Apparatus and method for encoding or decoding a multi-channel signal

Patent metadata

Field	Value
Publication number	US-11508384-B2
Application number	US-202016995537-A
Country	US
Kind code	B2
Filing date	Aug 17, 2020
Priority date	Mar 9, 2015
Publication date	Nov 22, 2022
Grant date	Nov 22, 2022

Abstract

An apparatus for encoding a multi-channel signal having at least three channels includes an iteration processor, a channel encoder and an output interface. The iteration processor is configured to calculate inter-channel correlation values between each pair of the at least three channels, for selecting a pair including a highest value or including a value above a threshold, and for processing the selected pair using a multi-channel processing operation to derive first multi-channel parameters for the selected pair and to derive first processed channels. The iteration processor is configured to perform the calculating, the selecting and the processing using at least one of the processed channels to derive second multi-channel parameters and second processed channels. The channel encoder is configured to encode channels resulting from an iteration processing to obtain encoded channels. The output interface is configured to generate an encoded multi-channel signal including the encoded channels and the first and second multi-channel parameters.

First claim

The invention claimed is:

1. Apparatus for encoding a multi-channel signal comprising at least three channels, comprising:
an iteration processor for calculating, in a first iteration step, inter-channel correlation values between each pair of the at least three channels, for selecting, in the first iteration step, a pair comprising a highest value or comprising a value above a threshold, and for processing the selected pair using a multichannel processing operation to derive first multichannel parameters for the selected pair and to derive first processed channels,
wherein the iteration processor is configured to perform the calculating, the selecting and the processing in a second iteration step using at least one of the processed channels to derive second multichannel parameters and second processed channels;
a channel encoder for encoding channels resulting from an iteration processing performed by the iteration processor to acquire encoded channels; and
an output interface for generating an encoded multi-channel signal comprising the encoded channels and the first and the second multichannel parameters.

2. Apparatus of claim 1 ,
wherein the output interface is configured to generate the encoded multi-channel signal as a serial bitstream and so that the second multichannel parameters are in the encoded signal before the first multichannel parameters.

3. Apparatus of claim 1 ,
wherein the iteration processor is configured to perform stereo processing comprising at least one of a group comprising rotation processing using a rotation angle calculation from the selected pair and prediction processing.

4. Apparatus of claim 1 ,
wherein the first multichannel parameters comprise a first identification of the channel in the selected pair for the first iteration step, and wherein the second multichannel parameters comprise a second identification of the channels in a selected pair of the second iteration step.

5. Apparatus of claim 1 ,
wherein the iteration processor is configured to calculate an inter-channel correlation using a frame of each channel comprising a plurality of bands so that a single inter-channel correlation value for the plurality of bands is acquired, and
wherein the iteration processor is configured to perform the multichannel processing for each of the plurality of bands so that the first or the second multichannel parameters are acquired for each of the plurality of bands.

6. Apparatus of claim 1 ,
wherein the iteration processor is configured to derive, for a first frame, a plurality of selected pair indications, and wherein the output interface is configured to comprise, into the multi-channel signal, for a second frame, following the first frame, a keep indicator, indicating that the second frame comprises the same plurality of selected pair indications as the first frame.

7. Apparatus of claim 1 ,
wherein the iteration processor is configured to only select a pair when the level difference of the pair is smaller than a threshold, the threshold being smaller than 40 dB, or 25 dB, or 12 dB, or smaller than 6 dB.

8. Apparatus of claim 1 ,
wherein the iteration processor is configured to calculate normalized correlation values, and wherein the iteration processor is configured to select a pair, when the correlation value is greater than 0.2 and advantageously 0.3.

9. Apparatus of claim 1 ,
wherein the iteration processor is configured to calculate stereo parameters in the multichannel processing, and wherein the iteration processor is configured to only perform a stereo processing in bands, in which a stereo parameter is higher than a quantized-to-zero-threshold defined by a stereo parameter quantizer.

10. Apparatus of claim 1 ,
wherein the iteration processor is configured to calculate rotation angles in the multichannel processing, and wherein the iteration processor is configured to only perform rotation processing in bands, in which a rotation angle is higher than a decoder-side dequantized-to-zero-threshold.

11. Apparatus of claim 1 ,
wherein the iteration processor is configured to not select the selected pair of the first iteration step in the second iteration step and, if applicable, in any further iteration steps.

12. Apparatus of claim 1 ,
wherein the iteration processor is configured to perform iteration steps until an iteration termination criterion is reached, wherein the iteration termination criterion is that a maximum number of iteration steps is equal to or higher than a total number of channels of the multi-channel signal by two, or wherein the iteration termination criterion is, when the inter-channel correlation values do not comprise a value greater than the threshold.

13. Apparatus of claim 1 ,
wherein the iteration processor is configured to process, in the first iteration step, the selected pair using the multichannel processing such that the processed channels are a mid-channel and a side-channel; and
wherein the iteration processor is configured to perform the calculating, the selecting and the processing in the second iteration step using only the mid-channel of the processed channels as the at least one of the processed channels to derive the second multichannel parameters and second processed channels.

14. Apparatus of claim 1 ,
wherein the channel encoder comprises channel encoders for encoding the channels resulting from the iteration processing, wherein the channel encoders are configured to encode the channels so that less bits are used for encoding a channel comprising less energy than for encoding a channel comprising more energy.

15. Apparatus of claim 1 , wherein multichannel processing means a joint stereo processing or a joint processing of more than two channels, and wherein a multichannel signal comprises two channels or more than two channels.

16. Apparatus for decoding an encoded multi-channel signal comprising encoded channels and at least first and second multichannel parameters, comprising:
a channel decoder for decoding the encoded channels to acquire decoded channels; and
a multichannel processor for performing a multichannel processing using a second pair of the decoded channels identified by the second multichannel parameters and using the second multichannel parameters to acquire processed channels, and for performing a further multichannel processing using a first pair of channels identified by the first multichannel parameters and using the first multichannel parameters, wherein the first pair of channels comprises at least one processed channel;
wherein a number of processed channels resulting from the multichannel processing and output by the multichannel processor is equal to a number of decoded channels input into the multichannel processor.

17. Apparatus of claim 16 , wherein the encoded multi-channel signal comprises, for a first frame, the first and the second multichannel parameters and, for a second frame, following the first frame, a keep indicator, and
wherein the multichannel processor is configured to perform the multichannel processing and the further multichannel processing in the second frame to the same second pair and the same first pair of channels as used in the first frame.

18. Apparatus of claim 16 ,
wherein the multichannel processing and the further multichannel processing comprise a stereo processing using a stereo parameter, wherein for individual scale factor bands or groups of scale factor bands of the decoded channels, a first stereo parameter is comprised by the first multichannel parameter and a second stereo parameter is c

Assignees

• Fraunhofer Ges Forschung

Inventors

• Dick Sascha
• Schuh Florian
• Rettelbach Nikolaus
• Schwegler Tobias
• Fueg Richard
• Hilpert Johannes
• Neusinger Matthias

Classifications

• G10L19/02 Primary

  using spectral analysis, e.g. transform vocoders or 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

• H04S3/008

  in which the audio signals are in digital form, i.e. employing more than two discrete digital channels (data reduction aspects thereof based on psychoacoustics G10L19/02) · CPC title

• H04S2400/01

  Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved · CPC title