Audio encoder, audio decoder, method for encoding and audio information, method for decoding an audio information and computer program using a modification of a number representation of a numeric previous context value

Patent metadata

Field	Value
Publication number	US-9633664-B2
Application number	US-201414491881-A
Country	US
Kind code	B2
Filing date	Sep 19, 2014
Priority date	Jan 12, 2010
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

Abstract

An audio decoder includes an arithmetic decoder for providing decoded spectral values on the basis of an arithmetically-encoded representation of the spectral values and a frequency-domain-to-time-domain converter for providing a time-domain audio representation using the decoded spectral values. The arithmetic decoder selects a mapping rule describing a mapping of a code value onto a symbol code in dependence on a context state described by a numeric current context value, and determines the numeric current context value in dependence on a plurality of previously-decoded spectral values. The arithmetic decoder modifies a number representation of a numeric previous context value, describing a context state associated with one or more previously decoded spectral values, in dependence on a context subregion value, to acquire a number representation of a numeric current context value describing a context state associated with one or more spectral values to be decoded. An audio encoder uses a similar concept.

First claim

The invention claimed is:

1. An audio decoder for providing a decoded audio information on the basis of an encoded audio information, the audio decoder comprising:
an arithmetic decoder for providing a plurality of decoded spectral values on the basis of an arithmetically-encoded representation of the spectral values comprised in the encoded audio information; and
a frequency-domain-to-time-domain converter for providing a time-domain audio representation using the decoded spectral values, in order to acquire the decoded audio information;
wherein the arithmetic decoder is configured to select a mapping rule describing a mapping of a code value of the arithmetically-encoded representation of spectral values onto a symbol code representing one or more of the decoded spectral values or at least a portion of one or more of the decoded spectral values in dependence on a context state described by a numeric current context value; and
wherein the arithmetic decoder is configured to determine the numeric current context value in dependence on a numeric previous context value and in dependence on a plurality of previously-decoded spectral values,
wherein the arithmetic decoder is configured to modify a number representation of the numeric previous context value, describing a context state for the decoding of one or more previously decoded spectral values, in dependence on a context subregion value describing a subregion of a context, to acquire a number representation of a numeric current context value describing a context state for the decoding of one or more spectral values to be decoded,
wherein correlations between the numeric previous context value and the numeric current context value are exploited;
wherein the audio decoder is implemented using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer.

2. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to provide the number representation of the numeric current context value such that portions of the number representation comprising different numeric weights are determined by different context subregion values.

3. The audio decoder according to claim 1 , wherein the number representation is a binary number representation of a single numeric current context value; and
wherein a first subset of bits of the binary number representation is determined by a first context subregion value associated with one or more previously decoded spectral values; and
wherein a second subset of bits of the binary number representation is determined by a second context subregion value associated with one or more previously decoded spectral values, wherein the bits of the first subset of bits comprise a different numeric weight than the bits of the second subset of bits.

4. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to modify a bit-wise masked subset of information bits of the number representation of the numeric previous context values, or of a bit-shifted version of the number representation of the numeric previous context value, in dependence on a context subregion value which has not been considered for the derivation of the numeric previous context value, in order to acquire the number representation of the numeric current context value.

5. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to bit-shift the number representation of the numeric previous context value, such that numeric weights of subsets of bits associated with different context subregion values are modified, in order to acquire the number representation of the numeric current context value.

6. The audio decoder according to claim 5 , wherein the arithmetic decoder is configured to bit-shift the number representation of the numeric previous context value, such that a subset of bits, which are associated with a context subregion value, is deleted from the number representation, in order to acquire the number representation of the numeric current context value.

7. The arithmetic decoder according to claim 1 , wherein the arithmetic decoder is configured to modify a first subset of bits of a binary number representation of a numeric previous context value, or of a bit-shifted version of a binary number representation of a numeric previous context value, in dependence on a context subregion value, and to leave a second subset of bits of the binary number representation of the numeric previous context value, or of the bit-shifted version of the binary number representation of the numeric previous context value unchanged,
to derive the binary number representation of the numeric current context value from the binary number representation of the numeric previous context value by selectively modifying one or more subsets of bits associated with context subregions considered for the decoding of the previously-decoded spectral values and not considered for the decoding of spectral values to be decoded using the numeric current context value.

8. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to provide the number representation of the numeric current context value such that a subset of least-significant bits of the number representation of the numeric current context value describes a context subregion value, which context subregion value is used for a decoding of spectral values for which a context state is defined by the numeric current context value, but which context subregion value is not used for a decoding of spectral values for which a context state is defined by a numeric subsequent context value.

9. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to evaluate at least one table, to determine whether the numeric current context value is identical to a table context value described by an entry of the table or lies within an interval described by entries of the table, and to derive a mapping rule index value describing a selected mapping rule in dependence on a result of an evaluation of the at least one table.

10. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to check whether a sum of a plurality of context subregion values is smaller than or equal to a predetermined sum threshold value, and to selectively modify the numeric current context value in dependence on a result of the check.

11. The audio decoder according to claim 10 , wherein the arithmetic decoder is configured to check whether a sum of a plurality of context subregion values, which context subregion values are associated with a same temporal portion of the audio content as the one or more spectral values to be decoded using a context state defined by the numeric current context value, and which context subregion values are associated with lower frequencies than the one or more spectral values to be decoded using the context state defined by the numeric current context value, is smaller than or equal to a predetermined sum threshold value, and to selectively modify the numeric current context value in dependence on a result of the check.

12. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to sum absolute values of a first plurality of previously decoded spectral values in order to acquire a first context subregion value associated with the first plurality of previously decoded spectral values, and to sum absolute values of a second plurality of previously-decoded spectral values in order to acquire a second context subregion value associated with the second plurality of previously decoded spectral values.

Assignees

• Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E V

Inventors

• Subbaraman Vignesh
• Fuchs Guillaume
• Multrus Markus
• Rettelbach Nikolaus
• Weiss Oliver
• Gayer Marc
• Warmbold Patrick
• Griebel Christian

Classifications

• G10L19/0017

  Lossless audio signal coding; Perfect reconstruction of coded audio signal by transmission of coding error (G10L19/24 takes precedence) · CPC title

• G10L19/00 Primary

  Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis (in musical instruments G10H) · CPC title

• G10L19/002

  Dynamic bit allocation (for perceptual audio coders G10L19/032) · CPC title

• G10L19/02 Primary

  using spectral analysis, e.g. transform vocoders or subband vocoders · CPC title

• G10L19/06

  Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients · CPC title