Aeyae Remux is a video joiner and remuxer based on Group Of Pictures - Still in Beta.
https://sourceforge.net/projects/aeyae-remux/Aeyae Remux can be used to extract portions of original video into a separate file. Aeyae Remux is a GOP-based editor (GOP = Group Of Pictures), which means it doesn't do any transcoding, only remuxing. However, it can truncate a GOP.
Aeyae Remux can be used to stitch together files... within reason. Since it is only a remuxer -- stitched files must be of compatible format. This means stitched files must have the same audio/video codecs, and codec properties (width, height, sample rate, etc...). That said... Aeyae Remux currently doesn't check or enforce this restriction, so beware -- garbage input will likely produce garbage output.
Linux binaries are provided as AppImage, built on Ubuntu 14.04.
8 GB of RAM (but more is better) is highly recommended if working with source files longer than 2 hours.
Features
video editor
remuxer
GOP viewer
https://sourceforge.net/projects/aeyae-remux/
https://github.com/pkoshevoy/aeyae