[LAU] online calls with decent auido for music lessons

David Kastrup dak at gnu.org
Fri Mar 19 15:57:56 CET 2021

Lorenzo Sutton <lorenzofsutton at gmail.com> writes:

> That all makes sense and thanks for the tips and kind offer... There
> is the 'speed of light' factor after all.

Don't overestimate it, at least in Europe.  If we reduce speed of light
to a third (to account for back-and-forth and probably overoptimistic
repeater performance), 1ms is good for 100km.  That doesn't bode well
for world-wide jamming, but with countries as small as those in Europe,
at least nationally it's workable.

> Thing is.. _I_ amd the student (blush..) here, so the idea is not to
> over-bourden my teacher who is probably already having to cope with
> setting-up the calls, schedules etc. :-)

Ah, ok.  Of course, "used to compensating latency" is not really a
specific "teacher" skill unless we are talking latency-heavy instruments
like some organs.

> I would be interested to see if I can actually get my band to try this
> out since it's months we can't play together live :-(

Looks like I need to work on subtitles for
<https://youtu.be/Vn1f70IH-Es> (my talk on Jamulus at the Chemnitzer
Linuxtage last Sunday, in German).  Or maybe start by translating at
least the slides.

>>> Software:
>>> - Jack
>>> - Zoom H5 shows 4 inputs in jack: the L/R mics and the inputs 1 and 2
>> Oh, can you just put the headphones right next to the mics (makes
>> astonishingly little difference in comparison to direct connections) and
>> use jack_iodelay for measuring out the latency of the H5 with your
>> settings?
> What exactly would you like me to measure? Roundtrip latency of _my
> own_ signal when using Jamulus, or...?

Not involving Jamulus at all.  Just the raw mic-to-headphone delay when
using jackd at your usual settings (likely 128 or 64 samples per

>> Numbers are surprisingly hard to come by for any audio interface.
> So true...
> Lorenzo

David Kastrup

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