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? Why do I have .SEC files? (YI 4K Action Camera) What is the bitrate for each resolution? What are the requirements for my microSD card?(YI 4K Action Camera) Why are the photos and videos distorted on the margins?(YI 4K+ Action Camera)