A filtering hook is already provided through the audio sysfx mechanism and this is in user mode. I believe the root problem in this particular discussion is a difference in the desired business model. The audio sysfx mechanism is designed for effects either as part of a device driver; developers of DSP should partner with OEMs or audio device manufacturers. It seems however that kevinrich47 wishes to deploy his DSP as some sort of independent product. Frank Yerrace Microsoft Corporation This posting is provided "AS IS" with no warranties, and confers no rights. From: wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Jose Catena Sent: Thursday, June 25, 2009 11:00 PM To: wdmaudiodev@xxxxxxxxxxxxx Subject: [wdmaudiodev] Re: How to filter microphone voice? Just one more request that would benefit from a user mode audio I/O hook. Is such a thing in some list of future features to consider? If such a list exists, this should be there with a high rank, IMO. Jose Catena DIGIWAVES S.L.