[Asterisk-Users] Asterisk Crackly Bad quality

[Steven Critchfield]

On Sat, 2004-12-18 at 18:34 +0100, Bruno Hertz wrote:
> On Fri, 2004-12-17 at 12:01 -0700, Nihal wrote:
> > I've freshly installed Asterisk on a Fedora C2 machine. Dual P4's, 2GB RAM. 15KRPM Drive.
> > Using the default configs and added one Soft Sip phone.
> > 
> > While listening to the demo the quality isnt very good. It's kind of crackly and skips a bit.
> > Should the sound be better or is that just what you get using IP phones/Asterisk?
> > 
> > (I ran the X-Lite phone).
> 
> Hi Nihal
> 
> don't know about FC2, but I can confirm that sound quality depends on
> the distribution/kernel used, where I didn't figure out yet why.
> 
> I myself have FC3 and Debian Sarge with 2.6.8 kernel on the same
> machine, and under both OS I compiled and installed an identical
> asterix cvs version.
> 
> While the FC3 installation works alright regarding sound, I see
> the same problems you described on Debian. I.e. the demo voice is
> crackling and has delays (short moments of silence). A tcpdump showed
> me that during those 'skips' actually no packets are transferred
> from the asterix server to the client machine. So somewhere on the
> server that voice data is buffered resp. delayed, god knows why.
> 
> As said, the same asterisk version works alright with FC3 on the same
> machine.
> 
> I even logged and compared the make runs on both OS, but there are no
> notable differences. Might be kernel, some external library, I have no
> idea actually at this point.

I haven't seen it mentioned here yet, but do you have a timing device
installed? Without a timing device such as a Digium PSTN card or a dummy
interface to drive the interupts, asterisk relies on the incoming data
stream. If your phone or soft phone is generating silence and uses VAD,
then there will be gaps where the audio won't be sent from your phone
and asterisk won't know it is time to send you more audio.

I highly suggest you work on getting either the RTC or USB driver loaded
to provide timing if you don't already have a PSTN card for that job.
-- 
Steven Critchfield <critch at basesys.com>