MP4Tools is a collection of free tools to manipulate MP4 files ... called
MP4Joiner and
MP4Splitter.
About
MP4Tools is a collection of cross-platform free tools to manipulate MP4 files. It contains following applications:
MP4Joiner is a free application that allows join multiple MP4 files into one without reencoding and without quality loss.
MP4Splitter is a free application that allows split a MP4 file in multiple files without reencoding and without quality loss
It is Open Source Software and is completely free.
Downloads
Windows binary: MP4Tools-3.7-win32.exe
Mac OS X binary: MP4Tools-3.7-MacOSX.dmg (OS X ≥ 10.10)
Source Code: MP4Tools-3.7.tar.bz2
https://www.mp4joiner.org/en/
http://sourceforge.net/projects/mp4joiner/