I've noticed that with the new Windows10 video thumbs bug that some of the FAQs mention FFDShow.
I'd like to mention an issue that I had a while back. While using FFDshow (64 bit) with Directory Opus I had a persistent bug where it wouldn't (for whatever reason!) allow Opus 11 or 12 to generate "persistent" video thumbnails. It didn't crash, or generate black thumbnails. They just weren't being cached. This was particularly noticeable for me as my movie files are on shared drives.
I struggled for a long time finding out why Opus would spend forever generating a new video thumbnail every time the folder was opened, and had almost given up the idea of thumbnails at all; it's only when I removed FFDShow and replaced it with LAVFilters that the matter was resolved. Instantly.
Of course if anyone out there isn't having problems they shouldn't change things, but I just thought I'd bring it up in case anyone has. Cheers.
Thumbnails won't be cached if they come via the shell, since the shell caches them itself.
For movie thumbnails, that means Opus will only cache them if they are generated via the Movie plugin (which you don't want to do right now, as it triggers the recent Windows 10 update's bug/crash).
The shell has its own rules for when it does and doesn't cache things, which may depend on whether it can write to the device, the type of device, and so on. I'd expect Explorer to exhibits the same thing if the issue is the shell should be but isn't caching things.
Back on our side, Opus also won't cache thumbnails if they are generated very quickly, as reading them out of the cache would be no faster and only waste disk space.
Thumbnails may be cached but then re-generated if the file's size or date has changed. e.g. If something modifies the metadata inside the file then it's probably changing size and/or date as well. There are sometimes also buggy components (video splitter DLLs, some shell extensions) which modify the file dates on every file they are asked to inspect, even though the inspection should be read-only and not modify things. There are also some buggy filesystems, particularly with non-Windows NAS devices, which do the same thing.
On my system with FFDShow, the shell wasn't caching video thumbnails either. I just could not get Explorer to cache video thumbnails, even with addons like Media Preview. Sorry, I should have mentioned that.
I'm fairly convinced it was an esoteric FFDShow problem. The version I had installed was rev4531_201406278_x64, although I'm fairly sure it has been there for a while and still may be in the most recent stable build.
More a matter for Windows and/or FFDShow in that case, or using an alternative codec if one works better on your system.
If LAVFilters works better for you then keep using that; it's a good codec as well. I'll make a mental note to suggest it as an alternative if anyone else runs into a similar problem. Thanks for mentioning it so we can share the info with the community.
There are many versions and forks of FFDShow, not all good, which complicates things as well. Video playback components are complex in general, unfortunately. It's getting better as more things are built into Windows, but they can still be broken when other software is installed, bringing the old complexities back when trying to repair or replace the broken components.