I've just finished major updates to PortMidi for Windows (MME API).
While trying to figure out why my tests worked, yet others were having
problems, we discovered a bug in the MIDI Yoke drivers. I added a
workaround for old drivers, but I see that MIDI Yoke NT driver has
already been fixed and updated. I also did some experiments and found
some cases where messages seemed to be dropped when there are few
buffers (e.g. double buffering may have been a bad idea), so the buffer
allocation policy has changed. I also discovered that my experiments
that indicated entire sysex messages must be sent in one buffer were
flawed -- probably some other bug allowed whole messages to work and
caused fragmented messages to fail. In any case, it is NOT necessary to
fit an entire sysex message into a single buffer, which means the
dynamic buffer reallocation is unnecessary. The new code is smaller and
simpler in many areas. Because of Fabien Costantini's report on
real-time problems with sysex, I optimized the sysex routines.
Previously, sysex was transmitted byte-by-byte in order to simplify the
complex error checking and parsing, e.g. there might be embedded
real-time messages among the sysex data, and you need to check for EOX.
There is now optimized code where the system-dependent layer
*optionally* passes back a pointer to a buffer to fill, a buffer offset
address, and a buffer length. The system-independent layer can then copy
bytes directly to the system-dependent data structure with very little
overhead. This makes PortMidi sysex code *much* faster, but I didn't
measure the time spent in the device driver. I also added a "shortcut"
to optimize copying sysex data from input buffer to the FIFO that
clients read from. By the way, the new FIFO queue is multi-processor
safe and non-blocking, even with out-of-order writes, although there are
still some flags elsewhere in PortMidi that might fail if out-of-order
writes occur. These are associated with error signalling. Finally, I
ported my old CMU MIDI Toolkit Midi Monitor program (mm) to PortMidi to
help with debugging, and it is now in pm_test/mm.c.
I am now checking up on some Mac OS X issues, but if anyone is able to
test the new Windows code, I'd like to just email you a zip file of the
current state.
Thanks to Fabien Costantini, Ben Allison, Jamie O'Connell, Oron Cherry,
Joe Newcomer, and anyone I'm forgetting for help on these Windows issues.
-Roger
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