ffmpeg -i input.mkv -pix_fmt yuv420p10le -c:v libvpx-vp9 -pass 1 -speed 8 -quality good -threads 16 -row-mt 1 -crf 25 -b:v 0 -g 240 -an -f webm nul
ffmpeg -i input.mkv -pix_fmt yuv420p10le -c:v libvpx-vp9 -pass 2 -deadline best -threads 16 -row-mt 1 -crf 25 -b:v 0 -g 240 -codec:a libopus -ab 128k output.webm