HLS HTTP Live Streaming

HTTP Live Streaming (also known as HLS) is an HTTP-based media streaming communications protocol implemented by Apple Inc. as part of their QuickTime X andiPhone software systems. It works by breaking the overall stream into a sequence of small HTTP-based file downloads, each download loading one short chunk of an overall potentially unbounded transport stream. As the stream is played, the client may select from a number of different alternate streams containing the same material encoded at a variety of data rates, allowing the streaming session to adapt to the available data rate. At the start of the streaming session, it downloads an extended M3U (m3u8) playlistcontaining the metadata for the various sub-streams which are available.

Since its requests use only standard HTTP transactions, HTTP Live Streaming is capable of traversing any firewall or proxy server that lets through standard HTTP traffic, unlike UDP-based protocols such as RTP. This also allows a Content delivery network to easily be implemented for any given stream.

Apple has documented HTTP Live Streaming as an Internet-Draft (Individual Submission), the first stage in the process of submitting it to the IETF as an Informational Standard. However, while Apple has submitted occasional minor updates to the draft, no additional steps appear to have been taken towards IETF standardization.^[1]