Jean-Sébastien Caux

Recovering the video of a crashed Zoom session

This morning, my online Electrodynamics lecture ended in a slight disaster when the Zoom session crashed at the end. Since the lecture videos are an important part of the study material, I was worried that this crash had caused the loss of the recording.

The situation

Here is a basic description of where I was at:

• Zoom running on laptop with Ubuntu 20.04
• As usual, Zoom had created a subdirectory in ~/Documents/Zoom/ containing the session data
• This session data contained the unconverted raw data files double_click_to_convert_01.zoom (1.4 GB) and double_click_to_convert_02.zoom (62 KB).

Since the beefiness of the first file meant the data was actually residing on disk, the remaining task was thus to convert these files into the required mp4 video file.

Misfires

The simplest solution of double-clicking-flles-to-convert obviously did not work: there is no free lunch. The next-simplest solution, as suggested at this Zoom support page, was to try to use the desktop client, and invoke the conversion from there. This did not work either: though the client started the conversion, the progress bar never got beyond 0% (even leaving it running for 4 hours).

The trick/hack/whatchawannacallit

Playing around, this workflow actually did the trick of recovering the original video:

• In the client, start a brand new meeting, and then start and pause the recording. Leave this meeting running;
• In the terminal, navigate to the folder of this new meeting (which you'll find as a timestamped folder inside ~/Documents/Zoom/ if you're using the defaults);
• You will find the famous double_click_to_convert_01.zoom and double_click_to_convert_02.zoom files there; overwrite those with the corresponding files of the meeting you're trying to recover;
• Going back to your client, unpause the recording briefly, then stop it, and stop the meeting.

If all goes well, Zoom will now start converting the video as expected, and you can process it further as per your own workflow. Precisely why this works must remain obscure to the sorry Open Source advocate that I am, since I can't look into the Zoom code... but a running meeting somehow magically manages to overcome and repair file corruption from a past, crashed meeting.