Impress freezes on any video
Summary: I'm using LibreOffice Impress (22.214.171.124) on Windows 10 to create and run shows with lots of photos and a few videos. Now suddenly a presentation that worked fine two weeks ago freezes when a slide containing a video is displayed. I'm sure this isn't a LibreOffice code problem per se, because the same presentation works fine on another computer (also Win10, same version of LO). What can I try?
Here's what happens. I open a presentation that contains one or more video slides. As soon as a slide containing a video appears on the screen (Slide Pane, Normal View, Slide Sorter, or Presentation mode), Impress freezes completely. None of the menu items responds, nor do any of the tools, nor does the X. I have to use Task Manager to shut it down. But until a video slide appears, everything is fine. That is, if the video slide is far enough down that it doesn't show in the Slide Pane, I can display slides and move around. But as soon as the video slide appears in the Slide Pane, the whole system freezes. Similarly, if the first video slide is far enough down that its thumbnail doesn't show in the Slide Sorter, everything is fine, but if it is within the first group of slides, then all of the previous slides display in the sorter and then the system freezes. Finally, if I create a new presentation, everything is fine until I insert a video (any of my videos), and then the system freezes.
If it's relevant, I create my videos with VideoPad, storing them as .avi files with H264 video compression and MP3 sound compression.
The problem appears on my Dell desktop, running LO 126.96.36.199 and 188.8.131.52 under Windows 10 Pro (10.0.14393). Everything works fine on my Lenovo laptop running LO 184.108.40.206 under Windows 10 Home (10.0.14393).
What have I tried: Initially I saw this under LO 220.127.116.11 on the desktop, so I upgraded to 18.104.22.168. No change. I uninstalled LO and reinstalled. No change. I used IoBit Uninstaller to do a "deep uninstall" and then reinstalled. No change.
Again, the presentations that fail on the desktop work fine on the laptop, and presentations that worked fine on the desktop a couple of weeks ago now fail on the desktop.
I can imagine that there is some sort of system service that Impress uses to display videos (or thumbnails from videos) and that that's what is failing. But I don't know how to verify or fix that.