Record media fragments in browser
Motivation: OfflineMediaContext, How to use Blob URL, MediaSource or other methods to play concatenated Blobs of media fragments?
$ ffmpeg -i concat:"int.mpg|int1.mpg" -c copy int_all.mpg, $ ffmpeg -i int_all.mpg -qscale:v 2 mix.webm
$ mkvmerge -w -o int_all.webm int.webm + int1.webm