<div dir="ltr"><div>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.</div>
<div><br></div><div>I've eliminated the following:</div><div><br></div><div>- T1 clocking</div><div>- Echo Cancellers (I've turned on and off all combinations of hardware and software EC)</div><div>- T1 board firmware (it's the latest, and the problem only happens on-conference).</div>
<div>- Packet length - it's the same (20 mS) for the conference engine, FreeTDM, and Dahdi</div><div>- mu-law vs. a-law encoding - behaves identically.</div><div>- Comfort noise - happens with and without.</div><div>- conference sampling rate (tried 8000 and 16000, even though I'm using TDM, which is 8000).</div>
<div>- FreeSWITCH version - happens on 1.2 stable, the latest master branch, and an older version that we were using.</div><div><br></div><div>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?</div>
<div><br></div><div> Thanks!</div><div> Bob</div></div>