I've tried many different video export formats, but the result is always the same:
- Audio is fine
- Text is fine
- Background doesn't show video, it's just pure black
I finally figured out how to do it. I had to go to Render > More Options > Render using Proxy Clips (Also I happend to use lossless FFV, a.k.a *.mkv)
Not sure why it required me to use proxy clips but it did. Probably because the clips were raws from a android/iphone app called Marco Polo which may have had some odd encoding to them.