[wdmaudiodev] DirectMusic and system exclusive problems

  • From: "Evert van der Poll" <e.j.van.der.poll@xxxxxxxxx>
  • To: <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Sun, 20 Jul 2003 01:44:32 +0200

Hi all,

I just subscribed to this list and was wondering if there are people here
who have experience with DirectMusic.

I am currently developing a DirectMusic driver for a MIDI interface. To test
it I wrote a little application that sends out MIDI messages and system
exclusive which is then captured by an input (I connect the output to the
input with a cable).
I then compare the input with the output to see if everything works as it
This goes reasonable well, except for the system exclusive. Whenever I send
blocks larger then about 5000 bytes strange things start to happen. Always
at the same point I receive an unexpected byte at the input (after having
sent 2161 bytes).
At first I thought the error occured within my driver. I use a debug version
that logs every byte it sends out and that comes in. After carefully going
through the logs I can only conclude that the driver sends all the bytes in
the right order. Somewhere in the portcls layer something goes wrong. The
problem is perfectly reproducible. If I have the same input it always goes
wrong at the same point, with the same data. To me that indicates that it's
not a timing issue.

The problem is that I don't have any other DirectMusic driver to compare
results with. I have a few Soundblaster compatible soundcards lying around
but they only have emulated MIDI ports when using DirectMusic. I tried to
get the Microsoft sample driver to work but I guess that Soundblaster
compatible is a pretty loose term. They refuse to work with that.

If anyone has experience with this I'd like to share knowledge.

Evert van der Poll


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