[asterisk-users] Asterisk 11.24.1 garbled audio

Matthew Jordan mjordan at digium.com
Fri Nov 11 14:02:24 CST 2016

On Fri, Nov 11, 2016 at 10:46 AM, Jerry Geis <jerry.geis at gmail.com> wrote:

> >Information on timing sources can be found here:
> >https://wiki.asterisk.org/wiki/display/AST/Timing+Interfaces
> >As noted on that page, ConfBridge can use any timing interface Asterisk
> >provides, and is not limited to the DAHDI timing interface. Generally,
> >timerfd is a good timing interface.
> >That aside, I would try to rule out external issues with the garbled audio
> >before changing the timing source. Things like:
> > - Analysis of the RTP traffic (along with potential jitter)
> > - CPU utilization with an active conference (95% idle doesn't mean that
> >some core isn't pegged)
> > - Any potential transcoding issues or codec issues
> >Matt
> Hi Matt - thanks.
> Looks like I am ONLY loading:
> res_timing_pthread
> res_timing_dahdi
> But I dont think the res_timing(x) is working on CentOS 5.
> res_timing_timerfd does not
> even seem to be compiled on this box.
> How do I tell for sure what its using and if its good. All I saw in the
> asterisk log was the
> two res_timing_pthread and res_timing_dadhi being loaded.
> Everything else is fine actually. It worked with the card, and withthout
> the card just sending audio to
> one endpoint has audio issues in a conference. The machine is doing
> nothign else at that time.
You're probably running a version of the Linux kernel that doesn't support
timerfd, hence why it isn't available.

res_timing_pthread is ... not very good. It exists as an absolute, last
ditch fall-back for Asterisk to provide a source of timing when none
exists. As such, and assuming you have ruled out all other sources of the
garbled audio, then I'm really not surprised that it isn't very effective.

Your best bet would be to:
 - Provide a hardware timing source that res_timing_dahdi can use. IIRC,
this should work even without a specific card, but does require the dahdi
kernel module to be installed and available. (I could be wrong on the need
for a physical card however, so your mileage may vary.)
 - Upgrade to a version of the kernel that res_timing_timerfd supports.
That should be Linux 2.6.26 and glibc 2.8 or later.

Personally, if I were in your shoes, I'd go with the latter. CentOS 6
should be good out of the box, and CentOS 5 is pretty long in the tooth.

Matthew Jordan
Digium, Inc. | CTO
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at: http://digium.com & http://asterisk.org
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