Shape and scale parameters for extended-band frequency coding

• US 20070174063A1
• Filed: 01/20/2006
• Published: 07/26/2007
• Est. Priority Date: 01/20/2006
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Chen, Wei-Ge, Koishida, Kazuhito, Mehrotra, Sanjeev, He, Chao
• Granted Patent: US 7,953,604 B2
• Time in Patent Office: Days
• US Class Current: 704/501
• CPC Class Codes: G10L 21/038 using band spreading techniques

Abstract

An audio encoder performs frequency extension coding that comprises determining one or more shape parameters using a displacement vector that corresponds to a displacement of an even number (e.g., an even number of sub-bands between a sub-band in a baseband frequency range and a sub-band in an extended-band frequency range). The shape parameters can be determined on a per-audio-block basis. Restricting a displacement to an even number (in frequency extension coding or in other signal modulation schemes) can improve the quality of reconstructed audio. An audio encoder also can perform frequency extension coding that comprises determining one or more scale parameters at one or more audio blocks, and determining one or more anchor points for interpolating the one or more scale parameters.

Claims

1. In an audio encoder, a computer-implemented method comprising:

receiving source audio data;

performing a time-to-frequency transform on the received source audio data to produce frequency-domain data for the received source audio data; and

performing frequency extension coding on the received source audio data, the frequency extension coding comprising determining one or more shape parameters for the frequency-domain data;

wherein the determining one or more shape parameters comprises using a displacement vector corresponding to a displacement of an even number of sub-bands.

2. The method of claim 1 wherein the one or more shape parameters are determined on a per-audio-block basis.

3. The method of claim 1 wherein the displacement vector measures a number of sub-bands between a sub-band in a baseband frequency range and a sub-band in an extended-band frequency range.

4. The method of claim 1 wherein the displacement vector for each the one or more shape parameters is restricted exclusively to even numbers of sub-bands.

5. The method of claim 1 wherein the shape parameters specify a portion of a baseband of the frequency-domain data that will act as a basis for coding coefficients in an extended band of the frequency-domain data.

6. The method of claim 5 wherein the baseband is at a lower frequency range than the extended band.

7. The method of claim 1 further comprising determining one or more scale parameters for the frequency domain data.

8. The method of claim 1 wherein the time-to-frequency transform is a modulated discrete cosine transform.

9. The method of claim 1 further comprising:

encoding the one or more shape parameters; and

sending the encoded one or more shape parameters to an audio decoder for use in reconstructing the source audio data.

10. A computer-readable medium storing computer-executable instructions for causing a computer programmed thereby to perform the method of claim 1.

11. In an audio encoder, a computer-implemented method comprising:

receiving source audio data;

performing a time-to-frequency transform on the received source audio data to produce frequency-domain data for the received source audio data; and

performing frequency extension coding on the received source audio data, the frequency extension coding comprising;

determining one or more scale parameters for the frequency-domain data at one or more audio blocks; and

determining one or more anchor points for interpolating the one or more scale parameters.

12. The method of claim 11 wherein each of the one or more audio blocks comprises plural frequency bands.

13. The method of claim 12 wherein the number of anchor points is variable between the plural frequency bands

14. The method of claim 12 wherein the number of anchor points is zero for at least one of the plural frequency bands.

15. The method of claim 12 wherein the determining one or more scale parameters comprises determining scale parameters for one or more of the plural frequency bands in each audio block.

16. The method of claim 11 wherein the interpolating the one or more scale parameters comprises adaptively switching the interpolating on or off in the audio encoder.

17. The method of claim 16 wherein the adaptively switching comprises adaptively switching the interpolating on or off for different frequency bands.

18. The method of claim 11 further comprising:

encoding the one or more scale parameters; and

sending the encoded one or more scale parameters to an audio decoder for use in reconstructing the source audio data.

19. A computer-readable medium storing computer-executable instructions for causing a computer programmed thereby to perform the method of claim 11.

20. In an audio encoder, a computer-implemented method comprising:

receiving source audio data;

performing a time-to-frequency transform on the received source audio data to produce frequency-domain data for the received source audio data; and

performing frequency extension coding on the received source audio data, the frequency extension coding comprising determining one or more shape parameters and one or more scale parameters for the frequency-domain data;

wherein the determining one or more shape parameters comprises using a displacement vector corresponding to a displacement of an even number of sub-bands; and

wherein the determining one or more scale parameters comprises determining one or more anchor points for interpolating the one or more scale parameters.