[wdmaudiodev] CMiniportDMusUART (ac97) + large midi sysex problems

  • From: uwe kirst <u.kirst@xxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Tue, 10 Jan 2006 15:50:43 +0100

Hello everyone,

I'm using the midi uart included in the ac97 ddk example. It seems that large sysex commands fail if they are not send into one buffer.
There was a previous post which reported the same / or similar error for usbaudio.sys (see below).

I'm using MIDIOX 7.0.0365

(the size of the low level output buffers * the number of output buffers) < sysex size

the sysex command will fail.
Any comments?

Okay in the short time since my post we have found the solution to this problem! Sending the data in *one* big sysex buffer works fine, while splitting the data into multiple smaller sysex buffers fails - but only with usbaudio.sys - other drivers work fine with this.

See this thread for more info:

So it would seem there is a bug in usbaudio.sys. Is this a known issue? Is a fix being worked on by Microsoft?


On 26 Sep 2005, at 16:07, Nick Dowell wrote:

Has anyone had any experience, good or bad, with sending large sysex messages using usbaudio.sys - based devices?

We have been developing some new class-compliant midi devices, which work fine with the Mac OS X driver, as well as the linux driver, but under Windows XP sending more than a small amount of sysex data results in the data getting corrupted. This normally appears as extra bytes being inserted into the stream, or bytes being swapped around.

Are there any known problems related to this?

Is it possible to have robust sysex output using this driver?



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  • » [wdmaudiodev] CMiniportDMusUART (ac97) + large midi sysex problems