afGetFrameSize man page
afGetFrameSize — calculate the frame size in bytes for an audio track
float afGetFrameSize (AFfilehandle file, int track, int expand3to4);
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.
expand3to4 is a boolean-valued integer indicating whether frame size calculation will treat 24-bit data as having a size of 3 bytes or 4 bytes.
afGetFrameSize returns the number of bytes in a frame in a given audio track.
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.
A non-zero value of expand3to4 should be used when calculating the frame size for storage in memory (since 24-bit audio data is presented in memory as a 4-byte sign-extended integer), while a value of zero should be used for calculating storage on disk where no padding is added. The parameter expand3to4 is ignored unless the specified audio track contains 24-bit audio data.
Michael Pruett <firstname.lastname@example.org>