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8.3 DVD-Playback (AC-3/DTS) under MME
When using popular DVD software player like WinDVD and PowerDVD, their audio data stream
can be send to any AC-3/DTS capable receiver, using the HDSP's SPDIF output. For this to
work the SPDIF output wave device has to be selected in 'Control Panel/Sounds and
Multimedia/Audio'. Also check 'use preferred device only'.
You will notice that the DVD software's audio properties now allow to use 'SPDIF Out' or to
'activate SPDIF output'. When selecting these, the software will transfer the non-decoded
digital multichannel data stream using the RME card.
This 'SPDIF' signal sounds like chopped noise at highest level. Therefore check 'Non-audio' in
the card's Settings dialog, to prevent most SPDIF receivers from accepting the signal, and to
prevent any attached equipment from being damaged.
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: The DVD player will be synced backwards from the RME card. This means when using
AutoSync and/or word clock, the playback speed and pitch follows the incoming clock signal.
8.4 Low Latency under MME (Buffer Size Adjustment)
Using Windows 95 or 98 the MME buffer size was nothing to worry about. Latencies below 46
ms were not possible. Meanwhile both computers and operating system have become much
more powerful, and since Windows ME/2000/XP latencies far lower can be used. SAWStudio
and Sonar allowed to use such low settings from the start. Sequoia was updated in version
5.91, WaveLab in version 3.04.
In the HDSP's Settings dialog the MME buffersize (in fact the DMA buffer size) is set with the
same buttons as the ASIO buffer size. Our test computers allow to use settings down to 64
samples without clicks. Please note that this setting only defines the buffer size of the
hardware. The true and effective latency is configured within the MME application!
Attention: the DMA buffers must not be larger than the application's buffers. This case can
happen unnoticed when using ASIO and MME at the same time (multi-client) and setting
ASIO to 186 ms, while the buffers in the MME application are still set for a lower latency.
Playback will be stuttering and audio will be distorted.
Example: when you set the Hammerfall to 512 you can't use 128 in any program. But setting
DMA to 128 allows to use 128 and all higher values within the software.
Please also note that this is a 'you're welcome to try' feature. We can't guarantee that you will
be able to use 3 or 6 ms with MME. Simply check out by yourself which lowest setting your
system and software allows. Some motherboards with insufficient PCI bandwidth (especially
VIA based) suffer from crackling at settings below 512. Be sure to set the buffer size to 512 or
higher in such a case.
User's Guide HDSP System Multiface © RME
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