Hollywood Directors Abhor Motion Interpolation

By Bob Raikes
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A number of Hollywood directors, encouraged by James Gunn who calls the effect ‘Satan’s Spectacles’, has complained about the technology in TVs that smooths out 24fps movie material to higher frame rates. Gunn has recruited Tom Cruise, Rian Johnson, Chris McQuarrie, Christopher Miller, Reed Moreno, Matt Reeves, Dan Trachtenberg and Edgar Wright to support the campaign. He also said that he has been around his parents’ house and reset all the TVs.

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Gunn was clear that he wasn’t talking about content that is deliberately recorded at higher frame rates, but just at the addition of extra frames by TVs and players. This group is not the first to raise this issue, but is, perhaps the highest profile. One of the main grumbles is that motion smoothing is the default setting on most sets and one suggestion has been is that TV brands change this.

For those that have not been around since before this technology was introduced, one reason for the smoothing is that while LCDs tend to work at 60Hz, movies are recorded at 24fps. TVs have to map 24 to 60 and would typically use 3:2 pulldown, showing the frame three times, then twice. Over two seconds, things lined up, but 3:2 pulldown causes judder that is not very nice, especially during panned scenes. This is not an issue with 120Hz panels. Some processing is also better than others at dealing with the issue. Motion interpolation is very complex because of the wide range of motion (such as rotation as well as linear motion) When this was a big topic, the makers of the algorithms all had demos that showed certain motion that their chips could deal with and didn’t show the kind of motion that looked bad. (BR)

Motion interpolation moves objects on the intermediate frames. Image:Meko