Hey, just to report again on this problem. We tracked down the problem into PJSIP, which applies automatic gain control (AGC) in the conference bridge. In combination with high end equipment (EDIROL UA-25EX, BeyerDynamics DT-790 and a "noise free" room) does this undocument feature introduce the problem, because there is very little(actually the fan of the notebook is the loudest) background noise. AGC kicks in, when the person stops talking by increasing the mix_adj (mixing volume adjustment). When the person starts talking again AGC slowly decreases the mix_adj... Interestingly, it sounds somehow like switch from wideband to narrowband or vice versa, but this is not the case (we checked with Audacity that the frequency spectra is not changing). We solved the problem by simply disabling SIMPLE_AGC in conference.c completely (which can only be done at compile time). I would personally prefer to change AGC during runtime, e.g. by introducing a new option to "enum pjmedia_conf_option"... Would you be interested in a patch? Best regards, --- Dennis Guse On Thu, Jan 16, 2014 at 3:18 PM, Dennis Guse < dennis.guse at alumni.tu-berlin.de> wrote: > > Hey, > > is there such a thing as automatic gain control in PJSIP? > We have the problem that the loudness is changing during a call (local network; codecs: G.722 or L16). We could track it down to the sending client and found the loudness change in a outgoing recordings (using PJSIP recorder). > Audacity shows no change in frequency, but only in the loudness. > > We changed already the sound cards and checked the sound input using > could reproduce the problem with two computers. > > Technical details: > * Ubuntu 13.10 32bit > * python-pjsip from here https://launchpad.net/~dennis.guse/+archive/sip-tools-beta (Version 2.1 svn ref. 4605). > > We are doing nothing special here, just get the appropriate sound device (EDIROL UA-25EX) and make call (plus start audio recording). > > Any hints would be appreciated.... > > PS: A wave recording can be provided. > --- > Dennis Guse -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.pjsip.org/pipermail/pjsip_lists.pjsip.org/attachments/20140409/1e6f16b5/attachment.html>
