[Freeswitch-dev] New "mod_dahdi_timer" - does the community want this?

Bob Hartwig bobjects at gmail.com
Tue Oct 22 04:48:45 MSD 2013

OK, I uploaded this as a tarball to Jira, as an "improvement" issue type,
for the FreeSWITCH project.  Here is a paste of the description that I left
there, for everyone's information:

I ran across a problem with a Dahdi-based FreeTDM system a few weeks ago.
 Because the timer for mod_conference was not synchronized to the T1 clock
source, there was significant periodic on-conference noise.  The problem
was not that the "soft" timer was inaccurate; on the contrary, it was a
very accurate 1 mS timer in a system that had a pretty inaccurate T1 clock
coming in.

My solution was to create a new "mod_dahdi_timer", which derives the ~1 mS
timer from 8 ticks of the 8 kHz /dev/dahdi/timer device.  Then a one-line
change to mod_conference.c to change "soft" to "dahdi", and the conference
sounds perfectly clean.

Installation guidelines:

- Untar the tarball under the freeswitch source directory
- Before ./configure build step, edit modules.conf, adding a line for
- Build as usual
- Add a line to modules.conf.xml enabling mod_dahdi_timer

Testing the timer:
- Only do this if you have a Dahdi T1 board installed and configured with
- "show timers" - verify that the new dahdi timer shows up.
- timer_test 10 10 dahdi
- timer_test 20 10 dahdi
- timer_test 40 10 dahdi
- timer_test 60 10 dahdi
- timer_test 120 10 dahdi

Using the timer:
- Into any config that allows for specifying a timer name, use "dahdi".
 This is especially useful for mod_conference.

- See TODO comments in mod_dahdi_timer.c .  Exception handling may not be
robust, and may fail spectacularly in systems with no configured Dahdi T1
- Comments at the top of mod_dahdi_timer.c may need to be expanded to
include the normal FreeSWITCH copyright notices, etc.

On Mon, Oct 21, 2013 at 2:59 PM, Moises Silva <moises.silva at gmail.com>wrote:

> On Mon, Oct 21, 2013 at 1:45 PM, Michael Jerris <mike at jerris.com> wrote:
>> Or for that matter, to put it right in to mod_freetdm.
> Agreed, that would be better.
> Moy
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