Pre-resampling to achieve continuously variable analysis time/frequency resolution

• US 20070100606A1
• Filed: 11/01/2005
• Published: 05/03/2007
• Est. Priority Date: 11/01/2005
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Rogers, Kevin
• Granted Patent: US 8,473,298 B2
• Time in Patent Office: Days
• US Class Current: 704/205
• CPC Class Codes: G10L 19/26 Pre-filtering or post-filtering

Abstract

A digital audio signal can be processed using continuously variable time-frequency resolution by selecting a portion of an input digital audio signal, resampling the selected portion of the input digital audio signal, generating a plurality of spectral characteristics associated with the resampled portion of the input digital audio signal, generating a portion of an output digital audio signal from the plurality of spectral characteristics, and resampling the portion of the output digital audio signal. Further, resampling the selected portion of the input digital audio signal can comprise determining a sampling ratio and resampling the selected portion of the input digital audio signal in accordance with the determined sampling ratio. Additionally, the portion of the output digital audio signal can be resampled in accordance with the inverse of the determined sampling ratio. The sampling ratio can be determined based on a time-frequency resolution requirement associated with an audio processing algorithm.

Claims

1. A method of processing a digital audio signal using continuously variable time-frequency resolution, the method comprising:

selecting a portion of an input digital audio signal;

resampling the selected portion of the input digital audio signal;

generating a plurality of spectral characteristics associated with the resampled portion of the input digital audio signal;

generating a portion of an output digital audio signal from the plurality of spectral characteristics; and

resampling the portion of the output digital audio signal.

2. The method of claim 1, further comprising:

processing the plurality of spectral characteristics associated with the resampled portion of the input digital audio signal.

3. The method of claim 2, wherein processing further comprises:

modifying either or both of a magnitude and a phase associated with one or more of the plurality of spectral characteristics.

4. The method of claim 1, wherein resampling the selected portion of the input digital audio signal comprises upsampling and resampling the portion of the output digital audio signal comprises downsampling.

5. The method of claim 1, wherein resampling the selected portion of the input digital audio signal comprises downsampling and resampling the portion of the output digital audio signal comprises upsampling.

6. The method of claim 1, wherein resampling the selected portion of the input digital audio signal comprises:

determining a sampling ratio; and

resampling the selected portion of the input digital audio signal in accordance with the determined sampling ratio.

7. The method of claim 6, further comprising:

resampling the portion of the output digital audio signal in accordance with the inverse of the determined sampling ratio.

8. The method of claim 6, further comprising:

determining the sampling ratio based on the size of an FFT.

9. The method of claim 6, further comprising:

determining the sampling ratio based on a time-frequency resolution requirement associated with an audio processing algorithm.

10. An article of manufacture comprising machine-readable instructions for processing a digital audio signal using continuously variable time-frequency resolution, the machine-readable instructions being operable to perform operations comprising:

selecting a portion of an input digital audio signal;

resampling the selected portion of the input digital audio signal;

generating a plurality of spectral characteristics associated with the resampled portion of the input digital audio signal;

generating a portion of an output digital audio signal from the plurality of spectral characteristics; and

resampling the portion of the output digital audio signal.

11. The article of manufacture comprising machine-readable instructions of claim 10, wherein the machine-readable instructions are further operable to perform operations comprising:

processing the plurality of spectral characteristics associated with the resampled portion of the input digital audio signal.

12. The article of manufacture comprising machine-readable instructions of claim 11, wherein the machine-readable instructions are further operable to perform operations comprising:

modifying either or both of a magnitude and a phase associated with one or more of the plurality of spectral characteristics.

13. The article of manufacture comprising machine-readable instructions of claim 10, wherein resampling the selected portion of the input digital audio signal comprises upsampling and resampling the portion of the output digital audio signal comprises downsampling.

14. The article of manufacture comprising machine-readable instructions of claim 10, wherein resampling the selected portion of the input digital audio signal comprises downsampling and resampling the portion of the output digital audio signal comprises upsampling.

15. The article of manufacture comprising machine-readable instructions of claim 10, wherein the machine-readable instructions are further operable to perform operations comprising:

determining a sampling ratio; and

resampling the selected portion of the input digital audio signal in accordance with the determined sampling ratio.

16. The article of manufacture comprising machine-readable instructions of claim 15, wherein the machine-readable instructions are further operable to perform operations comprising:

resampling the portion of the output digital audio signal in accordance with the inverse of the determined sampling ratio.

17. The article of manufacture comprising machine-readable instructions of claim 15, wherein the machine-readable instructions are further operable to perform operations comprising:

determining the sampling ratio based on the size of an FFT.

18. The article of manufacture comprising machine-readable instructions of claim 15, wherein the machine-readable instructions are further operable to perform operations comprising:

determining the sampling ratio based on a time-frequency resolution requirement associated with an audio processing algorithm.

19. A system for processing a digital audio signal using continuously variable time-frequency resolution, the system comprising processor electronics configured to perform operations comprising:

selecting a portion of an input digital audio signal;

resampling the selected portion of the input digital audio signal;

generating a plurality of spectral characteristics associated with the resampled portion of the input digital audio signal;

generating a portion of an output digital audio signal from the plurality of spectral characteristics; and

resampling the portion of the output digital audio signal.

20. The system of claim 19, wherein the processor electronics are further configured to perform operations comprising:

processing the plurality of spectral characteristics associated with the resampled portion of the input digital audio signal.

21. The system of claim 19, wherein the processor electronics are further configured to perform operations comprising:

resampling the selected portion of the input digital audio signal by upsampling; and

resampling the portion of the output digital audio signal by downsampling

22. The system of claim 19, wherein the processor electronics are further configured to perform operations comprising:

resampling the selected portion of the input digital audio signal by downsampling; and

resampling the portion of the output digital audio signal by upsampling.

23. The system of claim 19, wherein the processor electronics are further configured to perform operations comprising:

determining a sampling ratio; and

resampling the selected portion of the input digital audio signal in accordance with the determined sampling ratio.

24. The system of claim 23, wherein the processor electronics are further configured to perform operations comprising:

resampling the portion of the output digital audio signal in accordance with the inverse of the determined sampling ratio.

25. The system of claim 23, wherein the processor electronics are further configured to perform operations comprising:

determining the sampling ratio based on a time-frequency resolution requirement associated with an audio processing algorithm.