[Sound] get Levels from streaming sounds

Hi there,
Do you know how to get Levels from streaming sounds (very long sounds) to display it ?
Should I use rtAudio or Fmodex ?

I post the topic of my problems with fmod in the fmod forum :
http://forum.openframeworks.cc/t/openframeworks-videoplayer-appearing-white/12141/0">http://www.fmod.org/forum/http://forum.openframeworks.cc/t/openframeworks-videoplayer-appearing-white/12141/0

Thanks

Jerome