Techniques for comfort noise generation in a communication system
A technique of operating a communication device includes dividing a frequency band associated with a background noise signal into respective sub-bands. Respective individual level estimates for each of the respective sub-bands are then determined. A total level estimate for the background noise signal is determined. Finally, a comfort noise signal (whose characteristics are based on the respective individual level estimates and the total level estimate) is provided.
1. A method of operating a communication device, comprising:
determining respective individual level estimates for respective sub-bands included in a frequency band associated with a background noise signal at a transmitting device;
determining a total level estimate for the background noise signal;
generating respective white noise signals for each of the respective sub-bands;
filtering the respective white noise signals to provide filtered white noise signals;
gain adjusting the filtered white noise signals based on the respective individual level estimates to provide respective gain adjusted filtered white noise signals;
summing the respective gain adjusted filtered white noise signals to provide an intermediate noise signal; and
dynamically gain adjusting the intermediate noise signal based on the total level estimate to generate a comfort noise signal at a receiving device.
2. The method of claim 1 , further comprising:
filtering the background noise signal to derive respective sub-band level estimates for each of the respective sub-bands;
integrating the respective sub-band level estimates to derive the respective individual level estimates; and
integrating the background noise signal to derive the total level estimate.
3. The method of claim 2 , wherein the filtering the background noise signal further comprises:
filtering, using respective infinite impulse response filters, the background noise signal to derive the respective sub-band level estimates for each of the respective sub-bands.
4. The method of claim 1 , wherein the filtering the respective white noise signals further comprises:
filtering, using respective infinite impulse response filters, the respective white noise signals to provide the filtered white noise signals.
5. The method of claim 1 , wherein the respective sub-bands are not uniform.
6. The method of claim 5 , wherein at least some of the respective sub-bands overlap.
7. A communication device, comprising:
an analysis task block configured to:
divide a frequency band associated with a background noise signal into respective sub-bands, wherein the background noise signal is associated with a transmitting device;
determine respective individual level estimates for each of the respective sub-bands; and
determine a total level estimate for the background noise signal; and
a synthesis task block in communication with the analysis task block, wherein the synthesis task block is configured to:
generate respective white noise signals for each of the respective sub-bands;
filter the respective white noise signals to provide filtered white noise signals;
gain adjust the filtered white noise signals based on the respective individual level estimates to provide respective gain adjusted filtered white noise signals;
sum the respective gain adjusted filtered white noise signals to provide an intermediate noise signal; and
dynamically gain adjust the intermediate noise signal based on the total level estimate to generate a comfort noise signal at a receiving device.
8. The communication device of claim 7 , wherein analysis task block is further configured to:
filter the background noise signal to derive respective sub-band level estimates for each of the respective sub-bands;
integrate the respective sub-band level estimates to derive the respective individual level estimates; and
integrate the background noise signal to derive the total level estimate.
9. The communication device of claim 8 , wherein the analysis task block includes multiple infinite impulse response filters that are each configured to filter one of the respective sub-bands of the background noise signal to derive the respective sub-band level estimates.
10. The communication device of claim 7 , wherein the synthesis task block includes multiple infinite impulse response filters that are each configured to filter one of the respective white noise signals.
11. The communication device of claim 7 , wherein the synthesis task block includes:
multiple white noise generators each configured to generate the respective white noise signals for each of the respective sub-bands;
multiple infinite impulse response filters that are each in communication with one of the multiple white noise generators, wherein the multiple infinite impulse response filters are each configured to filter one of the respective white noise signals to provide the filtered white noise signals;
multiple individual gain controls each in communication with one of the multiple infinite impulse response filters, wherein the multiple individual gain controls are each configured to dynamically gain adjust one of the filtered white noise signals based on an associated one of the respective individual level estimates to provide the respective gain adjusted filtered white noise signals;
a summer configured to sum the respective gain adjusted filtered white noise signals to provide the intermediate noise signal; and
a global gain control configured to dynamically gain adjust the intermediate noise signal, based on the total level estimate, to provide the comfort noise signal.
12. The communication device of claim 7 , wherein the respective sub-bands are not uniform.
13. The communication device of claim 12 , wherein at least some of the respective sub-bands overlap.
14. The communication device of claim 7 , wherein the communication device includes a fixed-point digital signal processor.
15. The communication device of claim 7 , wherein the communication device is incorporated within an echo canceller.
16. A method of operating a communication device, comprising:
filtering a background noise signal to derive sub-band level estimates for respective sub-bands included in a frequency band associated with the background noise signal, wherein the background noise signal is associated with a transmitting device;
integrating the respective sub-band level estimates to derive respective individual level estimates;
generating respective white noise signals for each of the respective sub-bands;
filtering the respective white noise signals to provide filtered white noise signals;
dynamically gain adjusting the filtered white noise signals based on the respective individual level estimates to provide respective gain adjusted filtered white noise signals;
summing the respective gain adjusted filtered white noise signals to provide an intermediate noise signal;
integrating the background noise signal to derive a total level estimate; and
dynamically gain adjusting the intermediate noise signal based on the total level estimate to generate a comfort noise signal at a receiving device.