My typo. I meant "Known."
OK to trim little clips we need video editing software. On my shelf is Sony HD video software and Corel VideoStudio X5. The problem is that you want some guarantee that it will work. Sorry but I can't offer that.
I will share that if some video does not come in I'll use HANDBRAKE to convert it (it's free) and the industry is in quite a mess in this area. I make no apologies for them.