HTTP Live Streaming - HLS

HLS - HTTP Live Streaming

Şeklen şöyle. Burada verinin merkezi bir sunucu üzerinden aktığı görülebilir. Apple tarafından geliştirilen HLS, Flash'ın yerine geçti. Tarayıcı, televizyon ve telefonlarda çalışabilir.

Açıklaması şöyle.

HLS Technical Specifications

- Audio Codecs: AAC-LC, HE-AAC+ v1 and v2, xHE-AAC, Apple Lossless, FLAC.

- Video Codecs: H.265, H.264.

- Playback Compatibility: It was created for iOS devices, but is now supported  by: all Google Chrome browsers; Android, Linux, Microsoft, and macOS devices; several set-top boxes, smart TVs, and other players. 

- Benefits: Supports adaptive bit rate, it's reliable, and it's widely supported.

- Drawbacks: Video quality and viewer experience are prioritized over latency.

- Latency: HLS allows us to have 5-20 seconds of latency, but the Low-Latency HLS extension has now been incorporated as a feature set of HLS, promising to deliver sub-2-second latency.

Adaptive Streaming Nedir?

Açıklaması şöyle. Yani videonun farklı kalitelere göre daha küçük parçalara ayrılması ve gereken kalitedeki parçanın gönderilmesi

We then break the video into multiple small chunks; the resulting format will be an adaptive bitrate streaming format. 

HLS ve Adaptive Streaming

Şeklen şöyle

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HLS works like all adaptive streaming technologies. Multiple files are created for distribution to the player, which can adaptively change streams to make the viewer’s experience “perfect.” Since it is an HTTP-based technology, no streaming server is required, so all adjustments are made on the player device.

To distribute to HLS clients, the source is encoded into multiple files at different data rates and divided into short chunks (segments of data) which are usually around 10 seconds long. This process is also called segmented delivery. These are loaded onto an HTTP server along with a text-based manifest file with a .M3U8 extension that directs the player to additional manifest files for each of the encoded streams.

Segmented delivery allows the player to shift between different video qualities depending on available resources of the viewers’ conditions, while also driving down latency.

HLS vs MPEG-Dash

Açıklaması şöyle. Yani MPEG-Dash bir başka seçenek

There are different standards for adaptative bitrate streaming, like HLS or MPEG-Dash. The first one, HLS, is developed by Apple and is native on IOS. The Moving Pictures Group created the second one, MPEG-Dash, as an alternative to HLS.

Low-Latency HLS Nedir?

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Low-Latency HLS extends the protocol to enable low-latency video streaming while maintaining scalability. The new low-latency mode lowers video latencies over public networks into the range of standard television broadcasts.

HLS vs WebRTC 

Eğer latency önemliyse, WebRTC kullanmak gerekir.. Eğer video kalitesi önemliyse HLS kullanmak gerekir.