translation.en: Teaching a computer to read these facial emotions is hard, because these action units, they can be fast, they're subtle, and they combine in many different ways.
translation.zh: 教会电脑去读取这些面部情绪很难， 因为这些动作单元行动很微妙，而且稍纵即逝， 而且它们有很多的组合方式。