sd2(4)                                                                  sd2(4)


NAME
     sounddesigner2, sd2, sdII - Sound Designer II Audio File Format

SYNOPSIS
     #include <dmedia/audiofile.h>

DESCRIPTION
     The Audio File Library currently supports eight 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 Sound Designer II Audio File Format (sd2) was created by DigiDesign,
     Inc., as a replacement for their earier Sound Designer I format (not
     supported by the Audio File Library). Because it was developed for the
     Apple MacIntosh file system, this file format differs from all other
     currently supported audio file formats in that its representation on a
     UNIX file system varies depending on how the file is made available.  All
     involve a data fork or file containing the binary sample data and a
     resource fork or file containing all information about the file and its
     format.  Three representations are supported:

     Apple Single Format
          Resource and data forks are combined into a single file

     Apple Double Format
          Resource and data forks put into separate files;  the data fork file
          carries the actual file name, and the resource fork file has (in
          most cases) a percent (%) character prepended to the filename

     Xinet (IRISShare) Format
          Resource and data forks put into separate files;  the data fork file
          carries the actual file name, and the resource fork file is located
          in a subdirectory named ".HSResource".  This is always subdirectory
          of the directory containing the data fork file.  In addition, a
          third file named .HSAncillary contains additional "ancillary data"
          about every Apple file in the current directory.  This file stores
          information about the file type and file creation dates, among other
          things.

DATA FORMAT SPECIFICATIONS
     Sample Formats:
          Two's complement integer only


     Sample Widths:
          16-bit only

     Byte Orders:
          Bigendian only

     Channel Counts:
          1 and 2 channels only

     Compression Formats:
          None supported, and none in common usage

FILE FORMAT SPECIFICATIONS
     Sound Designer II files can contain large amounts of additional
     information.

     Instrument Configurations:
          Maximum of 1 allowed.  Any number of loops per inst.  Insts are
          stored as a set of loops with no associated instparams.  Loops are
          stored as a starting frame, an ending frame, a loop sense (forward
          or forward-backward) plus an index (set incrementally from 0 up) and
          a channel (currently set to 0).

     Markers:
          Any number of markers is allowed.  Unlike AIFF(3dm) and WAVE(3dm)
          files, there is no direct association between markers and loops.  An
          application may choose to specify loop start and end points via the
          traditional AIFF-style method using mark id's (afSetLoopStart(3dm),
          etc.) or via the newer afSetLoopStartFrame(3dm) and related
          routines.  In the former case, both the loops and the markers will
          be written out to the header; in the latter case, only the loops
          will be written out (unless other markers have been created).

     In addition, it is possible to associate both a name string and a comment
     string with each marker.  The routines afInitMarkName(3dm) and
     afInitMarkComment(3dm) will do this.  Both the name and comment will be
     written into a text buffer with the format <marker name>: <marker
     comment>.

     Miscellaneous Chunks:

               AF_MISC_COMMENT         text comment string

CAVEATS
     Due to the nature of the file structure as described above, the Audio
     File Library must take extra steps to identify and read this format.
     Specifically, it must have the full pathname of the file available for
     the call to identify the file (if used) and the call to open it.  The
     functions afIdentifyNamedFD(3dm) and afOpenNamedFD(3dm) exist for this
     purpose, as well as the usual afOpenFile(3dm) call.


     The current version of the AF can read Sound Designer II files in any of
     the above-three file representations, but all newly created files will be
     written in Xinet representation only.  Future releases of the AF may
     allow a choice.

SEE ALSO
     afInitFileFormat(3dm), afGetFileFormat(3dm), afIntro(3dm),
     afIdentifyNamedFD(3dm)


                                                                        Page 3