[FFmpeg-user] Loss of mp4 metadata when copying

[Andrew Brezovsky]

I have been trying to modify the handler_name metadata field of an audio
stream in a video file within an mp4 container.
However, ffmpeg seems to be discarding the handler_name field and replacing
it with a generic "SoundHandler" value.
While the values in the input and output read-outs are correct, at the end
of the copy I see "[mp4 @ 0x558cdfba2000] Unknown hldr_type for text,
writing dummy values".

Here is the command I'm trying to use:
ffmpeg -i mystery_source.mp4 -map 0 -map_metadata 0 -c copy -metadata:s:a:0
handler_name="Stereo" mystery.mp4

Here is the output: https://pastebin.com/r8kgt7Ny

I am trying to change these as I forgot to modify the name of the audio
stream when transcoding with HandBrake. I am trying to avoid re-encoding
the file just to rename the audio track (so it appears correctly in
programs such as VLC).
Thanks for any help.


-- 
Andrew Brezovsky
abrezovsky at gmail.com