SIGNAL PROCESSING APPARATUS AND METHOD, AND PROGRAM

• US 20130124214A1
• Filed: 07/27/2011
• Published: 05/16/2013
• Est. Priority Date: 08/03/2010
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yamamoto, Yuki, Chinen, Toru, Hatanaka, Mitsuyuki
• Granted Patent: US 9,406,306 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 19/26 Pre-filtering or post-filtering
• CPC Class Codes: G10L 21/038 using band spreading techniques

Abstract

A method, system, and computer program product for processing an encoded audio signal is described. In one exemplary embodiment, the system receives an encoded low-frequency range signal and encoded energy information used to frequency shift the encoded low-frequency range signal. The low-frequency range signal is decoded and an energy depression of the decoded signal is smoothed. The smoothed low-frequency range signal is frequency shifted to generate a high-frequency range signal. The low-frequency range signal and high-frequency range signal are then combined and outputted.

Claims

1. A computer-implemented method for processing an audio signal, the method comprising:

receiving an encoded low-frequency range signal corresponding to the audio signal;

decoding the encoded signal to produce a decoded signal having an energy spectrum of a shape including an energy depression;

performing filter processing on the decoded signal, the filter processing separating the decoded signal into low-frequency range band signals;

performing a smoothing process on the decoded signal, the smoothing process smoothing the energy depression of the decoded signal;

performing a frequency shift on the smoothed decoded signal, the frequency shift generating high-frequency range band signals from the low-frequency range band signals;

combining the low-frequency range band signals and the high-frequency range band signals to generate an output signal; and

outputting the output signal.

2. A computer-implemented method as in claim 1, wherein the encoded signal further comprises energy information for the low-frequency range band signals.

3. A computer-implemented method as in claim 2, wherein performing the frequency shift is based on the energy information for the low-frequency range band signals.

4. A computer-implemented method as in claim 1, wherein the encoded signal further comprises SBR (spectral band replication) information for the high-frequency range bands of the audio signal.

5. A computer-implemented method as in claim 4, wherein performing the frequency shift is based on the SBR information.

6. A computer-implemented method as in claim 1, wherein the encoded signal further comprises smoothing position information for the low-frequency range band signals.

7. A computer-implemented method as in claim 6, wherein performing the smoothing process on the decoded signal is based on the smoothing position information for the low-frequency range band signals.

8. A computer-implemented method as in claim 1, further comprising:

performing gain adjustment on the frequency-shifted smoothed decoded band signal.

9. A computer-implemented method as in claim 8 wherein the encoded signal further comprises gain information for the low-frequency range bands signals.

10. A computer-implemented method as in claim 9, wherein performing gain adjustment on the frequency-shifted decoded signal is based on the gain information.

11. A computer-implemented method as in claim 1, further comprising:

computing the average energies of the low-frequency range band signals.

12. A computer-implemented method as in claim 1, wherein performing a smoothing process on the decoded signal further comprises:

computing an average energy of a plurality low-frequency range band signals;

computing a ratio for a selected one of the low-frequency range band signals by computing a ratio of the average energy of the plurality of low-frequency range band signals to the energy for the selected low-frequency range band signal; and

performing a smoothing process by multiplying the energy of the selected low-frequency range band signal by the computed ratio.

13. A computer-implemented method as in claim 1, wherein the encoded signal is multiplexed.

14. A computer-implemented method as in claim 13 further comprising:

demultiplexing the multiplexed encoded signal.

15. A computer-implemented method as in claim 1, wherein the encoded signal is encoded using an AAC (Advanced Audio Coding) scheme.

16. A device for processing an audio signal, the device comprising:

a low-frequency range decoding circuit configured to receive an encoded low-frequency range signal corresponding to the audio signal and decode the encoded signal to produce a decoded signal having an energy spectrum of a shape including an energy depression;

a filter processor configured to perform filter processing on the decoded signal, the filter processing separating the decoded signal into low-frequency range band signals;

a high-frequency range generating circuit configured to;

perform a smoothing process on the decoded signal, the smoothing process smoothing the energy depression; and

perform a frequency shift on the smoothed decoded signal, the frequency shift generating high-frequency range band signals from the low-frequency range band signals; and

a combinatorial circuit configured to combine the low-frequency range band signals and the high-frequency range band signals to generate an output signal, and output the output signal.

17. A tangibly embodied computer-readable storage medium including instructions that, when executed by a processor, perform a method for processing an audio signal, the method comprising:

receiving an encoded low-frequency range signal corresponding to the audio signal;

decoding the encoded signal to produce a decoded signal having an energy spectrum of a shape including an energy depression;

performing filter processing on the decoded signal, the filter processing separating the decoded signal into low-frequency range band signals;

performing a smoothing process on the decoded signal, the smoothing process smoothing the energy depression of the decoded signal;

performing a frequency shift on the smoothed decoded signal, the frequency shift generating high-frequency range band signals from the low-frequency range band signals;

combining the low-frequency range band signals and the high-frequency range band signals to generate an output signal; and

outputting the output signal.

18. A computer-implemented method for processing a signal, the method comprising:

receiving an input signal;

extracting a low-frequency range signal from the input signal;

performing filter processing on the low-frequency range signal, the filter processing separating the signal into low-frequency range band signals;

calculating energy information for the low-frequency range band signals;

encoding the low-frequency range signal and the energy information; and

outputting the encoded low-frequency range signal and the encoded energy information.

19. A device for processing a signal, the device comprising:

a downsampler configured to receive an input signal and extract a low-frequency range signal from the input signal;

a high-frequency range coding circuit configured to;

perform filter processing on the low-frequency range signal, the filter processing separating the signal into low-frequency range band signals;

calculate energy information for the low-frequency range band signals; and

encode the energy information;

a low-frequency range coding circuit configured to encode the low-frequency range signal; and

a multiplexing circuit configured to output the encoded low-frequency range signal and the encoded energy information.

20. A tangibly embodied computer-readable storage medium including instructions that, when executed by a processor, perform a method for processing a signal, the method comprising:

receiving an input signal;

extracting a low-frequency range signal from the input signal;

performing filter processing on the low-frequency range signal, the filter processing separating the signal into low-frequency range band signals;

calculating energy information for the low-frequency range band signals;

encoding the low-frequency range signal and the energy information; and

outputting the encoded low-frequency range signal and the encoded energy information.