How to use Monitor application using 'mp3' file format?

how can use Monitor application using 'mp3 ’ format
i used :
exten => s,1,Monitor(mp3,record-${CHANNEL},bm)
but the recording file was empty and having zero size also couldont mix input & output file together;;

plz help…thanks

make sure the monitor is executed without any error.

  1. why would you want to record in a format that is over-engineered for telephone quality speech?

  2. I believe the patents on MP3 mean that Asterisk couldn’t include an MP3 encoder in the official release.