sf2(4)									sf2(4)

NAME    [Toc]    [Back]

     sf2, SoundFont, SoundFont2	- SoundFont Compatible Audio 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 SoundFont Compatible File Format (sf2)	was developed by  E-mu
     Systems, Inc., for	use on PC's. It	consists of a complex RIFF header
     containing	large amounts of information about the sound samples, plus an
     imbedded, contiguous block	of binary data representing the	sound samples.

DATA FORMAT SPECIFICATIONS    [Toc]    [Back]

     Sample Formats:
	  Two's	complement integer only.

     Sample Widths:
	  16 bit only.

     Byte Orders:
	  Always littleendian.

     Channel Counts:
	  1 channel only.

     Compression Formats:
	  None.

FILE FORMAT SPECIFICATIONS    [Toc]    [Back]

     SF2 file headers contain vast amounts of information.  The	Audio File
     Library parses a small portion of this information	for use	as an
     instrument	chunk.

     Instrument	Configurations:
	  SoundFont2 headers contain a multi-level architecture	of Presets,
	  Instruments, and Instrument Zones (a sample plus its articulation
	  data).  This "Instrument" is not the same level of structure as the
	  AF inst chunk;  an Instrument	can contain any	number of Instrument
	  Zones, each of which is the approximate equivalent to	an AF inst.
	  Each audio sample may	be used	any number of times in different
	  Instrument Zones.



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sf2(4)									sf2(4)



	  Currently a maximum of 1 allowed for writing,	though any number may
	  be found in a	file opened for	reading.  A single loop	per inst is
	  allowed.

	  The Audio File Library parses	each Instrument	Zone as	a separate
	  inst chunk --	which often results in literally thousands of insts!
	  Each one references a	set of instrument parameters (see below) which
	  provides a partial description of the	MIDI articulation for that
	  Instrument Zone.  In order to	allow this possibly-vast number	of
	  insts	to be grouped, an integer parameter for	the parent Instrument
	  or Preset is provided.

     Instparams	associated with	this inst:

	  Standard Params:

	  AF_INST_MIDI_BASENOTE
	  AF_INST_NUMCENTS_DETUNE
	  AF_INST_MIDI_LONOTE
	  AF_INST_MIDI_HINOTE
	  AF_INST_MIDI_LOVELOCITY
	  AF_INST_MIDI_HIVELOCITY
	  AF_INST_NUMDBS_GAIN

	  SoundFont - specific Params:

	  AF_INST_SAMP_STARTFRAME   Starting frame offset for sample

	  AF_INST_SAMP_ENDFRAME	    Ending frame for sample

	  AF_INST_SAMP_MODE	    Sample loop	mode.  One of three values:
	  -    AF_INST_LOOP_OFF		Loop not used ("one shot")
	  -    AF_INST_LOOP_CONTINUOUS	Sample loops through release
	  -    AF_INST_LOOP_SUSTAIN	Sample loops for sustain only ("sampled	release")

	  AF_INST_SAMP_RATE	    Sample rate	of sample referenced by	inst

	  AF_INST_TRACKID	    Track ID for inst

	  AF_INST_NAME		    Name of sample referenced by inst

	  AF_INST_PRESET_NAME	    Name of preset containing the inst

	  AF_INST_PRESETID	    ID of preset containing the	inst

	  Currently, all the SoundFont - specific params are read-only See
	  afSetInstParamLong(3dm) for more information about 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



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sf2(4)									sf2(4)



	  traditional AIFF-style method	using mark id's	(afSetLoopStart(3dm),
	  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.

     When a file is opened for reading,	the AF will generate a synthetic  pair
     of	markers	for each loop found in the file.  This is done to allow
     currently-existing	applications to	extract	loop points via	the old
     afGetLoopStart(3dm) mechanism.  It	is important to	remember that these
     markers are not actually present in the header or file.

     Miscellaneous Chunks:

	       AF_MISC_COPY		 copyright string

	       AF_MISC_AUTH		 author	string

	       AF_MISC_NAME		 name string

	       AF_MISC_COMMENT		 text comment string

	       AF_MISC_ICRD		 creation date string

	       AF_MISC_ISFT		 software name string

SEE ALSO    [Toc]    [Back]

     afInitFileFormat(3dm), afGetFileFormat(3dm), afIntro(3dm),
     afGetInstIDs(3dm),	afGetInstParams(3dm)


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