[FFmpeg-user] Preserving 'udta' atom when using -movflags +faststart

[Julian Cooper]

Hi,

I'm using the ffmpeg CLI to pre-process AVC and HEVC MP4s. Part of that
pre-processing involves moving the 'moov' atom to the head of the MP4. The
'moov' atom contains a 'udta' with metadata I would like to preserve. The
'moov/udta' atom is being dropped when calling:

ffmpeg -i source.mp4 -c copy -movflags +faststart faststart.mp4

https://trac.ffmpeg.org/ticket/6800 seems to be related, but I thought I
would double check to see if the ffmpeg CLI has the capability to preserve
the 'udta' atom before digging into the source.

Thank you,
- Julian