XnView Software

I'm running into an odd issue with video playback in XnView on Windows 10 machines. Videos play normally when opened in a separate tab from the browser (right click on file > click "Open"), so it appears that XnView has all of the codecs and hooks it needs to play videos on a basic level. However, when I try to play videos in XnView in any other context, they just show up as blank: in the preview window, in full-screen mode (right click on file > click "View in Fullscreen"), in the viewer window (right click on file in Explorer > open with XnView), and in slideshows, the video component never displays. The player bar pops up showing the time elapsed and total time, and any audio associated with the video still plays, but the video component itself is blank.

What would cause the behavior to be different when you "open" the file in XnView into a tab when compared to opening the file in the main viewer or in a preview, such that videos would play normally in the former, but fail to render in the latter?

I've tried installing and uninstalling LAV filters directly, installing and uninstalling K-Lite (in case it somehow configured the LAV filters differently than I would), and nothing makes a difference.

My issue seems very similar to what was reported here: XnView stopped playing multimedia files, although they don't mention being able to still view the videos properly in tabs within the browser window, so I wasn't sure if it's truly the same issue or not and decided to make a separate thread.

all video formats?

I have the same problem: videos are not displayed when viewing from browser mode to full screen (all type of videos).
I found a solution: launch a second instance of Xnview classic and browse to the same folder: it works normally.
It happened some time ago with windows 10 and I have no explanation!

Apologies for my delayed response. I had assumed I would receive email notification if there was a reply in the forum, so I hadn't been checking back in here and completely missed your question. To answer your original question, yes, it fails on all video formats.

Interestingly, I independently stumbled upon the exact same solution that Jean_59 did: Opening up one instance and having it fail to play a video, then opening up a second instance and using that one to play videos causes them to all play normally. I don't know if that behavior helps you troubleshoot the root issue, but I'd be happy to do more in-depth testing if there's anything I can do that would help.