Lines Matching +full:low +full:- +full:noise

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.
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),
52 to adapt best to the strongest parts of a signal. If the signal is white noise,
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
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
69 If the adaption is performed while transmitting noise (or something fairly
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,
86 noise may dominate and disturb the adaption process. If we can ensure that the
98 major mis-convergence in the adaption process. An assessment algorithm is
166 	/* Parameters for the optional Hoth noise generator */