Roku TVs sometimes use a technology they call "Action Smoothing" to artificially speed up the framerate of video, but it often ends up looking fake and ruins the cinematic look of movies.
What Is "Action Smoothing" Anyway?
Action Smoothing is Roku's implementation of motion smoothing, a common feature on high-end TVs. Motion smoothing works by increasing the framerate of the video on the TV. More frames make motion feel smoother, but there's a problem: since there's no way to create new frames out of nowhere, it has to take two frames and attempt to figure out what the "in between frame" is. This leads to a lot of motion-blurred frames and a fair number of artifacts.
Roku says "Action Smoothing" reduces "motion blur," which is true as far as it goes. It can help you to see fast moving objects easier, but it adds a bit of motion blur to the in between images to make them smoother. That can be good for fast-action live events like sports, but it can make movies and TV shows look weird
This feature isn't included on all Roku TVs. We couldn't find it on any of our TCL Roku TVs, but some manufacturers do include it.
How to Turn Off Action Smoothing
Luckily, you can disable this feature on your Roku TV. Roku hides the option under "Advanced Picture Settings" in the menu, which you can open by pressing the "*" button below the direction pad on the remote. Note that how this button press works changes depending on what's on your screen. It doesn't work on the Roku home page or on the home pages of streaming video apps, which all use the "*" button for other things. You must be playing a video in a streaming app to access the menu. You can also access the menu by simply pressing "*" when you've selected a specific HDMI or other input on your TV---no need for a video to be playing then.
If your Roku has motion smoothing, you'll see "Action Smoothing" options under Advanced Picture Settings. There are four different levels of Action Smoothing you can select: High, Medium, Low, and Off. If you just want to get rid of the motion smoothing effect, select "Off". The other levels will use less motion smoothing, but will still interpolate the content. (If you don't see the Action Smoothing options, your Roku TV doesn't have motion smoothing.)
Your Roku TV will save your settings, but it has different settings for different types of content. Here's what Roku says:
Action Smoothing settings are unique and persistent for every input, and for each type of content (e.g., 1080p, 4K, 4K HDR). For example, if you have a 4K Blu-ray™ player connected to HDMI 1, you can assign a different Action Smoothing setting for 1080p movies, 4K movies, and 4K HDR movies. Each time you return to HDMI 1 to watch a movie, the Action Smoothing setting automatically returns to the assigned value depending on the type of content being watched.
If you're having any other issues, you should consult the Roku TV Manual for additional help.