No control over aspect ratio due to it being set in so many places

[Klawdek]

I made video that was supposed to have a resolution of 1080 x 1920 giving it an aspect ratio of 9:16. The video has one still image with rotation animation and is 56 seconds long. The still image used has 1080 x 1920 resolution. The project video mode was left at the default. On export I set the resolution to 1080 x 1920 The exported video was shown in VLC as having 1080 x 1920 resolution. Yet YouTube wont list it as short which requires a vertical aspect ratio. I then used VLC to make a snapshot and it came out with 3413 x 1920 resolution. Which I believe is the real aspect ratio. On the export window, I notice that aspect ratio is set independently of resolution i.e changing resolution does not change aspect ratio. This way wrong. Resolution determines aspect ratio. I did not check that when exporting because that is completely unexpected.

Why does it have adjustable aspect ratio when that is defined by resolution? Why is aspect ratio set in so many places? And, why was the metadata wrong in the exported file?

[Hudson555x]

For a vertical video, you need to set a Vertical Video Mode.
Settings → Video Mode → Non Broadcast → Vertical 30 or 60 fps

Once the Video Mode is set, then you can open your media into Shotcut.
No need to go into Advanced in Export when you set the correct video mode.

Default Video Mode is “Automatic”.
So you started with a 1920x1080 video mode at 25fps.

[Klawdek]

Thank you very much for answering. I am still confused about setting aspect ratio independent of resolution. Sorry for whining. I see my mistake I have made a custom video mode for my settings.
It seems to work so far.
I am still a bit worried that the video I made had the wrong metadata for resolution.

[Elusien]

OK, so I created a 4sec video of color bars in video mode HD (1920 x 1080). I exported it in aspect ratio 16:9, then I exported it again in 9:16. Both videos have roughly the same number of bytes in them: 13.8kB vs 14.2kB.

I created a new Shotcut project and opened the 16x9 video (GREEN outline in image below) on track V1 and the 9x16 video(YELLOW outline) on track V2.

You can see the 16x9 video fills the screen exactly, while the 9x16 video has the color bars in the middle, the width being 1920x(9/16)x(9/16) pixels and the height being 1080x(9/16)x(9/16). The rest of the vertical area is filled with black.

If anyone can explain why the color bars are reduced in size by the aspect ratio SQUARED, I’d be interested to know.

The moral of the story is “Don’t alter the aspect ratio in export, unless you really know what you are doing”.