Apparatus and method for adjusting spatial cue information of a multichannel audio signal

1. A method comprising:

estimating a value representing a direction of arrival associated with a first audio signal from at least a first channel and a second audio signal from at least a second channel of at least two channels of a multichannel audio signal;

determining a scaling factor based on the direction of arrival associated with the first audio signal and the second audio signal;

determining a reliability estimate for the value representing the direction of arrival associated with the first audio signal and the second audio signal;

applying the scaling factor, based on the reliability estimate, to a parameter associated with a difference in audio signal levels between the first audio signal and the second audio signal; and

determining a value representing the coherence of the first audio signal and the second audio signal.

2. The method of claim 1 wherein estimating the value representing the direction of arrival associated with a first audio signal and a second audio signal comprises:

using a first model based on a direction of arrival of a virtual audio signal, wherein the virtual audio signal is associated with an audio signal derived from the combining of at least two audio signals emanating from at least two audio signal sources.

3. The method of claim 2 , wherein the first model based on the direction of arrival of the virtual audio signal is based on a difference in audio signal levels between two audio signals.

4. The method of claim 2 , wherein the first model based on the direction of travel of the virtual audio signal comprises a spherical model of the head.

5. The method of claim 1 , wherein determining the reliability estimate for the value representing the direction of arrival associated with the first audio signal and the second audio signal comprises:

estimating at least one further value representing the direction of arrival associated with the first audio signal and the second audio signal, wherein estimating the at least one further value representing the direction of arrival associated with the first audio signal and the second audio signal further comprises using a second model based on the direction of arrival of a virtual audio signal, wherein the virtual audio signal is associated with an audio signal derived from the combining of at least two audio signals emanating from at least two audio signal sources; and

determining whether the difference between the value representing the direction of arrival associated with the first audio signal and the second audio signal, and the at least one further value representing the direction of arrival associated with the first audio signal and the second audio signal lies within a predetermined error bound.

6. The method of claim 5 , wherein the second model based on the direction of arrival of the virtual audio signal is based on a difference in a time of arrival between two audio signals.

7. The method of claim 5 , wherein the second model based on the direction of travel of the virtual audio signal comprises a model based on the sine wave panning law.

8. The method of claim 1 wherein determining the scaling factor based on the direction of arrival associated with the first audio signal and the second audio signal comprises:

assigning the scaling factor a value from a first pre determined range of values of at least one pre determined range of values, wherein the first pre determined range of values is selected according to the value representing a direction of travel of a virtual audio signal associated with the first audio signal and the second audio signal.

9. The method of claim 1 , wherein applying the scaling factor to the parameter associated with the difference in audio signal levels between the first audio signal and the second audio signal comprises:

multiplying the scaling factor with the parameter associated with the difference in audio signal levels between the first audio signal and the second audio signal.

10. The method of claim 1 , wherein the multichannel audio signal is a frequency domain signal.

11. The method of claim 1 , wherein the multichannel audio signal is partitioned into a plurality of sub bands, and the method for enhancing the multichannel audio signal is applied to at least one of the plurality of sub bands.

12. An apparatus comprising at least one processor and at least one memory including computer program code the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

estimate a value representing a direction of arrival associated with a first audio signal from at least a first channel and a second audio signal from at least a second channel of at least two channels of a multichannel audio signal;

determine a scaling factor based on the direction of arrival associated with the first audio signal and the second audio signal;

determine a reliability estimate for the value representing the direction of arrival associated with the first audio signal and the second audio signal;

apply the scaling factor, based on the reliability estimate, to a parameter associated with a difference in audio signal levels between the first audio signal and the second audio signal; and

determine a value representing the coherence of the first audio signal and the second audio signal.

13. The apparatus of claim 12 , wherein the at least one memory and the computer program code configured, with the at least one processor, cause the apparatus at least to estimate the value representing the direction of arrival associated with a first audio signal and a second audio signal is further configured to cause the apparatus at least to:

use a first model based on a direction of arrival of a virtual audio signal, wherein the virtual audio signal is associated with an audio signal derived from the combining of at least two audio signals emanating from at least two audio signal sources.

14. The apparatus of claim 13 , wherein the first model based on the direction of arrival of the virtual audio signal is based on a difference in audio signal levels between two audio signals.

15. The apparatus of claim 13 , wherein the first model based on the direction of travel of the virtual audio signal comprises a spherical model of the head.

16. The apparatus of claim 12 , wherein the at least one memory and the computer program code configured, with the at least one processor, cause the apparatus at least to determine the reliability estimate for the value representing the direction of arrival associated with the first audio signal and the second audio signal is further configured to cause the apparatus at least to:

estimate at least one further value representing the direction of arrival associated with the first audio signal and the second audio signal, wherein estimating the at least one further value representing the direction of arrival associated with the first audio signal and the second audio signal further comprises using a second model based on the direction of arrival of a virtual audio signal, wherein the virtual audio signal is associated with an audio signal derived from the combining of at least two audio signals emanating from at least two audio signal sources; and

determine whether the difference between the value representing the direction of arrival associated with the first audio signal and the second audio signal, and the at least one further value representing the direction of arrival associated with the first audio signal and the second audio signal lies within a predetermined error bound.

17. The apparatus of claim 16 , wherein the second model based on the direction of arrival of the virtual audio signal is based on a difference in a time of arrival between two audio signals.

18. The apparatus of claim 16 , wherein the second model based on the direction of travel of the virtual audio signal comprises a model based on the sine wave panning law.

19. The apparatus of claim 12 , wherein the at least one memory and the computer program code configured, with the at least one processor, cause the apparatus at least to determine the scaling factor based on the direction of arrival associated with the first audio signal and the second audio signal is further configured to cause the apparatus at least to:

assign the scaling factor a value from a first pre determined range of values of at least one pre determined range of values, wherein the first pre determined range of values is selected according to the value representing a direction of travel of a virtual audio signal associated with the first audio signal and the second audio signal.

20. The apparatus of claim 12 , wherein the at least one memory and the computer program code configured, with the at least one processor, to cause the apparatus at least to:

multiply the scaling factor with the parameter associated with the difference in audio signal levels between the first audio signal and the second audio signal.

21. The apparatus of claim 12 , wherein the multichannel audio signal is a frequency domain signal.

22. The apparatus of claim 12 , wherein the multichannel audio signal is partitioned into a plurality of sub bands, and the apparatus is configured to enhance at least one of the plurality of sub bands of the multichannel audio signal.