[Speex-dev] Is 17 dB ERLE normal?

Jean-Marc Valin Jean-Marc.Valin at USherbrooke.ca
Wed May 27 07:23:24 PDT 2009

Quoting Johan Nilsson <han at svep.se>:
> Now we achieve ERLE of about 17 dB which tells me that the AEC is doing
> something however we are subjectively not satisfied.  Some references of ERLE
> taken from this mailing list tells that 15 dB [1,2] is not good enough and
> that 30 dB would be fine [3].
> My question is if 17 dB is in line with what is expected from the Speex
> algorithm?

An ERLE of 17 dB *without* the preprocessor is pretty much what you can expect
from the Speex AEC. Of course, it depends a lot on the conditions, recording
equipment, double-talk, ... See Fig. 5 of this paper:
http://people.xiph.org/~jm/papers/valin_tasl2007.pdf and Fig. 2 of this one:
http://people.xiph.org/~jm/papers/valin_icassp2007.pdf for some ERLE curves
with the Speex AEC. As you say, 17 dB is not enough to really remove the echo,
so you probably want to apply the preprocessor on the output to remove the
residual echo (see example and manual for how to link the two). This should be
able to do the job.


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