afInitSampleFormat(3dm)				       afInitSampleFormat(3dm)

NAME    [Toc]    [Back]

     afInitSampleFormat, AFinitsampfmt,	afInitByteOrder, afInitChannels,
     afInitRate	- initialize the audio data format in an AFfilesetup for a
     specified audio track

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/audiofile.h>

     void afInitSampleFormat(AFfilesetup setup,	int track,
			     int sampfmt, int sampwidth)

     void afInitByteOrder(AFfilesetup setup, int track,	int byteorder)

     void afInitChannels(AFfilesetup setup, int	track, int channels)

     void afInitRate(AFfilesetup setup,	int track, double rate)

PARAMETER    [Toc]    [Back]

     setup	 is an AFfilesetup structure, previously created by a call to
		 afNewFileSetup(3dm).

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

		 Since all currently supported file formats contain only one
		 audio track, the value	AF_DEFAULT_TRACK should	always be used
		 here.

     sampfmt	 an integer constant which denotes a sample format.

     sampwidth	 a positive integer value which	specifies the number of	bits
		 in a sample data point.

     channels	 is a positive integer value which indicates the number	of
		 interleaved audio channels in the audio track.

     byteorder	 is a positive integer token which indicates the byte order of
		 the samples in	the audio track.

     rate	 is a positive double-precision	floating point value which
		 specifies an audio sample rate	in Hz to be associated with
		 track.

     afInitSampleFormat() initializes the sample format	and width parameters
		 in an AFfilesetup structure for an audio track.

     The following values may be used for sampfmt

     AF_SAMPFMT_TWOSCOMP    [Toc]    [Back]
	  Two's	complement samples.  This is currently the only	legal value
	  for AIFF(4)/AIFF-C and 9-32 bit WAVE(4) format files,	and is a legal
	  value	for all	other supported	file formats as	well.




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afInitSampleFormat(3dm)				       afInitSampleFormat(3dm)



     AF_SAMPFMT_UNSIGNED    [Toc]    [Back]
	  Unsigned samples.  This is the standard value	for 1-8	bit WAVE(4)
	  format files.

     AF_SAMPFMT_FLOAT    [Toc]    [Back]
	  32-bit floating point	samples.  This may be used with	NeXT(4)	and
	  BICSF(4) format files, as may	AF_SAMPFMT_TWOSCOMP.

     AF_SAMPFMT_DOUBLE    [Toc]    [Back]
	  64-bit double-precision floating point samples.  Currently, this may
	  only be used with the	NeXT(4)	format files.

     afInitByteOrder() initializes the byte order (big-	or little-endian) of
     the samples in an AFfilesetup structure for an audio track.

     The following values may be used for byteorder

     AF_BYTEORDER_BIGENDIAN    [Toc]    [Back]
	  Big-endian byte order	samples.  This is the only legal value for
	  AIFF/AIFF-C, NeXT(4),	BICSF(4) and Sound Designer II (sd2(4))	files,
	  and is the default value.

     AF_BYTEORDER_LITTLEENDIAN    [Toc]    [Back]
	  Little-endian	byte order samples.  This is the standard value	for
	  WAVE(4) format files.

     afInitChannels() initializes the number of	interleaved channels
	  in an	AFfilesetup structure for an audio track.  Legal values	vary
	  depending on the file	format (see afInitFileFormat(3dm)).

     afInitRate() initializes the sample rate in Hz in an AFfilesetup
     structure for an audio track.  Most file formats have no restrictions on
     sample rate values, the exception being the NeXT(4) format, which
     requires integer values only.

     When a file is opened for writing by passing setup	to afOpenFile(3dm),
     the track will be configured to store data	according to the data format,
     width, number of channels,	or sample rate specified.

CAVEATS    [Toc]    [Back]

     The Audio File Library will continue to support additional	file formats.
     The ability of these file formats to store	data of	various	sample formats
     will vary.	 If you	are choosing a file format other than the default
     format, you should	make sure that you explicitly specify a	sample format
     for this file's tracks which is compatible	with that file format.	See
     afGetSampleFormat(3dm) for	important information about handling this
     situation.

     In	the case where the audio track in a file is configured for
     compression, sampfmt and sampwidth	should match the data format specified
     by	the compression	algorithm.  For	example, the software G.722 compressor
     expects to	encode 16-bit two's complement linear PCM input	data. In



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afInitSampleFormat(3dm)				       afInitSampleFormat(3dm)



     addition, many compression	formats	have restrictions on sample rate
     and/or channel count as well.  See	afInitCompression(3dm) for more
     information.

SEE ALSO    [Toc]    [Back]

     afNewFileSetup(3dm), afOpenFile(3dm), afWriteFrames(3dm),
     afSetVirtualSampleFormat(3dm), afGetVirtualSampleFormat(3dm),
     afInitCompression(3dm)


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