A combined LPC-based speech coder and filtered-X LMS algorithm for acoustic echo cancellation

This paper presents a novel acoustic echo canceller structure based on combining the filtered-X LMS algorithm with an LPC-based speech coder for use in videoconferencing and VoIP. The algorithm updates coefficients using filtered versions of the input and error signals obtained by directly tapping the short-term excitation signal from the speech decoder, and by filtering the error signal with a bank of FIR decorrelation filters constructed from the LPC synthesis filter coefficients. The proposed algorithm was implemented using ITU G.729, and simulation results with 2000-tap room impulse responses show a faster and more constant rate of convergence than NLMS using speech input signals and an average 10 dB greater ERLE observed during convergence.