i use avif files on my site wherever i want to convert a video to an animated image. avif files are significantly smaller than gifs while retaining much more quality, have pretty good support on modern browsers, can be used with the img html tag, and are able to be hosted on neocities even on free accounts. the backgrounds for my places page, for example, use avif but fall back to jpg if avif isn’t supported.
the following method requires a version of ffmpeg which has the libsvtav1 encoder library, which should be ffmpeg versions newer than 5.1.0. see updating ffmpeg for a link to the ffmpeg build i use (includes builds for windows and linux) as well as how to update ffmpeg on pop os and other debian based distros. you can also use ezgif.com to convert videos to avif. ezgif also supports converting gifs to avif, but if you have the original video file i would highly suggesting using that as the step from video to gif introduces a lot of extra noise, which if you then convert to avif would lead to a larger image size and worse quality than if you had converted the video straight to avif. if you color your gifs in photoshop, you can export to mp4 instead of gif.
basic command
ffmpeg -hide_banner -i "input.mkv" -c:v libsvtav1 "output.avif"an example with time trimming and scaling
ffmpeg -hide_banner -ss 11.736986301369864 -to 24.095362 -i "input.mp4" -vf "scale=640:-2" -c:v libsvtav1 "output.avif"an example with time trimming, cropping, scaling, and extra compression
ffmpeg -hide_banner -ss 00:00:26 -to 00:00:53 -i input.mp4 -vf "crop=in_w-4:in_h-22:2:0,scale=850:-2" -c:v libsvtav1 -crf 40 -preset 6 "output.avif"batch convert
windows
when i used windows i kept the following in a .ps1 file
foreach ($f in gci *.mp4) { ffmpeg -hide_banner -i $f -c:v libsvtav1 "$($f.basename).avif" }linux
for f in *.mp4; do ffmpeg -i "$f" -c:v libsvtav1 "$("$f".basename).avif"; done