[LINK] Propose Video Bandwidth Limit During COVID19 Emergency

[Glen Turner]

Jan wrote:
> One of the biggest challenges is the lack of mic muting. Any rustle
> of paper or kid coming in or door slam or toilet flush can cause
> total disruption.
> Although cumbersome, the best option is a push to talk mic. Maybe I'm
> just old fashioned. I doubt they exist any more.

Using Zoom: the meeting convenor can tick "Mute participants upon
entry". A participant can hold down the spacebar whilst whilst talking.
Simple and effective Push to Talk without modified hardware.  I'd
strongly recommend this approach for tutorials and other group
meetings.

Zoom has already dialled back the bandwidth (HD requires a option to be
selected) and chooses datarates depending on detected available
bandwidth.

The aggregated bandwidth from many simultaneous Zoom sessions is large.
I expect there to be considerable traffic between the home-serving ISPs
and the videoconference server farms of AARNet, Google, Microsoft, etc.
Everyone in the industry is working on this right now.

NBN users can expect to see slightly reduced performance when someone
in the house is using videoconferencing. That's the result of the
narrow upstream bandwidth use forcing Acks from other applications to
queue.  The effect is not large, but it is noticeable to a networking
professional :-)

-glen

PS: Other useful Zoom settings for tutes:

 - Audio type: computer audio (allowing the option for phone audio just
gets confusing. If you have lots of tech failures then you might need
to turn this option on, but remind people it will use their prepay
minutes).

 - Join before host: allow (gives students the chance to shake-down
their gear, I suggest you encourage people to join 10m early the first
time they try this)

 - Screen sharing. Who can share? Host only

 - Embed password in meeting link: yes

 - Disable desktop/screen share for users: only allow sharing of
selected applications (forces you to share just the PowerPoint or
whatever, saving embarrassment from other desktop content appearing)

 - Remote control: off (prevent students from controlling your
PowerPoint)

 - Allow removed participants to rejoin: no (or yes if it's a nice
class, as sometime booting someone and having them rejoin is the
easiest way to solve tech issues)

If you do need HD, such as for a medical tute, then

 - Group HD video: Full HD

although note that colour registration on home computing equipment is
poor, so describing the colour of what you are showing is important.



If you are hosting a videoconference with lots of students then please
give them a good experience:

 - the time on your computer is usually right, so use that to start
your videoconference exactly on time.  Being even two minutes late is
really annoying to videoconference participants, as it makes them start
to question their settings, if they are in the right place. The number
of people joined will start to quickly fall off after five minutes of
the meeting convenor not being present.

 - mute when not talking.

 - light your face.  The simplest way to do this is to put a domestic
lamp behind your monitor, angled upwards to shine upon the wall. The
soft reflected light from the wall does good face-fill lighting

 - don't aim the camera into a window in the background. The automated
light adjustment in the webcam will under-expose your face.

 - use a headset.  A lot of the trendy noise-cancelling Bluetooth
headsets have good mics.  Set the videoconference mic setting to use
the headset's mic.  If you have to use the laptop mic then acoustically
isolate the laptop from the desk, say by sitting it on top of a few
journals (don't block the laptop's airflow). If using the laptop mic
then all typing will be heard by students unless you remember to mute. 
USB-connected headsets tend to work with less setup hassle than
traditional 1/8th inch tip-ring analog headsets. But any headset is
usually better than none. If using a mobile phone headset then watch
the rustle from clothing, use a paperclip to fasten the mic's cable to
the clothing.

 - the camera goes at face level or higher. Your face should be 2/3rds
of the screen.  That might mean putting the laptop on a few books. 
Most uni-issued laptops (aka "enterprise-range laptops") will have good
webcams, so unless you can source a good-quality glass-lens webcam (eg,
Logitech C920) then use the one in the laptop.

 - take a moment to look at your own video, look at the background. If
areas of blank wall shimmer then that's the "power line frequency"
automated detection failing. Find the device settings for the webcam,
set the power line frequency to "50Hz". The automation is probably
biased towards choosing 60Hz, the USA setting.

 - if you can, use wired ethernet cabling from the laptop to the home
router.  Wifi glitches will be seen by many people and can be annoying
if frequent. If you have to use wifi, see if the 5GHz setting exists
and gives more solid performance than the 2.4GHz setting.  If you are
using the 2.4GHz band then don't use the microwave oven during the
videoconference.  Most other equipment in the 2.4GHz band should be
WLAN-compatible these days.

 - treat it as a television production, so tape a running sheet to the
wall, make points punchy, tell stories rather than read slides.  If you
run a flipped classroom you're about to win big time.

 - have and use a backchannel. You need some chat which reaches out to
everyone. Zoom has a basic chat system. Or use the webchat in your LMS.
Whichever you use, state in the videoconference invitation what the
backchannel will be.  Don't get too fancy on day one -- unless people
are already using Slack or Discord then you're asking them to
successfully set up another bit of software.  Announce the official
backchannel into the other available backchannels at the start of the
videoconference.

 - get experience. Rehearse the class with a co-worker, ask their
feedback.


Hope the above is useful.