[FFmpeg-user] Concatenating mp4 files rotates the video

[Ferdi Scholten]

> Anyways, what do I need to do to avoid these unrequested rotations?
Remove the rotation metadata of the original files if they have the same 
rotation,
Then concatenate the original video's using codec copy without loss of 
quality. (Converting to MPEG-2 does reduce quality (a lot) while 
creating much larger files).
After that simply add the metadata for the proper rotation again.