IP Library › Granted Patent US 9,424,852
Granted Patent B2
US 9,424,852 · App. 13/980,427 · Granted Aug 23, 2016

Determining the inter-channel time difference of a multi-channel audio signal

Inventors: Manuel Briand (Nice, FR); Tomas Jansson Toftgård (Uppsala, SE)
Assignee: Telefonaktiebolaget LM Ericsson (publ)
G10L19/008H04S7/00
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Quick Facts
Patent No.
US 9,424,852
App. No.
13/980,427
Granted
Aug 23, 2016
Kind
B2
Abstract

There is provided a method and device for determining an inter-channel time difference of a multi-channel audio signal having at least two channels. A determination is made, at a number of consecutive time instances, of inter-channel correlation based on a cross-correlation function involving at least two different channels of the multi-channel audio signal. Each value of the inter-channel correlation is associated with a corresponding value of the inter-channel time difference. An adaptive inter-channel correlation threshold is adaptively determined based on adaptive smoothing of the inter-channel correlation in time. A current value of the inter-channel correlation is then evaluated in relation to the adaptive inter-channel correlation threshold to determine whether the corresponding current value of the inter-channel time difference is relevant. Based on the result of this evaluation, an updated value of the inter-channel time difference is determined.

Claims (34)

1. A method for determining an inter-channel time difference of a multi-channel audio signal having at least two channels, wherein said method comprises the steps of:

performing operations as follows on circuits of an electronic device:

determining, at a number of consecutive time instances, an inter-channel correlation based on a cross-correlation function involving at least two different channels of the multi-channel audio signal, wherein each value of the inter-channel correlation is associated with a corresponding value of the inter-channel time difference;

adaptively determining an adaptive inter-channel correlation threshold based on adaptive smoothing of the inter-channel correlation in time;

evaluating a current value of inter-channel correlation in relation to the adaptive inter-channel correlation threshold to determine whether the corresponding current value of the inter-channel time difference is relevant; and

determining an updated value of the inter-channel time difference based on the result of this evaluation. and

performing at least one of decoding the multi-channel audio signal based on the updated value of the inter-channel time difference to generate a decoded multi-channel audio signal communicated toward speakers, and encoding the multi-channel audio signal based on the updated value of the inter-channel time difference to generate an encoded multi-channel audio signal transmitted toward speakers.

2. The method of claim 1 , wherein said step of evaluating a current value of inter-channel correlation in relation to the adaptive inter-channel correlation threshold is performed to determine whether or not the current value of the inter-channel time difference is used when determining the updated value of the inter-channel time difference.

3. The method of claim 1 , wherein said step of determining an updated value of the inter-channel time difference includes the step of taking, responsive to the current value of the inter-channel time difference being determined to be relevant, the current value into account when determining the updated value of the inter-channel time difference.

4. The method of claim 3 , wherein said step of taking the current value into account when determining the updated value of the inter-channel time difference includes selecting the current value of the inter-channel time difference as the updated value of the inter-channel time difference.

5. The method of claim 3 , wherein said step of taking the current value into account when determining the updated value of the inter-channel time difference includes the step of using the current value of the inter-channel time difference together with one or more previous values of the inter-channel time difference to determine the updated value of the inter-channel time difference.

6. The method of claim 5 , wherein said step of using the current value of the inter-channel time difference together with one or more previous values of the inter-channel time difference to determine the updated value of the inter-channel time difference includes determining a combination of several inter-channel time difference values according to the values of the inter-channel correlation, with a weight applied to each inter-channel time difference value being a function of the inter-channel correlation at the same time instant.

7. The method of claim 1 , wherein said step of determining an updated value of the inter-channel time difference includes the step of using, in response to the current value of the inter-channel time difference being determined to not be relevant, one or more previous values of the inter-channel time difference for determining the updated value of the inter-channel time difference.

8. The method of claim 1 , wherein said step of adaptively determining an adaptive inter-channel correlation threshold based on adaptive smoothing of the inter-channel correlation in time includes the step of estimating a relatively slow evolution and a relatively fast evolution of the inter-channel correlation and defining a combined, hybrid evolution of the inter-channel correlation by which changes in the inter-channel correlation are followed relatively quickly if the inter-channel correlation is increasing in time and changes are followed relatively slowly if the inter-channel correlation is decreasing in time.

9. The method of claim 8 , wherein said step of adaptively determining an adaptive inter-channel correlation threshold based on adaptive smoothing of the inter-channel correlation in time includes the step of selecting the adaptive inter-channel correlation threshold as the maximum of the hybrid evolution, the relatively slow evolution and the relatively fast evolution of the inter-channel correlation at the considered time instance.

10. An audio encoding method comprising a method for determining an inter-channel time difference according to claim 1 .

11. An audio decoding method comprising a method for determining an inter-channel time difference according to claim 1 .

12. A device for determining an inter-channel time difference of a multi-channel audio signal having at least two channels, wherein said device comprises:

an inter-channel correlation determiner configured to determine, at a number of consecutive time instances, inter-channel correlation based on a cross-correlation function involving at least two different channels of the multi-channel audio signal, where each value of the inter-channel correlation is associated with a corresponding value of the inter-channel time difference;

an adaptive filter configured to perform adaptive smoothing of the inter-channel correlation in time;

a threshold determiner configured to adaptively determine an adaptive inter-channel correlation threshold based on the adaptive smoothing of the inter-channel correlation;

an inter-channel correlation evaluator configured to evaluate a current value of inter-channel correlation in relation to the adaptive inter-channel correlation threshold to determine whether the corresponding current value of the inter-channel time difference is relevant;

an inter-channel time difference determiner is configured to determine an updated value of the inter-channel time difference based on the result of this evaluation; and

circuits configured to perform at least one of decoding the multi-channel audio signal based on the updated value of the inter-channel time difference to generate a decoded multi-channel audio signal communicated toward speakers, and encoding the multi-channel audio signal based on the updated value of the inter-channel time difference to generate an encoded multi-channel audio signal transmitted toward speakers.

13. The device of claim 12 , wherein said inter-channel correlation evaluator is configured to evaluate the current value of inter-channel correlation in relation to the adaptive inter-channel correlation threshold to determine whether or not the current value of the inter-channel time difference is used by the inter-channel time difference determiner when determining the updated value of the inter-channel time difference.

14. The device of claim 12 , wherein said inter-channel time difference determiner is configured for taking, responsive to the current value of the inter-channel time difference being determined to be relevant, the current value into account when determining the updated value of the inter-channel time difference.

15. The device of claim 14 , wherein said inter-channel time difference determiner is configured to select the current value of the inter-channel time difference as the updated value of the inter-channel time difference.

16. The device of claim 14 , wherein said inter-channel time difference determiner is configured to determine the updated value of the inter-channel time difference based on the current value of the inter-channel time difference together with one or more previous values of the inter-channel time difference.

17. The device of claim 16 , wherein said inter-channel time difference determiner is configured to determine a combination of several inter-channel time difference values according to the values of the inter-channel correlation, with a weight applied to each inter-channel time difference value being a function of the inter-channel correlation at the same time instant.

18. The device of claim 12 , wherein said inter-channel time difference determiner is configured to determine, responsive to the current value of the inter-channel time difference being determined to not be relevant, the updated value of the inter-channel time difference based on one or more previous values of the inter-channel time difference.

19. The device of claim 12 , wherein said adaptive filter is configured to estimate a relatively slow evolution and a relatively fast evolution of the inter-channel correlation and define a combined, hybrid evolution of the inter-channel correlation by which changes in the inter-channel correlation are followed relatively quickly if the inter-channel correlation is increasing in time and changes are followed relatively slowly if the inter-channel correlation is decreasing in time.

20. The device of claim 19 , wherein said threshold determiner is configured to select the adaptive inter-channel correlation threshold as the maximum of the hybrid evolution, the relatively slow evolution and the relatively fast evolution of the inter-channel correlation at the considered time instance.

21. An audio encoder comprising a device for determining an inter-channel time difference according to claim 12 .

22. An audio decoder comprising a device for determining an inter-channel time difference according to claim 12 .

Assignments (1)
ASSIGNMENT OF ASSIGNOR'S INTEREST Recorded Jul 18, 2013
From: BRIAND, MANUEL; JANSSON, TOMAS
To: TELEFONAKTIEBOLAGET L M ERICSSON (PUBL)
Reel/Frame 030826/0668 →
Continuity (2)
Provisional Application 61438720 · Feb 2, 2011
Related Publication 20130301835A1 · Nov 14, 2013