float afGetFrameSize (AFfilehandle file, int track, int expand3to4);

file is a valid AFfilehandle.

track is always AF_DEFAULT_TRACK for now.

If expand3to4 is a non-zero value, then 3-byte frames will be treated
as 4-byte frames.  This is useful for calculating how much memory will
be needed to store audio data suitable for playback since 24-bit audio
data is typically aligned on 32-bit boundaries.

(At least that's how it's done on SGI systems.  I know of no other
computer system that has support for 24-bit audio.)

afGetFrameSize returns the number of bytes in a frame in the given
track of the specified file.
