LosslessCut
The swiss army knife of lossless video/audio editing
...Everything is extremely fast because it does an almost direct data copy, fueled by the awesome FFmpeg which does all the grunt work. Lossless merge/concatenation of arbitrary files (with identical codecs parameters, e.g. from the same camera). Lossless stream editing: Combine arbitrary tracks from multiple files (ex. add music or subtitle track to a video file).