Hello All, I have been trying for the last two weeks (without much success) to make some sense out of the DDK documentation. I real Water Oney´s book understood some of it :). The problem is, I want to write a driver that I believed was very simple, but still haven´t figured out the best approach. Maybe someone can enlighten me. Basically I have a USB audio adapter that is fulley compliant with usbadudio.sys BUT, I would like to create two virtual devices ( called for exemple LeftChannelUSB and RightChannelUSB ), and would like allow this devices to behave as a "standard audio device". What I mean by this is that I would like for example to be able to select LeftChannelUSB as a "Default Device" for sound playback on CP Sound and Audio Devices Properties. When a user app writes to one of these virtual audio devices ( for example LeftAudioUSB) , it should mix Left and Right channels and write both of them on the Left Channel of usbaudio. Would it be possible to write a Virtual Device driver (like a filter driver) and stack it on top of usbaudio using the LowerFilter reg key? I successfully intalled MSVAD example , and a modified filter example ( from W. Onney´s book ) and was able to use MSVAD as a lowerfilter to filter.sys. When I wrote to MSVAD it worked without the filter driver. When I selected the filter driver , it correctly logged debugging info and transfered the IRPs to MSVAD. Would I be better off trying a rewrite of usbaudio.sys? Is there an easier way of accomplishing this? Is it easy or even possible to do some minimal audio filtering using a filter ( in the sense of IRP filtering ) driver ( changing data before and then forwarding an IRP )? As you can see I am totally lost, any info in this subject will be greatly appreciated. Dimitri Prado ****************** WDMAUDIODEV addresses: Post message: mailto:wdmaudiodev@xxxxxxxxxxxxx Subscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=subscribe Unsubscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=unsubscribe Moderator: mailto:wdmaudiodev-moderators@xxxxxxxxxxxxx URL to WDMAUDIODEV page: http://www.wdmaudiodev.de/