4k Cinematic for YouTube

I want to display a 16:9 video as 21:9 on Youtube, that is, the black bars top and bottom but it seems tI’m not able to achieve the effect.

I have created and saved 2 .mlt files
.mlt1 : Cinematic 3840x1600 16 9 Aspect
.mlt2 : Cinematic 3840x1600 21 9 Aspect

I have then 2 exports with each .mlt
.mlt1 export with 3840x1600 16 9 Aspect
.mlt1 export with 3840x1600 21 9 Aspect

.mlt2 export with 3840x1600 16 9 Aspect
.mlt2 export with 3840x1600 21 9 Aspect

When uploaded to YT .mlt1 & .mlt2 exports (16:9) the video fills the entire screen as expected. When I upload .mlt1 & .mlt2 exports (21:9) both of them display as Letterbox, that is black bars top and bottom and black bars left and right.

I’ve read other posts here suggesting as long as a custom preset is created and saved then that should be it but I’m unable to achieve the effect. Any advice appreciated.

3840 / 1600 = 2.4 aspect ratio
21 / 9 = 2.333 aspect ratio

The pixel dimensions do not produce the same aspect ratio as the 21:9 being requested. This means pixels have to become non-square in order to stretch themselves to the 21:9 requested ratio. This will make the picture look blurry or create black bars where you didn’t want them.

Since normal 21:9 resolution is 5120x2160, I’ll assume you’re cropping 4K video to 21:9 given that the width is 3840. So the associated height would be 3840 * 9 / 21 = 1646. If you make a custom Shotcut video mode (Settings > Video Mode > Custom) with that resolution and specify 21:9 as the aspect ratio, everything should export and play just fine.

Hi Austin,
Many thanks for the response. I have attempted that but it still black bars the left/right.

What whet my appetite for this was this

and the comments beneath that video:-

As an owner of a 21:9 monitor, it’s great that more people realizing that this is the right way to achieve wider aspect ratios for youtube.
However, I’d like to point some things out:

  1. It’s never a good idea to use an odd number for either width or height of the video frame. Youtube will round it to nearest value divisible by 2 on conversion anyway.
  2. For some codecs, the requirement is even more strict, like the frame height must be divisible by at least 8 ( and width by 16 ). If you refer to the common 16:9 standards, like 1820x720, 1920x1080, 2560x1440, 3840x2160, you’ll see they all comply with this.
    And while with most codecs youtube will just add a few black pixels to match the right height, with some others, like cineform, it might add a very noticeable green or grey line to the bottom ( something I personally struggled a few months back before realizing my mistake - I was uploading 1620p which isn’t disibile by 8).
  3. Hence, I see the best and most convenient values are 1920x800 and 3840x1600. Both 800 and 1600 are round, easy to remember, are divisible by 8 ( and even 16 ), and correspond to 2.40:1. If that’s too wide for someone, another options are 1920x816 and 3840x1632 respectively ( 2.35:1 )
    All of the above is unprofessional personal opinion, but based on issues I’ve faced by experimenting with upload resolutions.

I can throw an image of black bars but that defeats the purpose of the exercise of course.


The actual bars are representstive within Shotcut so it’s not an issue with YT

You have to create a custom video mode.

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Thanks Hudson,
I have created a custom video mode with those parameters but the same o/p in YT sadly.

On the export tab the aspect Ratio isn’t represented as the 21:9

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Exports to how I have it set.

Custom Mode:
Exports (what Shotcut set - no intervention from me)

So I change to your recommendation (I manually have to change the aspect ratio to 21:9)
O/P on YT

The only reason I changed was because I thought the aspect ratio didn’t look correct so I manually changed it to 21:9. Anyhow I created a new custom, exported and uploaded to YT, same result. I’m on the latest Shotcut,. So I’m not sure what I’m doing different. When you view your uploaded video do you see the vieo right across the player then, no black bars right and left?

I appreciate the explanation but I think I’m still not grasping the concept. The guy in that video suggests that if a 21:9 video is uploaded to YT then the black bars are visible, which is true for our uploaded videos but I wasn’t expecting the black bars on the left & right. I thought they would not be visible at that aspect ratio but this may be my lack of knowledge.

With the project, which is set with custom mode I have now also set the aspect ratio of the original video from 16:9 to 21:9 then added size& position filter. The video is auto set to the full width of the source viewer. I then centre the video (top and bottom is cropped by doing this).

Here is the result in YT

That’s the actual right way to do it. I was just thinking suggest you to do that but you have got it.

I actually thought my solution was a fudge-fix because all the posts on the forum only suggest adding the custom mode. Forum members then try the solution and go away happy. In those posts they don’t mention those additional steps but anyhow the o/p I see on YT is the effect I was looking for. Cheers.

You are trying to create an ultra-wide video from a source that is not ultra-wide. The other forum members and I took it for granted that you would do some type of cropping or scaling on the source video to make it fill the 21:9 space. Sorry we skipped a step in our explanations.

You’ve discovered the issue already, but let’s walk through the math anyway because there is a much better solution available than what you’re doing now.

I assume your source video is 3840x2160. Shotcut by default is going to make the entire source video fit on the screen. It does not automatically scale or crop to fill the entire output space because discarding video data due to scaling should be a creator’s artistic decision, not a default decision. Since your source video is taller than your output aspect ratio, Shotcut is going to squish it down uniformly so the entire video can be seen on-screen, which leaves empty black space on the sides that will be visible even in Shotcut. You’re correct this is not a YouTube problem.

At this point, we need to stretch the source video to fill the width of the screen. If we maintain aspect ratio of the source while zooming/scaling/stretching it to fill the width, then the top and bottom will stretch/grow into the letterbox area and effectively be cropped out.

To find the exact scale factor to use, the shortened formula in this scenario is ZoomFactor = SourceHeight / OutputHeight. So 2160 / 1600 = 135% scale factor. Or 1440 / 1080 = 133.4% scale factor. At this point, the easiest thing to do in Shotcut is apply a Rotate and Scale filter, set the Scale parameter to 135%, and boom, done. You can then change the Y Offset if you want to pan the source video up or down to change what’s visible within the letterboxed area. This is substantially easier than fiddling with math in the Size and Position filter.

As you noticed, that is double effort. We can save you a lot of time here. If all your sources are 3840x2160, you can put a single Rotate and Scale filter on your V1 trackhead rather than the clip itself, and it will be applied to every clip on that track automatically. If you want to vertically shift an individual clip, you can add an additional Rotate and Scale filter to that specific clip. It doesn’t get easier than that.

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Hi Austin,
Firstly, no apologies required from yourself or indeed anybody. I appreciate all input when trying some of the video techniques that can be applied within Shotcut.

Many thanks for the comprehensive explanation. The layman’s explanation really helps my understanding. I will apply what you’ve explained here with another short video uploaded to YT. Speaking of which, I do love viewing some of the “cinematic” effect videos on YT. In the right context, for example, an aerial shot, they seem aesthetically pleasing, for me anyhow.

I enjoy trying to replicate the techniques talked about here. Last night I used the solution used in the video.

Again this brings me to another subject that springs to mind, proxy editing. This is something I read about on the forum and something I need to utilise especially as most of what I’m experimenting with in Shotcut is 4K and the editing is a bit jittery.

Forgive the babbling and again thanks for the help, it’s appreciated!

Absolutely! I’m eager to see what you create. And I forgot to mention something else…

The phrase “21:9 ultra-wide” is an incredibly generic marketing term that is applied to a lot of resolutions that are not true 21:9 in the mathematical sense. Like my first post showed, 3840x1600 is 2.4 whereas 21:9 is 2.333, and pixels will have to be squished non-square to correctly make up the difference. (That’s a bad thing.)

There is a chart on Wikipedia of common “21:9” monitor resolutions and their true aspect ratios:

  • 3840x1600 is actually 12:5
  • 2560x1080 is actually 64:27

Remember to use these values instead of 21:9 when setting up your custom video mode and when doing your export.

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Excellent! This page is bookmarked.

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