[LAD] [64studio-users] MIDI jitter

[Ralf Mardorf]

On Mon, 2010-07-05 at 09:16 +0200, Clemens Ladisch wrote:
> Niels Mayer wrote:
> > Here's the new results with "-w 20" (nb: "-w" == "-w 0")
> > 
> >> A) Edirol UM-2
> > 
> >  best latency was 2.07 ms
> >  worst latency was 3.11 ms, which is great.
> 
> As long we're optimizing for benchmarks:  In recent enough kernel
> versions, Roland (Edirol/BOSS) USB MIDI devices have a mixer control
> "MIDI Input Mode" (the same as the "Light Load" checkbox in the Windows
> driver) which doesn't have much effect in practice but can improve
> benchmark behaviour.
> 
> For bulk transfers (used by Roland devices in "High Load" mode, and
> always by all other devices), the UHCI driver has a feature called FSBR
> (full-speed bandwidth reclamation) which makes the controller poll the
> device continuously instead of every 1 ms, as long as new input is
> available every 10 ms.  So to get better benchmark numbers, use "-w 1"
> instead of "-w 20".  (If your music doesn't have new notes every 10 ms,
> this isn't very realistic, but it can improve latency between the
> consecutive notes of a chord.)
> 
> 
> Regards,
> Clemens

I noticed that I run my test without the "-R" switch
"alsa-midi-latency-test -i20:0 -o20:0" and Gustin who already used "-w
20 -r" did also miss the "-R" switch, "alsa-midi-latency-test -i 16:0 -o
16:0 -w 20 -r".

alsa-midi-latency-test --help
  -R, --realtime             use realtime scheduling (default: no)

Did you add "-R"?

Cheers!

Ralf