Low-complexity tonality-adaptive audio signal quantization

Patent metadata

Field	Value
Publication number	US-10468043-B2
Application number	US-201514812465-A
Country	US
Kind code	B2
Filing date	Jul 29, 2015
Priority date	Jan 29, 2013
Publication date	Nov 5, 2019
Grant date	Nov 5, 2019

Abstract

The invention provides an audio encoder for encoding an audio signal so as to produce therefrom an encoded signal, the audio encoder including: a framing device configured to extract frames from the audio signal; a quantizer configured to map spectral lines of a spectrum signal derived from the frame of the audio signal to quantization indices, wherein the quantizer has a dead-zone, in which the input spectral lines are mapped to quantization index zero; and a control device configured to modify the dead-zone; wherein the control device includes a tonality calculating device configured to calculate at least one tonality indicating value for at least one spectrum line or for at least one group of spectral lines, wherein the control device is configured to modify the dead-zone for the at least one spectrum line or the at least one group of spectrum lines depending on the respective tonality indicating value.

First claim

The invention claimed is:

1. Audio encoder for encoding an audio signal so as to produce therefrom an encoded signal, the audio encoder comprising:
a framing device configured to extract frames from the audio signal;
a quantizer configured to map spectral lines of a spectrum signal derived from the frame of the audio signal to quantization indices, wherein the quantizer comprises a dead-zone, in which the spectral lines are mapped to quantization index zero; and
a control device configured to modify the dead-zone;
wherein the control device comprises a tonality calculating device configured to calculate at least one tonality indicating value for at least one spectrum line or for at least one group of spectral lines,
wherein the control device is configured to modify the dead-zone for the at least one spectrum line or the at least one group of spectrum lines depending on the respective tonality indicating value in such way that the dead-zone for the at least one spectrum line or the at least one group of spectral lines is selected before mapping the at least one spectrum line or the at least one group of spectral lines to the quantization indices,
wherein a size of the dead-zone for the at least one spectrum line or the at least one group of spectrum lines is determined based on the respective tonality indicating value.

2. Audio encoder according to claim 1 , wherein the control device is configured to modify the dead-zone in such way that the dead-zone at one of the spectral lines is larger than the dead-zone is at one of the spectral lines comprising a larger tonality or in such way that the dead-zone at one of the groups of spectral lines is larger than the dead-zone is at one of the groups of spectral lines comprising a larger tonality.

3. Audio encoder according to claim 1 , wherein the control device comprises a power spectrum calculating device configured to calculate a power spectrum of the frame of the audio signal, wherein the power spectrum comprises power values for spectral lines or groups of spectral lines, wherein the tonality calculating device is configured to calculate the at least one tonality indicating value depending on the power spectrum.

4. Audio encoder according to claim 3 , wherein the tonality indicating value for one of the spectral lines is based on a comparison of the power value for the respective spectral line and the sum of a predefined number of its surrounding power values of the power spectrum, or wherein the tonality indicating value for one of the groups of the spectral lines is based on a comparison of the power value for the respective group of spectral lines and the sum of a predefined number of its surrounding power values of the power spectrum.

5. Audio encoder according to claim 1 , wherein the tonality indicating value for one of the spectral lines is based on the tonality indicating value of the spectral line of a preceding frame of the audio signal, or wherein the tonality indicating value for one of the groups of the spectral lines is based on the tonality indicating value of the group of spectral lines for a preceding frame of the audio signal.

6. Audio encoder according to claim 3 , wherein the tonality indicating value is calculated by a formula

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Assignees

• Fraunhofer Ges Forschung

Inventors

• Dietz Martin
• Fuchs Guillaume
• Helmrich Christian
• Markovic Goran

Classifications

• G10L25/03

  characterised by the type of extracted parameters · CPC title

• H03M7/30

  Compression (speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N); Expansion; Suppression of unnecessary data, e.g. redundancy reduction · CPC title

• G10L25/21

  the extracted parameters being power information · CPC title

• G10L19/035 Primary

  Scalar quantisation · CPC title

• G10L25/18

  the extracted parameters being spectral information of each sub-band · CPC title