Auto-tuning of acoustic echo canceller

1. A gain control system for dynamically tuning an echo canceller, the echo canceller being configured to estimate an echo of a far-end signal, the system comprising:

a monitoring unit configured to estimate an energy of an impulse response of an adaptive filter configured to generate the echo estimate from the far-end signal, wherein estimating the energy comprises combining a plurality of values each associated with the impulse response in a predefined section i of a microphone signal of length T 1 , where 1≤i≤T 1 /T ms , where T ms is the length of the section of microphone signal under consideration; and

a gain tuner configured to, if it determines that the adaptive filter has saturated, increase an attenuation of the microphone signal in dependence on the estimated energy;

wherein the echo canceller is configured to subtract the echo estimate from the attenuated microphone signal to output an echo cancelled signal.

2. A gain control system as claimed in claim 1 , the gain tuner being further configured to, if the energy of the impulse response is relatively high, determine that the adaptive filter has saturated.

3. A gain control system as claimed in claim 1 , the gain tuner being further configured to, if the energy of the impulse response is relatively low, determine that the adaptive filter has not saturated.

4. A gain control system as claimed in claim 3 , the gain tuner being further configured to, if it determines that the adaptive filter has not saturated, decrease the attenuation of the microphone signal.

5. A gain control system as claimed in claim 1 , the gain tuner being further configured to:

decrease the attenuation of the microphone signal if the estimated energy is below a first threshold;

maintain the attenuation of the microphone signal if the estimated energy is greater than or equal the first threshold and less than or equal to a second threshold; and

increase the attenuation of the microphone signal if the estimated energy is above the second threshold.

6. A gain control system as claimed in claim 1 , the gain tuner being further configured to, before it increases the attenuation of the microphone signal:

compare the attenuation of the microphone signal and the attenuation of the far-end signal; and

if the far-end signal attenuation is lower than the microphone signal attenuation, increase the attenuation of the microphone signal; and

otherwise, decrease the attenuation of the far-end signal and maintain the attenuation of the microphone signal.

7. A gain control system as claimed in claim 1 , the monitoring unit comprising an energy estimator configured to estimate the energy of an impulse response by treating the microphone signal as comprising a plurality of sections, the energy estimator being configured to:

estimate an energy associated with the impulse response corresponding to each section of the microphone signal;

determine that one or more of the identified impulse responses is associated with a dominant energy; and

adjust an attenuation of at least one of the microphone signal and the far-end signal in dependence on the dominant energy.

8. A gain control system as claimed in claim 7 , the energy estimator being further configured to determine that an impulse response is associated with a dominant energy if a ratio of the estimated energy associated with that impulse response to a total estimated energy for the impulse responses associated with all of the plurality of sections is greater than a predetermined threshold.

9. A gain control system as claimed in claim 1 , the energy estimator being further configured to estimate an energy associated with an impulse response by:

dividing the impulse response into a plurality of overlapping sections;

identifying a set of said overlapping sections that are associated with the section of the microphone signal to which the impulse response corresponds;

estimating an energy comprised in each section of the set; and

summing the estimated energies for the set.

10. A method for dynamically tuning an echo canceller, the echo canceller being configured to estimate an echo of a far-end signal, the method comprising:

estimating an energy of an impulse response of an adaptive filter configured to generate the echo estimate from the far-end signal, wherein estimating the enemy comprises combining a plurality of values each associated with the impulse response in a predefined section i of a microphone signal of length T 1 , where 1≤i≤T 1 /T ms , where T ms is the length of the section of microphone signal under consideration;

increasing an attenuation of the microphone signal in dependence on the estimated energy, if it determined that the adaptive filter has saturated;

subtracting the echo estimate from the attenuated microphone signal; and

outputting an echo cancelled signal.

11. A non-transitory machine readable storage medium having stored thereon processor executable instructions implementing a method according to claim 10 .