> It would also be possible
> with sfront, but slightly more complex due to the issue of
> having an intermediate C-compiling step. Perhaps John
> has thought about this issue and can comment.
Sfront is capable of hosting a MIDI-only streamer today, I
think (or at the most, with moderate changes to the sfront
core). Basically, it would involve writing a control driver
along the lines of the control driver that lets you hook up
a real-time MIDI keyboard into sfront. See:
http://www.cs.berkeley.edu/~lazzaro/sa/sfman/devel/driver/index.html#control
for very rough documentation about writing control drivers.
Sfront also supports SASL control drivers (the example gliss
shipped with sfront glisses up a piano keyboard using a MIDI
control driver, and down a piano keyboard using SASL control
driver events), but extending this to a streamer is more
complex -- basically, the control driver needs to know the
name (or for encoded MP4-SA, the token number) associated
with the SAOL instrs, in order to hook up the SASL and SAOL
events appropriately. A dynamic way to do this is to generate
a control driver on the fly for a given SAOL program, that
then handles the SASL stream. Incidently, this is also a way
a sequencer program would probably deal with sfront -- the
sequencer would have some sort of library system built in
that holds the various SAOL instruments, and would generate
a SAOL file from these instruments, generate a control driver
for these instruments, run sfront to make a binary, then use
sockets to connect to the sa.c binary and play the file. As
always, one trades off the benefits of compilation for a
more complex setup ...
> If you go up to the next level at the overall Audio standard
> (14496-3 sec1), you will see the syntax for a real MPEG-4 Audio
> stream, which contains calls to SASC() and SA_a_u() in streams
> that use SA coding. And if you go up one more level, the Systems
> standard (14496-1) tells you how to packetize this audio stream,
> timestamp the packets and AU transmissions, and synchronize
> and multiplex it with other audio and video streams.
Any chance that current versions of these documents will be made
available for download by non-MPEG members soon? Last time I
checked the general-purpose MPEG info sites pointed to by mpeg.org,
versions of these documents were of the FDIS era ...
--jl
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