Audio encoder and decoder

Patent metadata

Field	Value
Publication number	US-9489957-B2
Application number	US-201414772001-A
Country	US
Kind code	B2
Filing date	Apr 4, 2014
Priority date	Apr 5, 2013
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

The present disclosure provides methods, devices and computer program products for encoding and decoding a multi-channel audio signal based on an input signal. According to the disclosure, a hybrid approach of using both parametric stereo coding and discrete representation of the processed multi-channel audio signal is used which may improve the quality of the encoded and decoded audio for certain bitrates.

First claim

The invention claimed is:

1. A decoding method in a multi-channel audio processing system for reconstructing M encoded channels, wherein M>2, comprising the steps of:
receiving N waveform-coded downmix signals comprising spectral coefficients corresponding to frequencies between a first and a second cross-over frequency, wherein 1<N<M;
receiving M waveform-coded signals comprising spectral coefficients corresponding to frequencies up to the first cross-over frequency, each of the M waveform-coded signals corresponding to a respective one of the M encoded channels;
downmixing the M waveform-coded signals into N downmix signals comprising spectral coefficients corresponding to frequencies up to the first cross-over frequency;
combining each of the N waveform-coded downmix signals comprising spectral coefficients corresponding to frequencies between a first and a second cross-over frequency with a corresponding one of the N downmix signals comprising spectral coefficients corresponding to frequencies up to the first cross-over frequency into N combined downmix signals;
extending each of the N combined downmix signals to a frequency range above the second cross-over frequency by performing high frequency reconstruction, whereby each extended downmix signal comprises spectral coefficients corresponding to a range extending below the first cross-over frequency and above the second cross-over frequency;
performing a parametric upmix of the N frequency extended combined downmix signals into M upmix signals comprising spectral coefficients corresponding to frequencies above the first cross-over frequency, each of the M upmix signals corresponding to one of the M encoded channels; and
combining the M upmix signals comprising spectral coefficients corresponding to frequencies above the first cross-over frequency with the M waveform-coded signals comprising spectral coefficients corresponding to frequencies up to the first cross-over frequency.

2. The decoding method of claim 1 wherein the step of combining each of the N waveform-coded downmix signals comprising spectral coefficients corresponding to frequencies between a first and a second cross-over frequency with a corresponding one of the N downmix signals comprising spectral coefficients corresponding to frequencies up to the first cross-over frequency into N combined downmix is performed in a frequency domain.

3. The decoding method of claim 1 , wherein the step of extending each of the N combined downmix signals to a frequency range above the second cross-over frequency is performed in a frequency domain.

4. The decoding method of claim 1 , wherein the step of combining the M upmix signals comprising spectral coefficients corresponding to frequencies above the first cross-over frequency with the M waveform-coded signals comprising spectral coefficients corresponding to frequencies up to the first cross-over frequency is performed in a frequency domain.

5. The decoding method of claim 1 , wherein the step of performing a parametric upmix of the N frequency extended combined downmix signals into M upmix signals is performed in a frequency domain.

6. The decoding method of claim 1 , wherein the step of downmixing the M waveform-coded signals into N downmix signals comprising spectral coefficients corresponding to frequencies up to the first cross-over frequency is performed in a frequency domain.

7. The decoding method of claim 2 , wherein the frequency domain is a Quadrature Mirror Filters, QMF, domain.

8. The decoding method of claim 1 , wherein the step of downmixing the M waveform-coded signals into N downmix signals comprising spectral coefficients corresponding to frequencies up to the first cross-over frequency is performed in the time domain.

9. The decoding method of claim 1 , wherein the first cross-over frequency depends on a bit transmission rate of the multi-channel audio processing system.

10. The decoding method of claim 1 , wherein the step of extending each of the N combined downmix signals to a frequency range above the second cross-over frequency by performing high frequency reconstruction:
receiving high frequency reconstruction parameters; and
extending each of the N combined downmix signals to a frequency range above the second cross-over frequency by performing high frequency reconstruction using the high frequency reconstruction parameters.

11. The decoding method of claim 1 , wherein the step of extending each of the N combined downmix signals to a frequency range above the second cross-over frequency by performing high frequency reconstruction comprises performing spectral band replication, SBR.

12. The decoding method of claim 1 , wherein the step of performing a parametric upmix of the N frequency extended combined downmix signals into M upmix signals comprises:
receiving upmix parameters;
generating decorrelated versions of the N frequency extended combined downmix signals; and
subjecting the N frequency extended combined downmix signals and the decorrelated versions of the N frequency extended combined downmix signals to a matrix operation, wherein the parameters of the matrix operation are given by the upmix parameters.

13. A computer program product comprising a computer-readable medium with instructions for performing the method of claim 1 .

14. A decoder for a multi-channel audio processing system for reconstructing M encoded channels, wherein M>2, comprising:
a first receiving stage configured to receive N waveform-coded downmix signals comprising spectral coefficients corresponding to frequencies between a first and a second cross-over frequency, wherein 1<N<M;
a second receiving stage configured to receive M waveform-coded signals comprising spectral coefficients corresponding to frequencies up to the first cross-over frequency, each of the M waveform-coded signals corresponding to a respective one of the M encoded channels;
a downmix stage downstreams of the second receiving stage configured to downmix the M waveform-coded signals into N downmix signals comprising spectral coefficients corresponding to frequencies up to the first cross-over frequency;
a first combining stage downstreams of the first receiving stage and the downmix stage configured to combine each of the N downmix signals received by the first receiving stage with a corresponding one of the N downmix signals from the downmix stage into N combined downmix signals;
a high frequency reconstructing stage downstreams of the first combining stage configured to extend each of the N combined downmix signals from the combining stage to a frequency range above the second cross-over frequency by performing high frequency reconstruction, whereby each extended downmix signal comprises spectral coefficients corresponding to a range extending below the first cross-over frequency and above the second cross-over frequency;
an upmix stage downstreams of the high frequency reconstructing stage configured to perform a parametric upmix of the N frequency extended signals from the high frequency reconstructing stage into M upmix signals comprising spectral coefficients corresponding to frequencies above the first cross-over frequency, each of the M upmix signals corresponding to one of the M encoded channels; and
a second combining stage downstreams of the upmix stage and the second receiving stage configured to combine the M upmix signals from the upmix stage with the M waveform-coded signals received by the second receiving stage.

15. An encoding method for a multi-channel audio processing system for encoding M channels, wherein M>2, comprising the steps of:
receiving M signals c

Assignees

• Dolby Int Ab

Inventors

• Kjoerling Kristofer
• Purnhagen Heiko
• Mundt Harald
• Roeden Karl Jonas
• Sehlstrom Leif

Classifications

• H04S2420/03

  Application of parametric coding in stereophonic audio systems · CPC title

• G10L19/0212

  using orthogonal transformation · 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

• H04S2400/03

  Aspects of down-mixing multi-channel audio to configurations with lower numbers of playback channels, e.g. 7.1 -> 5.1 (H04S2400/01 takes precedence) · CPC title

• G10L19/167

  Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes · CPC title