Luma Touch Support Forums

Iphone (and cellphones in general) generate variable frame rate video. It means that there is a target frame rate, for example 30 fps, but the actual frame rate is varying and is not stable. Do anyone know why cellphones do this? The consequence is that edited and exported video have glitches like duplicate frames which is very annoying as the smooth motion is interrupted from time to time. It looks similar than dropped frames in the player. I believe there is no way to avoid this or has anyone found a workaround to fix this?

Interesting but I’ve never noticed any problem using the iPhone as my principal camera. Reading a bit suggests that it is an efficiency method to reduce file size and happens even if you can set frame rate (with Filmic Pro which I don’t use normally). In practice I wonder whether I’d notice say a one frame glitch visible for only a thirtieth of a second?

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Mark

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iPad 6 (2018 9.7 inch)
iPhone 7 Plus
iOS 13
LumaFusion 2.3.0.1254

Good one thanks. Looks like it may not be an issue in the iOS realm (so I’m ok) but important for some professional video work.

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Mark

I tested this a bit more. I recorded 3 min video clip with IPhone XR 4k/24p and 4k/30p with native camera app.. I put those files in 24p and 30p projects in Davinci Resolve and exported 24p and 30p movies. Result: 24p file didn't have any duplicate frames and 30p file had 4 duplicate frames showing glitch in the footage.

Then I did the same with Lumafusion. Exported 30p file had 3 duplicate frames showing glitch in the footage.

This was quick test which showed to me that even Lumafusion will generate some amount of duplicate frames at least with Iphone XR native camera app 4k/30p video.

My experience with real video edits with shorted clips, is that there will be duplicate frames about every 20 seconds in average in the final video.

Other problem with handheld Iphone handheld video is that sometimes the stablization and/or autofocus generates quick glitch which looks ugly and little bit similar that duplicate frame.

Without these problems IPhone would be quite perfect "run and gun" video camera.

PS. The reason why I don't want to shoot 24p is that my computer monitor runs at 30p and I don't like how the 24p motion looks in 30p monitor.