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.