Re: [linux-audio-user] jaming over the internet?

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Subject: Re: [linux-audio-user] jaming over the internet?
From: Juhan Leemet (juhan_AT_logicognosis.com)
Date: Mon Sep 29 2003 - 22:28:22 EEST


On Monday 29 September 2003 12:50, Rob wrote:
>On Monday 29 September 2003 12:50, Robert Jonsson wrote:
>> Anybody know of an application that allows streaming of midi
>> and/or audio over the net for the purpose of allowing several
>> people to jam together?
>
>I seem to remember something like that for Windows too, but
>remember that latency that would be more than acceptable for
>gaming (30-40ms) could make it impossible to jam as you're
>envisioning.

Yes, I remember someone (non-technical) telling me about this great system
that allowed musicians on both coasts of North America to perform a "live"
piece together, across the internet. It was some kind of university project.
They even pulled out a newspaper or magazine article about it. I read it
through several times. I could not believe that you can get latencies (esp.
cross-continent) down low enough to allow "interactive jamming", where both
sides hear each other in real time.

Let's see (calculating on the back of an envelope): 3000 miles / 186000
miles/second... that's nominally 16msec... that could be tolerable... but
what about slowdown due to dielectric (speed of electric fields is less than
speed in vacuum)? what about delays in electronic circuits? what about
store/forward digital gear? At one point some traffic went via sattelite,
which adds 2 x 22K miles (or about 1/4 second). Hmm, that's why the delay on
some speech circuits (like when I phone my sister in the Dominican Republic)
is very noticeable! Lately, I think ground fibre is cheaper (and faster) than
satellite. For the moment, ignoring costs, I'm not even sure the network
wizards are able to splice together a dedicated circuit coast-to-coast with
audio hi-fi stereo bandwidth, even for "proof of concept". Even if they could
(like a permanent phone call?), there would be little point, because in a
digital (internet) network there would be real traffic, and hence variability
(jitter), which can only be smoothed by buffering and delay. Stutter is
usually worse than delay. So, I conclude that I'm mystified! Huh?

Now, if one is only concerned with one-way traffic, one can "cheat"! I
concluded from the article (and thinking hard about it) that they must have
used one site as a "reference site", piped their (partial) performance across
the continent (with whatever additional delay/buffering), and then had the
other orchestra "dub in" their part, and have that played at the 2nd site for
their "live" audience. Or the audience might have been at a 3rd site, at this
point it does not matter, just as long as it's not the 1st site! I seem to
recall that the audience was seated in an auditorium on 2nd coast. So, yes
they were "playing together" in some sense. And the audience was hearing the
performance "live". However, I cannot believe that the orchestra at the 1st
site was able to hear the 2nd site "live" at the same time they were playing?

Has anyone else heard about this? Details? Thoughts?

p.s. I used to do some sound recording for 16mm newsreel film stuff, decades
ago. Have you (with headphones on) ever tried to speak into a Nagra tape
recorder with a true read head after the write tape monitoring head? You hear
yourself about 1/2 second later. I had to take my headphones off, so I
wouldn't hear a delayed "echo". I think that is also true for "real" (long
delay) echo in recording? It can be paralyzing! Is that like stutterers?

p.p.s. I have recently been thinking a bit about psycho-acoustics, as I'm
(re)learning some guitar playing. If you consider nerve transmission speeds,
being able to play those real fast weedle-weedle-weedle guitar leads would
seem impossible. What must be happening is that you are telling your fingers
to move a fraction of a second before they actually move. Now add in the long
echo delay, and I suspect that's too much to handle: 3 time bases: what you
want to play, what you are playing (feel?), and what you hear. Comments?

-- 
Juhan Leemet
Logicognosis, Inc.


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