Playing an mp3 while it is downloading

[squidge]

I'd imagine you would do the same as if the file was being retrieved from over the network (which is, in effect, what is happening)

As for buffering, you would know that yourself. You will know how much of the file has been read and how much you have received from the network. However, I wouldn't worry about it, if you run out of data theres not much you can do.

I'm not sure how well this kind of technique will work with MP3 files - typically you seek to the end of an MP3 to search for an ID3 tag before seeking back to the start to play the file. I don't know if Phonon does this, but if it does, maybe you would need to emulate this behavior (possibly with fake information, knowing the file type being retrieved of your I/O interface)