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

[Robin Gareus]

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