Unable to play sound file mp3 or g729

hello everyone. i am running asterisk 11 in my server and i would like to send the call to play a sound file exten => s,n,Playback(/opt/files/audio/abbsence.mp3.
the problem is that i am getting an error which i cannot find why.
– Executing [s@app-announcement-1:4] System(“SIP/TRUNK-00000006”, “/usr/sbin/alert-summer.sh 2114041234 02/08/2016 11:18:50”) in new stack
– Executing [s@app-announcement-1:5] Playback(“SIP/TRUNK-00000006”, “/opt/files/audio/abbsence.mp3”) in new stack [Aug 2 11:18:50] WARNING[3089][C-00000006]: file.c:701
ast_openstream_full: File /opt/files/audio/abbsence.mp3 does not exist in any format [Aug 2 11:18:50] WARNING[3089][C-00000006]: file.c:1017 ast_streamfile:
Unable to open /opt/files/audio/abbsence.mp3 (format (g729)): No such file or directory [Aug 2 11:18:50] WARNING[3089][C-00000006]: app_playback.c:484
playback_exec: ast_streamfile failed on SIP/TRUNK-00000006 for
– Executing [s@app-announcement-1:6] Wait(“SIP/TRUNK-00000006”,
“2”) in new stack
– Executing [s@app-announcement-1:7] Hangup(“SIP/TRUNK-00000006”,
"") in new stack

i got the same error even with g729 file.
has anyone got any ideas?

The file extension needs to be left off of the filename. Asterisk will find the best match it can based on the available files.