How to change rotation header field for MP4 video without re-encoding?

[pstein]

As far as I know the  file header of an MP4 video contains some information about the auto-rotation of a video file when played in video player (e.g.VLC).

So I guess users can change this header field (e.g. to 90deg clockwise) without re-encoding the full video.

How does this work in Avidemux?

Peter

[eumagga0x2a]

This is not possible in Avidemux, but you can set the field using ffmpeg with the -metadata option (https://stackoverflow.com/questions/15335073/can-i-set-rotation-field-for-a-video-stream-with-ffmpeg). First edit the video in Avidemux, then set the field with ffmpeg, otherwise it will be discarded.