Thursday, October 15, 2020

Tuning Zoom Videoconferencing for a Slow computer and Low Speed Broadband

Greetings from the 2020 UQ Work Integrated Learning Symposium, currently on Zoom from Queensland University. This is free and on for four hours, so there may be time for you to join. The students are running the event, which shows commendable dogfooding by UQ.

To improve the performance of Zoom on my slow laptop, and low speed wireless broadband connection, I am trying a router with UDP shaping

Previously I noticed that with Zoom in full screen mode the sounds would break up and image freeze. If I reduced the window size it worked better, but this was fiddly. Also when a presenter shares their screen, Zoom tends to force the display back to full screen, after which I have to shrink it again.

An approach I tried in the past was to slow my Internet connection, which Zoom responded to by using lower resolution video, making everything more stable. However, this also slowed down all my other network use. There are software utilities which will slow just one application, but I found these did not work with Zoom.

The Internet uses two sorts of data transmission: TCP and UDP. Most applications, such as email and web browsing use TCP, as this provides a reliable connection. Video conferencing programs typically use UDP for the audio and video, as this has less overheads. The utilities I tried to slow an Internet connection only act on TCP, not UDP, so did not slow Zoom.

Not being able to find a software solution I turned to hardware. Many routers allow for slowing, or "shaping" of the speed of the connection. A few allow this to be targeted at TCP or UDP specifically. I tried a TP-Link TL-MR3020 V3 router (around $50 AU), and switched on the UDP shaping. So far it is working well.
Currently I have the data rates for UDP set to: 800 kbps transmitting and 512 kbps receiving. I want to provide a good quality standard definition image of myself when speaking, but a lower quality for the video I receive, so have sent the sending rate higher than receiving.

Zoom is currently providing an image of the speaker at 320 x 180 pixels, 12 frames per second and screen-sharing at 1440 x 900 pixels, 1 frame per second. The screen share looks very clear and readable, with a clear thumbnail of the speaker next to it. If a video is played in the screen sharing it looks jerky, but fortunately most presenters don't play videos.

A bigger test will come this evening, when I am speaking on "The Virtual University" (6pm, all welcome).

ps: One small glitch: after a short break when my computer went to standby mode the router was no longer connected: I had to reboot it.

pps: The video from some speakers was not appearing in Zoom gallery mode. So I increased the down speed from 512 kbps to 1024 kbps. The increased speed also allowed for screen sharing at 1920 x 1080 pixels at 8 frames per second, which is enough to follow a mouse around the screen and simple animation. In speaker's view the video is now at 640 x 360 pixels 26 frames per second. However, this is using too much of the limited CPU in my computer, so I will try setting up and down speeds to 800 kbps.

ppps: Had problems with the  TP-Link TL-MR3020 router, so changed it for the desktop version, a TL-MR3420, which is working well.

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