[time-nuts] an interesting timing problem

[jimlux]

Given that there's a lot more people spending time zooming, webexing, 
teaming, skype, facetime, etc. these days, I'm curious if anyone has 
figured out to *quantify* the issues of lag, desynchronization, etc.

How would one go about instrumenting it (without access to the source 
code or servers involved)?

There's two areas of some interest to me:
1) there's several studies that say that when voice and image aren't 
perfectly synchronized, particularly if it's not a consistent delay, or 
if there are gaps and jumps, that it is more stressful and creates a 
cognitive workload that does not exist with actual in-person meetings 
(the "why am I more tired after a day of telework than the real thing")

2) If you wanted to do group music playing or singing, relative timing 
among the streams is critical.  Is there a threshold where it all breaks 
down?  For instance, in an orchestra or choir, one has visual cues from 
the conductor, but most people do not sing or play using the conductor 
as a metronome triggering the next measure's notes. They also listen to 
the players around them (or perhaps on the other side of the stage, some 
30-40 milliseconds late)


I can think of ways to "test" a given teleconferencing system (blinking 
LEDs in a pattern, tone bursts on audio), but I think there's some 
challenges in things like compression algorithms (do they have constant 
latency?) and highly structured test signals might not measure the same 
as actual video and audio.

I will note that there are subjective difference among the various 
tools, and there's differing effects from compression artifacts and 
bandwidth/packet transport.