Systems, methods, apparatus, and computer-readable media for backward-compatible audio coding

Patent metadata

Field	Value
Publication number	US-9288603-B2
Application number	US-201313844447-A
Country	US
Kind code	B2
Filing date	Mar 15, 2013
Priority date	Jul 15, 2012
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

Systems, methods, and apparatus for backward-compatible coding of a set of basis function coefficients that describe a sound field are presented.

First claim

What is claimed is:

1. A method of processing a plurality of basis function coefficients that describes a sound field during a time interval, said method comprising:
performing a reversible transform on a first group of the plurality of basis function coefficients to produce a plurality of channel signals, wherein each of the plurality of channel signals is associated with a corresponding different region of space; and
based on the plurality of channel signals, producing a data structure that includes (A) a representation of a second group of the plurality of basis function coefficients, wherein the second group is different than the first group, and (B) a representation of the plurality of channel signals that is separate from said representation of the second group.

2. The method according to claim 1 , wherein said plurality of basis function coefficients is a plurality of coefficients of spherical harmonic basis functions.

3. The method according to claim 1 , wherein said plurality of channel signals includes a first channel signal associated with a first loudspeaker location and a second channel signal associated with a second loudspeaker location that is different than the first loudspeaker location.

4. The method according to claim 1 , wherein said plurality of channel signals includes a first channel signal associated with a first spatial direction and a second channel signal associated with a second spatial direction that is different than the first spatial direction.

5. The method according to claim 4 , wherein, for each of the coefficients of the first group, said coefficient corresponds to a basis function whose energy is concentrated along at least one direction within a first plane at least as much as along any direction outside the first plane, wherein the first plane includes the first and second spatial directions.

6. The method according to claim 4 , wherein a first coefficient of the first group corresponds to a basis function that is omnidirectional, and
wherein, for each of the other coefficients of the first group, said coefficient corresponds to a basis function whose energy is concentrated along at least one direction within a first plane, wherein the first plane includes the first and second spatial directions.

7. The method according to claim 4 , wherein, for each of at least some of the coefficients of the second group, said coefficient corresponds to a basis function whose energy is concentrated along at least one direction outside a plane that includes the first and second spatial directions.

8. The method according to claim 1 , wherein said plurality of channel signals includes a set of channel signals, wherein each signal of the set of channel signals is associated with a corresponding different one of a set of coplanar directions that are evenly spaced from one another.

9. The method according to claim 1 , wherein each among the plurality of basis function coefficients has a corresponding order within the plurality of basis function coefficients, and
wherein, for each among the first group of the plurality of basis function coefficients, said order of said coefficient is less than the lowest among said orders of the coefficients of the second group of the plurality of basis function coefficients.

10. The method according to claim 1 , wherein each among the plurality of basis function coefficients has a corresponding order within the plurality of basis function coefficients, and
wherein, for each among the second group of the plurality of basis function coefficients, said order of said coefficient is greater than the highest among said orders of the coefficients of the first group of the plurality of basis function coefficients.

11. The method according to claim 1 , wherein said performing the reversible transform comprises calculating a product of (A) the first group of the plurality of basis function coefficients and (B) an invertible matrix.

12. The method according to claim 1 , wherein said data structure includes a first stream that includes said representation of the second group and a second stream that includes the representation of the plurality of channel signals.

13. The method according to claim 1 , wherein said method includes transforming each of the plurality of channel signals into a sequence of time-domain samples, and
wherein said representation of the plurality of channel signals is based on said sequences of time-domain samples.

14. The method according to claim 1 , wherein said method includes encoding a plurality of audio input signals to produce the plurality of basis function coefficients.

15. The method according to claim 14 , wherein each of said plurality of audio input signals is based on a signal produced by a corresponding microphone of a microphone array.

16. A method of obtaining a plurality of basis function coefficients that describes a sound field during a time interval, said method comprising:
from a data structure, obtaining (A) a representation of a second group of the plurality of basis function coefficients and (B) a representation of a plurality of channel signals that is separate from said representation of the second group, wherein each of a subset of the plurality of channel signals is associated with a corresponding different region of space; and
performing a transform on the subset of the plurality of channel signals to produce a first group of the plurality of basis function coefficients, wherein the first group is different than the second group.

17. The method according to claim 16 , wherein each of said plurality of basis function coefficients corresponds to a unique one of a set of orthogonal basis functions.

18. The method according to claim 16 , wherein each of said plurality of basis function coefficients corresponds to a unique one of a set of spherical harmonic basis functions.

19. The method according to claim 16 , wherein said method comprises, based on said plurality of basis function coefficients, producing a second plurality of channel signals,
wherein each signal of the subset of the plurality of channel signals is associated with a corresponding different one of a set of coplanar directions, and
wherein each of the second plurality of channel signals is associated with a corresponding different one of a set of directions that span a three-dimensional space.

20. The method of claim 16 , wherein the transform comprises a reversible transform.

21. The method of claim 16 , wherein the transform comprises an inverse transform.

22. The method of claim 16 , wherein the transform comprises an inverse of a reversible transform.

23. An apparatus for processing a plurality of basis function coefficients that describes a sound field during a time interval, said apparatus comprising:
means for performing a reversible transform on a first group of the plurality of basis function coefficients to produce a plurality of channel signals, wherein each of the plurality of channel signals is associated with a corresponding different region of space; and
means for producing a data structure, based on the plurality of channel signals, that includes (A) a representation of a second group of the plurality of basis function coefficients, wherein the second group is different than the first group, and (B) a representation of the plurality of channel signals that is separate from said representation of the second group.

24. The apparatus according to claim 23 , wherei

Assignees

• Qualcomm Inc

Inventors

• Sen Dipanjan
• Xiang Pei

Classifications

• H04H20/89

  using three or more audio channels, e.g. triphonic or quadraphonic · CPC title

• H04S7/30 Primary

  Control circuits for electronic adaptation of the sound field · CPC title

• H04S2420/11

  Application of ambisonics in stereophonic audio systems · 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