ffmpeg -i 1.webm -c:v libvpx -b:v 10k -threads 8 -speed 0 -g 9999 -auto-alt-ref 1 -lag-in-frames 25 -c:a libopus -b:a 2k -sn -y 2.webm
ffmpeg -i 2.webm -c:v libvpx -b:v 10k -threads 8 -speed 0 -g 9999 -auto-alt-ref 1 -lag-in-frames 25 -c:a libopus -b:a 2k -sn -y 1.webm
ffmpeg -i 1.webm -c:v libvpx -b:v 10k -threads 8 -speed 0 -g 9999 -auto-alt-ref 1 -lag-in-frames 25 -c:a libopus -b:a 2k -sn -y 2.webm
ffmpeg -i 2.webm -c:v libvpx -b:v 10k -threads 8 -speed 0 -g 9999 -auto-alt-ref 1 -lag-in-frames 25 -c:a libopus -b:a 2k -sn -y 1.webm
ffmpeg -i 1.webm -map 0:v -c:v vp9 -pass 1 -f null -
ffmpeg -i 1.webm -map 0:v -map 0:a -b:a 2k -pass 2 -b:v 10k 2.webm