Asterisk NOW MP3 Problem


Please help us with this issue;

We have 2 asterisk servers for our business, one is at our office (installed asterisk now) and second is in our virtual data center. Both asterisk are reliable but we sure want to migrate to Virtual one, but we are having problem with recordings, on our office (metal) asterisk server we have recordings for IVR in MP3 format and it work fine, but when we tried to migrate everything to our virtual asterisk server, we couldn’t make it work with MP3 files, so please help us with it

I prefer MP3 format because it sounds smoother (inc bass and low sound effects) and wav is has less quality and its too loud.

p.s. we have Asterisk NOW on both servers, asterisk version is 1.4

  1. Using a virtual machine for something as real time as Asterisk is inadvisable.

  2. When presented at 44,100 samples a second, 16 bit, MP3 may sound good. When presented at 8,000 samples a second, 8 bit μ-law, it will sound telephone quality and when presented at 13.6kpbs GSM full rate, it will sound awful. There is no point in storing sounds in anything better than the highest quality codec that you actual use for the telephony.

Couple of pointers.

If you are runnning on VMware, make sure you have a VMware happy kernel, if not you’ll have so much grief with timing of recordings and music on hold, you might as well give up…seriously.

Try to store yur music in the native format you ar working with. ie ulaw / alaw etc, less conversion = less stress / distortion etc. You may need to do some compression / level reduction to get it to “fit” in the bandwidth and dynamic range without sounding too “hot” or overmodulated, which I find a common problem with native wav files ripped from a CD. You can use Audacity, which I do use, on odd occasions, to do this.

Once you have the tracks in wav format, you can convert the files to ulaw / alaw from the asterisk CLI or linux command line. Check out

Back to the VM. This is what I have managed to do to get Asterisk working on CentOS on a VMWare VPS in an “acceptable” way:

  • Grab a kernel and matching sources packages from or the 64 bit one if needed, and install.
  • Edit /boot/grub/grub.conf and add clock=pit to the end of the kernel= line.
  • reboot
  • Recompile dahdi
  • Recompile asterisk
  • Don’t forget internal_timer=yes in asterisk.conf

A full step-by-step is located at Not my post, but useful none the less

Hope this helps.