ffmpeg -i anim.mp4 -vf "select=not(mod(n,6))" -vsync vfr img1/f%04d.jpg -preset photo
ffmpeg -i anim.mp4 -vf "select=not(mod(n,6))" -vsync vfr img/f%04d.webp -qscale 20 -lossless false -preset photo -compression_level 6