Hello,
o ?????????? [03/18/09 17:07]:
Greetings!
Recently there was a problem with voice through SEMS, as B2BUA. I'm
using my own module for SEMS, but the problem is repeated in the original
modules SEMS (eg serviceline).
The problem was that after some random time intervals and not at each voice
conversation arose artifacts: the phrase duplicated, sometimes in that moment
there was only one-sided audibility.
Suspicion for the PLC, but the channel is wide and stable ping to the server
1ms, and verified at the time of voice distortion. Dedicated firewall was
disabled, the scheme has been used only sems, openser and two UA. An example of
distortion, you can listen here:
http://www.voiptroubleshooter.com/sound_files/male1_2_sil_20ms_5.wav (or other
examples of this and similar problems
http://www.voiptroubleshooter.com/problems/plc.html).
I made various attempts to remedy the situation, disable all processing in the
PLC source sems, tried different modes of channels PLAYOUT_BUFFER.
...
It seems to me that the problem was to use various channels to `playout_buffer`
caller and the callee, but with `simple_playout` (which appears by default) the
problem was. Perhaps disable dtmf as assist. Other things to note that when
using jitter_buffer artifacts appear more frequently and consistently, but
gently.
>
> It would like to know what is still the case, and in which direction
to look. Thanks in advance!
simple_playout does not at all buffer the audio it receives. This means
that when the audio for a packet that is to be sent is read and on the
input audio for that exact time has not yet arrived, it sends empty
audio. So for any application where the audio is to be sent through SEMS
in realtime, you need to use a buffering playout_buffer. My
recommendation is ADAPTIVE_PLAYOUT, because it minimizes the total
delay, but if you know that you have only little jitter or a bounded
amount of jitter, you may have better quality with JB_PLAYOUT.
Stefan
--
Stefan Sayer
VoIP Services
[email protected]
www.iptego.com
IPTEGO GmbH
Wittenbergplatz 1
10789 Berlin
Germany
Amtsgericht Charlottenburg, HRB 101010
Geschaeftsfuehrer: Alexander Hoffmann
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