How to Differentiate Subtitle Track Language Between Simplified and Traditional Chinese? I'm using MP4Box (command line tool) to add subtitles to mp4 movies. The language of the subtitle seems to be set using ISO 639 codes. There's no differentiation between Simplified and Traditional Chinese in ISO 639 (as the difference is not in the language, but in the script).

My question is: Does the MP4 format allows making this differentiation, and if so, how?

Thanks in advance for your answers.
You should be able to define you own 3 character long language code for imported media using the option :lang=LAN when specifying your media file for import. LAN being your own language code. So you could use something like SCN and TCN.