[asterisk-users] Internal timing bad for Fax?

[Kevin P. Fleming]

On 06/22/2010 12:24 PM, Kristijan Vrban wrote:
> Hello, i just made the reproducible watching:
> I send a Fax from asterisk (trunk) with spandsp (latest snapshot) via
> T.38 -> Audiocodes Mediant 2000 (FW 5.60.43.5) -> PSTN Fax
> With Internal timing Enabled, the Fax break after the first quarter
> from the first page is transfered.
> With Internal timing Disabled, the fax is transferred flawless.
> 
> Both test with pthread timing module on a QEMU Virtual maschine
> 
> So, is internal timing bad for Fax?

No, but you've chosen a very bad combination to provide timing;
res_timing_pthread uses a great deal of CPU to do its job (much more
than the other options), and you are running in a virtual machine on top
of that. If you are running on Linux and can run a kernel that supports
res_timing_timerfd, you'll have better results, but running in a virtual
machine will always means that you are subject to random
scheduling-related problems.

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
skype: kpfleming | jabber: kfleming at digium.com
Check us out at www.digium.com & www.asterisk.org