[wdmaudiodev] Re: USB audio filter dirver
- From: Walter Oney <waltoney@xxxxxxxxxxxx>
- To: wdmaudiodev@xxxxxxxxxxxxx
- Date: Fri, 03 Jan 2003 08:27:35 -0500
Frank wrote:
> I need to apply a self-designed digital filter on the audio stream
> before out put to a USB audio device, regardless of which application
> generates the audio source. The way I planned to do is to write a USB
> audio filter driver and insert as a lower filter under the usbaudio.sys.
I would suggest instead that you first write a DirectShow filter as a
user-mode DLL and see if you get adequate performance. Microsoft has not
documented how to write, and in fact actively discourages people from
trying to write, kernel-mode audio filters.
Note that the DDK uses the word "filter" in two different ways. A WDM
filter driver sits above or below a WDM function driver and filters
IRPs. A streaming filter is actually a free-standing function driver
that helps manage the flow of audio or video data from source to sink.
You're probably interested in writing the latter.
--
Walter Oney, Consulting and Training
Basic and Advanced Driver Programming Seminars
Now teaming with John Hyde for USB Device Engineering Seminars
Check out our schedule at http://www.oneysoft.com
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