Asterisk mark echo canceller

Echo cancellation in Asterisk — ECHO_CAN_MARK


This echo canceller is a simple Least Mean Squares Echo canceller with DoubleTalk detection. It has no Residual Error Supressor, nor does it have a high-pass filter.

It's based in part on the TI application note Digital Voice Echo Canceller with a TMS32020 using M=1 in equation 6.

Note that the number of taps is fixed at compile time and is not configurable in zapata.conf.

Parameters (in mec.h):

NUM_TAPS_POW2log2 of the number of taps
SIGMA_LU_POW -log2 of the filter constant for the suppressed signal power estimate
SIGMA_LY_POW -log2 of the filter constant for the reference signal power estimate (used to calculate the update stepsize)
SIGMA_YT_POW -log2 of the filter constant for the short-term reference signal average
SIGMA_ST_POW -log2 of the filter constant for the short-term near-end signal average
BETA_POW -log2 of the compromise stepsize constant, beta1
MIN_QUALITY Minimum suppressed/reference power ratio at which to allow updates of the coefficients
OPTIMIZEDIV ? Some fudge to improve efficiency of the algorithm ?
MIN_UPDATE ? Some fudge to improve efficiency of the algorithm ?
MIN_SKIP ? Some fudge to improve efficiency of the algorithm ?
HANG_T Number of samples after near-end speech detected to not update the coefficients


See also


Echo cancellation in Asterisk — ECHO_CAN_MARK


This echo canceller is a simple Least Mean Squares Echo canceller with DoubleTalk detection. It has no Residual Error Supressor, nor does it have a high-pass filter.

It's based in part on the TI application note Digital Voice Echo Canceller with a TMS32020 using M=1 in equation 6.

Note that the number of taps is fixed at compile time and is not configurable in zapata.conf.

Parameters (in mec.h):

NUM_TAPS_POW2log2 of the number of taps
SIGMA_LU_POW -log2 of the filter constant for the suppressed signal power estimate
SIGMA_LY_POW -log2 of the filter constant for the reference signal power estimate (used to calculate the update stepsize)
SIGMA_YT_POW -log2 of the filter constant for the short-term reference signal average
SIGMA_ST_POW -log2 of the filter constant for the short-term near-end signal average
BETA_POW -log2 of the compromise stepsize constant, beta1
MIN_QUALITY Minimum suppressed/reference power ratio at which to allow updates of the coefficients
OPTIMIZEDIV ? Some fudge to improve efficiency of the algorithm ?
MIN_UPDATE ? Some fudge to improve efficiency of the algorithm ?
MIN_SKIP ? Some fudge to improve efficiency of the algorithm ?
HANG_T Number of samples after near-end speech detected to not update the coefficients


See also


Created by: richvdh, Last modification: Wed 13 of Jul, 2005 (17:52 UTC)
Please update this page with new information, just login and click on the "Edit" or "Discussion" tab. Get a free login here: Register Thanks! - Find us on Google+