converting to .MJP files I would like to convert some short videos to .MJP format, and none of my preferred tools for video conversion can do this. Can anybody suggest free software that can achieve this? OSX preferred, but Windows is available if necessary.

EDIT: 

All I can tell you is that I have a (newish) device that has a video screen and contains a memory card holding four .MJP files that can be shown on the screen. 

The videos play, with sound, so I know the files are valid. If I copy them over to my Mac, no software that I've found can play them. 

I would like to replace the video files that the device shows, but this requires converting my videos to .MJP format. I have put one of the existing files at https://app.box.com/s/kbtvfbpowqwbp1aym88m if anybody wants to examine it.
http://www.openthefile.com/ext/mjp/4458 and http://www.fileinfo.com/extension/mjp both suggest mplayerx (http://mplayerx.org/) can play them. It would make sense to post a file for people to examine. If mplayer or ffmpeg can play them, chances are mencoder or ffmpeg can encode to the format.