SELECTIVE SCALING MASK COMPUTATION BASED ON PEAK DETECTION

• US 20100169100A1
• Filed: 12/29/2008
• Published: 07/01/2010
• Est. Priority Date: 12/29/2008
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Ashley, James P., Mittal, Udar
• Granted Patent: US 8,140,342 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• 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 set of peaks in a reconstructed audio vector Ŝ of a received audio signal is detected and a scaling mask ψ(Ŝ) based on the detected set of peaks is generated. A gain vector g* is generated based on at least the scaling mask and an index j representative of the gain vector. The reconstructed audio signal is scaled with the gain vector to produce a scaled reconstructed audio signal. A distortion is generated based on the audio signal and the scaled reconstructed audio signal. The index of the gain vector based on the generated distortion is output.

Claims

1. An apparatus operable to code an audio signal, the method comprising:

a gain selector of a gain vector generator of an enhancement layer encoder that detects a set of peaks in a reconstructed audio vector Ŝ

of a received audio signal, generates a scaling mask ψ

(Ŝ

) based on the detected set of peaks;

a scaling unit of the gain vector generator that generates a gain vector g* based on at least the scaling mask and an index j representative of the gain vector, scales the reconstructed audio signal with the gain vector to produce a scaled reconstructed audio signal;

an error signal generator of the gain vector generator that generates a distortion based on the audio signal and the scaled reconstructed audio signal; and

a transmitter of the enhancement layer encoder that outputs the index of the gain vector based on the generated distortion.

2. The apparatus of claim 1, wherein the gain selector detects the set of peaks further in accordance with a peak detection function given as:

3. The apparatus of claim 1, wherein the audio signal is embedded in multiple layers.

4. The apparatus of claim 1, wherein the reconstructed audio vector Ŝ

is in the frequency domain and the set of peaks are frequency domain peaks.

5. The apparatus of claim 1,

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 the 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;

wherein the gain vector generator of the enhancement layer encoder 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,

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

6. The apparatus of 5, wherein the 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

wherein the 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.

7. An apparatus operable to encode an audio signal, the method comprising:

an encoder that receives an audio signal and encodes the audio signal to generate a reconstructed audio vector Ŝ

;

a scaling unit of a gain vector generator of an enhancement layer encoder 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 of the gain vector generator that generates a plurality of distortions based on the audio signal and the plurality of scaled reconstructed audio signals;

a gain selector of the gain vector generator that chooses a gain vector from the plurality of gain vectors based on the plurality of distortions; and

a transmitter of the enhancement layer encoder that outputs for at least one of transmitting and storing the index representative of the gain vector.

9. The apparatus of claim 7, wherein the scaling unit detects the set of peaks in accordance with a peak detection function given as:

10. The apparatus of claim 7, wherein the audio signal is embedded in multiple layers.

11. The apparatus of claim 7, wherein the reconstructed audio vector Ŝ

is in the frequency domain and the set of peaks are frequency domain peaks.

8. The apparatus of 7, wherein the gain vector is chosen that corresponds with a minimum distortion of the plurality of distortions.

12. A method for encoding an audio signal, the method comprising:

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.

13. The method of claim 12, wherein detecting the set of peaks further comprises a peak detection function given as:

14. The method of claim 12, wherein the audio signal is embedded in multiple layers.

15. The method of claim 12, wherein the reconstructed audio vector Ŝ

is in the frequency domain and the set of peaks are frequency domain peaks.

16. The method of claim 12, further 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.

17. The method of claim 12, further 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;

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 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;

generating 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;

evaluating 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;

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