Notes On Wdm; Multi-Client Operation - RME Audio Hammerfall DSP System MADI User Manual

12.3 Notes on WDM

The driver offers a WDM streaming device per stereo pair, like HDSP MADI (1+2). WDM
streaming is Microsoft's current driver and audio system, directly embedded into the operating
system. WDM streaming is hardly usable for professional music purposes, as all data is proc-
essed 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 (option Interleaved, see chapter 12.4),
Sonar not only finds the stereo device mentioned above, but also the 8-channel interleaved
devices, and adds the channel number at the end:
HDSP MADI (1+2) is the first stereo device
HDSP MADI (3+4) is the next stereo device
HDSP MADI (1+2) 3/4 are the channels 3/4 of the first 8-channel interleaved device.
We recommend to not use these special interleaved devices. Also note that it is not possible to
use one stereo channel twice (the basic and the interleaved device), even with different applica-
tions.
Information on multichannel WDM is found in chapter 12.4.

12.4 Multi-client Operation

RME audio interfaces support multi-client operation. This means several programs can be used
at the same time. Also all formats (ASIO, WDM, GSIF) can be used simultaneously. The use of
multi-client operation requires to follow two simple rules:
•
Multi-client operation requires identical sample rates!
I.e. it is not possible to use one software with 44.1 kHz and the other with 48 kHz.
•
Different software can not use the same channels at the same time.
If for example Cubase uses channels 1/2, this playback pair can't be used in WaveLab, no mat-
ter if ASIO or WDM. However, this is no limitation at all, because TotalMix allows for any output
routing, and therefore a playback of multiple software on the same hardware outputs. Note that
identical inputs can be used at the same time, as the driver simply sends the data to all applica-
tions simultaneously.
User's Guide HDSP MADI © RME
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