Detecting track changes during playback.

[Doozer]

First off, lemme know if I'm posting in the right forum, or if there is a different one that's more appropriate.

We're writing the equivalent of a crossfader, and we need to be able to tell when we've reached the end of a track. We can get the rough track length in seconds using IPC_GETOUTPUTTIME, but that's pretty inaccurate. Disk-writer plug-ins have to be able to tell exactly, since they start a new file between tracks. How are they doing this?