Anyways, I noticed, just like in Ubuntu since 9.10, that I was not getting thumbnails generated for my 10bit .mkv files or avi, and that the thumbnail generation is very slow.
Anyways, using ffmpegthumbnailer and this small tweak, you can get flawless thumbnail generation for ALL videos and pictures. I was able to generate thumbnails for a folder with around 2500 jpg, gif, and png files in under 2 minutes with this tweak, and my laptop has a core 2 duo.
First install ffmpegthumbnailer from a terminal if you haven't already, as we will use that for generating thumbnails.
sudo apt-get install ffmpegthumbnailer
Also make sure you still have totem player installed. It was installed by default. (shows up as movie player) You will need to tweak totem, which grabs the thumbnails by default, to work with ffmpegthumbnailer for all file types. A few years ago someone somewhere on the internet uploaded a tweaked totem.thumbnailer file. I do not remember who it was or where I got it, but credit goes to them for this.
Download the included archive, which has the file you need in it. After extracting it, you need to sudo into nemo using the following command
You need to copy/cut the totem.thumbnailer file you extracted from the included archive to the following directory:
There will be three files in this folder, evince.thumbnailer, gnome-font-viewer.thumbnailer, and totem.thumbnailer. When you copy/cut the file into this folder, make sure to hit REPLACE on the dialog that pops up.
Thats it! Now your computer should generate thumbnails for those pesky 10 bit .mkvs.
You will need to delete your thumbnail cache if you want it to work correctly in most cases, and in Mint 14 the thumbnail directory has changed from .thumbnails in your home directory to .cache/thumbnails
Delete everything in the thumbnails folder (normal, failed folders) and then see how your thumbnail generation goes!
Also, please vote in the poll if this works for you. I have never had a problem, and I thinks something like this needs to be included in Mint (and Ubuntu) in the future.