MP4 File Structure Explained: Boxes, Atoms, and Tracks - Sima Labs
It is the backbone of protocols like MPEG-DASH and HLS , allowing your player to switch between different video qualities (e.g., 4K to 720p) instantly without buffering if your internet speed drops. dfrmp4
It reduces "startup latency" by placing critical index information (the moof or sidx boxes) at the beginning of each fragment. MP4 File Structure Explained: Boxes, Atoms, and Tracks