I want to put rotation information in my mp4 video file, but I have no idea about it.
Is there any program that I can add “rotation” metadata to? It would be nice if there was a way to edit video content using the hexa editor.
+1 for FFMpeg. More specifically, I had good results correcting orientation metadata using
ffmpeg -i input.mp4 -metadata:s:v rotate=90 -vcodec copy -acodec copy output.mp4
Check out the FFMpeg software, use ffprobe to give you the rotation metadata of any video file, if any.
Check this answer for functions that allow you to rotate the video.