SYSTEMS, METHODS, APPARATUS, AND COMPUTER-READABLE MEDIA FOR BACKWARD-COMPATIBLE AUDIO CODING

• US 20140016784A1
• Filed: 03/15/2013
• Published: 01/16/2014
• Est. Priority Date: 07/15/2012
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Sen, Dipanjan, Xiang, Pei
• Granted Patent: US 9,288,603 B2
• Time in Patent Office: Days
• US Class Current: 381/17
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G10L 19/167 Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes
• CPC Class Codes: G10L 19/18 Vocoders using multiple modes
• CPC Class Codes: H04H 20/89 using three or more audio channels, e.g. triphonic or quadraphonic
• CPC Class Codes: H04L 65/765 intermediate
• CPC Class Codes: H04S 2400/01 Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved
• CPC Class Codes: H04S 2400/03 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 Class Codes: H04S 2400/07 Generation or adaptation of the Low Frequency Effect [LFE] channel, e.g. distribution or signal processing
• CPC Class Codes: H04S 2400/15 Aspects of sound capture and related signal processing for recording or reproduction
• CPC Class Codes: H04S 2420/11 Application of ambisonics in stereophonic audio systems
• CPC Class Codes: H04S 3/002 Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution control circuits for electronic adaptation of the sound field H04S7/30
• CPC Class Codes: H04S 3/006 in which a plurality of audio signals are transformed in a combination of audio signals and modulated signals, e.g. CD-4 systems
• CPC Class Codes: H04S 3/008 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 Class Codes: H04S 7/30 Control circuits for electronic adaptation of the sound field

Abstract

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

Claims

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, 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, 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.

38. A non-transitory computer-readable data storage medium having tangible features that cause a machine reading the features to perform a method according to claim 1.

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. 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.

21. The apparatus according to claim 20, wherein said plurality of basis function coefficients is a plurality of coefficients of spherical harmonic basis functions.

22. The apparatus according to claim 20, 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.

23. The apparatus according to claim 20, 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.

24. The apparatus according to claim 20, 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.

25. The apparatus according to claim 20, wherein each among the plurality of basis function coefficients has a corresponding order within the plurality, 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.

26. The apparatus according to claim 20, wherein said means for performing the reversible transform comprises means for calculating a product of (A) the first group of the plurality of basis function coefficients and (B) an invertible matrix.

27. The apparatus according to claim 20, wherein said apparatus includes means for 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.

28. The apparatus according to claim 20, wherein said apparatus includes means for encoding a plurality of audio input signals to produce the plurality of basis function coefficients.

29. An apparatus for processing a plurality of basis function coefficients that describes a sound field during a time interval, said apparatus comprising:

a calculator configured to perform 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

a data formatter configured to produce 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.

30. The apparatus according to claim 29, wherein said plurality of basis function coefficients is a plurality of coefficients of spherical harmonic basis functions.

31. The apparatus according to claim 29, 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.

32. The apparatus according to claim 29, 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.

33. The apparatus according to claim 29, 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.

34. The apparatus according to claim 29, wherein each among the plurality of basis function coefficients has a corresponding order within the plurality, 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.

35. The apparatus according to claim 29, wherein said calculator is configured to calculate a product of (A) the first group of the plurality of basis function coefficients and (B) an invertible matrix.

36. The apparatus according to claim 29, wherein said apparatus includes a second calculator configured to transform 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.

37. The apparatus according to claim 29, wherein said apparatus includes an encoder configured to encode a plurality of audio input signals to produce the plurality of basis function coefficients.