Hi Peter.

I thought about the bit reservoir, and I wonder if the bit reservoir could be sufficiently filled by decoding (only) the previous mp3-frame. That is if an mp3 file consists of frames A,B,C,D,E,F and I don't have enough memory to decode it completely to reverse it, would it be possible to
decode E to get the correct bit reservoir for F, decode F and reverse (play) it.
decode D to get the correct bit reservoir for E, decode E and reverse (play) it.
...

Would that seem sensible (apart from the fact that you decode 2n-1 frames to play n frames)?

cu,
sven