No video thumbnails in Caja

[Linx_]

I'm running ~amd64 and Mate desktop, and Caja is not generating any thumbnails for video files. Photos and other types of media are generating fine, just not video. Caja preferences --> Preview is set to "always" and "files smaller than 4GB" so that's not it.

I've tried adding all kinds of global USE flags like x264 and x265, but no use flags I've tried seem to make a difference. I've also tried installing totem and some other media players to see if thumbnailing might be part of that functionality, but no. I'm aware of ffmpegthumbnailer, but I'm not sure whether that's what I want here or not, or how exactly to make it work with Caja.

I have a Mint 19.2 Mate installation on my laptop, and Caja generates them fine on there, so I know it can be done. What am I missing to get it to work in Gentoo?
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[fedeliallalinea]

Try to install ffmpegthumbnailer and restart caja, see https://github.com/mate-desktop/caja/issues/1009
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Questions are guaranteed in life; Answers aren't.

[Linx_]

I did see that issue on my search, but that seems only to relate to files on network shares. My issue is on local drives, and so I didn't know if it was applicable to me.

I've installed ffmpegthumbnailer, but nothing has changed. Do I have to do something with it to tell Caja that it's there?
_________________
I occasionally post sober.
My overlay of Mate tools and desktop apps is here.

[Juippisi]

Try installing totem and, well, ALL gst-plugins pretty much (controllable by gst-plugins-meta).

[Linx_]

So it did finally start working, but I have no idea why. I installed ffmpegthumbnailer and created /usr/share/thumbnailers/mate-ffmpegthumbnailer.thumbnailer as follows: