Paco Brufal wrote:
I have an asterisk 1.2.18 working fine, the only problem is that all
applications that play audio, sound like "tremolo" or "vibrato", but
musiconhold plays fine.
The same audio file (wav, mp3, ...) works fine with Musiconhold()
but not with Playback() or Background()...
Do you know what is happening and how can I fix it? It's an only SIP
system, no fxo/fxs cards.
Paco,
You are in luck, because we just solved this problem. It turned out to
be a timing issue, which surprised me because I thought timing was only
important for IAX trunks, meetme rooms, and music-on-hold. Now I know
that anything playing back audio files, except native music-on-hold,
needs a reliable timing source. This includes the Playback() and
Background() applications, as well as queue announcements.
You have two options. One of them is free and might work and the other
will cost about $75 per server but should work reliably. The first
option is to use ztdummy, but there are a few points that you have to be
aware of:
1. The kernel version must be at least 2.6.13
2. The kernel must be configured with a timer frequency of 1000 HZ
3. The kernel must be configured to provide RTC interrupts
4. The kernel must be configured with enhanced real time clock support
With a properly configured 2.6.13 or greater kernel, ztdummy will use
the RTC instead of kernel jiffies. This method is more accurate and
should help alleviate your problems. Just remember that if you install
a new kernel you'll have to rebuild Zaptel against it.
We tried this and it helped, but it introduced another problem. The
Playback() application would intermittently lock up. We are running on
Dell PowerEdge 6850s, so I'm assuming the following issue documented at
<http://www.voip-info.org/wiki/view/Asterisk+Zaptel+Installation> was
the cause:
Mar 2006: Specifically, with many Dell servers, RTC will fail to give
out interrupts, causing ztdummy to give no timing information. If you
are using ztdummy, and having issues with the Playback() command
causing the application to hang, then try the above step of disabling
acpi. In addition, a recompiled kernel, with HPET_EMULATE_RTC option
enabled, may solve the problem. (This option was removed in 2.6.13 kernel)
The second option is to install a TDM400P without any FXS/FXO modules as
a timing source. We've been running like this since Saturday and
everything seems good so far. In this case, there are two points to
keep in mind:
1. The server must have an available PCI slot that is compatible with
the TDM400P
2. The wctdm module must be passed the 'timingonly=1' parameter at load
Bare TDM400Ps are available from Atacomm at
<http://voipstore.atacomm.com/Shops/ViewItem.aspx/27934028032-45624523776.htm>
for under $75, which is pretty cheap for a "just works" solution.
Remember that you can use zttest to verify the accuracy of your timing
source. I ran it on each of the servers I installed a TDM400P in, and
they all reported an average accuracy of better than 99.99%. Digium
recommends an accuracy of at least 99.98%, which ztdummy using the RTC
wasn't able to provide.
Matthew Roth
InterMedia Marketing Solutions
Software Engineer and Systems Developer
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