sfront with CoreMIDI support released ...
sfront with CoreMIDI support released ...
- Subject: sfront with CoreMIDI support released ...
- From: John Lazzaro <email@hidden>
- Date: Mon, 14 Oct 2002 14:22:41 -0700
Hi everyone,
The new sfront release that supports CoreMIDI went out today,
just wanted to thank everyone who helped answer questions along the
way ... it is GPL'd, downloadable from:
http://www.cs.berkeley.edu/~lazzaro/sa/index.html
To see the -cin coremidi control driver in action, run the
sfront/examples/rtime/linbuzz softsynth, it will find external MIDI
sources (up to 4, no virtual source support ...) and use them to drive
the SA program in real-time. In the linbuzz example, the pitch wheel
(set up to do vibrato) mod wheel (spectral envelope) and channel
volume controllers are all active -- you can look at the linbuzz.saol
SAOL program to see how they are used.
The actual CoreMIDI code is in:
sfront/src/lib/csys/coremidi.c
The most interesting aspect of this code is that a single
AF_UNIX SOCK_DGRAM socketpair pipe (named csysi_readproc_pipepair) is
used for communication between an arbitrary number of CoreMIDI
readprocs (one for each active source) and the SA sound engine (which
runs inside the CoreAudio callback -- the actual main thread sleeps
and does nothing). Writing the pipe is blocking (but should rarely
block, and never for significant time), but reading the pipe is
non-blocking.
The semantics of the AF_UNIX SOCK_DGRAM (AF_UNIX is reliable,
SOCK_DGRAM guarantees the messages from the CoreMIDI readprocs don't
mix) makes it a good choice for doing the multi-source MIDI merge. The
actual messages sent in the pipe consists of a preamble to identify
the readproc, and the (error-checked for SA semantics) MIDI commands
in each MIDIPacket.
At this point, the Linux and OS X real-time implementations
support all of the same features (audio input, audio output, MIDI In,
RTP networking) ... I'm not sure if AudioUnits support makes sense for
sfront, I'll probably take a closer look at the issue soon ...
-------------------------------------------------------------------------
John Lazzaro -- Research Specialist -- CS Division -- EECS -- UC Berkeley
lazzaro [at] cs [dot] berkeley [dot] edu www.cs.berkeley.edu/~lazzaro
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