[Freeswitch-users] Better results from mod_vmd

Piotr Gregor piotrek.gregor at gmail.com
Wed Mar 30 19:09:42 MSD 2016


Hi Abaci,

after FS-8875 was merged yesterday in PR 775
I have tested avmd on your Verizon voicemail (contains 1000hz beep)
and on another Voipfone voicemail (contains beep of lower frequency,
724.1914 is detected).
Detection of tone works just fine while not giving many false positives
in the same time.
But you should note the avmd module is in beta stage so not everything
is working as expected yet. In case of Verizon sometimes it gives false
alarm on silence, this can be handled at this moment by adjusting avmd
session parameters

AVMD_SAMLPE_TO_SKIP_N  increase
BEEP_TIME increase
SAMPLES_CONSECUTIVE_STREAK increase
VARIANCE_THRESHOLD may need to decrease

or starting avmd after 3 - 4 first ring tones. Regardless of this it will be
treated in more generic way - by adding of estimation of amplitude.
Related to this is a need for adjusting parameters on a basis of expected
characteristics of incoming signal, e.g. SNR. And it should be possible
to be set the settings on a per call basis.

So you may wish to checkout master branch,
build, test, and let us know the results.

cheers,
Piotr
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