Audio encoder, audio decoder, method for encoding an audio information, method for decoding an audio information and computer program using a detection of a group of previously-decoded spectral values

Patent metadata

Field	Value
Publication number	US-11443752-B2
Application number	US-201715845616-A
Country	US
Kind code	B2
Filing date	Dec 18, 2017
Priority date	Oct 20, 2009
Publication date	Sep 13, 2022
Grant date	Sep 13, 2022

Abstract

An audio decoder for providing a decoded audio information includes a arithmetic decoder for providing a plurality of 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 is configured to select a mapping rule describing a mapping of a code value onto a symbol code in dependence on a context state. The arithmetic decoder is configured to determine or modify the current context state in dependence on a plurality of previously-decoded spectral values. The arithmetic decoder is configured to detect a group of a plurality of previously-decoded spectral values, which fulfill, individually or taken together, a predetermined condition regarding their magnitudes, and to determine the current context state in dependence on a result of the detection.
An audio encoder uses similar principles.

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; 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 onto a symbol code in dependence on a context state;
wherein the arithmetic decoder is configured to determine the current context state in dependence on a plurality of previously-decoded spectral values;
wherein the arithmetic decoder is configured to detect a group of a plurality of previously-decoded spectral values, which fulfill, individually or taken together, a predetermined condition regarding their magnitudes, and to determine or modify the current context state in dependence on a result of the detection;
wherein the arithmetic decoder is configured to set the current context state to be within a range of values which signals the detection of a group of a plurality of previously-decoded adjacent spectral values which fulfill, individually or taken together, a predetermined condition regarding their magnitudes, in response to the detection; and
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 determine or modify the current context state independent from the previously decoded spectral values in response to the detection that the predetermined condition is fulfilled.

3. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to detect a group of a plurality of previously-decoded adjacent spectral values, which fulfill, individually or taken together, a predetermined condition regarding their magnitudes.

4. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to detect a group of a plurality of previously-decoded adjacent spectral values which, individually or taken together, comprise a magnitude which is smaller than a predetermined threshold magnitude, and to determine or modify the current context state in dependence on a result of the detection.

5. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to detect a group of a plurality of previously-decoded adjacent spectral values, wherein each of the previously-decoded spectral values is a zero value, and to determine or modify the context state in dependence on a result of the detection.

6. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to set the current context state to a predetermined value in response to the detection that a group of a plurality of previously-decoded adjacent spectral values fulfill, individually or taken together, a predetermined condition regarding their magnitudes.

7. The audio decoder according to claim 6 , wherein the arithmetic decoder is configured to selectively omit a calculation of the context state in dependence on numeric values of a plurality of previously-decoded spectral values in response to the detection that a group of a plurality of previously-decoded adjacent spectral values fulfill, individually or taken together, a predetermined condition regarding their magnitudes.

8. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to map a symbol code onto a decoded spectral value.

9. The audio decoder according to claim 1 , wherein the arithmetic decoder is configured to evaluate one or more hash tables to select a mapping rule in dependence on the context state.

10. An audio encoder for providing an encoded audio information on the basis of an input audio information, the audio encoder comprising:
an energy-compacting time-domain-to-frequency-domain converter for providing a frequency-domain audio representation on the basis of a time-domain representation of the input audio information, such that the frequency-domain audio representation comprises a set of spectral values; and
an arithmetic encoder configured to encode a spectral value or a preprocessed version thereof, using a variable length codeword, wherein the arithmetic encoder is configured to map a spectral value, or a value of a most significant bitplane of a spectral value onto a code value,
wherein the arithmetic encoder is configured to select a mapping rule describing a mapping of a spectral value, or of a most significant bitplane of a spectral value, onto a code value, in dependence on a context state; wherein the arithmetic encoder is configured to determine the current context state in dependence on a plurality of previously-encoded spectral values;
wherein the arithmetic encoder is configured to detect a group of a plurality of previously-encoded spectral values, which fulfill, individually or taken together, a predetermined condition regarding their magnitudes, and to determine or modify the current context state in dependence on a result of the detection;
wherein the arithmetic encoder is configured to set the current context state to be within a range of values which signals the detection of a group of a plurality of previously-encoded adjacent spectral values which fulfill, individually or taken together, a predetermined condition regarding their magnitudes, in response to the detection; and
wherein the audio encoder is implemented using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer.

11. The audio encoder according to claim 10 , wherein the arithmetic encoder is configured to determine or modify the current context state independent from the previously encoded spectral values in response to the detection that the predetermined condition is fulfilled.

12. The audio encoder according to claim 10 , wherein the arithmetic encoder is configured to detect a group of a plurality of previously-encoded adjacent spectral values, which fulfill, individually or taken together, a predetermined condition regarding their magnitudes.

13. A method for providing a decoded audio information on the basis of an encoded audio information, the method comprising:
providing a plurality of decoded spectral values on the basis of an arithmetically-encoded representation of the spectral values; and
providing a time-domain audio representation using the decoded spectral values, in order to acquire the decoded audio information;
wherein providing the plurality of decoded spectral values comprises selecting a mapping rule describing a mapping of a code value representing a spectral value, or a most-significant bit-plane of a spectral value, in an encoded form onto a symbol code representing a spectral value, or a most-significant bit-plane of a spectral value, in a decoded form, in dependence on a context state;
wherein the current context state is determined in dependence on a plurality of previously decoded spectral values;
wherein a group of a plurality of previously-decoded spectral values, which fulfill, individually or taken together, a predetermined condition regarding their magnitudes is detected, and wherein the current context state is determined or modified in dependence on a result of the detection: and
wherein the method comprises setting the current context state to be within a range of

Assignees

• Fraunhofer Ges Forschung

Inventors

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

Classifications

• G10L19/0208

  Subband vocoders · CPC title

• G10L19/008 Primary

  Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing · CPC title

• G10L19/0017 Primary

  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