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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_POW2||log2 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|
Created by: richvdh, Last modification: Wed 13 of Jul, 2005 (17:52 UTC)
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