The official TED Talks app allows to swithc between subtitles.
I want an upgraded version:
1. to be able to view 1, 2 or 3 subtitle tracks simultaneously.
2. to automatically convert Japanese subtitles into additional furigana subtitle track, auto convert Chinese into pinyin track, and auto convert Korean into photnetic subtitle track.
3. to keep the original app's functionality to download the videos and watch them offline.
Details by e-mail or here.