afGetLoopStartFrame(3dm)                              afGetLoopStartFrame(3dm)


NAME
     afGetLoopStartFrame, afGetLoopEndFrame, afGetLoopCount - get the
     start/end frame and loop count from an AFfilehandle structure for a
     specified loop.

SYNOPSIS
     #include <dmedia/audiofile.h>

     AFframecount afGetLoopStartFrame(AFfilehandle file, int instid,
                                        int loopid)
     AFframecount afGetLoopEndFrame(AFfilehandle file, int instid,
                                        int loopid)
     int afGetLoopCount(AFfilehandle file, int instid,
                                        int loopid)

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

     instid   is a positive integer value which identifies an instrument
              configuration in file.  instid should be an element from an
              array of IDs retrieved via a call to afGetInstIDs(3dm).

     loopid   is a positive integer value which identifies a loop structure in
              an instrument parameter chunk.  You obtain loopid's by calling
              afGetLoopIDs(3dm).

RETURN VALUE
     afGetLoopStartFrame() returns a non-negative AFframecount type
     representing the frame number for the loop start point, or -1 if there is
     an error.

     afGetLoopEndFrame() returns a non-negative AFframecount type representing
     the frame number for the loop end point, or -1 if there is an error.

     afGetLoopCount() returns a non-negative integer indicating the number of
     times a loop should be repeated.  This information is only available
     and/or storable in certain file formats (see WAVE(4)).  For all formats
     which do not store this information, afGetLoopEndFrame() will return 0.

DESCRIPTION
     Each takes a loopid argument which provides a handle to a set of loop
     parameters.

     You can obtain a list of loop ID's for an audio track by calling
     afGetLoopIDs(3dm).  Logically, an audio file contains chunks of
     instrument parameters (specified by instid handles), and each chunk of
     instrument parameters may contain several loops.

     AIFF(4) (and AIFF-C) files contain at most one instrument configuration,
     but other file formats may contain multiple configurations, so it is now
     recommended that afGetInstIDs(3dm) be used to retrieve an array of IDs.


     afQuery(3dm) may be used to determine in advance whether a particular
     format supports multiple inst chunks.

     These routines allow you to obtain direct information about loops in an
     audio file without the added overhead of looking up associated markers
     (see afGetLoopStart(3dm)).  This is necessary because several file
     formats now supported by the Audio File Library contain loop information
     (i.e., start and end points) which is completely independent of marker
     information.  In other words, the markers (if any) stored in the file
     header may and usually will refer to locations in the file other than the
     loop start and end points.

EXAMPLE
     afGetLoopStartFrame() returns the value 125000.  This is the frame number
     in the audio track for the beginning of the specified loop.

CAVEATS
     These functions may return any configurations of loops within an inst,
     not just the value 2 found in AIFF/AIFF-C files.  Other file formats have
     different loop configurations than AIFF/AIFF-C.  As mentioned above,
     afQuery(3dm) can be used to determine the possible loop configurations
     for a given file format.  Programs should be written to expect and ignore
     loop configurations it does not understand.

SEE ALSO
     afOpenFile(3dm), afGetInstIDs(3dm), afGetInstParamLong(3dm),
     afGetLoopIDs(3dm), afGetLoopStart(3dm), aiff(4), avr(4), wave(4), sd2(4)


                                                                        Page 2