Enhanced layered gain factor balancing within a multiple-channel audio coding system

• US 8,175,888 B2
• Filed: 12/29/2008
• Issued: 05/08/2012
• Est. Priority Date: 12/29/2008
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola Mobility, Inc. (Lenovo Group Ltd.)
• Inventors: Ashley, James P., Mittal, Udar
• Primary Examiner(s): Opsasnick, Michael N
• Application Number:
  US12/345,165
• Publication Number:
  US 20100169101A1
• Time in Patent Office: 1,226 Days
• Field of Search: 704/500
• US Class Current: 704/500
• 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

During operation a multiple channel audio input signal is received and coded to generate a coded audio signal. A balance factor having balance factor components each associated with an audio signal of the multiple channel audio signal is generated. A gain value to be applied to the coded audio signal to generate an estimate of the multiple channel audio signal based on the balance factor and the multiple channel audio signal is determined, with the gain value configured to minimize a distortion value between the multiple channel audio signal and the estimate of the multiple channel audio signal. The representation of the gain value may be output for transmission and/or storage.

Claims

1. An apparatus operable to code a multiple channel audio signal, comprising:

an encoder that receives a multiple channel audio signal that comprises a plurality of audio signals and codes the multiple channel audio signal to generate a coded audio signal;

a balance factor generator of an enhancement layer encoder that receives a coded audio signal and generates a balance factor having a plurality of balance factor components each associated with an audio signal of the plurality of audio signals of the multiple channel audio signal;

a gain vector generator of an enhancement layer encoder that determines a gain value to be applied to the coded audio signal to generate an estimate of the multiple channel audio signal based on the balance factor and the multiple channel audio signal, wherein the gain value is configured to minimize a distortion value between the multiple channel audio signal and the estimate of the multiple channel audio signal; and

a transmitter that transmits a representation of the gain value for at least one of transmission and storage.

2. The apparatus of claim 1, further comprising:

a scaling unit of the enhancement layer encoder that scales the coded audio signal with a plurality of gain values to generate a plurality of candidate coded audio signals, wherein at least one of the candidate coded audio signals is scaled;

wherein the scaling unit and the balance factor generator generate the estimate of the multiple channel audio signal based on the balance factor and the at least one scaled coded audio signal of the plurality of candidate coded audio signals; and

a gain selector of the enhancement layer encoder that evaluates the distortion value based on the estimate of the multiple channel audio signal and the multiple channel audio signal to determine a representation of an optimal gain value of the plurality of gain values.

3. The apparatus of claim 1, wherein the encoder encodes the audio signal to generate a reconstructed audio vector Ŝ

and the gain vector generator further comprising;

a scaling unit that detects a set of peaks in the reconstructed audio vector Ŝ

of a received audio signal, generates a scaling mask ψ

(Ŝ

) based on the detected set of peaks, generates a plurality of gain vectors gj based on the scaling mask, and scales the reconstructed audio signal with the plurality of gain vectors to produce the plurality of scaled reconstructed audio signals;

an error signal generator that generates a plurality of distortions based on the audio signal and the plurality of scaled reconstructed audio signals; and

a gain selector that chooses a gain vector from the plurality of gain vectors based on the plurality of distortions,

wherein the transmitter outputs for at least one of transmitting and storing the index representative of the gain vector.

4. The apparatus of claim 3, wherein the gain selector detects the set of peaks further in accordance with a peak detection function given as:

5. An apparatus operable to code a multiple channel audio signal, comprising:

an encoder that receives a multiple channel audio signal that comprises a plurality of audio signals and codes the multiple channel audio signal to generate a coded audio signal;

a scaling unit of an enhancement layer encoder that scales the coded audio signal with a plurality of gain values to generate a plurality of candidate coded audio signals, wherein at least one of the candidate coded audio signals is scaled;

a balance factor generator that generates a balance factor having a plurality of balance factor components each associated with an audio signal of the plurality of audio signals of the multiple channel audio signal;

wherein the scaling unit and the balance factor generator generate an estimate of the multiple channel audio signal based on the balance factor and the at least one scaled coded audio signal of the plurality of candidate coded audio signals;

a gain selector of the enhancement layer encoder that evaluates a distortion value based on the estimate of the multiple channel audio signal and the multiple channel audio signal to determine a representation of an optimal gain value of the plurality of gain values;

a transmitter that transmits the representation of the optimal gain value for at least one of transmission and storage.

6. The apparatus of claim 5, wherein a gain value of the plurality of gain values is a gain matrix with vector g_j as the diagonal component and wherein the gain matrix is frequency selective.

7. The apparatus of claim 5, wherein the representation of the optimal gain value is given by:

8. The apparatus of claim 5, wherein each balance factor component is given by:

9. The apparatus of claim 5, wherein the balance factor generator generates a correlation value between the scaled coded audio signal and at least one of the audio signals of the multiple channel audio signal.

10. The apparatus of claim 5, wherein the balance factor generator generates a self correlation between at least one of the audio signals of the multiple channel audio signal and generates a square root of the self correlation.

11. The apparatus of claim 5, wherein the gain selector generates a distortion value based on the estimate of the multiple channel audio signal and the multiple channel audio signal and wherein the gain value is based upon the distortion value.

12. The apparatus of claim 5, wherein the estimate comprises a plurality of estimates corresponding to the plurality of candidate coded audio signals.

13. The apparatus of claim 5, wherein the coded audio signal is one of a mono and a multiple channel signal.

14. The apparatus of claim 13, wherein the coded multiple channel audio signal is a stereo signal.

15. A method for coding a multiple channel audio signal, comprising:

receiving a multiple channel audio signal that comprises a plurality of audio signals;

coding the multiple channel audio signal to generate a coded audio signal;

generating a balance factor having a plurality of balance factor components each associated with an audio signal of the plurality of audio signals of the multiple channel audio signal;

determining a gain value to be applied to the coded audio signal to generate an estimate of the multiple channel audio signal based on the balance factor and the multiple channel audio signal, wherein the gain value is configured to minimize a distortion value between the multiple channel audio signal and the estimate of the multiple channel audio signal; and

outputting a representation of the gain value for at least one of transmission and storage.

16. The method of claim 15, further comprising:

scaling the coded audio signal with a plurality of gain values to generate a plurality of candidate coded audio signals, wherein at least one of the candidate coded audio signals is scaled;

generating the estimate of the multiple channel audio signal based on the balance factor and the at least one scaled coded audio signal of the plurality of candidate coded audio signals; and

evaluating the distortion value based on the estimate of the multiple channel audio signal and the multiple channel audio signal to determine a representation of an optimal gain value of the plurality of gain values.

17. The method of claim 15,

detecting a set of peaks in a reconstructed audio vector Ŝ

of a received audio signal;

generating a scaling mask ψ

(Ŝ

) based on the detected set of peaks;

generating a gain vector g* based on at least the scaling mask and an index j representative of the gain vector;

scaling the reconstructed audio signal with the gain vector to produce a scaled reconstructed audio signal;

generating a distortion based on the audio signal and the scaled reconstructed audio signal; and

outputting the index of the gain vector based on the generated distortion.

18. The method of claim 15, further comprising:

receiving an audio signal;

encoding the audio signal to generate a reconstructed audio vector Ŝ

;

detecting a set of peaks in the reconstructed audio vector Ŝ

of a received audio signal;

generating a scaling mask ψ

(Ŝ

) based on the detected set of peaks;

generating a plurality of gain vectors g_j based on the scaling mask;

scaling the reconstructed audio signal with the plurality of gain vectors to produce the plurality of scaled reconstructed audio signals;

generating a plurality of distortions based on the audio signal and a plurality of scaled reconstructed audio signals;

choosing a gain vector from the plurality of gain vectors based on the plurality of distortions; and

outputting for at least one of transmitting and storing the index representative of the gain vector.