*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->IRIX man pages -> audiofile/afSetVirtualSampleFormat (3d)              
Title
Content
Arch
Section
 

Contents


afSetVirtualSampleFormat(3dm)			 afSetVirtualSampleFormat(3dm)


NAME    [Toc]    [Back]

     afSetVirtualSampleFormat, afSetVirtualByteOrder, afSetVirtualChannels,
     afSetVirtualRate, afSetVirtualPCMMapping -	set the	virtual	data format
     for a specified audio track

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/audiofile.h>

     int afSetVirtualSampleFormat(AFfilehandle file, int track,
				   int sampfmt,	int sampwidth)

     int afSetVirtualByteOrder(AFfilehandle file, int track, int byteorder)

     int afSetVirtualChannels(AFfilehandle file, int track, int	channels)

     int afSetVirtualRate(AFfilehandle file, int track,	double rate)

     int afSetVirtualPCMMapping(AFfilehandle file, int track,
				 double	slope, double intercept,
				 double	minclip, double	maxclip)

PARAMETER    [Toc]    [Back]

     Parameters	for the	virtual	routines are identical to those	for the
     equivalent	afInit routines, except	the first argument is an AFfilehandle
     structure rather than an AFfilesetup.

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

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

		 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 virtual sample format.

     sampwidth	 a positive integer value which	specifies the number of	bits
		 in a virtual 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 double precision floating	point value indicating the
		 sampling rate for the virtual audio data.






									Page 1






afSetVirtualSampleFormat(3dm)			 afSetVirtualSampleFormat(3dm)



     slope	 is a double precision floating	point value

     intercept	 is a double precision floating	point value indicating the
		 audio data sample zero-crossing value for the given sample
		 format	and width

     minclip	 is a double precision floating	point value indicating the
		 minimum or most negative audio	data sample value to be
		 returned.  Any	value less than	this will be set to minclip

     maxclip	 is a double precision floating	point value indicating the
		 maximum or most positive audio	data sample value to be
		 returned.  Any	value greater than this	will be	set to maxclip

DESCRIPTION    [Toc]    [Back]

     When a audio data is read from a file into	the application's data buffer
     using afReadFrames(3dm), the format of the	data loaded into the buffer
     can vary independently of the actual file data format.  This independent
     format is call the	virtual	format of the data.  Once some aspect of the
     virtual data format is set	via one	of the above-described routines, the
     conversion	of the file format into	the virtual format happens
     automatically and transparently.  This allows an application to choose to
     ignore the	data format in the file	entirely, and specify only the format
     in	which it wants the data	to appear in the afReadFrames(3dm) buffer.
     See afIntro(3dm) for more information about the virtual format.

     afSetVirtualSampleFormat()	sets the virtual sample	format and width
     parameters	for the	audio data buffer.

     The following values may be used for sampfmt

     AF_SAMPFMT_TWOSCOMP   Two's complement samples.

     AF_SAMPFMT_UNSIGNED   Unsigned samples.

     AF_SAMPFMT_FLOAT	   32-bit floating point samples.

     AF_SAMPFMT_DOUBLE	   64-bit double-precision floating point samples.

     afSetVirtualByteOrder() sets the virtual byte order (big- or littleendian)
 of	the samples in the audio buffer.

     The following values may be used for byteorder

     AF_BYTEORDER_BIGENDIAN	 Big-endian byte order samples.	 This is the
				 default value.

     AF_BYTEORDER_LITTLEENDIAN	 Little-endian byte order samples.

     afSetVirtualChannels() sets the number of virtual interleaved channels in
     the audio buffer.	If the virtual channel count does not equal the	track
     channel count, channel conversion is performed via	a channel mix matrix.



									Page 2






afSetVirtualSampleFormat(3dm)			 afSetVirtualSampleFormat(3dm)



     If	this matrix is not specified, a	default	matrix will be used.  This
     default matrix follows the	same channel conversion	rules as the Audio
     Library (libaudio).  See afSetChannelMatrix(3dm) for details.

     afSetVirtualRate()	sets the virtual sampling rate for the audio buffer.
     If	the track sampling rate	is different, the data will be rate-converted
     using one of several conversion algorithms.  See
     afSetConversionParams(3dm)	for more information.

     afSetVirtualPCMMapping() sets the virtual PCM mapping values for the
     audio buffer.  The	range, zero-crossing, and clipping values for the data
     placed in the audio buffer	will be	determined via a transformation
     calculated	from the relationship between the file's PCM mapping and the
     requested mapping.	 In general, all two's complement and floating point
     sample formats are	expected to be symmetrical about zero, i.e., the
     intercept will be 0.0 and minclip and maxclip will	be negative and
     positive N, where N is some non-zero positive value.  If this routine is
     used, it must be called after any calls to	afSetVirtualSampleFormat().
     Resetting the virtual sample format automatically resets the PCM mapping
     to	the default values for the requested format.

SEE ALSO    [Toc]    [Back]

      
      
     afOpenFile(3dm), afReadFrames(3dm), afWriteFrames(3dm),
     afGetVirtualSampleFormat(3dm), afGetVirtualChannels(3dm),
     afSetChannelMatrix(3dm), afGetVirtualByteOrder(3dm),
     afGetVirtualPCMMapping(3dm), afGetVirtualRate(3dm)


									PPPPaaaaggggeeee 3333
[ Back ]
 Similar pages
Name OS Title
afSetVirtualFormatParams IRIX set/get the virtual audio data format in an AFfilehandle for a specified audio track via dmParams
AFgetsampfmt IRIX get the track / virtual sample format or byte order for a specified audio track from an AFfilehandle structure
afInitFormatParams IRIX initialize the audio data format in an AFfilesetup for a specified audio track via dmParams
AFinitsampfmt IRIX initialize the audio data format in an AFfilesetup for a specified audio track
afGetFormatParams IRIX get the audio data format in an AFfilehandle for a specified audio track via dmParams
AFgetchannels IRIX get the number of interleaved track / virtual channels from an AFfilehandle structure for an audio track
afGetFrameSize IRIX get the track / virtual frame size in bytes for a specified audio track from an AFfilehandle structure
afGetPCMMapping IRIX get the track / virtual PCM mapping values for a specified audio track from an AFfilehandle structure
AFgetrate IRIX get the track/virtual sample rate for a specified audio track from an AFfilehandle structure
afSetConversionParams IRIX set/get the parameters associated with format conversion for a specified audio track via dmParams
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service