I\'m trying to find a cross platform audio library that will have the following abilities (in order of importance):
You can take a look at GStreamer and FFmpeg.
EDIT:
Since you are willing to use Qt, you should definitely check Qt MultimediaKit, which is a part of the Qt Mobility project. Phonon is fading away because Qt is investing on MultimediaKit to replace it.
This example shows how to do simple audio playback. This example shows how to create a multimedia player. This example shows a more advanced music player, using Qt and QML.