midi timing testing

Len Ovens len at ovenwerks.net
Thu Jul 19 20:18:56 UTC 2012

On Wed, July 18, 2012 10:14 pm, Ralf Mardorf wrote:
> Using USB for MIDI is tough ;).

Testing it seems to be harder. There are things I can do where I can hear
a problem, but anything I have tried so far to create a measurable problem
has failed. While it is obvious to my ear that giving audio group access
to the high rez timers helps, I can't say by how much. I want to stay away
from subjective tests as much as I can. This is because as the MIDI timing
gets tighter, I can't hear problems or fixes... so I need something I can
measure. I know there are midi events that can be used for time keeping as
the old 401 did. They had a so many ticks since the last event thing and
when it overflowed it forced an event. This meant the software could
always place the note where it belonged not matter how long it took to get
to the recorder. I am thinking that hydrogen does the same thing and
qtractor records it and plays it back negating the problem with USB MIDI
IFs. The only time I have been able to hear the problem has been recording
and playing back the demo from an old yamaha PSR synth (read toy with MIDI
ports). Unfortunately, the demo seems to have been authored by someone who
knew how to swing, so there are not that many on beat notes to look at. I
will have to try using the march out of the beatbox part I guess.

> However, to play MIDI events by external equipment I'm using jack2's
> "-Xalsarawmidi" in combination with a2jmidi_bridge and PCI (Two Envy24
> TerraTec 24/96)/PCIe (RME HDSPe AIO) MIDI interfaces only. I'm not using
> my swissonic USB MIDI.

I don't normally use USB MIDI either. In fact I bought this one for
testing MIDI timing and perhaps to use it a bit on my netbook (USB only).
I am not much of a KB player, Like Holstein, I am mostly a Bass player,
though not his caliber for sure.

> Don't disable your ac97, perhaps it ships with a parallel port MIDI that
> might be good. Unfortunately my machine don't has parallel port MIDI.

As far as I know, my ac97 has no MIDI, certainly no MIDI modules load when
it is the only audio IF active. I am instead using the game port of an old
ensoniq card which seems to be very stable, even with cheap synth input.
It is a 401 "compatible" IF.

> Btw. are you subscribed to
> https://lists.sourceforge.net/lists/listinfo/qtractor-devel ?

Nope, I will keep it in mind, right now I am having trouble keeping up
with this list and LAU (which I still haven't managed to post to yet).

Len Ovens

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