avr(4)									avr(4)

NAME    [Toc]    [Back]

     avr - Audio Visual	Reseach	File Format

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/audiofile.h>

DESCRIPTION    [Toc]    [Back]

     The Audio File Library currently supports 13 of the commonly found	audio
     file formats, i.e., is able to recognize, read, and write sample data and
     header information	to and from files in these formats.  It	is important
     not to confuse sample or audio data formats with file formats.  The
     former refers to the bit-wise organization	of the sound samples in	the
     file, i.e., whether the format is 8-bit integer or	16-bit unsigned, etc.
     Audio file	format refers to the structure of the audio file header, the
     chunk of on-disk data which preceeds the samples and which	provides
     information about the file	to the audio program.  A single	audio file
     format may	support	a large	variety	of sample formats.

     The Audio Visual Research File Format (avr) was developed for use on
     Apple MacIntosh computers.	It consists of a 128-byte header followed by a
     contiguous	block of binary	data representing the sound samples.

DATA FORMAT SPECIFICATIONS    [Toc]    [Back]

     Sample Formats:
	  Two's	complement integer (for	16-bit)	and unsigned (for 8-bit) only.

     Sample Widths:
	  8 and	16 bit only (see above).

     Byte Orders:
	  Always bigendian.

     Channel Counts:
	  1 and	2 channels only.

     Compression Formats:
	  None supported by the	AF.

FILE FORMAT SPECIFICATIONS    [Toc]    [Back]

     AVR file headers can contain additional information.

     Instrument	Configurations:
	  Maximum of 1 allowed.	 A single loop is allowed.  Instparams
	  associated with this inst:  AF_INST_MIDI_BASENOTE,
	  AF_INST_MIDI_LONOTE, and AF_INST_MIDI_HINOTE.	 See
	  afSetInstParamLong(3dm) for more information about these parameters.

     Markers:
	  Unlike AIFF(3dm) and WAVE(3dm) files,	there is no direct association
	  between markers and loops.  However, for backwards compatibility, an
	  application may choose to specify loop start and end points via the
	  traditional AIFF-style method	using mark id's	(afSetLoopStart(3dm),



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avr(4)									avr(4)



	  etc.)	or via the newer afSetLoopStartFrame(3dm) and related
	  routines.  In	both cases, only the loop information will be written
	  out to the header because this format	does not support markers.
	  Using	the first-listed method, two markers are allowed, one for the
	  start	location and one for the end point of the loop.

     Miscellaneous Chunks:

	       AF_MISC_NAME	       name string

SEE ALSO    [Toc]    [Back]

     afInitFileFormat(3dm), afGetFileFormat(3dm), afIntro(3dm),
     afSetLoopStart(3dm), afSetLoopEnd(3dm)


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