User Manual

User's Guide HDSPe RayDAT © RME

12.3 Notes on WDM

The driver offers a WDM streaming device per stereo pair, like RayDAT ADAT (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:

RayDAT ADAT (1+2) is the first stereo device

RayDAT ADAT (3+4) is the next stereo device

RayDAT ADAT (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.

12.4 Channel Count under WDM

The HDSP system’s ADAT optical interfaces allow to record sample rates of up to 192 kHz us-

ing a standard ADAT recorder. For this to work single-channel data is spread to two or four

ADAT channels using the Sample Multiplexing technique. This reduces the number of available

ADAT channels from 8 to 4 or 2 per ADAT port.

It is nearly impossible to change the number of WDM devices without a reboot of the computer.

Therefore whenever the RayDAT changes into Double Speed (88.2/96 kHz) or Quad Speed

mode (176.4/192 kHz) all devices stay present, but are partly inactive.