Hi Uwe, >I have got one question concerning your issu: What does >IOCTL_KS_READ_STREAM return? Does the IOCTL fail? What windows error code >do you get with GetLastError if the IOCTL returns the buffer immediately? >0x57 == Invalid Parameter? Actually, in both the working and not working modes, I get ERROR_IO_PENDING, as I believe I would expect? Andrew Sherbrooke ****************** 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/