Mux two mp4 videos losslessly

[HKO2006]

How can I merge two mp4 files without losing quality?
http://superuser.com/questions/43588/ho ... ng-quality

Avidemux. It's just like VirtualDub, only with more formats supported and built-in codecs and filters. I always use it in preference; it joins AVC+AAC.MP4 files (without recoding) fine for me.

To join them in AviDemux:

File -> Open -> Select File
File -> Append -> Select File
Set all to Copy
File -> Save -> FileName
Wait..
According to AViDemux forums, this join process is lossless (http://www.avidemux.org/smf/index.php?topic=9467.0)

Avidemux
http://fixounet.free.fr/avidemux/

Example
SMILETRON - Disco Just Won't Cut It This Time

https://www.youtube.com/watch?v=4_6EWGJRhQs

This video is made by combining the following two official gameplay video by the developer. I replaced the audio with the original high quality mp3. I also cut the last few seconds of the first video and the first few of the second video to make the transition smoother.
Waves - Official Gameplay Trailer
https://www.youtube.com/watch?v=HxxOdqKvnpA
Waves - WIP Chase Mode Free Update
https://www.youtube.com/watch?v=ac6Hgz1dMG0