[Galene] Re: fq-codel trashing

["Michael Ströder" <michael@stroeder.com>]

On 1/12/21 7:10 PM, Juliusz Chroboczek wrote:
> We just had a meeting with 70 people and at around 40 cameras switched on,

Which send quality were they all using? "normal"?

Frankly I understand only ~5% of what you're talking about in this thread.

But do you really expect all users' end devices to decode 40 video
streams? Not to speak of all the crappy Internet connections, already
over-loaded while other family members are watching Netflix or similar
situations in shared flats.

As said before I'm running Galène in a VM on an insanely slow hardware.
But even with this setup and send quality set to "lowest" we managed to
overwhelm some older iPad devices or older laptops with just 7 video
streams. In my local tests with slow and ancient 10+ years old laptops I
even get video drop-outs within my LAN with only 3 video streams.

> Galène became unusable — there were too many voice drops, which indicates
> two issues:
> 
>   * I need to think of a better way of prioritising voice over video when
>     under load;

We had one hearing impaired user who hears a little bit with in-ear
devices. Normally the user also follows spoken text by lip-reading to
get more context. But this is nearly impossible for her in a video
session because audio and video are not sufficiently synchronised with
our setup.

It probably would be helpful that the prioritising voice over video
could be changed per user to at least have a chance for such a special case.

>   * there are fairness issues — some clients were receiving okay-ish
>     audio, others were not.

Not sure whether that's really a fairness issue within Galène. I can see
differing latencies in /stats for different connections. The connection
with higher latency, most times on all "Down" streams, has the higher
latency consistently throughout whole session. I suspect the receiver
side is the issue.

> Galène recovered after some people switched their cameras off, I didn't
> need to restart anything.

I can confirm that Galène behaves pretty predictable if streams are
turned on or off.

> At the highest point, Galène was at 270% CPU,
> and the TURN server was using another 50%.  That's on a four-core VM.

I'm far away from such a setup. So I wonder whether my response is
useful at all.

Ciao, Michael.