Greetings. I can see MKV thumbnails on my desktop and in windows explorer. In DO they are not generated in the folders (just see a black thumbnail).
I did try various codec options, currently using Shark codecs.
Any suggestions how to get MKV thumbnails working in Do folders?
Edz..
Go to Preferences / Viewer / Viewer Plugins and configure the Movie plugin.
You can either experiment with the thumbnail settings there or turn off thumbnail generation entirely (in which case Opus will fall back on the same code that Windows Explorer uses).
Thanks! Turning off thumbnail generation in DO did do the trick to get the thumbnails working. Sounds as a oxymoron to turn it off to get it to work 
Is it possible to get the cover as thumbnail? In MKV files you can attach cover.jpg for cover. Can DOPUS show that in thumbnail view?
If you configure the Movie plugin not to make thumbnails, it will be done by the Windows shell instead, and will give you the same as you get in Explorer, if that's what you want. (You can install shell extensions which change how mkv thumbnails are generated if needed.)