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<p>Karim,</p>
<p>Thanks for this in-depth reply. I think what it has convinced
me is that I'm going to make a little stand to hold the laptop
camera in alignment pointed at the desktop screen, and just play
videos on the desk top. The downside is that, unlike the
"presenter" function, it doesn't really control the session. So
when others speak, the video goes away. I guess that can be fixed
by asking everyone to "pin" my screen during the video, yes?</p>
<p>Karim, your knowledge sometimes astounds me.</p>
<p>cheers,</p>
<p>David</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 7/13/20 1:21 PM, Karim Virani wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAKtnkixoueN5u16AKfEcyi1qkd3CLnPTU_9X+85nTrVh6_nKWQ@mail.gmail.com">
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<div dir="ltr">Hey David, regarding your questions about sharing
video...<br>
<br>
Bottom line - we could switch to Google Meet (from Hangout Meets
which I think we are still using) and anyone who wants to share
a video should post it on a video streaming service like youtube
ahead of time. You can post it as "unlisted" if you don't want
it showing up in search engines. This will let us use the <a
href="https://gsuiteupdates.googleblog.com/2020/04/high-quality-video-audio-meet.html"
moz-do-not-send="true">Share Chrome Tab feature</a> with its
support for high quality video streaming. It's important to <b>not</b>
use the full screen or application share options here.<br>
<br>
If you want the details, read on: <br>
<br>
We are asking a lot of our systems when we share video while
presenting our desktops. At the very least your system is
decoding that video to raw (possibly up scaled) pixels. So
you've lost the inter-frame optimizations. If the source is
remote you are also consuming downstream bandwidth. Now if you
are sharing your desktop, screen updates are being broken down
with VNC-like (I'm not sure what remote rendering engine Meets
uses) frames. The system tries to optimize things down to simple
graphics primitives for a lot of the screen drawing like text
and vectors, but bitmaps have to be re-encoded. Your decoded
video is now a series of high res bitmaps updated at your native
screen refresh rate. Even if your video source is skipping
frames, your screen buffer doesn't know that. So now you have an
uncompressed high hz sequence of high res bitmaps that have to
be re-encoded and the VNC subsystem is usually able to detect
and treat this at least as a motion jpeg stream which gives up
the interframe differencing optimizations. Now you have a higher
bandwidth, lower quality and less optimized video embedded
within the screen frames you are uploading to the broadcaster.<br>
<br>
If you have a fast processor and high bandwidth upstream
internet service you might get away with this. But at best it's
still going to be lower quality with extra layers of compression
artifacts than your original video. Likely it will stutter badly
if there are any bottlenecks in the path.<br>
<br>
When you point your webcam at a screen you are already at lower
pixel count because the video resolution of most webcams is
capped well below screen resolutions. It's also using interframe
optimizations and some webcams do this internally and not on the
host processor. It's definitely not having to do a decode first
and it's not consuming downstream bandwidth.<br>
<br>
It's hard to discover the details of how they did it, so I'm
speculating here. But Google Meet is claiming it supports high
quality video and audio sharing. Since you have to use the
Chrome browser for this feature, they might just be using the
Casting function built into the browser - which I think is smart
enough to echo back the source video stream without recoding it.
It's also possible that it is detecting the source video stream
and just telling the broadcaster to share the cloud source with
all of the meeting participants - skipping the need to upstream
from your local computer. So you are only providing
start/stop/seekcommands. That at least is how video streaming
works for the larger (thousands of participants) conference
sharing services.<br>
<br>
Anyhow, I'd be happy to test it out with you and see if we get
an improvement. We could try this in a one-to-one anytime
convenient to you. Google Meet is free to everyone now. But you
have to basically "cave in to the man" and adopt the whole
google pipeline (Meet/Chrome/Youtube). Though it's possible it
will work with the mpegs you post on the SMU server.<br>
<br>
Sorry if I went into too much detail. In a previous life I built
some of the first mpeg streaming servers - the early 90s.<br>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sun, Jul 12, 2020 at 11:58
PM David Anderson via DPRGlist <<a
href="mailto:dprglist@lists.dprg.org" moz-do-not-send="true">dprglist@lists.dprg.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hello
DPRG,<br>
<br>
Here's the video I mentioned in the meeting Saturday but
forgot to post <br>
the link:<br>
<br>
<a
href="http://www.geology.smu.edu/dpa-www/robo/mpeg/rcat-202005-9-2.mpg"
rel="noreferrer" target="_blank" moz-do-not-send="true">http://www.geology.smu.edu/dpa-www/robo/mpeg/rcat-202005-9-2.mpg</a><br>
<br>
Still haven't figured out how to show video in google meetup.
Lou <br>
mentioned that also. Maybe it's not possible. It did seem to
work at <br>
last months meeting when I just pointed the laptop camera at
the desktop <br>
screen, and played the video on the desktop. But the
"presenter" <br>
function doesn't seem to be able to keep up.<br>
<br>
Likely I just don't know what I'm doing.<br>
<br>
onward into the fog,<br>
<br>
David<br>
<br>
<br>
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