[Asterisk-Users] Offtopic: improving softphone latency on Linux?

Steve Kann
Mon, 17 Jan 2005 14:51:36 -0000

Bruno Hertz wrote:

>Hi folks
>
>last weekend, I tried Windows Messenger first time and was stunned by
>the little latency it gives. Until now, I've been using softphones on
>Linux exclusively, like iaxcomm, linphone and sjphone, and they all give
>me about 1, at times even 2 secs delay. Whereas Messenger really seems
>to be in the millisec range.
>
>Of course, I'm now curious why there is that difference. Clearly,
>Messenger is more tightly integrated with the OS and accordingly tuned.
>
>So where does this time go? Kernel? Application level? Web searches seem
>to suggest that sound latency generally is a problem on Linux, so I
>tried the low latency kernel from
>http://ccrma.stanford.edu/planetccrma/software/planetccrma.html
>(there are two kernels, actually, where I only got the stable version to
>boot - bleeding edge didn't do on my machine).
>
>Still, that kernel did not really improve things in a noticeable way.
>
>Question hence: did some of you guys experience and investigate this
>same issue? Any recommendations or hints how to make VoIP even more
>enjoyable on linux?
>
>
>

What softphone are you using on Linux?

If you use an iaxclient-based softphone on linux as root, it runs with
RT priority, and pretty low latency -- it certainly is much less than 2
seconds, usually less than 100-200ms or so, depending on the network.

There's certainly room to squeeze down the path through the library, but
there's isn't that much latency in there..

-SteveK