Why do I have .SEC files? (YI 4K+ Action Camera) .SEC files are much lower in bit-rate which allows you to quickly preview videos on the app. Related articles What is a .thm file? Video files cannot be played back.(YI 4K Action Camera) Where can I download YI Action Camera App?(YI 4K Action Camera) How to create an account in the Yi Home or Kami Home app? Why does the battery percentage indication display inaccurately?