Multi-channel audio encoding and decoding

• US 8,099,292 B2
• Filed: 11/11/2010
• Issued: 01/17/2012
• Est. Priority Date: 09/04/2002
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Thumpudi, Naveen, Chen, Wei-Ge
• Primary Examiner(s): RIDER, JUSTIN W
• Application Number:
  US12/944,604
• Publication Number:
  US 20110054916A1
• Time in Patent Office: 432 Days
• Field of Search: None
• US Class Current: 704/500
• CPC Class Codes: G10L 19/00 Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis in musical instruments G10H
• 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 19/0212 using orthogonal transformation

Abstract

An audio encoder and decoder use architectures and techniques that improve the efficiency of multi-channel audio coding and decoding. The described strategies include various techniques and tools, which can be used in combination or independently. For example, an audio encoder performs a pre-processing multi-channel transform on multi-channel audio data, varying the transform so as to control quality. The encoder groups multiple windows from different channels into one or more tiles and outputs tile configuration information, which allows the encoder to isolate transients that appear in a particular channel with small windows, but use large windows in other channels. Using a variety of techniques, the encoder performs flexible multi-channel transforms that effectively take advantage of inter-channel correlation. An audio decoder performs corresponding processing and decoding. In addition, the decoder performs a post-processing multi-channel transform for any of multiple different purposes.

Claims

1. In a computing device that implements an audio encoder, a computer-implemented method comprising, with the computing device that implements the audio encoder:

receiving multi-channel audio data;

transforming the audio data according to a hierarchy of plural multi-channel transforms in plural stages; and

outputting information for the hierarchy of plural multi-channel transforms.

2. The method of claim 1 wherein the multi-channel audio data is in two channels.

3. The method of claim 1 wherein the multi-channel audio data is in more than two channels.

4. The method of claim 1 wherein each of the plural stages includes one or more of the transforms.

5. The method of claim 1 wherein the encoder selects the transforms.

6. The method of claim 1 wherein channel groups are the same in at least two of the plural stages.

7. The method of claim 1 wherein channel groups are different in at least two of the plural stages.

8. The method of claim 1 wherein the output information comprises channel group information and transform information.

9. The method of claim 1 wherein the plural stages consist of two stages.

10. The method of claim 1 wherein the hierarchy emulates another transform while reducing computational complexity compared to the other transform.

11. The method of claim 1 wherein at least one of the transforms is an identity transform, and wherein at least one of the transforms is a general unitary transform factored into plural matrices.

12. A computer-readable medium storing computer-executable instructions for causing a computer programmed thereby to perform the method of claim 1.

13. In a computing device that implements an audio decoder, a computer-implemented method comprising, with the computing device that implements the audio decoder:

receiving encoded multi-channel audio data;

retrieving information for a hierarchy of plural inverse multi-channel transforms in plural stages; and

decoding the audio data, including transforming the audio data according to the hierarchy of the plural inverse multi-channel transforms.

14. The method of claim 13 wherein the multi-channel audio data is in two channels.

15. The method of claim 13 wherein the multi-channel audio data is in more than two channels.

16. The method of claim 13 wherein channel groups are the same in at least two of the plural stages.

17. The method of claim 13 wherein channel groups are different in at least two of the plural stages.

18. The method of claim 13 wherein the plural stages consist of first and second stages, and wherein the retrieving comprises:

(a) getting a bit;

(b) if the bit indicates there are no more transforms in the first stage, continuing to step (c), otherwise, getting transform information for a transform in the first stage, getting a new bit, and repeating step (b) with the new bit; and

(c) getting transform information for one or more transforms in the second stage.

19. The method of claim 18 further comprising getting channel group information along with at least some of the transform information.

20. The method of claim 13 wherein at least one inverse multi-channel transform of the plural inverse multi-channel transforms is a custom inverse multi-channel transform, and wherein the retrieving information for the hierarchy of plural inverse multi- channel transforms comprises:

retrieving one or more signals to select the custom inverse multi-channel transform; and

retrieving information for individual elements of the custom inverse multi-channel transform.

21. The method of claim 13, further comprising:

retrieving frequency band on/off information for the plural inverse multi-channel transforms.

22. The method of claim 21, further comprising:

based on the frequency band on/off information, selectively turning at least one of the plural inverse multi-channel transforms on/off at plural frequency bands in at least one of the plural stages.

23. A computer-readable storage medium storing computer-executable instructions for causing a computer programmed thereby to perform a method for decoding audio, the method comprising:

receiving encoded multi-channel audio data;

retrieving information for a hierarchy of plural inverse multi-channel transforms in plural stages; and

decoding the audio data, including transforming the audio data according to the hierarchy of the plural inverse multi-channel transforms.