Robust foreground/background filtering control for acoustic echo cancellation

A non-transitory computer-readable medium storing instructions that, when executed by one or more processors, cause the one or more processors to perform operations comprising:

• filtering, by a foreground filter, a received frequency-domain far end signal, the filtering by the foreground filter resulting in a foreground echo estimation, the foreground filter being an adaptive echo cancellation filter that operates based on foreground coefficients;
• filtering, by a background filter, the received frequency-domain far end signal, the filtering by the background filter resulting in a background echo estimation, the background filter being an adaptive echo cancellation filter that operates based on background coefficients;
• determining a filtered result based on a near-end microphone signal and a selected one of the foreground echo estimation and the background echo estimation, the filtered result being subsequently used to generate a near-end voice signal, wherein the one or more processors are configured to select one of the foreground echo estimation and the background echo estimation based on a comparison of a difference between the near-end microphone signal and the foreground echo estimation and a difference between the near-end microphone signal and the background echo estimation;
• and
• freezing values of coefficients used in the background filter when a deviation signal is at a logical high, wherein determining the deviation signal comprises:
• determining a respective cross-correlation coefficient for both the foreground echo estimation and the background echo estimation for each frequency bin of the received frequency-domain far end signal, each cross-correlation coefficient being based on a comparison of received microphone input signals and respective echo estimations of each frequency bin;
• summing the determined cross-correlation coefficients across a plurality of the frequency bins for each of the foreground echo estimation and the background echo estimation;
• selecting one of the sum of the cross-correlation coefficients for the foreground echo estimation and the sum of the cross-correlation coefficients for the background echo estimation, wherein the selected sum corresponds to the selected one of the foreground echo estimation and the background echo estimation;
• and
• applying a hysteresis function to the selected sum of cross-correlation coefficients, such that when the selected sum is less than a first threshold, the hysteresis function outputs a high value representing the logical high, and when the selected sum is greater than a second threshold, the hysteresis function outputs a low value.

An acoustic echo cancelling system, comprising:

• a foreground filter that filters a received frequency-domain far end signal, the filtering by the foreground filter resulting in a foreground echo estimation, the foreground filter being an adaptive echo cancellation filter that operates based on foreground coefficients;
• a background filter that filters the received frequency-domain far end signal, the filtering by the background filter resulting in a background echo estimation, the background filter being an adaptive echo cancellation filter that operates based on background coefficients;
• and
• control logic in communication with each of the foreground filter and the background filter, the control logic being configured for:
• determining a filtered result based on a near-end microphone signal and a selected one of the foreground echo estimation and the background echo estimation, the filtered result being subsequently used to generate a near-end voice signal, wherein the control logic is configured to select one of the foreground echo estimation and the background echo estimation based on a comparison of a difference between the near-end microphone signal and the foreground echo estimation and a difference between the near-end microphone signal and the background echo estimation;
• and
• freezing values of coefficients used in the background filter when a deviation signal is at a logical high, wherein determining the deviation signal by the control logic comprises:
• determining a respective cross-correlation coefficient for both the foreground echo estimation and the background echo estimation for each frequency bin of the received frequency-domain far end signal, each cross-correlation coefficient being based on a comparison of received microphone input signals and the respective echo estimations of each frequency bin;
• summing the determined cross-correlation coefficients across a plurality of the frequency bins for each of the foreground echo estimation and the background echo estimation;
• selecting one of the sum of the cross-correlation coefficients for the foreground echo estimation and the sum of the cross-correlation coefficients for the background echo estimation, wherein the selected sum corresponds to the selected one of the foreground echo estimation and the background echo estimation;
• and
• applying a hysteresis function to the selected sum of cross-correlation coefficients, such that when the selected sum is less than a first threshold, the hysteresis function outputs a high value representing the logical high, and when the selected sum is greater than a second threshold, the hysteresis function outputs a low value.