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How to work around Zoom's no-audio bug

The proprietary "Zoom" meeting system has an error (bug) in its GNU/Linux version that sometimes causes sound to cut out. I have confirmed this bug exists in at least versions 3.5.385850.0413 (April 2020) and 5.3.465578.0920.

It is possible to "work around" this bug as follows (assuming you've already clicked "Join audio" if necessary---remembering that some desktop environments hide this button behind a bottom toolbar if you've made the Zoom window too large; it's easier if Zoom has been set to always join audio when you join a new meeting)---

  1. When you're in the meeting where you can't hear sound, press Alt-Tab (or Alt-` if you're using the Gnome desktop) until you see Zoom's main settings window:
    (as shown in this screenshot)

    (On older versions of Zoom the text might be too small to read, because Zoom's developers apparently didn't know about DPI settings---they fixed that on the GNU/Linux platform in Version 5.1.418436.0628.)

  2. Just below the top right corner of that window, there is a very tiny cog-wheel. You have to aim the mouse pointer at that and click. This is difficult if you have any kind of disability that affects mouse work, and I am not aware of any keyboard shortcut.
  3. Select the third item on the left of the Settings window, to bring up the audio settings:
    (as shown in this screenshot)
    • An alternative way of getting to this screen from the meeting is to click on the very small arrow beside the microphone icon (which is even more difficult to aim the mouse cursor at on an older version of Zoom), and select "Audio settings" and "Test speaker and microphone".
  4. The first blue slider on the right, on the third row, is a volume control. It might look like it is already turned up. But use the mouse to drag it down and up again.

Performing this action appears to "fix" the sound issue, at least for the current meeting.

(Why does it work? Well as Zoom is closed-source proprietary software, I don't get to see the code, so I have no idea. My guess is that some timing-related bug can cause Zoom to fail to send the correct volume level to the sound system on startup, but fiddling with Zoom's internal volume control causes that value to be re-sent. It's important to tell meeting participants that the volume control to fiddle with is the one in the Zoom settings and not their main system volume if this is already turned up: turning the main system volume down and up again will not solve the issue.)

32-bit version crashing in 5.1+

Zoom versions 5.1.x introduced a separate bug that can cause Zoom to crash just after joining a meeting if you're running the 32-bit GNU/Linux binary (at least under LXDE in Ubuntu 18.04-derived distributions). The 64-bit binary is not affected. So if you're upgrading from 5.0 or earlier to 5.1+, you might also wish to move to 64-bit if you haven't already done so.

Reducing Zoom's incoming video bandwidth

If you don't really need to see the incoming video and prefer to save bandwidth, it seems you cannot turn off incoming video (at least not without using a telephone line instead), but you can reduce bandwidth by shrinking the meeting window to be as small as possible without minimising it.

If you cannot use the mouse, then some desktops let you shrink windows via the keyboard. For example, in Gnome 3, provided the window has not been maximised, use the following key sequence: Alt-F8, Left Shift-Right Shift-Right, Up Shift-Down Shift-Down, Enter. (If the window has been maximised then press Alt-F10 to toggle that first.) Do not touch the physical mouse during these keyboard sequences, as doing so will interfere with the resulting window size.

Playing a prerecorded video to a Zoom meeting

There are command lines to do this more efficiently on my mplayer notes page.
All material © Silas S. Brown unless otherwise stated.