www.makemkv.com

It's not often I've come across this, but I've noticed on discs for some of the Doctor Who Series as well as the Shrek films that they have a video commentary that is like a PiP overlay with a small video in the corner. I have not been able to find any MKV files where these are referenced--is there any way to get extract these videos?

I'm not sure if this is related or not in terms of how they author this on the Blu-ray disc, but on possibly a similar or related note, I posted some findings about video PiP overlays on the Toy Story 3 Blu-ray:

https://makemkv.com/forum/viewtopic.php?f=8&t=17089