Multi-channel signal encoding and decoding

• US 20030191635A1
• Filed: 03/14/2003
• Published: 10/09/2003
• Est. Priority Date: 09/15/2000
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Minde, Tor Bjorn, Lundberg, Tomas
• Granted Patent: US 7,263,480 B2
• Time in Patent Office: Days
• US Class Current: 704/220
• 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 19/24 Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding

Abstract

A multi-channel linear predictive analysis-by-synthesis signal encoding method determines (S1) a leading channel and encodes the leading channel as an embedded bitstream. Thereafter trailing channels are encoded as a discardable bitstream exploiting cross-correlation to the leading channel.

Claims

1. A multi-channel linear predictive analysis-by-synthesis signal encoding method, characterized by

determining a leading channel and at least one trailing channel lagging behind said leading channel;

encoding said leading channel as an embedded bitstream;

encoding trailing channels as a discardable bitstream; and

selecting a trailing channel encoding mode depending on inter-channel correlation to said leading channel.

2. The method of claim 1, characterized in that selectable encoding modes result in a fixed gross bit-rate.

3. The method of claim 1 or 2, characterized in -that selectable-encoding modes may result in a variable gross bit-rate.

4. The method of any of the preceding claims, characterized by

using channel specific LPC filters for low inter-channel correlation;

and

sharing said leading channel LPC filter for high inter-channel correlation.

5. The method of any of the preceding claims, characterized by

using channel specific fixed codebooks for low inter-channel correlation;

and

sharing said leading channel fixed codebook for high inter-channel correlation.

6. The method of claim 5, characterized by using an inter-channel lag from said leading channel fixed codebook to each trailing channel.

7. The method of any of the preceding claims, characterized by adaptively distributing bits between trailing channel fixed codebooks and said leading channel fixed codebook depending on inter-channel correlation.

8. The method of any of the preceding claims, characterized by

using channel specific adaptive codebook lags for low inter-channel correlation;

and

using a shared adaptive codebook lag for high inter-channel correlation.

9. The method of claim 8, characterized by using an inter-channel adaptive codebook lag from said leading channel adaptive codebook to each trailing channel.

10. A multi-channel linear predictive analysis-by-synthesis signal encoder, characterized by

means (40) for determining a leading channel and at least one trailing channel lagging behind said leading channel;

means for encoding said leading channel as an embedded bitstream;

means for encoding trailing channels as a discardable bitstream; and

means (40) for selecting a trailing channel encoding mode depending on inter-channel correlation to said leading channel.

11. The encoder of claim 10, characterized by

channel specific LPC filters for low inter-channel correlation;

and

a shared leading channel LPC filter for high inter-channel correlation.

12. The encoder of claims 10 or 11, characterized by

channel specific fixed codebooks for low inter-channel correlation;

and

a shared leading channel fixed codebook for high inter-channel correlation.

13. The encoder of claim 12, characterized by

an inter-channel lag (D) from said leading channel fixed codebook to each trailing channel.

14. The encoder of any of the preceding claims 10-13, characterized by means (40) for adaptively distributing bits between trailing channel fixed codebooks and said leading channel fixed codebook depending on inter-channel correlation.

15. The encoder of any of the preceding claims 10-14, characterized by

channel specific adaptive codebook lags (P₁₁, P₂₂) for low inter-channel correlation;

and

a shared adaptive codebook lag for high inter-channel correlation.

16. The encoder of claim 15, characterized by an inter-channel adaptive codebook lag (P₁₂) from said leading channel adaptive codebook to each trailing channel.

17. A terminal including a multi-channel linear predictive analysis-by-synthesis signal encoder, characterized by

means (40) for determining a leading channel and at least one trailing channel lagging behind said leading channel;

means for encoding said leading channel as an embedded bitstream;

means for encoding trailing channels as a discardable bitstream; and

means (40) for selecting a trailing channel encoding mode depending on inter-channel correlation to said leading channel.

18. The terminal of claim 17, characterized by

channel specific LPC filters for low inter-channel correlation;

and

a shared leading channel LPC filter for high inter-channel correlation.

19. The terminal of claim 17 or 18, characterized by

channel specific fixed codebooks for low inter-channel correlation;

and

a shared leading channel fixed codebook for high inter-channel correlation.

20. The terminal of claim 19, characterized by an inter-channel lag (D) from said leading channel fixed codebook to each trailing channel.

21. The terminal of any of the preceding claims 17-20, characterized by means (40) for adaptively distributing bits between trailing channel fixed codebooks and said leading channel fixed codebook depending on inter-channel correlation.

22. The terminal of any of the preceding claims 17-21, characterized by

channel specific adaptive codebook lags (P₁₁, P₂₂) for low inter-channel correlation;

and

a shared adaptive codebook lag for high inter-channel correlation.

23. The terminal of claim 22, characterized by an inter-channel adaptive codebook lag (P₁₂) from said leading channel adaptive codebook to each trailing channel.