Lines Matching +full:very +full:- +full:high

1 /* SPDX-License-Identifier: GPL-2.0-only */
3  * SpanDSP - a series of DSP components for telephony
5  * echo.c - A line echo canceller.  This code is being developed
24 This module aims to provide G.168-2002 compliant echo cancellation, to remove
25 electrical echoes (e.g. from 2-4 wire hybrids) from voice calls.
40 things like modem line equalisers and line echo cancellers. There it works very
42 very poorly for things like speech echo cancellation, where the signal level
43 varies widely.  This is quite easy to fix. If the signal level is normalised -
44 similar to applying AGC - LMS can work as well for a signal of varying
47 other algorithms exist - e.g. RLS (essentially the same as Kalman filtering),
53 the NLMS algorithm works very well. However, speech has more low frequency than
54 high frequency content. Pre-whitening (i.e. filtering the signal to flatten its
56 final residual signal is not heavily biased towards high frequencies. A very
57 low complexity filter is adequate for this, so pre-whitening adds little to the
60 An FIR filter adapted using pre-whitened NLMS performs well, provided certain
63     - The transmitted signal has poor self-correlation.
64     - There is no signal being generated within the environment being
70 noise like, such as voice) the adaption works very well. If the adaption is
74 random signal - the impulse response of the line. For a repetitive signal,
94 energy is that we must do this very quickly. Given a reasonably long sample of
98 major mis-convergence in the adaption process. An assessment algorithm is
99 needed which produces a fairly accurate result from a very short burst of far
160 	/* optional High Pass Filter states */