Hi, I've written an AVStream audio driver for a USB audio device and is facing some issue when I try to run the DTM DRM Test on my driver. I'm failing the last test item in the DRM test, which state the failure reason being portcls.sys not found in the list of authenticate drivers that was expected to fail. Does anyone know anything about this, for it does not seem to make sense to me since the AVStream architecture is implemented directly in KS.sys and does not sit under portcls.sys, which is true for other miniport audio drivers. I've also tried to run the same test using the MS usbaudio.sys and this failure does not occurs. I've also check that the list of drivers verified by the DRM test is the same for both the usbaudio.sys and my AVStream driver (ks.sys, usbccgp.sys, usbd.sys, usbohci.sys, drmk.sys and the audio driver) Thanks for any information. KS