METHOD AND APPARATUS FOR GENERATING AN ENHANCEMENT LAYER WITHIN AN AUDIO CODING SYSTEM

• US 20090112607A1
• Filed: 08/07/2008
• Published: 04/30/2009
• Est. Priority Date: 10/25/2007
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Ashley, James P., Mittal, Udar, Gibbs, Jonathan A.
• Granted Patent: US 8,209,190 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

During operation an input signal to be coded is received and coded to produce a coded audio signal. The coded audio signal is then scaled with a plurality of gain values to produce a plurality of scaled coded audio signals, each having an associated gain value and a plurality of error values are determined existing between the input signal and each of the plurality of scaled coded audio signals. A gain value is then chosen that is associated with a scaled coded audio signal resulting in a low error value existing between the input signal and the scaled coded audio signal. Finally, the low error value is transmitted along with the gain value as part of an enhancement layer to the coded audio signal.

Claims

1. A method for an audio encoder to embed coding of a signal, comprising the steps of:

the audio encoder receiving an input signal to be coded;

the audio encoder coding the input signal to produce a reconstructed audio signal;

the audio encoder scaling the reconstructed audio signal with a plurality of gain values to produce a plurality of scaled reconstructed audio signals, each having an associated gain value;

the audio encoder determining a plurality of error values based on the input signal and each of the plurality of scaled reconstructed audio signals;

the audio encoder choosing a gain value from the plurality of gain values based on the plurality of error values; and

the audio encoder transmitting or storing the gain value as part of an enhancement layer to a coded audio signal.

2. The method of claim 1 wherein the plurality of gain values comprise frequency selective gain values.

3. The method of claim 1 wherein the plurality of gain values are a function of a previously encoded signal layer.

4. A method for an audio decoder receiving a coded audio signal and an enhancement to the coded audio signal, the method comprising the steps of:

the audio decoder receiving the coded audio signal; and

the audio decoder receiving the enhancement to the coded audio signal, wherein the enhancement to the coded audio signal comprises a gain value and an error signal associated with the gain value, wherein the gain value was chosen by a transmitter from a plurality of gain values, wherein the gain value is associated with a scaled reconstructed audio signal resulting in a particular error value existing between an audio signal and the scaled reconstructed audio signal; and

the audio decoder enhancing the coded audio signal based on the gain value and the error value.

5. The method of claim 4 wherein the gain value comprises a frequency selective gain value.

6. The method of claim 5 wherein the frequency selective gain values

7. An apparatus comprising:

an encoder receiving an input signal to be coded and coding the input signal to produce a reconstructed audio signal;

a scaling unit scaling the reconstructed audio signal with a plurality of gain values to produce a plurality of scaled reconstructed audio signals, each having an associated gain value;

an error signal generator determining plurality of error values existing between the input signal and each of the plurality of scaled reconstructed audio signals;

a gain selector choosing a gain value from the plurality of gain values, wherein the gain value is chosen based on the plurality of error values existing between the input signal and the scaled reconstructed audio signal; and

a transmitter transmitting the selected gain value as part of an enhancement layer to a coded audio signal.

8. The apparatus of claim 7 wherein the plurality of gain values comprise frequency selective gain values.

9. The apparatus of claim 8 wherein the frequency selective gain values

10. An apparatus comprising:

a decoder receiving a coded audio signal; and

an enhancement layer decoder receiving enhancement to the coded audio signal and producing an enhanced audio signal, wherein the enhancement to the coded audio signal comprises a gain value and an error signal associated with the gain value, wherein the gain value was chosen by an encoder from a plurality of gain values, wherein the gain value is associated with a scaled reconstructed audio signal resulting in a particular error value existing between an input audio signal and the scaled reconstructed audio signal.

11. An apparatus comprising:

a decoder receiving codewords to produce a reconstructed audio signal; and

an enhancement layer decoder receiving codewords for enhancement to the coded audio signal and outputting an enhanced reconstructed audio signal, wherein the enhancement to the reconstructed audio signal comprises a frequency selective gain value and an error signal associated with the gain value, wherein the frequency selective gain value is based on the reconstructed audio signal.

12. A method for a decoder to decode a multi-layer encoded audio signal, the method comprising the steps of:

the decoder receiving a first reconstructed audio vector Ŝ

₃ a first signal decoder;

the decoder receiving a first frequency domain error vector Ê

₃ from a first enhancement layer decoder;

the decoder generating a frequency selective gain vector g^* based on at least the first frequency domain error vector;

the decoder scaling the first reconstructed audio signal with the frequency selective gain vector to produce a scaled reconstructed audio signal;

the decoder receiving a codeword i_E for input to a second enhancement layer decoder to produce a second enhancement layer error vector E^*; and

the decoder combining the scaled reconstructed audio signal with the second enhancement layer error vector to produce a decoded multi-layer audio signal output Ŝ

₄.

13. The method of claim 12 wherein the frequency domain comprises the MDCT domain.

14. The method of claim 12 wherein the step of generating the frequency selective gain vector further comprises:

receiving a gain codeword i_g; and

generating the frequency selective gain vector based on the gain codeword and the first frequency domain error vector.

15. The method of claim 12 wherein the frequency selective gain vector comprises g_j(k), wherein g_j(k) is the gain of a k-th frequency component of a j-th candidate vector.