The Moving Picture Expert Group, better known by its acronym MPEG, started designing MPEG-DASH in 2010. Here is an example of a basic implementation: Hls.js has a very complete (and very well documented!) API which allows to manage the video and the stream directly from Javascript. Used in particular by Dailymotion, hls.js is compatible with a large number of browsers and includes advanced features, such as adaptive streaming management or multi-threading (if the client browser is compatible) to improve, among other things, the fluidity of caching. The open-source library hls.js is certainly one of the most viable when it comes to implementing a client managing HTTP Live Streaming.

The following diagram illustrates this possibility very well: Thus, the compatible client will be able to switch from one quality to another in real time, depending on the available bandwidth or the user’s choice. #EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=1755600,CODECS='avc1.42001f,mp4a.40.2',RESOLUTION=640x360Įach #EXT-X-STREAM-INF tag indicates the data needed to read the segment, each of them of a given quality and encoding. The example M3U file below is from a live broadcast of the platform: The segmented files, usually in MPEG-2 TS format, are accessed via a “manifest”, an index file in M3U format that describes content segments as well as metadata that the client can/must use. Here we see the workflow that allows the raw audio/video to reach the client as a stream. How does it work ?Ī diagram explains it better than a long speech:

The Twitch.js platform, the world’s leading gaming streaming site (owned by Amazon), will serve as an example throughout this section. Major streaming platforms use this protocol to serve their live video streams or replays. Like other protocols serving the same purpose, HLS sends audio and/or video segments of a given length, leaving it up to the client to chain the display of these segments. As its name indicates, this protocol uses HTTP as a transport protocol, which makes it very adaptable and easily usable via Nginx, Apache or any web servers. HLS (HTTP Live Streaming) is an audio/video streaming protocol designed by Apple in the late 2000s, originally for the QuickTime player.

HLS and DASH will be detailed here in order to understand how they work in general.

This article deals with the two main technologies allowing video streaming via a web application. Despite being used by big names like Apple, Microsoft, Youtube or Netflix, video streaming technologies are not among the best known.

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