Is it bad to apply frame completion to a film, given how projectors work?

[zarusoba10]

The practice of using software frame completion to increase the frame rate for video works is controversial.

However, in the process of playing back a film on a projector, a rotating shutter is used to apply what is known today as BFI to a film, for example.This should make a 24 fps film have a clarity similar to that of a 48 fps image viewed on a hold-type display.

Does this mean that displaying a 24fps film as-is on a hold-type display is considered to be a departure from the "original motion of the film," and that those who use frame completion are rather seeing the "original motion of the film"?

[DeltaForCain]

I think this is completely down to taste. I, for one, hate stuttery imagery and am very sensitive to flickering. As such, I always crank my TV’s frame interpolation to the max, and I have a really hard time enjoying a film in the theatre, as I notice the low frame rate.

[William Sokol Erhard]

I haven't heard interpolation referred to as "frame completion" before but I expect you're talking about the same thing.

I will first note that low quality built in TV interpolation or even PC based optical flow interpolation is far worse than high quality depth-aware machine-learning based interpolation. All interpolation is necessarily worse than a native high framerate video but depth-aware ML interpolation gets surprisingly close in many circumstances and is the best you can do for most content available.

Personally, I don't think creative intent in viewing experience is necessarily always the best way to consume media. Further, often low framerates are not chosen for creative intent but rather for cost savings or more often just without any creative consideration whatsoever, just using it as the default easiest option.

It's definitely fair to call it a matter of preference. In the same way that a 4k bluray has far higher spatial resolution fidelity than a DVD, a higher framerate video has higher motion fidelity than a 24FPS film. Some prefer watching old TV shows or movies from a DVD on a CRT in letterbox or pan-and-scan. I think higher fidelity is always better but others don't agree.

Even theaters have issues playing back films at 24FPS with a 180° shutter in the same manner that they were recorded in. Most modern projection of 24FPS movies involves a three blade rolling shutter to project each frame multiple times therefore increasing the flicker rate and making it less painful to watch.

You are right to say that you cannot preserve the original display format creative intent by playing back 24FPS film normally on a simple sample and hold display.

I made a software tool called Vint which offers high quality depth-aware ML interpolation as well as CRT emulation and multiple BFI options like multi-projection. This allows you to enable strobing on a sample and hold display.

Ultimately, you have a variety of ways to consume films on modern devices and displays so you can try them out and see which you prefer.

I am writing more about this topic so check that out when it's posted soon.