[Asterisk-Users] Re: sipuras 841 bad sound

[alan]

> Re: sipuras 841 bad sound (Juan Jose Comellas)

> On Tuesday 20 September 2005 20:46, Anton Krall wrote:
> > I have a problems with some sipuras 841 and asterisk 1.0.9.
>
> (upgrade the firmware was suggested and completed, and didn't fix the
> problem.)

There are a few little configuration details which are hard to catch on
the SPA-841, which can affect sound quality.

* RTP packet size: 0.20

On the "SIP" tab of the Advanced Admin page, the "RTP packet size" is
shown, measured in seconds. It defaults to 0.03, however Asterisk is
hardcoded to use 0.02.  This mismatch can cause sound issues.

* Silence Supp Enable: Off

On the "Ext1" and "Ext2" tabs of Advanced Admin, the "Silence Supp
Enable" option must be turned off. This is Silence Suppression, which
causes the phone to stop sending RTP packets when the phone detects
silence in the handset. Asterisk 1.0.9 does not support silence
suppression, so this option must be turned off, or audio stream timing
will fail a lot.


We have a bunch of SPA-841's in service, and we're just finishing
working out the bugs in the system. Our latest audio issue, as far as we
can tell, was caused by a Duplex Mismatch between the ethernet port on
the Asterisk server, and the ethernet port on the switch it was
connected to. When one is set to full duplex and the other half duplex,
you get random, intermittant periods of massive packet loss/jitter,
which messes up audio something fierce.

I've found http://www.voiptroubleshooter.com/ to be a good source of
info on diagnosing random "audio is bad" issues. It has sound clips of
the different kinds of "audio is bad" problems, along with info on what
might cause that kind of problem.

Alan