Multi-channel audio encoding and decoding

• US 8,069,050 B2
• Filed: 11/10/2010
• Issued: 11/29/2011
• 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:
  US12/943,701
• Publication Number:
  US 20110060597A1
• Time in Patent Office: 384 Days
• Field of Search: 704/200.1, 704/500
• 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;

computing an arbitrary unitary transform matrix for a multi-channel transform;

factorizing the arbitrary unitary transform matrix into plural rotation matrices and a sign matrix;

performing the factorized transform on the audio data; and

outputting information for the factorized transform.

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 the output information includes angles for the plural rotation matrices and signs for the sign matrix.

5. The method of claim 4 further comprising quantizing the angles to 6-bit precision.

6. A computer-readable storage medium, not comprising a signal, storing computer-executable instructions for causing a computer programmed thereby to perform the method of claim 1.

7. 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 factorized transform of an arbitrary unitary inverse transform matrix; and

performing the factorized transform on the audio data.

8. The method of claim 7 wherein the multi-channel audio data is in two channels.

9. The method of claim 7 wherein the multi-channel audio data is in more than two channels.

10. The method of claim 7 wherein the retrieved information includes angles for plural rotation matrices and signs for a sign matrix.

11. The method of claim 10 wherein the angles are quantized to 6-bit precision.

12. A computer-readable storage medium, not comprising a signal, 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 factorized transform of an arbitrary unitary inverse transform matrix; and

performing the factorized transform on the audio data.

13. The method of claim 12 wherein the multi-channel audio data is in two channels.

14. The method of claim 12 wherein the multi-channel audio data is in more than two channels.

15. The method of claim 12 wherein the retrieved information includes angles for plural rotation matrices and signs for a sign matrix.

16. The method of claim 15 wherein the angles are quantized to 6-bit precision.