Method and apparatus for estimating high-band energy in a bandwidth extension system
A method ( 100 ) includes receiving ( 101 ) an input digital audio signal comprising a narrow-band signal. The input digital audio signal is processed ( 102 ) to generate a processed digital audio signal. A high-band energy level corresponding to the input digital audio signal is estimated ( 103 ) based on a transition-band of the processed digital audio signal within a predetermined upper frequency range of a narrow-band bandwidth. A high-band digital audio signal is generated ( 104 ) based on the high-band energy level and an estimated high-band spectrum corresponding to the high-band energy level.
1. A method comprising:
receiving an input digital audio signal comprising a narrow-band signal within a first band;
processing the input digital audio signal to generate a processed digital audio signal;
selecting a transition band within the first band, the said transition band having a width but smaller than the width of the first band, and located adjacent to an upper frequency edge of the first band; and
estimating a high-band energy level corresponding to an audio signal within a second band located higher and adjacent to the first band based on the processed digital audio signal within the selected transition band wherein the estimation is done without receiving an audio signal within the second band.
2. The method of claim 1 further comprising generating a high-band digital audio signal based at least on the high-band energy level and an estimated high-band spectral envelope corresponding to the high-band energy level.
3. The method of claim 2 , further comprising combining the input digital audio signal and the high-band digital audio signal to generate a resultant digital audio signal having an extended signal bandwidth.
4. The method of claim 1 wherein the processing comprises up-sampling the input digital audio signal to generate the processed digital audio signal.
5. The method of claim 1 wherein the estimating comprises calculating an energy level of the processed digital audio signal by computing a frequency spectrum of the processed digital audio signal and summing energies of spectral components within the transition-band.
6. The method of claim 1 wherein the estimating further comprises utilizing at least one predetermined speech parameter, based on the input digital audio signal, to generate a parameter space.
7. The method of claim 6 , wherein the predetermined speech parameter is at least one of a zero-crossing parameter, a spectral flatness measure parameter, a transition-band spectral slope parameter, and a transition band spectral envelope shape parameter.
8. The method of claim 6 , wherein the estimating further comprises partitioning the parameter space into regions and assigning coefficients for each region to estimate the high-band energy level.
9. The method of claim 1 wherein the narrow-band signal has a bandwidth of about 300- 3400 Hz.
10. The method of claim 1 wherein the transition-band has a range of about 2500-3400 Hz.
11. The method of claim 1 further comprising generating a low-band digital audio signal.
12. The method of claim 11 , further comprising combining the input digital audio signal, the high-band digital audio signal, and the low-band digital audio signal to generate a resultant wide-band digital audio signal having an extended signal bandwidth.
13. An apparatus, comprising:
an input configured and arranged to receive an input digital audio signal comprising a narrow-band signal received within a first bandwidth;
a processor operably coupled to the input and being configured and arranged to:
process the input digital audio signal to generate a processed digital audio signal;
select a transition band within the first band, the said transition band having a width smaller than the width of the first band, and located adjacent to an upper frequency edge of the first band; and
estimating a high-band energy level corresponding to an audio signal within a second band located higher and adjacent to the first band based on the processed digital audio signal within the selected transition band wherein the estimation is done without receiving an audio signal within the second band.
14. The apparatus of claim 13 wherein the processor is further configured and arranged to generate a high-band digital audio signal based at least on the high-band energy level and an estimated high-band spectral envelope corresponding to the high-band energy level.
15. The apparatus of claim 13 , wherein the digital audio signal comprises synthesized vocal content.
16. The apparatus of claim 13 , wherein the processor is further configured and arranged to combine the input digital audio signal and the high-band digital audio signal to generate a resultant digital audio signal having an extended signal bandwidth.
17. The apparatus of claim 13 , wherein the processor is further configured and arranged to up-sample the input digital audio signal to generate the processed digital audio signal.
18. The apparatus of claim 13 , wherein the narrow-band signal has a bandwidth of about 300- 3400 Hz, and the transition-band has a range of about 2500-3400 Hz.
19. The apparatus of claim 13 , wherein the processor is further configured and arranged to generate a low-band digital audio signal.
20. The apparatus of claim 19 , wherein the processor is further configured and arranged to combine the input digital audio signal, the high-band digital audio signal, and the low-band digital audio signal to generate a resultant wide-band digital audio signal having an extended signal bandwidth.