I’m confued which Apple TV you own. There is no such device called an Apple TV HD 4K. There is an Apple TV HD, which is not 4K capable, and there is an Apple TV 4K 2017 (1st gen) which is 4K capable.
I can’t speak for the Apple TV HD as I don’t have one.
But if by chance you are talking about the Apple TV 4K 2017, then you should try going into settings and selecting the option to match frame rates and dynamic range. I would let the Apple TV 4K select how to format the video and send it to the TV rather than try to set the TV to format it.