Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
The problem with 'aspect ratio' that you are describing, might possibly be related to any one of these factors - and certainly you are stressing the limits of what the software and the TVs can actually do!:
- aspect ratios may be fixed (or only a certain number available) on the TVs you tested with... which might add more black spacer on the sides/top-bottom.
- the varied footage you used may have different pixel densities which are determining things, rather than just their own aspect ratio. The whole video would of course have a certain pixel density and/or a certain width-in-pixels by height-in-pixels. And the sections of variously sourced video clips, would have to be fitted into that somehow.
That might cause extra bars / spacers on a TV, if the largest footage (in terms of width-in-pixels by height-in-pixels) is a certain width and height, that the lesser-density footage cannot match... and thus force spacers around much or even all of the footage in consequence.
- seek in all settings, whether on the software you prepare with, or on the TV(s) you display with, there is a 'Letterbox' setting or option, that is being activated by some of the footage at least if not all of it. That might have to be disabled.
- I also advise, as a practical matter, testing whether just *one* of the types of video footage you want to include, when prepared as the total video was, turns out to have vertical spacer as well as horizontal black / spacer bars. This would allow you - by successively adding another type of footage, then seeing whether the result, finished again, produced superfluous black bars, to determine what footage is inducing it... or if the excess black bars appear from the first, you could determine this way, that settings or options rather than footage is producing the problem.