Signal processing apparatus and method, and program
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.
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.