[LAU] rtirq

[Joakim Hernberg]

On Thu, 19 Mar 2015 19:01:33 +0100
Ralf Mardorf <ralf.mardorf at alice-dsl.net> wrote:

> Tape synced to the Computer by SMPTE (Atari) or by Click (C64). Record
> a MIDI synth and after that record the same synth on another tape
> track. This will double the synth sound, all you get is a phasing,
> that doesn't move.
> 
> Do the same with a Linux or Windows PC. Record a track with Qtractor
> or Cubase and after that record the same external synth on another
> Qtractor or Cubase track. Sounds do not start at the same time,
> there's always audible shift, comparable to slow early reflections
> and the phasing is moving.

One thing that isn't clear to me in the above test, what is sending
MIDI to the instrument?  I know that there were quite a lot of problems
on windows regarding midi timing, especially keeping it synced, as
windows had 3 different multimedia timers used, so depending on which
timers were in use, the midi timer might have drifted compared to the
audio timer.  But this is just drifting clocks, and has nothing to do
with jitter.  Further, at least on windows the midi isn't handled at all
by the ASIO driver, so I doubt that the ASIO buffer size would have any
impact at all on midi timing.  I think this is different on linux using
jack midi, but i suspect that the alsa sequencer won't be tied at all
to any buffer size that JACK uses.  I might be wrong about this though?

-- 

   Joakim