MP4Cam2AVI is a handy MP4/MOV/M2TS to AVI converter/joiner for digital cameras. If you want to convert you camera (phone) video clips to make them editable in Windows Movie Maker, VirtualDub or similiar tools, MP4Cam2AVI is for you. It was developed specially for this, and it’s absolutyle free.
Also, with MP4Cam2AVI you can join multiple video clips from your camera into a single gapless movie.
Project page at sourforge.net (download link there)
Manual (a bit outdated, but quite detailed):