Mediaplayerstream buffer percentage
I have found that when mediaplayerstream returns the number -2147483648 it seems to mean that the stream is live (and not a file) and a it can't not return a percentage (since I guess there is no percentage read off a live stream or something). When the stream is not live and is a file, like an MP3 file being streamed off a server then the percentage will show correctly (i.e. 20%, 30%, etc).
Anyway, that is the best I can figure out how mediaplayerstream does it's buffer percentage. Hope that helps.