BPM detection of songs in mp3 and mp4 formats for mac apps

i am working on a mac on a mac application which needs the functionality of detecting the Beats Per Minute (bpm) of songs in mp3 and m4a formats. For detecting bpm we are using the codes from  http://www.surina.net/soundtouch but it is giving wrong bpm values for m4a files even though they are converted to mp3开发者_开发百科 or wav format using ffmpeg(Please note that bpm detection for mp3 files are working fine ). For detecting bpm we also tried the binary named SoundStretch which is also provided by soundtouch (http://www.surina.net/soundtouch). Can any one explain what is going on?!. The m4a files even when converted to mp3 or wave are not working. Is any other open source libraries or classes for bpm detection are available for mac?

Any one please give some directions