number, and in case the number of coefficients of the previous segment and the number of coefficients of the current segment are not different, the number of coefficients in the set of coefficients is a second number which is equal to the first number, andselecting at least some of the coefficients of the previous segment so that a spectral spacing between the selected coefficients of the previous segment is larger in case of the number of coefficients of the previous segment is larger as compared to a case that the number of coefficients of the previous segment the number of coefficients of the previous segment is smaller than the number of coefficients of the current segment, andcomputing the entropy coding context for the current coefficient on the basis of the set of coefficients.
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Abstract
An audio encoder for encoding segments of coefficients, the segments of coefficients representing different time or frequency resolutions of a sampled audio signal, the audio encoder including a processor for deriving a coding context for a currently encoded coefficient of a current segment based on a previously encoded coefficient of a previous segment, the previously encoded coefficient representing a different time or frequency resolution than the currently encoded coefficient. The audio encoder further includes an entropy encoder for entropy encoding the current coefficient based on the coding context to obtain an encoded audio stream.
40 Citations
32 Claims
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1. An audio encoding apparatus for encoding a sequence of segments of coefficients, the segments being subsequent to each other in time, the audio encoding apparatus comprising
a provider for providing the sequence of segments of coefficients from an audio stream representing a sampled audio signal by using different transform lengths such that segments of coefficients for which different transform lengths are used, spectrally represent the sampled audio signal at different frequency resolutions and comprise different numbers of coefficients; -
a processor for deriving an entropy coding context for a currently encoded coefficient of a current segment based on a previously encoded coefficient of a previous segment; and an entropy encoder for entropy encoding the current coefficient based on the entropy coding context to acquire an encoded audio stream, wherein the processor is configured to compute the entropy coding context for the current coefficient by selecting a set of coefficients of the previous segment in a manner so that in case the number of coefficients of the previous segment and the number of coefficients of the current segment are different, a number of coefficients in the set of coefficients is a first number, and in case the number of coefficients of the previous segment and the number of coefficients of the current segment are not different, the number of coefficients in the set of coefficients is a second number which is equal to the first number, and selecting at least some of the coefficients of the previous segment so that a spectral spacing between the selected coefficients of the previous segment is larger in case of the number of coefficients of the previous segment is larger as compared to a case that the number of coefficients of the previous segment the number of coefficients of the previous segment is smaller than the number of coefficients of the current segment, and computing the entropy coding context for the current coefficient on the basis of the set of coefficients. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. Method for encoding a sequence of segments of coefficients, the segments being subsequent to each other in time, the method comprising
providing the sequence of segments of coefficients from an audio stream representing a sampled audio signal by using different transform lengths such that segments of coefficients for which different transform lengths are used, spectrally represent the sampled audio signal at different frequency resolutions and comprise different numbers of coefficients; -
deriving an entropy coding context for a currently encoded coefficient of a current segment based on a previously encoded coefficient of a previous segment; and entropy encoding the current coefficient based on the entropy coding context to acquire an encoded audio stream, wherein the deriving the entropy coding context comprises computing the entropy coding context for the current coefficient by selecting a set of coefficients of the previous segment in a manner so that in case the number of coefficients of the previous segment and the number of coefficients of the current segment are different, a number of coefficients in the set of coefficients is a first number, and in case the number of coefficients of the previous segment and the number of coefficients of the current segment are not different, the number of coefficients in the set of coefficients is a second number which is equal to the first number, and selecting at least some of the coefficients of the previous segment so that a spectral spacing between the selected coefficients of the previous segment is larger in case of the number of coefficients of the previous segment is larger as compared to a case that the number of coefficients of the previous segment the number of coefficients of the previous segment is smaller than the number of coefficients of the current segment, and computing the entropy coding context for the current coefficient on the basis of the set of coefficients. - View Dependent Claims (12, 13, 14, 15, 16)
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17. An audio decoding apparatus for decoding an encoded audio stream representing a sampled audio signal to acquire a sequence of segments of coefficients being subsequent to each other in time and representing the sampled audio signal by using different transform lengths such that segments of coefficients for which different transform lengths are used, spectrally represent the sampled audio signal at different frequency resolutions and comprise different numbers of coefficients, comprising
a processor for deriving an entropy coding context for a currently decoded coefficient of a current segment based on a previously decoded coefficient of a previous segment; - and
an entropy decoder for entropy decoding the current coefficient based on the entropy coding context and the encoded audio stream, wherein the processor is configured to compute the entropy coding context for the current coefficient by selecting a set of coefficients of the previous segment in a manner so that in case the number of coefficients of the previous segment and the number of coefficients of the current segment are different, a number of coefficients in the set of coefficients is a first number, and in case the number of coefficients of the previous segment and the number of coefficients of the current segment are not different, the number of coefficients in the set of coefficients is a second number which is equal to the first number, and selecting at least some of the coefficients of the previous segment so that a spectral spacing between the selected coefficients of the previous segment is larger in case of the number of coefficients of the previous segment is larger as compared to a case that the number of coefficients of the previous segment the number of coefficients of the previous segment is smaller than the number of coefficients of the current segment, and computing the entropy coding context for the current coefficient on the basis of the set of coefficients. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A method for decoding an encoded audio stream representing a sampled audio signal to acquire a sequence of segments of coefficients being subsequent to each other in time and representing the sampled audio signal by using different transform lengths such that segments of coefficients for which different transform lengths are used, spectrally represent the sampled audio signal at different frequency resolutions and comprise different numbers of coefficients, comprising
deriving an entropy coding context for a currently decoded coefficient of a current segment based on a previously decoded coefficient of a previous segment; - and
entropy decoding the current coefficient based on the entropy coding context and the encoded audio stream, wherein the deriving the entropy coding context comprises computing the entropy coding context for the current coefficient by selecting a set of coefficients of the previous segment in a manner so that in case the number of coefficients of the previous segment and the number of coefficients of the current segment are different, a number of coefficients in the set of coefficients is a first number, and in case the number of coefficients of the previous segment and the number of coefficients of the current segment are not different, the number of coefficients in the set of coefficients is a second number which is equal to the first number, and selecting at least some of the coefficients of the previous segment so that a spectral spacing between the selected coefficients of the previous segment is larger in case of the number of coefficients of the previous segment is larger as compared to a case that the number of coefficients of the previous segment the number of coefficients of the previous segment is smaller than the number of coefficients of the current segment, and computing the entropy coding context for the current coefficient on the basis of the set of coefficients. - View Dependent Claims (28, 29, 30, 31, 32)
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Specification