Using Ubuntu 18.04 I have some screencast video files in mp4 container (h.264/mp3 codecs) that I want at times merge (i.e. C.mp4 = A.mp4+B.mp4) or at times cut removing some intervals (e.g. D.mp4 = A.mp4[0,320{seconds}]+A.mp4[325,340]+C.mp4).

I am now using kdenlive, it woks but it re-encode everything and it seems a bit too much for such a task.

Is there a simpler way to do that without re-encoding (even, and perhaps preferred, command line or stable Python/Julia/R/.. way) ?

I am thinking at something like PDFtk for the pdfs :-))

PS: I did try `ffmpeg -ss 00:00:05 -to 00:00:10 -i test1.mp4 test2.mp4` but I have an error:

> 
> Option to (record or transcode stop time) cannot be applied to input
>  url test1.mp4 -- you are trying to apply an input option to an output
>  file or vice versa. Move this option before the file it belongs to.
> 
> 
> 

My files have the same container, codec and resolution.

(I know nothing of video stuff..)

EDIT: I don't want to look pessimistic, but more I look on it more I behave that what I thought to be super simple is indeed super complicate. What a pity nobody wrote a high-level interface to perform something like that.. I'm sure I am not the first one with such a need.. 

EDIT2: I found [moviepy](https://pypi.org/project/moviepy/), but it is still far from my original idea (it re-encodes and it has longer than needed API.. I can script it but the reencoding problem remains):

```
pip install moviepy

from moviepy.editor import VideoFileClip, concatenate_videoclips
c1 = VideoFileClip("test1.mp4").subclip(0,5)
c2 = VideoFileClip("test1.mp4").subclip(10,15)
f = concatenate_videoclips([c1,c2])
f.write_videofile(test2.mp4)

```