Adding "loop" atom to the video header?

[Vikram Parmar]

 Hi,

Is it possible to add some custom atom in the header of a video file?

I need to add the term "loop" in the header of MP4 files before the "moov"
atom.

More information can be found here :

https://stackoverflow.com/questions/44893316/whatsapp-
video-as-gif-sharing-on-android-programatically

Note: Just opening the video file using any text editor shows the file
header and atoms.

I do not want to edit the headers via too much calculations, as the answer
suggests. Is there a simple FFMPEG command to add the atom "loop" to any
MP4 files?

Use Case :-

WhatsApp does a smart thing. Their animated GIFs are actually MP4 files
(which contain this atom "loop"), and the MP4 files which it wants to treat
as videos in their UI, they do not add that "loop" atom

I tried loads of -loop and stream loop commands.. Nothing is adding the
atom "loop" to my mp4 files

My current command for converting a GIF to MP4 is as follows :

ffmpeg -i giphy9.gif -c:v libx264 -c:a aac -pix_fmt yuv420p -movflags
> +faststart  giphy9_loop.mp4
>

I wish to add some parameter to the above command (or maybe run a separate
command) so that the output mp4 file has that "loop" atom in the header.

Please help!
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