[Asterisk-Users] IAX2 Asymmetric Latency

[Bruno Hertz]

On Sat, 2005-01-29 at 20:20 +0100, Zdik Kudrle wrote:

> I called from my home thru Asterisk to my Cellphone. I've picked up the
> phone and set up input channel instead of microphone my TV card. I started
> the TV a listened to the latency cellphone<->TV. Then I said something to
> phone and listened to the latency cellphone<->Speakers. Simple, but it
> works for me. Today I did the same thing without cellphone - somebody was
> sitting in the office and answered local call (no calling out, just intra
> PBX call). He sent me a message using ICQ and that exact moment said
> something to the phone and vice versa. The result was pretty same using
> the cellphone...

Alright, no nifty network latency measurement then :) It's basically
what I do all the time too, either echo tests with * or having two
clients call each other.

> I don't think my soundcard has latency problems (Live!5.1). The really
> strange think is that latency is _increasing_. It means that somewhere all
> the data must be stored but I've got no idea where. Maybe I'll run some
> crashtest - one part or other will crash with out of memory... :-)

I should have mentioned that I'm on Linux. It's not a card issue
actually (I have a SB too), but rather how driver buffers are set up
by the client application. I found that it makes a huge difference
with respect to latency on my system.

Regarding the 'increasing' point, that's really something I can't
confirm. Usually, my latencies are constant, or huge at the beginning
and decreasing afterwards. So I guess something's definitely out of the
order in your case.

> This sounds promising, I'll give it a try.

Possible only if you're on Linux, too, since gnomemeeting doesn't run
on Windows. Sorry I didn't mention that, but sometimes I forget that
there are other OSes out there.

Assumed that you're on Windows, I'd still try other softphones like
XLite or SJPhone. Especially XLite seems to be pretty good. It's a SIP
phone, and in my experience many latency issues are due to IAX or it's
implementation. Just today I experienced them on native bridging, and
although IAX is marketed as VoIP swiss knife protocol, especially
regarding softphones I get best results with SIP and H323.

> Sorry to disappoint you, I'm not that kind of network magician..

Me neither, that's alright. Good luck.

Regards, Bruno.