Say you want to sound like you are huffing Helium.
Recoding with Cheese, save a file (on Fedora 37, this becomes a .webm)
Cut the audio out of the video: ffmpeg -i 2023-02-13-203611.webm -vn -acodec copy "output.oga" Shift the pitch up: ffmpeg -i output.oga -filter:a "rubberband=pitch=2.059463094352953" out_balloon2.wav Then add the audio to a ffmpeg -loop 1 -y -i balloon.png -i out_balloon2.wav -shortest -acodec copy -vcodec mjpeg the_ballon_knows.avi