There's a related question at SO, but that's about exporting the metadata to a text file. And here is syntax for adding metadata back into a video file using ffmpeg. So I used this syntax to export the ffprobe output to a file, and used the previous command to save it to a new video file with the metadata... to no avail. Any suggestions?
ffprobe -v quiet -show_format -show_streams in.mp4 > in.txt ffmpeg -i in.mp4 -f ffmetadata -i in.txt -c copy -map_metadata 1 out.mp4