[PD] Limit bandwith for MIDI output / precise metro

Miller Puckette msp at ucsd.edu
Tue Nov 27 18:06:11 CET 2012

Pd tries to time-stamp MIDI on input and tries to delay sending MIDI output
until the correct time; but Pd's accuracy in doing this is limited by the
fact that it can't input or output MIID while it is either sleeping or running
(only when the scheduler polls for what-to-do-next after either a task or a
sleep has finished.)

It would be more accurate for Pd to rely on either software interrupts or even
better on some underlying OS time-tagging mechanism (for instance by exploiting
whatever portmidi does).  But I have to admit I've never treated this as a high
priority (which one might take as an implied value judgement about MIDI).


On Tue, Nov 27, 2012 at 11:44:06AM +0100, Cyrille Henry wrote:
> Le 27/11/2012 10:36, IOhannes m zmoelnig a écrit :
> ...
> >with MIDI, Pd doesn't do any buffering and no synchronisation to some
> >external clock is done, so messages appear in bursts which you notice
> >as a inaccurate timing.
> There is 1 strange thing however : pd did some kind of buffering with midi, in order to synchronise with audio out.
> if you configure 100ms audio latency, then a midi loop will be between 100 and 105ms.
> with 10ms audio buffer out, the midi loop is between 10 and 15ms.
> but this buffer should not change anything on timing except adding latency.
> cheers
> c
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