Latency describes the time between a video stream and the start of its transmission. A good example of the importance of low latency is the live transmission of big sports events. Imagine yourself sitting on the couch with some friends, chicken wings, and beer watching the Superbowl, and suddenly, your neighbor screams, while nothing has happened so far in the game, you’re watching. Maybe your neighbor has a better stream connection with lower latency, so his stream is closer to real-time than yours. For spoiler-prevention, it is crucial to have the lowest possible latency during your live events.
But about how many seconds delay are we talking, when it comes to a standard grade of latency? The typical latency when it comes to live streaming is about 30 to 50 seconds. That doesn’t matter when streaming a concert or show event, but when it comes to sports events, video chat, or everything else where you need a real-time connection, you can reduce the latency to up to under 1 second. Depending on how high or low the latency is, you’re talking about (typical) latency (19-50 seconds), reduced latency (5-18 seconds), low latency (1-5 seconds), and near real-time / ultra-low latency (under one second).
Several factors cause latency. Significant can be the streaming protocol, the player, the length of the segments (when using adaptive bitrate streaming), the CDN used, and much more. This is exactly where to start to reduce your latency. With some optimizations of the player and the streaming protocol and the segment length, a significant reduction of latency can be achieved.