Systems, methods, apparatus, and computer-readable media for three-dimensional audio coding using basis function coefficients

1. A method of audio signal processing, the method comprising:

transforming a first audio signal and spatial information for the first audio signal into a first set of basis function coefficients that describes a first sound field, wherein the first audio signal is in one of the following formats: channel-based or object-based;

combining the first set of basis function coefficients with a second set of basis function coefficients to produce a combined set of basis function coefficients that describes a combined sound field, wherein the second set of basis function coefficients describes a second sound field associated with a second audio signal; and

encoding the combined set of basis function coefficients.

2. The method according to claim 1 , wherein at least one of the first audio signal or the second audio signal is a frame of a corresponding stream of audio samples.

3. The method according to claim 1 , wherein at least one of the first audio signal or the second audio signal is a frame of a pulse-code-modulation (PCM) stream.

4. The method according to claim 1 , wherein the respective spatial information for each of the first audio signal and the second audio signal indicates a direction in space.

5. The method according to claim 1 , wherein the respective spatial information for each of the first audio signal and the second audio signal indicates a location in space of a respective source of the first audio signal or the second audio signal.

6. The method according to claim 1 , wherein the respective spatial information for each of the first audio signal and the second audio signal indicates a respective diffusivity of the first audio signal or the second audio signal.

7. The method according to claim 1 , wherein the first audio signal comprises a loudspeaker channel.

8. The method according to claim 1 , further comprising obtaining an audio object that includes the audio signal and the spatial information for the first audio signal.

9. The method according to claim 1 , wherein each basis function coefficient of the first set of basis function coefficients corresponds to a unique one of a set of orthogonal basis functions.

10. The method according to claim 1 , wherein the first set of basis function coefficients describes a space with higher resolution along a first spatial axis than along a second spatial axis that is orthogonal to the first spatial axis.

11. The method according to claim 1 , wherein each basis function coefficient of the first set of basis function coefficients corresponds to a unique one of a set of spherical harmonic basis functions.

12. The method according to claim 1 , wherein at least one of the first set of basis function coefficients or the second set of basis function coefficients describes the corresponding sound field with higher resolution along a first spatial axis than along a second spatial axis that is orthogonal to the first spatial axis.

13. The method according to claim 1 , wherein the first set of basis function coefficients describes the first sound field in at least two spatial dimensions, and wherein the second set of basis function coefficients describes the second sound field in at least two spatial dimensions.

14. The method according to claim 1 , wherein at least one of the first set of basis function coefficients or the second set of basis function coefficients describes the corresponding sound field in three spatial dimensions.

15. The method according to claim 1 , wherein a total number of basis function coefficients included in the first set of basis function coefficients is less than a total number of basis function coefficients included in the second set of basis function coefficients.

16. The method according to claim 15 , wherein a total number of basis function coefficients included in the combined set of basis function coefficients is at least equal to the total number of basis function coefficients included in the first set of basis function coefficients and is at least equal to the total number of basis function coefficients included in the second set of basis function coefficients.

17. The method according to claim 1 , wherein combining the first set of basis function coefficients with the second set of basis function coefficients comprises, for each of at least a plurality of the basis function coefficients of the combined set of basis function coefficients, summing a corresponding basis function coefficient of the first set of basis function coefficients and a corresponding basis function coefficient of the second set of basis function coefficients to produce the basis function coefficient.

18. A non-transitory computer-readable data storage medium having stored thereon instructions that, when executed, cause one or more processors of a device for audio signal processing to:

transform a first audio signal and spatial information for the first audio signal into a first set of basis function coefficients that describes a first sound field, wherein the first audio signal is in one of the following formats: channel-based or object-based;

combine the first set of basis function coefficients with a second set of basis function coefficients to produce a combined set of basis function coefficients that describes a combined sound field, wherein the second set of basis function coefficients describes a second sound field associated with a second audio signal; and

encode the combined set of basis function coefficients.

19. An apparatus for audio signal processing, the apparatus comprising:

means for transforming a first audio signal and spatial information for the first audio signal into a first set of basis function coefficients that describes a first sound field, wherein the first audio signal is in one of the following formats: channel-based or object-based;

means for combining the first set of basis function coefficients with a second set of basis function coefficients to produce a combined set of basis function coefficients that describes a combined sound field, wherein the second set of basis function coefficients describes a second sound field associated with a second audio signal; and

means for encoding the combined set of basis function coefficients.

20. The apparatus according to claim 19 , wherein the respective spatial information for each of the first audio signal and the second audio signal indicates a direction in space.

21. The apparatus according to claim 19 , wherein the first audio signal comprises a loudspeaker channel.

22. The apparatus according to claim 19 , wherein the apparatus further includes means for parsing an audio object that includes the first audio signal and the first spatial information for the first audio signal.

23. The apparatus according to claim 19 , wherein each basis function coefficient of the first set of basis function coefficients corresponds to a unique one of a set of orthogonal basis functions.

24. The apparatus according to claim 19 , wherein each basis function coefficient of the first set of basis function coefficients corresponds to a unique one of a set of spherical harmonic basis functions.

25. The apparatus according to claim 19 , wherein the first set of basis function coefficients describes the first sound field in at least two spatial dimensions, and wherein the second set of basis function coefficients describes the second sound field in at least two spatial dimensions.

26. The apparatus according to claim 19 , wherein at least one of the first set of basis function coefficients or the second set of basis function coefficients describes the corresponding sound field in three spatial dimensions.

27. The apparatus according to claim 19 , wherein a total number of basis function coefficients in the first set of basis function coefficients is less than a total number of basis function coefficients in the second set of basis function coefficients.

28. A device for audio signal processing, the device comprising:

an analyzer configured to transform a first audio signal and spatial information for the first audio signal into a first set of basis function coefficients that describes a first sound field, wherein the first audio signal is in one of the following formats: channel-based or object-based;

a combiner configured to combine the first set of basis function coefficients with a second set of basis function coefficients to produce a combined set of basis function coefficients that describes a second sound field, wherein the second set of basis function coefficients describes a second sound field associated with a second audio signal; and

an encoder configured to encode the combined set of basis function coefficients.

29. The device according to claim 28 , wherein the respective spatial information for each of the first audio signal and the second audio signal indicates a direction in space.

30. The device according to claim 28 , wherein the first audio signal comprises a loudspeaker channel.

31. The device according to claim 28 , further comprising a parser configured to parse an audio object that includes the first audio signal and the first spatial information for the first audio signal.

32. The device according to claim 28 , wherein each basis function coefficient of the first set of basis function coefficients corresponds to a unique one of a set of orthogonal basis functions.

33. The device according to claim 28 , wherein each basis function coefficient of the first set of basis function coefficients corresponds to a unique one of a set of spherical harmonic basis functions.

34. The device according to claim 28 , wherein the first set of basis function coefficients describes the first sound field in at least two spatial dimensions, and wherein the second set of basis function coefficients describes the second sound field in at least two spatial dimensions.

35. The device according to claim 28 , wherein at least one of the first set of basis function coefficients or the second set of basis function coefficients describes the corresponding sound field in three spatial dimensions.

36. The device according to claim 28 , wherein a total number of basis function coefficients in the first set of basis function coefficients is less than a total number of basis function coefficients in the second set of basis function coefficients.

37. The device according to claim 28 , further comprising one or more microphones configured to capture audio data associated with at least one of the first audio signal or the second audio signal.