Resize Mp4 file into 9:16 YT short size using FFMPEG

Question

I recently programmed a bot, which uses the Twitch API to scrape Twitch videos, and then post them on YouTube. This is my youtube channel if you want to see an example: https://www.youtube.com/channel/UCuhWw8LbPWdkybIF9olAszw

The problem that I am having is I want to find a way to convert these regular twitch videos, into youtube shorts which I can automatically upload. The facecam does not need to be included, and the entire video can just be compressed into a 9:16 format.

I already tried FFMPEG but I don't know if I am doing it correctly, and really need help or advice on how to do this.

Here is an example of a video I would try to convert: https://www.youtube.com/watch?v=hZecXrvd6_g

(excuse the explicit language, this is just the first video I saw on my bot channel)

Tldr: Convert mp4 file into a 9:16 video format

Edit: FFMPEG command I ran: ffmpeg -i video.mp4 -vf scale=1280:720 output.mp4

Thank you so much in advance! This has been bugging me for days.

Answer 1

scale will resize the video. To change the aspect ratio you can try something like:

ffmpeg -i video.mp4  -vf setdar=9/16 output.mp4

Answer 2

Crop the clip to 9/16 like this:

ffmpeg -i video.mp4 -vf crop=ih*(9/16):ih output.mp4

Answer 3

Youtube Shorts' maximum length is 60 seconds. You can split and resize the video into segments using this command.

ffmpeg -i video.mp4 -ss 00:00:00 -t 00:01:00 -vf "[in]scale=iw*min(1080/iw\,1920/ih):ih*min(1080/iw\,1920/ih),pad=1080:1920:(1080-iw)/2:(1920-ih)/2[out]" newVideo.mp4

This command will cut the 1st minute, in order to cut other sections you should write some math logic to calculate and do it. Already I did it for PHP, check below: https://gist.github.com/drpshtiwan/45fd233695b168056af980c56b93579c

Optional

Or you should overlay the split video (newVideo.mp4) into a background video which should have a black background, 60 seconds duration, and a 9/16 ratio. This is ffmpeg command to do the magic ;) I used a full HD video and I overlaid the video in the center.

ffmpeg -i background.mp4 -i newVideo.mp4 -filter_complex "[1:v]scale=1080:-1[v2];[0:v][v2]overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/2" -map 1:a  -c:v libx264 -c:a  copy shortVide.mp4