[Tinwarble]

Because I have 10+ years of a media collection and not the resources/desire to re-encode them all. Also what container do you recommend? I find it incredibly hard to believe that playing old 480p video in Xvid/Divx should be a problem considering my xbox running xbmc4xbox streams it flawlessly. There's gotta be a simple solution if it was mastered 10+ years ago.

Again, those are just containers. Most likely they are MPEG 4 (codec), which is supported by the Fire TV, but that does not mean that divx/xvid/MPEG 4 is supported, Amazon doesn't make the distinction.

Yes, h.264 may be having the same or similar issues but that doesn't mean that they are caused by the same thing and it depends on what you mean by "jerky" since if you have a lot of jerkiness then it's not the same as h.264 which is small and irregular.

But as far as recommendation, either mkv/h.264 or mp4/h.264 which are more "universal".

Also, you don't necessarily need to re-encode. You could just run them through mkvtoolnix and do container swap, which should only take a couple of mins. per vid.