afGetLoopStartFrame(3dm)			      afGetLoopStartFrame(3dm)

NAME    [Toc]    [Back]

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

SYNOPSIS    [Toc]    [Back]

     #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    [Toc]    [Back]

     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    [Toc]    [Back]

     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    [Toc]    [Back]

     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.



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afGetLoopStartFrame(3dm)			      afGetLoopStartFrame(3dm)



     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    [Toc]    [Back]

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

CAVEATS    [Toc]    [Back]

     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    [Toc]    [Back]

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


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