MPEG-4 Synthesis Standard Reaches Committee DraftFree Software Available from MIT Media Lab November 27, 1997
This message is to announce the first wide release of the MIT
public-domain SAOL implementation, called "saolc". SAOL is the
music-synthesis language at the heart of the MPEG-4 Structured Audio
standard. This release is not entirely complete or bug-free, and
won't run in real-time, but should be quite useful for musicians who
want to examine the expressive power of SAOL, and for potential
implementors who want to compare the standards document with a
reference software. saolc has been tested by me on SGI, Alpha, and
Win32 platforms, and by the University of Hannover on Linux and
Solaris platforms, but is intended to be widely portable to other
machines as well.
This implementation is available from the SAOL WWW page. The README file describes exactly what is and isn't working
and supported in this release.
SAOL BACKGROUND
About six months ago, I announced on various lists that I was involved
with a project at the Media Lab to create a new music synthesis
language. This language, called SAOL, was developed within the MPEG
Consortium, in order to fill the need for a standard syntax for
algorithmic synthesis.
I'm pleased to report that that this proposal has been accepted, and
the first official draft of the MPEG-4 standard contains extensive
provisions for algorithmic synthesis and other algorithmic sound
functions. Using the MPEG-4 "Structured Audio" toolset, you can
describe the synthesis of music and sound effects, the application of
synthetic post-production methods to "natural" sound sources like
speech, the automatic synchronization and mixing of natural and
synthetic sounds, and the creation of interactive, virtual worlds
which combine all of this with 3-D audio and synthetic and natural
video.
Any fully compliant "MPEG-4 decoder" must contain an implementation,
in hardware, software, or both, of this music-synthesis language.
SAOL CONCEPTS
SAOL is pronounced "sail" and stands for Structured Audio Orchestra
Langauge.
SAOL as a language has similar concepts to Csound. It preserves
the orchestra/score distinction (although the orchestra language is
now powerful enough to write a score generator in) and the control
rate/sampling rate distinction. However, it features a more modern
syntax and modern language features such as encapsulated functions,
variable scoping, a weak object-oriented system, and explicitly
defined rate semantics.
SAOL lives within the MPEG-4 paradigm of "streaming" data and
"decoding" processes. Thus, the Structured Audio toolset is
not only a method of synthesis, but a streaming format appropriate
for WWW-based (or any other channel) transmission of audio
data. The 'saolc' package contains a program for encoding
score and orchestras into the streaming format, and facility
for decoding this format (so it can be used as a WWW helper app).
MORE INFORMATION
There's a mailing list available for users of SAOL. For a while,
I'll be active on this list, since there's not much other way
to quickly find the answers to questions. Send email to
saol-users-request@media.mit.edu to be added.
There's also a mailing list available for people interested in
developing new SAOL implementations. Send email to
saol-dev-request@media.mit.edu to be added.
The draft standard describing MPEG-4 Structured Audio is also
now available to the general public. This
document is extremely detailed (and fairly well written, I
like to think) but is targeted at implementors, not at users.
I'm trying to get some WWW-based user documentation together in
the near future; volunteers would be greatly appreciated.
There are some example orchestras and scores, as well as
MPEG-4 bitstreams, available on the same webpage as referenced
above. I'm happy to include your music in this archive also,
if you want to donate it and make it an example.
Please download the draft standard and the 'saolc' implementation
and use it to make music. Your comments and feedback are essential
at this point, as we clean up the standard for finalization over
the next year. For more information, visit their web site at sound.media.mit.edu/~eds/mpeg4. | 
