VideoTrack, BIAB gathers tracks from the original source in hard drive every time it re-generates. This was confirmed to me by PG. Regardless of what it does next, this indexing process of gathering stuff from hard drive by itself takes most of rendering time.

It is like having a full basket of blueberries with a few rasberries burried somewhere, mixed in. So re-generation process has to find those "rasberries" each time and put it in your cup, instead of finding them once and keeping them separate.

So when program asks: WhEre ArE mY RasBeRRiEs?!?! it would be logical to have them separate and say: "Here they are, master..." And not do this: "One second master, here is one....ohh.. I found another one....here, here there is one more" and so on...