afGetFrameSize(3dm)                                        afGetFrameSize(3dm)


NAME
     afGetFrameSize, afGetVirtualFrameSize - get the track / virtual frame
     size in bytes for a specified audio track from an AFfilehandle structure

SYNOPSIS
     #include <dmedia/audiofile.h>

     int afGetFrameSize(AFfilehandle file, int track, int extend3to4)

     int afGetVirtualFrameSize(AFfilehandle file, int track, int extend3to4)

PARAMETER
     file         is an AFfilehandle structure, previously created by a call
                  to afOpenFile(3dm).

     track        is an integer which identifies an audio track in file.

     extend3to4   is a integer boolean value (i.e., 0 or 1) indicating whether
                  the routine should extend the value of the frame size for
                  24-bit uncompressed data out to 32 bits.

                  Since all currently supported file formats contain exactly
                  one audio track per file, the constant AF_DEFAULT_TRACK
                  should always be used here for now.

RETURN VALUE
     afGetFrameSize() returns the size in bytes of a sample frame in the file
     referenced by track.  afGetVirtualFrameSize() returns size in bytes of a
     sample frame in the audio buffer as specified by the current virtual
     format.  See afIntro(3dm) for an explanation of virtual format.

     In case of error, -1 is returned.

DESCRIPTION
     afGetFrameSize() returns the size of a sample frame in an audio track in
     the file represented by the AFfilehandle argument.

     afGetVirtualFrameSize() does the same for the virtual format for the
     given track, as set by any combination of calls to
     afSetVirtualSampleFormat(3dm) and afSetVirtualChannels(3dm).

     For monaural data, a sample frame consists of a single audio sample.  For
     stereo data, a sample frame consists of a <left, right> stereo sample
     pair.

     The extend3to4 allows the application to choose, in the case where 24-bit
     uncompressed data is present in the file associated with track, whether
     to return the actual size in bytes of a frame of data in that track (3 *
     number_of_channels) or the size of the frames which will be presented to
     the user (since this will always be 4-byte sign-extended integer).  The
     former is useful for informational purposes, but the latter is necessary
     for determining the size of the audio buffer to be handed to


     afReadFrames(3dm).  Note that extend3to4 only applies to 24-bit sample
     width.  It is ignored in all other cases.

SEE ALSO
     afWriteFrames(3dm), afReadFrames(3dm), afGetChannels(3dm),
     afGetVirtualChannels(3dm), afSetVirtualSampleFormat(3dm)


                                                                        Page 2