As reported by
jasper1977 in his post
here, Craig Michaels from Apple has confirmed that there is no 24Hz output capability in the ATV4K. Because of this, 24Hz content (typical movie rate) is output at 60Hz instead (typical TV rate), which causes a framerate mismatch leading to visual judder.
If you would like to see this change, please leave feedback at the following link. It will take less than 1 minute. Apple claims to read every single one:
https://www.apple.com/feedback/appletv.html
Before you take the time to respond to me about how nothing will come of this... well you might be right. But the time you took to knock me down is time that you could've posted feedback to Apple instead.
Ridiculous request. The problem isn't Apple it's the TVs.
Sure, you can find a few (expensive) TVs that support 24Hz refresh, but almost everything shipping is 30 or 60Hz fixed on the HDMI side or the TV will resample to a final refresh rate like 60 or 120Hz. Until HDMI 2.1 lands on TVs (next 2 years) allowing for variable refresh this is much ado about nothing.
Read on...
You only want to watch programming at its native frame rate. That said, it is WAY more complicated than simply setting your Apple TV 4K to 24Hz.
Whatever you choose it is going to be a compromise and that is if and only if the TV respects the input frequency the way you think it does. For example, what if your TV screen is still refreshing at 60 or 120Hz as some do?
Do you truly know what is happening on the TV end? Do you even trust the software running on your TV to do the right thing? Probably not, and configuring a TV to not perform additional image processing/color correction/motion compensation can require time and research.
Using 60Hz is a compromise, but it is a well understood compromise. For one, the user interface, apps, games and TV programming will look great at this frame rate. The one thing that might not be ideal is film, most often recorded at 24FPS (but not always), which will of course introduce things like judder because of 3:2 pull down. However, this problem isn't new and it isn't really addressed simply by setting your output to 24Hz. Even if we assume some films are best shown at 24FPS and your TV will refresh at a multiple of that frequency you're compromising every other use of the box.
The best thing for everyone is to wait for
HDMI 2.1 and variable refresh rate TVs so everything just works. Until that time 60Hz is the best compromise and will provide the best overall experience.