afGetFrameSize returns the frame size in bytes for a specified audio
track.

SYNOPSIS
#include <audiofile.h>

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

PARAMETERS
file is a valid AFfilehandle.

track is an integer which refers to a specific audio track in the
file.  At present no supported audio file format allows for more than
one audio track within a file, so track should always be
AF_DEFAULT_TRACK.

If expand3to4 is a non-zero value, then 3-byte frames will be treated
as taking up 4 bytes in memory.  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.)

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

A sample frame consists of one or more samples.  For a monaural track,
a sample frame will always contain one sample.  For a stereophonic
track, a sample frame will always contain two samples, one for the left
channel and one for the right channel.

The parameter expand3to4 is ignored unless the specified audio track
contains 24-bit sampled audio data.