HLS
HTTP Live Streaming
HLS is a streaming protocol that was developed by Apple which is based on HTTP communication. It fully supports adaptive bitrate streaming and was released in 2009. A lot of the streaming video services for Apple devices such as iPhones, iPads and AppleTVs are using HLS streaming.
HLS streaming breaks the overall streaming content into a sequence of fragments, or "chunks", which are smaller files that can be transferred over a HTTP connection. The client will download these fragments and concatenates them together to re-create the contiguous stream.
To start playing out a stream, the video client requests a manifest file over the HTTP connection. This file typically has the extension .m3u8. This manifest, which is a text file, is often referred to as a Master Manifest. It provides information about the streaming, including the ABR bitrate ladder. For each such bitrate, there is then a subsequent Child Manifest, which specifies the actual file fragments that the client needs to download. The fragments are presented in an ordered playlist, with additional information including e.g. markers for ad insertion.
LINKS