[Freeswitch-users] On-conference distortion for FreeTDM channels, but not SIP channels

[Bob Hartwig]

Melanie, et. al., I came up with a fix for this a couple of months ago.  On
the freeswitch-dev list, search for my message thread with subject "New
"mod_dahdi_timer" - does the community want this?"

    Bob



On Wed, Dec 11, 2013 at 1:42 AM, Melanie Treitinger <
treitinger at as-infodienste.de> wrote:

>  Nobody has an idea on this?
> Here again Bob's Message from 2013-09-20:
>
> I've tried everything I can think of on this, so now I'm reaching out to
> you good people.  I have a FreeSWITCH system that has the latest version of
> FreeTDM, Dahdi, libpri, and a Rhino R4T1 quad T1 board with up-to-date
> firmware.  When I call into one of the PRI channels, a "playback"-played
> file sounds clean, but when I go into conference, the conference audio is
> distorted.  This does not happen with a SIP channel.  I would classify the
> distortion as a "crackle", but it is very regularly periodic.  Repeating
> ticks at (roughly) 10-20 Hz repeat rate, I would say.  I can only hear them
> when audio is present, i.e. the audio seems to be modulated with the ticks.
>  And that conference audio can be the MOH guitar recording.
>
> I've eliminated the following:
>
> - T1 clocking
> - Echo Cancellers (I've turned on and off all combinations of hardware and
> software EC)
> - T1 board firmware (it's the latest, and the problem only happens
> on-conference).
> - Packet length - it's the same (20 mS) for the conference engine, FreeTDM,
> and Dahdi
> - mu-law vs. a-law encoding - behaves identically.
> - Comfort noise - happens with and without.
> - conference sampling rate (tried 8000 and 16000, even though I'm using
> TDM, which is 8000).
> - FreeSWITCH version - happens on 1.2 stable, the latest master branch, and
> an older version that we were using.
>
> If you haven't heard of anything like this, could you please give me your
> thoughts on why this could happen only on-conference, not while playing WAV
> files, and only with FreeTDM channels?
>
>     Thanks!
>     Bob
>
>
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