I've recently re-encoded a whole load of MPEG2 video I've got into MPEG4 (using H.264). I thought that I'd put it all in MKV containers. Sadly, this turns out not to be the case: HandBrake's presets explicitly set the output container — mostly to MP4. So I'm now left with a large number of videos in a format that I didn't intend. What's worse, I can't easily flip forward and back in the files I do have, using either my Popcorn Hour or any of the video players I have on my Linux desktop. Here's what I did to fix this sorry state of affairs.