Hi,

I¹m resending this e-mail to the list, because I suspect that it was never
actually distributed when I sent it a week ago. (Can¹t find it in the
archives). It might be because I attached 2 audio files, which might have
caused it to (invisibly) bounce. Please excuse me if some of you did receive
the original e-mail.

--this is what I sent a week ago --

In one of my previous post I described the service we built with SEMS. You
can find an archived version of this post here:
http://lists.iptel.org/pipermail/sems/2013-May/004171.html

We recently found out that in some cases we experience poor quality of the
relayed media in the B2ABUASession. I¹ve attached 2 audio files, which I¹ve
captured using tcpdump and converted to audio files using wireshark. The
naming of the files describes the direction. I¹m not sure if the attachments
will be distributed on the mailinglist, so I¹ve uploaded them to SoundCloud
as well:
https://soundcloud.com/tvdgeer/from-a-to-sems
https://soundcloud.com/tvdgeer/from-sems-to-b

NB. There is another set of files which I did not upload/attached
(from_B_to_SEMS.au and from_SEMS_to_A.au) and they have the same problem. So
the problem is in both directions.

You can clearly hear that the audio coming from the A leg is OK, but the
audio from SEMS to the B leg is distorted. Does anybody recognise this type
of distortion? It¹s not a PCMU/PCMA incompatibility. It sounds more like a
timing problem, like every sample/packet is slightly corrupted. The stream
analyses of Wireshark do not display any problem.

It might be good to mention that the problem seems to appear and disappear
out of nowhere. At one time the problem disappeared by restarting SEMS. On
one occasion it disappeared overnight (without restart) but the next day it
was back (again without restart).

In our setup we run SEMS 1.5 on a virtual system (VMWare hypervisor). Could
this be the cause of this problem?

Any help is appreciated. Thanks in advance!
Best regards,

Tom van der Geer





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