FFMPEG WebM a MP4
ffmpeg -i input.mkv -codec copy output.mp4
Old-fashioned Opossum
ffmpeg -i input.mkv -codec copy output.mp4ffmpeg -i "01 - file.webm" -crf 23 "file.mp4"ffmpeg -i input.mp4 -b:v 0 -crf 30 -pass 1 -an -f webm -y /dev/null
ffmpeg -i input.mp4 -b:v 0 -crf 30 -pass 2 output.webm
# lower -crf value = higher quality & larger output
ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 30 -b:v 0 -b:a 128k -c:a libvorbis output.webm