Tips and tricks with ffmpeg

This is a quick cheatsheet for me and for anyone that would be interested by ffmpeg. I use ffmpeg for many things but especially: screen recording and to be able to upload larger files on Discord without Nitro.

Recording screen and audio

Recording screen without audio

ffmpeg -f x11grab -i :0.0 -preset ultrafast screenrecording.mkv

Recording screen with audio

ffmpeg -f x11grab -i :0.0 -f pulse -ac 2 -i default -preset ultrafast screenrecording.mkv

Recording audio without screen

ffmpeg -f pulse -ac 2 -i default audiorecording.mp3

Shrink file size

To be able to upload files on Discord (or just have easier time to edit the video if your computer is low end) you can shrink the file isze by a lot this way:

Shrink file size by re-encoding. This doesn't really reduce quality but has a huge impact on filesize (sometimes even x10 times smaller).

ffmpeg -i input.mkv -vcodec libx265 -crf 28 output.mp4

Make the file previewable (I've had the bad surprise the files converted by ffmpeg cannot be previewed in WhatsApp and Discord). This may increase the file size a bit.

ffmpeg -i input.mp4 -movflags faststart output.mp4

EDIT: the above command might be completely wrong, try this one instead:

ffmpeg -i input.mp4 -pix_fmt yuv420p output.mp4