[raymond_goo]

Explanation: HTTP Live Streaming slices the bitstream into “segments” (traditionally 6–10 s each) and only starts playing after it has downloaded several of them. Out of the box that means 30–60 s of startup and live-edge latency—fine for linear TV, terrible for anything interactive.

Apple’s LL-HLS spec shrinks those segments into “partial segments” and uses CMAF to let the player start decoding while a chunk is still arriving. With careful encoder tuning, HTTP/2/3 push, CDN support, and a compatible player you can reach 2–5 s, sometimes a bit lower—but every link in the chain has to cooperate, so implementations are still called “heroic” for a reason.

Safari plays HLS natively and on other browsers you can bolt on hls.js via Media Source Extensions. DASH, RTMP, SRT, etc. all need extra code or plugins, so HLS became the “safe default” for on-demand and broadcast-style streaming even though it isn’t low-latency friendly.