avr(4)avr(4)NAMEavr - Audio Visual Reseach File Format
SYNOPSIS
#include <dmedia/audiofile.h>
DESCRIPTION
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
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
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 ALSOafInitFileFormat(3dm), afGetFileFormat(3dm), afIntro(3dm),
afSetLoopStart(3dm), afSetLoopEnd(3dm)
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