[wdmaudiodev] Re: sAPO must be real-time compatible
- From: "Andrew Sha......" <universalkludge@xxxxxxxxxxx>
- To: wdmaudiodev wdmaudiodev <wdmaudiodev@xxxxxxxxxxxxx>
- Date: Fri, 9 Jul 2010 18:34:45 -0500
Yes, it is based on the assumption that the driver completes requests
synchronously, so the ERROR_IO_PENDING means that a filter got introduced
screwing the picture
I guess it is not such a good idea just to return from an ADOProcess call when
some encoding supposed to be done, is it?
But it is a good idea to return processed results of a previous ADOProcess
call, submitting data of the current ADOProcess call to the driver, the only
question is how to handle the very first call. Any bright ideas?
Date: Fri, 9 Jul 2010 16:20:37 -0700
From: timr@xxxxxxxxx
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Re: sAPO must be real-time compatible
Andrew Sha...... wrote:
It looks like DeviceIoControl w/ overlapped I/O +
GetOverlappedResult(..bWait=FALSE) is the way to go and upon
ERROR_IO_INCOMPLETE returned just fail processing
ERROR_IO_PENDING is that one that means "the driver is still working on this".
Your behavior depends on what you need. If you are confident that your driver
will always complete requests immediately, then that might be an OK plan. But
in other cases, you might just leave the request running and return so the
audio graph continues to run. At some later point (in a separate thread maybe,
or just at the next data packet), you can check to see if your outstanding I/O
has completed yet.
There are lots of ways to handle it. The key is that the audio engine is a
real-time process, and if you block it, audio will suffer.
--
Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.
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