Derivative work

Copyright gives the rights holder control over derivatives as well as straight copies, so recutting, dubbing or remixing somebody else's footage can infringe even though what you made is new. That is the ground reaction, commentary, review and edit channels are standing on. Fair use in the United States, or fair dealing elsewhere, may cover a particular derivative, but it is a defence weighed case by case after the fact rather than a permission you can claim in advance. Effort is irrelevant to the question: spending forty hours on an edit does not make it non-infringing. Licensed source material, or footage you own, removes the argument entirely.