ffmpeg -i 1.webm -lavfi '[0:v]scale=ih*16/9:-1,boxblur=3:3[bg];[bg][0:v]overlay=(h*16/9-w)/2:(h*W/w - h)/2,crop=h=ih*9/16' -c:v libvpx -b:v 0 -crf 4 -y 2.webm