[Ardour-Users] A3 MIDI latency adjustment technique/advice

Brett Clark brett.clark at zirous.com
Thu Nov 14 07:16:47 PST 2013

Thanks Robin!!!

Ill try those tools and run them several times to see if i can figure out
the amount of jitter i have.  Ill try it with both my stock kernel and the
RT kernel.  I havent needed the RT yet, so im currently running the plain
Fedora kernel.  My hardware isnt high end either, so Ill keep in mind that
this may not be something i can do with my current setup.

I didnt think a 20ft cable could cause enough jitter to be noticable by the
human ear.

Thanks again!!!

*Brett Clark | * *Senior Fusion Middleware Specialist *
*Zirous – Oracle Gold Partner *
1503 42nd Street, Suite 210 | West Des Moines, IA | 50266
(515) 225-9015 (ext. 5527) | www.zirous.com

On Thu, Nov 14, 2013 at 9:04 AM, Robin Gareus <robin at gareus.org> wrote:

> On 11/14/2013 03:41 PM, Brett Clark wrote:
> [..]
> > Question: Is there a technique, A3 option, or other software that i can
> use
> > to determine the precise measurement of the latency?  I see that A3
> allows
> > latency adjustments with incredible precision beyond what a human could
> > figure out.
> Audio latency is fixed (only depending on hardware and jack settings).
> You can measure it using jack_delay (or the spin-off jack_iodelay that
> comes with jackd). Ardour 3.5 has this also built in. It is imperative
> to measure it and configure jack so that ardour can properly compensate
> latency. see also
> http://manual.ardour.org/synchronization/latency-and-latency-compensation/
> Midi latency is a more tricky subject. While there is zero latency
> inside the jack-graph, Hardware MIDI I/O is usually done asynchronously.
> This adds a variable latency (compared to audio) and jitter. A notable
> exception to this are firewire devices (iso-stream, sync audio+midi
> transfers) as well as some high-quality professional gear PCI devices.
> As of now, jackd does not allow to configure MIDI physical port latency
> (neither jack1, nor jack2) for this reason.
> There are tools to measure midi latency and jitter:
>  https://github.com/x42/jack_midi_latency
>  https://github.com/koppi/alsa-midi-latency-test
> but also note that you may simply be running into some A3 MIDI bugs.
> Many of its MIDI features are far from robust (something that is going
> to be addressed in the not too distant future).
> HTH,
> robin
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