Signal processing apparatus and method, and program

• US 9,406,306 B2
• Filed: 07/27/2011
• Issued: 08/02/2016
• 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
• Primary Examiner(s): Sirjani, Fariba
• Application Number:
  US13/498,234
• Publication Number:
  US 20130124214A1
• Time in Patent Office: 1,833 Days
• US Class Current: 1/1
• 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;

performing filter processing on the decoded signal, the filter processing separating the decoded signal into low-frequency range band signals, wherein filter processing is performed by a QMF (Quadrature Mirror Filter) analysis filter;

performing a smoothing process on the low-frequency range band signals, the smoothing process smoothing the non-zero energy depression of the decoded signal;

performing a frequency shift on the smoothed low-frequency range band signals, 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, wherein combining is performed by a QMF synthesis filter; and

outputting the output signal,

wherein performing the smoothing process on the low-frequency range band signals further comprises;

computing an average energy of a plurality of 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 an energy for the selected low-frequency range band signal; and

multiplying the selected low-frequency range band signal by the computed ratio.

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 low-frequency range band signals 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 low-frequency range band signals.

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 low-frequency range band signals is based on the gain information.

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

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

demultiplexing the multiplexed encoded signal.

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

14. A computer-implemented method as in claim 1, wherein the smoothing process is performed based on an average power of the low-frequency range band signals.

15. 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 a non-zero 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, wherein filter processor comprises a QMF (Quadrature Mirror Filter) analysis filter;

a high-frequency range generating circuit configured to;

perform a smoothing process on the low-frequency range band signals, the smoothing process smoothing the energy depression;

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, wherein the combinatorial circuit comprises a QMF synthesis filter,

wherein the high-frequency range generating circuit is further configured to perform the smoothing process on the low-frequency range band signals by;

computing an average energy of a plurality of 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 an energy for the selected low-frequency range band signal; and

multiplying the selected low-frequency range band signal by the computed ratio.

16. A device as in claim 15, wherein the high-frequency range generating circuit is configured to perform the smoothing process based on an average power of the low-frequency range band signals.

17. A non-transitory 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;

performing filter processing on the decoded signal, the filter processing separating the decoded signal into low-frequency range band signals, wherein filter processing is performed by a QMF (Quadrature Mirror Filter) analysis filter;

performing a smoothing process on the low-frequency range band signals, the smoothing process smoothing the energy depression of the decoded signal;

performing a frequency shift on the smoothed low-frequency range band signals, 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, wherein combining is performed by a QMF synthesis filter; and

outputting the output signal,

wherein performing the smoothing process on the low-frequency range band signals further comprises;

computing an average energy of a plurality of 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 an energy for the selected low-frequency range band signal; and

multiplying the selected low-frequency range band signal by the computed ratio.

18. A non-transitory computer-readable storage medium as in claim 17, wherein the smoothing process is performed based on an average power of the low-frequency range band signals.

19. 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 having at least one non-zero energy depression, wherein filter processing is performed by a QMF (Quadrature Mirror Filter) analysis filter;

smoothing the at least one non-zero energy depression of the 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,

wherein smoothing the at least one non-zero energy depression of the low-frequency range band signals further comprises;

computing an average energy of a plurality of 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 an energy for the selected low-frequency range band signal; and

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

20. A computer-implemented method as in claim 19, wherein the smoothing is performed based on an average power of the low-frequency range band signals.

21. 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 having at least one non-zero energy depression, wherein filter processing is performed by a QMF (Quadrature Mirror Filter) analysis filter;

smooth the at least one non-zero energy depression of the 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,

wherein the high-frequency range coding circuit is further configured to smooth the at least one non-zero energy depression of the low-frequency range band signals by;

computing an average energy of a plurality of 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 an energy for the selected low-frequency range band signal; and

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

22. A device as in claim 21, wherein the high-frequency range coding circuit is configured to perform the smoothing based on an average power of the low-frequency range band signals.

23. A non-transitory 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 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 having at least one non-zero energy depression, wherein filter processing is performed by a QMF (Quadrature Mirror Filter) analysis filter;

smoothing the at least one non-zero energy depression of the 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,

wherein smoothing the at least one non-zero energy depression of the low-frequency range band signals further comprises;

computing an average energy of a plurality of 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 an energy for the selected low-frequency range band signal; and

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

24. A non-transitory computer-readable storage medium as in claim 23, wherein the smoothing is performed based on an average power of the low-frequency range band signals.