MDCT M/S stereo

Patent metadata

Field	Value
Publication number	US-11527252-B2
Application number	US-202017005417-A
Country	US
Kind code	B2
Filing date	Aug 28, 2020
Priority date	Aug 30, 2019
Publication date	Dec 13, 2022
Grant date	Dec 13, 2022

Abstract

The invention refers to audio encoders, audio decoders, and audio encoding methods and audio decoding methods. In some examples, the invention refers to improved stereo coding. An encoder provides an encoded representation of an audio signal. The encoder applies a spectral whitening to a separate-channel representation of the input audio signal, to obtain a whitened separate-channel representation of the signal. The audio encoder applies a spectral whitening to a mid-side representation of the signal, to obtain a whitened mid-side representation of the signal. The audio encoder decides whether to encode the whitened separate-channel representation of the signal, to obtain the encoded representation of the signal, or to encode the whitened mid-side representation of the signal, to obtain the encoded representation of the signal.

First claim

The invention claimed is:

1. A multi-channel audio encoder for providing an encoded representation of a multi-channel input audio signal,
wherein the multi-channel audio encoder includes a first whitening block that configured to apply a spectral whitening to a separate-channel representation of the multi-channel input audio signal to output a whitened separate-channel representation of the multi-channel input audio signal;
wherein the multi-channel audio encoder includes a second whitening block configured to apply a spectral whitening to a mid-side representation of the multi-channel input audio signal, to output a whitened mid-side representation of the multi-channel input audio signal, wherein the encoder is configured to derive the mid-side representation from a non-spectrally-whitened version of the separate-channel representation;
wherein the multi-channel audio encoder includes a stereo decision block configured to make a decision whether to encode the whitened separate-channel representation of the multi-channel input audio signal, to output the encoded representation of the multi-channel input audio signal, or to encode the whitened mid-side representation of the multi-channel input audio signal, to output the encoded representation of the multi-channel input audio signal, in dependence on the whitened separate-channel representation and in dependence on the whitened mid-side representation.

2. The multi-channel audio encoder according to claim 1 , wherein the multi-channel audio encoder is configured to acquire a plurality of whitening parameters.

3. The multi-channel audio encoder according to claim 2 , wherein the multi-channel audio encoder is configured to derive a plurality of whitening coefficients from the whitening parameters.

4. The multi-channel audio encoder according to claim 1 , wherein the multi-channel audio encoder is configured to derive whitening coefficients associated with signals of the mid-side representation from whitening coefficients associated with individual channels of the multi-channel input audio signal.

5. The multi-channel audio encoder according to claim 4 , wherein the multi-channel audio encoder is configured to derive the whitening coefficients associated with signals of the mid-side representation from the whitening coefficients associated with individual channels of the multi-channel input audio signal using a non-linear derivation rule.

6. The multi-channel audio encoder according to claim 4 , wherein the multi-channel audio encoder is configured to determine an element-wise minimum, to derive the whitening coefficients associated with signals of the mid-side representation from the whitening coefficients associated with individual channels of the multi-channel input audio signal.

7. The multi-channel audio encoder according to claim 1 , wherein the multi-channel audio encoder is configured to apply an inter-channel level difference compensation to two or more channels of the multi-channel input audio signal, in order to acquire level-compensated channels, and
wherein the multi-channel audio encoder is configured to use the level-compensated channels as the separate-channel representation of the multi-channel input audio signal.

8. The multi-channel audio encoder according to claim 1 , wherein the first whitening block is configured to apply channel-specific whitening coefficients to different channels of the separate-channel representation of the multi-channel input audio signal-, in order to output the whitened separate-channel representation, and
wherein the second whitening block is configured to apply whitening coefficients to a mid signal and to a side signal, in order to output the whitened mid-side representation.

9. A multi-channel audio decoder for providing a decoded representation of a multi-channel audio signal on the basis of a bitstream including an encoded representation of the multi-channel audio signal and side information,
wherein the multi-channel audio decoder includes a dewhitening block configured to derive a joint-signal representation of the multi-channel audio signal from the encoded representation,
wherein the joint-signal representation of the multi-channel audio signal is selected between a mid-side representation of the multi-channel audio signal and a separate-channel representation of the multi-channel audio signal, wherein the dewhitening block is configured to determine, from stereo information included in the side information, whether the joint-signal representation of the multi-channel audio signal is the mid-side representation of the multi-channel audio signal or the separate-channel representation of the multi-channel audio signal;
wherein the dewhitening block is configured to apply a spectral de-whitening to the joint-signal representation of the multi-channel audio signal, to acquire a dewhitened representation of the multi-channel input audio signal;
wherein the multi-channel audio decoder is configured, in case the representation of the multi-channel audio signal is the mid-side representation of the multi-channel audio signal, to derive the separate-channel representation of the multi-channel audio signal on the basis of the dewhitened mid-side representation of the multi-channel audio signal.

10. The multi-channel audio encoder according to claim 9 , wherein the multi-channel audio encoder is configured to acquire a plurality of whitening parameters,
wherein the multi-channel audo decoder is configured to derive a plurality of whitening co-efficients from the whitening parameters, and
wherein the multi-channel audio encoder is configured to derive whitening coefficients associated with signals of the mid-side representation from whitening coefficients associated with individual channels of the multi-channel audio signal.

11. The multi-channel audio decoder according to claim 10 , wherein the multi-channel audio decoder is configured to derive the whitening coefficients associated with signals of the mid-side representation from the whitening coefficients associated with individual channels of the multi-channel audio signal using a non-linear derivation rule.

12. The multi-channel audio decoder according to claim 10 , wherein the multi-channel audio decoder is configured to determine an element-wise minimum, to derive the whitening coefficients associated with signals of the mid-side representation from the whitening coefficients associated with individual channels of the multi-channel audio signal.

13. The multi-channel audio decoder according to claim 9 , wherein the multi-channel audio decoder is configured to apply an inter-channel level difference compensation to two or more channels of a dewhitened separate-channel representation of the multi-channel audio signal, in order to acquire a level-compensated representation of channels.

14. The multi-channel audio decoder according to claim 9 , wherein the multi-channel audio decoder is configured to apply an Intelligent Gap Filling.

15. A method for providing an encoded representation of a multi-channel input audio signal, wherein the method comprises:
applying a spectral whitening to a separate-channel representation of the multi-channel input audio signal, to output a whitened separate-channel representation of the multi-channel input audio signal;
applying a spectral whitening to a mid-side representation of the multi-channel input audio signal, to output a whitened mid-side representation of the multi-channel input audio signal;
making a decision whether to encode the whitened separate-channel representation of the multi-channel input audio signal, to output the encode

Assignees

• Fraunhofer Ges Forschung

Inventors

• Markovic Goran
• Dick Sascha
• Fotopoulou Eleni
• Bayer Stefan

Classifications

• G10L19/22

  Mode decision, i.e. based on audio signal content versus external parameters · 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