Embedded speech and audio coding using a switchable model core

• US 8,442,837 B2
• Filed: 12/31/2009
• Issued: 05/14/2013
• Est. Priority Date: 12/31/2009
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Inventors: Ashley, James P., Gibbs, Jonathan A., Mittal, Udar
• Primary Examiner(s): Neway, Samuel G
• Application Number:
  US12/650,970
• Publication Number:
  US 20110161087A1
• Time in Patent Office: 1,230 Days
• Field of Search: 704200-230, 704500-504
• US Class Current: 704/501
• 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 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;

wherein producing the corresponding processed frame includes producing a speech processed frame and producing a generic audio processed frame; and

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

2. The method of claim 1 further comprising:

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 further comprising:

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:

wherein 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; and

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 further comprising:

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 further comprising:

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 further comprising classifying the input frame before producing either the speech encoded bit stream or the generic audio encoded bitstream.

8. The method of claim 6:

wherein 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; and

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 further comprising:

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; and

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

10. The method of claim 1 further comprising 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.

11. The method of claim 1:

wherein 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; and

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