Notes On Wdm - RME Audio Hammerfall HDSPe AIO User Manual

Multichannel
PowerDVD can also operate as software decoder, sending a DVD's multichannel data stream
directly to the analog outputs of the HDSPe AIO. Supported are all modes, from 2 to 8 chan-
nels, at 16 bit resolution and 48 kHz sample rate. Playback via the ADAT output of the HDSPe
AIO is also supported.
For this to work the option Interleaved has to be activated in the Settings dialog, an output wave
device of the HDSP has to be selected in >Control Panel/ Sounds and Audio Devices/ Audio<,
and 'Use only default devices' has to be checked. Additionally the loudspeaker setup, found
under >Volume/ Speaker Settings/ Advanced< has to be changed from Stereo to 5.1 Surround.
PowerDVD's and Win DVD's audio properties now lists several multichannel modes. If one of
these is selected, the software sends the decoded analog multichannel data to the HDSP.
The device selected as Default Sound playback device defines the first playback channel. Note
that this device can not be chosen freely. An interleaved playback with more than 2 channels
can only be done in blocks of eight channels. The first device is channel 1+2 in case an AO4S-
192 is present (8 analog outputs). Else it is ADAT 1+2.
The typical channel assignment for surround playback is:
1 (first chosen playback channel) - Left
2 - Right
3 - Center
4 - LFE (Low Frequency Effects)
5 - SL (Surround Left)
6 - SR (Surround Right)
Note 1: Setting the card to be used as system playback device is against common sense, as
professional cards are not specialized to play back system sounds, and shouldn't be disturbed
by system events. To prevent this, be sure to re-assign this setting after usage, or to disable
any system sounds (tab Sounds, scheme 'No audio').
Note 2: The DVD player will be synced backwards from the HDSPe card. So when using Auto-
Sync and/or word clock, the playback speed and pitch follows the incoming clock signal.

12.3 Notes on WDM

The driver offers a WDM streaming device per stereo pair, like AIO Analog (1+2). WDM
streaming is Microsoft's current driver and audio system, directly embedded into the operating
system. WDM streaming is nearly unusable 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. Therefore, for general operation, RME recom-
mend not to use WDM devices.
WDM streaming also replaces the former DirectSound. Synthesizers and Samplers, which
achieved latencies below 10 ms using DirectSound, are forced to use WDM in Windows XP,
now operating at high latency. Meanwhile most of these programs support ASIO as low latency
driver interface.
Several programs do not offer any direct device selection. Instead they use the playback device
selected in Windows under <Control Panel/ Sounds and Multimedia/ Audio>. Such software
often requires the special functions provided by WDM, and therefore will operate better when
using a WDM device. Please note that selecting the HDSPe to be used as system playback
device is against our recommendations, as professional interfaces should not be disturbed by
system events.
User's Guide HDSPe AIO © RME
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