Notes On Wdm - RME Audio Fireface UCX User Manual

9.3 Notes on WDM

The driver offers a WDM streaming device per stereo pair, like Analog 3+4 (Fireface UCX).
WDM streaming is Microsoft's current driver and audio system, directly embedded into the op-
erating system. WDM streaming is hardly usable for professional music purposes, as all data is
processed by the so called Kernel Mixer, causing a latency of at least 30 ms. Additionally, WDM
can perform sample rate conversions unnoticed, cause offsets between record and playback
data, block channels unintentionally and much more.
Several programs do not offer any direct device selection. Instead they use the playback device
selected in Windows under
XP: <Control Panel/ Sounds and Multimedia/ Audio>
Vista/7: <Control Panel/ Sound/ Playback>
The program Sonar from Cakewalk is unique in many ways. Sonar uses the so called WDM
Kernel Streaming, bypassing the WDM mixer, thus achieves a similar performance to ASIO.
Because of the driver's multichannel streaming ability Sonar not only finds the stereo device
mentioned above, but also the 8-channel interleaved devices, and adds the channel number at
the end:
Fireface Analog (1+2) 1/2 is the first stereo device
Fireface Analog (3+4) is the next stereo device
Fireface Analog (1+2) 3/4 are the channels 3/4 of the first 8-channel interleaved device.
It is not recommended to use these special interleaved devices. Also it is not possible to use
one stereo channel twice (the basic and the interleaved device).
Multi-Channel using WDM
The WDM Streaming device Loudspeaker (Analog 1+2) of the RME driver can operate as usual
stereo device, or as up to 8-channel device.
An 8-channel playback using the Windows Media Player requires the speaker setup 7.1 Sur-
round. Configure as follows:
XP: >Control Panel /Sounds and Multimedia /Audio /Volume /Speaker Settings /Advanced <
Vista/7: >Control Panel /Sound /Playback /Loudspeaker /Configure <
User's Guide Fireface UCX © RME
19