How to properly convert 16:9 to 21:9 - big issues here!

Hey guys, just started working with Shotcut after watching a ton of tutorials. Thought it would be easy, but already tripping over the first major issue. Saw a lot of problems posted here being solved efficiently, so here I am with mine.

I am trying to produce a cinematic trailer and thus use 21:9 as aspect ratio. My original footage was shot in 4k (3840x2160) 16:9. For this source file I calculated a project resolution of 3840x1646 for my new preset to achieve 21:9.
Now, what I did assume was to just put the original 3840x2160 video in the timeline and let the bottom and top get “naturally cropped” by the limited height of 1646p of the project.
But for some reason when adding the files to the project they all shrink to 2926x1646 (and sometimes even 2926x1664 ???) - at least thats what the “Size, Position & Rotate” filter indicates as “new” 100% - see picture. I don’t get why, especially when it shows 2926x1664 - this is neither the source resolution or the projects preset resolution. It does not even match the vertical pixels - why??

I now have to manually scale up every single piece of video via SPR Filter to 131,2% to get back to 3840x2160 which not only is annoying but also leaves me wondering if I loose any quality.

Even more confusing is the newly introduced presence of thin black bars on the left and right. Excuse me, but shouldn’t a 3840x horizontal video fit perfectly into a 3840x horizontal project in terms of width??? It’s almost like my video file suddenly is a few pixels more narrow, more like 3820x or so. I do have to check “distort” as size model and I don’t understand why.


Vos vidéos sont en 3840x2160 et vous voulez une vidéo finale en 3840x1646
Au démarrage de SC réglez votre projet sur 3840x1646 (le format de la vidéo finale que vous souhaitez).
Puis pour chaque vidéo que vous intégrez au projet, appliquez lui un filtre Crop: Source AVANT tout autre filtre.

Your videos are in 3840x2160 and you want a final video in 3840x1646
At the start of SC set your project to 3840x1646 (the format of the final video you want).
Then for each video you include in the project, apply a Crop: Source filter BEFORE any other filter.

3840x1646 is not 21:9. It’s close, as this is why you’re seeing the gap.
3840 is not divisible by 21 into a whole number.

3840 / 21 = 182.8571~
3840 / 16 = 240

The closest to the 4k width would be 3822x1638
Reference link

I made an example PNG image.

Custom Video Mode:

You can either use the Crop: Source filter as @Namna has suggested, or the Size, Position & Rotate filter.

Hi, I don’t use the shotcut crop and resize filter to do what you want to do. I use a different process. I batch convert my videos and crop using a script in a folder. I am on Linux but there will be a way to do this on Windows.

I also convert to an edit friendly format to keep my CPU cycles working as
efficiently as possible. One is to prevent shotcut from unnecessarily rendering unwanted parts of the image. Two is to stay within Shotcut’s native rendering system. Thanks to @Austin for the DNXHR ffmpeg recommendation.

for f in *.MP4; do ffmpeg -i "$f" -filter:v crop=3840:1646:0:257,scale=flags=bicubic+accurate_rnd+full_chroma_inp+full_chroma_int:sws_dither=ed,format=yuv422p -c:v dnxhd -profile:v dnxhr_hq -c:a copy -movflags +write_colr+faststart "${f%.MP4}.mov"; done

This batch converts the contents into 21:9 format all of the video files in a directory. I convert to mov because my mp4s have lpcm audio which prevents me from reusing an mp4 container. mkv would do just as well.

Additionally, there is a bug with odd sized files when importing I’ve found. You need to first import one file when using Auto detect format. Rather than as a group of files otherwise strange things happen with pillarboxes and letterboxes.

This topic was automatically closed after 90 days. New replies are no longer allowed.