Patent ID: 7817797

Claim:
An echo canceller for cancelling echo from a near-end signal, comprising: a first adaptive filter having N_long coefficients for converging to an echo path of said near-end signal and for adapting slowly when a reference signal is present; a non-adaptive filter representing a direct echo path portion of said echo path and having N_short default coefficients, where N_long>N_short, for quick convergence of said echo canceller at start-up, said default coefficients being replaced by the first N_short coefficients from said first adaptive filter responsive to an improvement in echo return loss enhancement (ERLE) of said first adaptive filter; a second adaptive filter having N_short default coefficients for modeling said direct echo path and for adapting quickly when said reference signal is present, said second adaptive filter used only for echo path detection; decision logic connected to said first and second adaptive filters of said non-adaptive filter for detecting and distinguishing between an echo path change and a state of double-talk by (i) calculating respective energy levels of signals output from said first and second adaptive filters and said non-adaptive filter, (ii) in the event the signal energy ratio between said first and second adaptive filters is equal or greater than a first threshold then indicating one of either said echo path change and said double-talk, and (iii) in the event the signal energy ratio between said second adaptive filter and said non-adaptive filter is equal or less than a second threshold then indicating said echo path change, or (iv) in the event the signal energy ratio between said second adaptive filter and said non-adaptive filter is greater than said second threshold and equal or greater than a third threshold then indicating said double talk; and a non-linear processor responsive to said echo path change being detected by said decision logic for attenuating said near-end signal.