The problem

We filmed 3 hours of 4k Video with an iPhone X with the wonderful Filmic Pro app. I used MoondogLab's 1.33x anamorphic lens to create a wide-angle effect.

I checked Filmic's option to fix the ratio ONLY in the preview. Meaning the output video was all vertically stretched. All the content is there, but the display ratio is wrong. There are some advantages to this (no quality loss) but the video is streched when you play it.

The solution

Moondoglabs' lens basically changes your display ratio from the usual 16:9 to 2.40:1.

In wide angle format, the display ratio for a HD video (1920x1080) needs to be 1920x800 (because 1920 divided by 2.40 = 800). As it's a ratio it doesn't matter if I apply it to HD or 4K video. I could as well use 3840x1600 or 24x10.

I learned MPEG-4 video includes a parameter for the display ratio. So you can just change the parameter, and don't have to re-encode the video. It is just squeezed / streched on display as needed by the player. Not only will it save hours, you also lose none of the original bits, as would happen with re-encoding. This means that if you need to zoom/upscale the video a bit during editing, those additional vertical pixels will be there to enhance the quality.

Thankfully ffmpeg (easily installed via HomeBrew) is here to save the day. This command will copy the video feed and just change the metadata in the destination to fit the desired display ratio.

ffmpeg -i -aspect 1920:800 -c copy

And magically my video doesn't look stretched anymore.

A simple bash script applies the same thing to all the videos in the folder. In a few minutes, 22 Gb of video were fixed and play nicely in VLC and any player that respect this settings (I hear not all do but I can't give names).


for i in *.mov; do ffmpeg -i "$i" -aspect 1920:800 -c copy "${i%.*}"; done