asterisk-mp3 is broken in Ubuntu 10.04. The following is reported in the log when trying to load format_mp3.so:
[Jun 3 19:54:34] WARNING[2504] loader.c: Module 'format_mp3.so' was not compiled with the same compile-time options as this version of Asterisk.
[Jun 3 19:54:34] WARNING[2504] loader.c: Module 'format_mp3.so' will not be initialized as it may cause instability.
[Jun 3 19:54:34] WARNING[2504] loader.c: Module 'format_mp3.so' could not be loaded.
It worked fine in Ubuntu 9.10.
ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: asterisk-mp3 1.6.2.0-1
ProcVersionSignature: Ubuntu 2.6.32-22.35-generic 2.6.32.11+drm33.2
Uname: Linux 2.6.32-22-generic x86_64
Architecture: amd64
Date: Thu Jun 3 20:08:42 2010
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release amd64 (20091027)
ProcEnviron:
LANG=en_US.utf8
SHELL=/bin/bash
SourcePackage: asterisk-addons
Same error here, upgrading from karmic -> lucid all of our music on hold files went silent. Worked around this here by converting the mp3's to .sln files:
apt-get remove asterisk-mp3
apt-get install sox libsox-fmt-all mpg321
# convert mp3 to wav
mpg321 -w myfile.mp3 myfile.wav
# convert wav to sln
sox myfile.wav -t raw -r 8000 -s -c1 myfile.sln
The "-c1" up there is important if your mp3 is stereo. If you care more about filesize than sound quality you can convert them to GSM instead:
sox unknown.wav -r 8000 -c1 unknown.gsm
Best