caf muxer doesn't obey Apple Core Audio Format Specification 1.0, section Information Entry Keys
|Reproduced by developer:
|Analyzed by developer:
Apple reserves keys that are all lowercase.
Application-defined keys should contain at least one uppercase character.
Each key can be used only once. You can specify multiple values
for a single key by separating the values with commas.
ffmpeg just directly writes it's internal tag key. It doesn't convert to upcase keys, nor it does respect predefined keys by Apple.