I'm looking for some help about a latency problem with midi processing using pd under Windows XP.

Here is the point : I'm using pd to process some midi data coming from electronic drums. These data are then sent to another software (e.g. Nuendo) thanks to virtual midi ports (MIDI Yoke). Assuming '<->' is a midi connection (virtual or physical), it looks like,

drums module <-> Sound Card (Midi Ports) <-> Pure Data <-> Midi Yoke <-> Nuendo

The problem is that pd introduces some latency... and pd is definitely responsible for that... because the following setup does not introduce latency :

drums module <-> Sound Card (Midi Ports) <-> Midi CC <-> Midi Yoke <-> Nuendo

(Midi CC allows to connect virtual ports between them)

The last point is that latency does not seem to be sensitive to the patch. I tried a simple midi thru patch and another patch with complex treatments and nothing changed...

Help

I think the -sleepgrain start-up flag should help with MIDI latency.

From "pd -help"

-sleepgrain <n> -- specify number of milliseconds to sleep when idle

You need to set this in the .bat file or shortcut that you start Pd with, I don't know if the new Pd settings system works for this.

Alternatively, I think turning DSP on might help, even if you don't need it - this will make Pd 'wake up' and (hopefully) process MIDI more often. You can prevent Pd from opening sound devices (so they can be used by other apps) and still use DSP, useful for streaming over the internet, for example.