Embedded Speech and Audio Coding Using a Switchable Model Core

• US 20110161087A1
• Filed: 12/31/2009
• Published: 06/30/2011
• Est. Priority Date: 12/31/2009
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Gibbs, Jonathan A., ASHLEY, James P., Mittal, Udar
• Granted Patent: US 8,442,837 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 method for processing an audio signal including classifying an input frame as either a speech frame or a generic audio frame, producing an encoded bitstream and a corresponding processed frame based on the input frame, producing an enhancement layer encoded bitstream based on a difference between the input frame and the processed frame, and multiplexing the enhancement layer encoded bitstream, a codeword, and either a speech encoded bitstream or a generic audio encoded bitstream into a combined bitstream based on whether the codeword indicates that the input frame is classified as a speech frame or as a generic audio frame, wherein the encoded bitstream is either a speech encoded bitstream or a generic audio encoded bitstream.

Claims

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

classifying an input frame as either a speech frame or a generic audio frame, the input frame is based on the audio signal;

producing an encoded bitstream and a corresponding processed frame based on the input frame;

producing an enhancement layer encoded bitstream based on a difference between the input frame and the processed frame; and

multiplexing the enhancement layer encoded bitstream, a codeword, and either a speech encoded bitstream or a generic audio encoded bitstream into a combined bitstream based on whether the codeword indicates that the input frame is classified as a speech frame or as a generic audio frame,

wherein the encoded bitstream is either a speech encoded bitstream or a generic audio encoded bitstream.

2. The method of claim 1,

producing at least a speech encoded bitstream and at least a corresponding speech processed frame based on the input frame when the input frame is classified as a speech frame, and producing at least a generic audio encoded bitstream and at least a generic audio processed frame based on the input frame when the input frame is classified as a generic audio frame,

multiplexing the enhancement layer encoded bitstream, the speech encoded bitstream, and the codeword into the combined bitstream only when the input frame is classified as a speech frame, and

multiplexing the enhancement layer encoded bitstream, the generic audio encoded bitstream, and the codeword into the combined bitstream only when the input frame is classified as a generic audio frame.

3. The method of claim 2,

producing the enhancement layer encoded bitstream based on the difference between the input frame and the processed frame

wherein the processed frame is a speech processed frame when the input frame is classified as a speech frame, and

wherein the processed frame is a generic audio processed frame when the input frame is classified as a generic audio frame.

4. The method of claim 3, the processed frame is a generic audio frame, the method further comprising

obtaining linear prediction filter coefficients by performing a linear prediction coding analysis of the processed frame of the generic audio coder,

weighting the difference between the input frame and the processed frame of the generic audio coder based on the linear prediction filter coefficients.

5. The method of claim 1,

producing the speech encoded bitstream and a corresponding speech processed frame only when the input frame is classified as a speech frame,

producing the generic audio encoded bitstream and a corresponding generic audio processed frame only when the input frame is classified as a generic audio frame,

multiplexing the enhancement layer encoded bitstream, the speech encoded bitstream, and the codeword into the combined bitstream only when the input frame is classified as a speech frame, and

multiplexing the enhancement layer encoded bitstream, the generic audio encoded bitstream, and the codeword into the combined bitstream only when the input frame is classified as a generic audio frame.

6. The method of claim 5,

producing the enhancement layer encoded bitstream based on the difference between the input frame and the processed frame

wherein the processed frame is a speech processed frame when the input frame is classified as a speech frame, and

wherein the processed frame is a generic audio processed frame when the input frame is classified as a generic audio frame.

7. The method of claim 6, classifying the input frame before producing either the speech encoded bit stream or the generic audio encoded bitstream.

8. The method of claim 6, the processed frame is a generic audio frame, the method further comprising

obtaining linear prediction filter coefficients by performing a linear prediction coding analysis of the processed frame of the generic audio coder,

weighting the difference between the input frame and the processed frame of the generic audio coder based on the linear prediction filter coefficients.

9. The method of claim 1,

producing the corresponding processed frame includes producing a speech processed frame and producing generic audio processed frame,

classifying the input frame based on the speech processed frame and the generic audio processed frame.

10. The method of claim 9,

producing a first difference signal based on the input frame and the speech processed frame and producing a second difference signal based on the input frame and the generic audio processed frame,

classifying the input frame based on a comparison of the first difference and the second difference.

11. The method of claim 10, classifying the input signal as either a speech signal or a generic audio signal based on a comparison of an energy characteristic of a first set of difference signal audio samples associated with the first difference signal and a second set of difference signal audio samples associated with the second difference signal.

12. The method of claim 1, the processed frame is a generic audio frame, the method further comprising

obtaining linear prediction filter coefficients by performing a linear prediction coding analysis of the processed frame of the generic audio coder,

weighting the difference between the input frame and the processed frame of the generic audio coder based on the linear prediction filter coefficients,

producing the enhancement layer encoded bitstream based on the weighted difference.

15. The method of claim 1, the decoded enhancement layer frame is a weighted error signal and the encoded bitstream is a generic audio encoded bitstream, the method further comprising applying an inverse weighting matrix to the weighted error signal before combining.

13. A method for decoding an audio signal, the method comprising:

de-multiplexing a combined bitstream into an enhancement layer encoded bitstream, a codeword and an encoded bitstream, the codeword indicating whether the encoded bitstream is a speech encoded bitstream or a generic audio encoded bitstream;

decoding the enhancement layer encoded bitstream into a decoded enhancement layer frame;

decoding the encoded bitstream into a decoded audio frame, wherein the encoded bitstream is decoded using either a speech decoder or a generic audio decoder depending on whether the codeword indicates that the encoded bitstream is a speech encoded bitstream or a generic audio encoded bitstream; and

combining the decoded enhancement layer frame and the decoded audio frame.

14. The method of claim 13, determining whether to decode the encoded bit stream using a speech decoder or a generic audio decoder based on whether the codeword indicate that the decoded audio signal is a speech signal or a generic audio signal.