Alesis Hammerfall DSP System Low Latency under MME Buffer Size Adjustment, Multi-client Operation

12.3 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. Playback will be stuttering and audio will be distorted.

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.

Example: when you set the Hammerfall to 512 you can't use 128 in any program. But setting the buffer size to 128 allows to use 128 and all higher values within the software.

Please also note that this is a you're-welcome-to-tryfeature. 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 (like older VIA boards) suffer from crackling at settings below 512. Be sure to set the buffer size to 512 or higher in such a case (or get a new motherboard).

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, like ASIO, MME and 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 Gigasam- pler/Studio (GSIF) nor under MME (WaveLab etc.) anymore. This is no limitation at all, because TotalMix allows any output routing, and with this a playback of multiple software on the same hardware outputs. Note that the inputs can be used at the same time, as the driver sends the data to all applications simultaneously.

ASIO-Multiclient

RME audio interfaces support ASIO multi-client operation. It is possible to use more than one ASIO software at the same time. Again the sample rate has to be identical, and each software has to use its own playback channels. Once again the same inputs can be used simultaneously.

RME's sophisticated tool DIGICheck is an exception to this rule. It operates like an ASIO host, using a special technique to access playback channels already occupied. Therefore DIGICheck is able to analyse and display playback data from any software, no matter which format the software uses.

20 User's Guide HDSP MADI © RME