Hackernoon logoWhat is the HLS Streaming Protocol and How Does it Work? by@antmedia

What is the HLS Streaming Protocol and How Does it Work?

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@antmediaAnt Media Server

Ant Media provides a scalable and adaptive WebRTC based Ultra Low Latency Video Streaming Platform.

HTML5 live streaming solutions have become more popular lately. One of them is the HLS protocol. There are some reasons why this is so popular, the most important of which is that RTMP lost its support by the end of 2020. 

In 2017, Adobe announced that it will no longer support RTMP after the end of 2020. After this date, the question of what is HLS gained more importance. Adobe’s RTMP protocol is now a thing of the past.

However, will it be beneficial for viewers and broadcasters to switch to HLS and therefore HTML5? We mentioned one of the most important reasons above. HTTP-based protocols deliver the best video quality and viewer experience possible regardless of the connection, software, or device.

But, it is necessary to plan this change process well. Although HTML5 protocols are exciting technologies, the transition to HTML5 protocols requires time and effort. As we mentioned, HTML5 standards deeply affected the live streaming world.

In this blog post, you will find the answer to the question of what is HLS streaming, learn the advantages of HLS and its technical information, and at the same time, you will see why you should switch your live streaming solution to HLS.

Let’s dive into the definition of HLS!

What is HLS Streaming Protocol (HTTP Live Streaming)?

So, what is HLS? HLS stands for HTTP Live Streaming. HLS is an adaptive HTTP-based protocol used for transporting video and audio data from media servers to the end-user’s device.

HLS was created by Apple in 2009. Apple announced the HLS at about the same time as the legendary device iPhone 3. Earlier generations of iPhone 3 had live streaming playback problems, and Apple wanted to fix this problem with HLS.

Features of HLS video streaming protocol

  • Closed captions
  • Fast forward and rewind
  • Alternate audio and video
  • Fallback alternatives
  • Timed metadata
  • Ad insertion
  • Content protection

HLS Technical Specifications

  • Audio Codecs: AAC-LC, HE-AAC+ v1 & v2, xHE-AAC, Apple Lossless, FLAC
  • Video Codecs: H.265, H.264
  • Playback Compatibility: It was created for iOS devices. But now all Google Chrome browsers; Android, Linux, Microsoft, and macOS devices; several set-top boxes, smart TVs, and other players support HLS. It is now a universal protocol.
  • Benefits: Supports adaptive bitrate, reliable, and widely supported.
  • Drawbacks: Video quality and viewer experience are prioritized over latency.
  • Latency: HLS allows us to have 5-20 seconds latency, but the Low-Latency HLS extension has now been incorporated as a feature set of HLS, promising to deliver sub-2-second latency.

What is Low-Latency HLS?

Here’s how Apple explained Low Latency HLS:

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.

What is a Protocol?

Yes, HLS is a live streaming protocol. But, it is useful to explain this term protocol, which we constantly hear.  So, What is a streaming protocol? A streaming protocol is a standardized method of transmitting video or audio content between devices over the internet.

A video streaming protocol sends “chunks” of video or audio content from one device to another device. The method of converting these “chunks” into replayable content on the player device is called the “reassembling” method.

For a successful process, the end device must support the protocol used by the sender. Otherwise, it will not be possible to play the broadcast. Another important point is that the protocol is thought to mean the same as the codec. 

What is a codec?

Codecs are compression technologies with two components; an encoder to compress the file in the first device and a decoder to decode the file when played by the end device(viewers)

HLS supports many popular codecs such as:

  • Audio: AAC-LC, HE-AAC+ v1 & v2, xHE-AAC, Apple Lossless, FLAC
  • Video: H.265, H.264

How Does HLS Work?

Now that we’ve answered the question of what is HLS video streaming, we can go one step further. Before comparing HLS with other solutions, it would be better to learn how HLS works.

Image Source: Streaming Media

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 viewers’ conditions, while also driving down latency.

Advantages of HLS Streaming Protocol

The biggest advantage of HLS is its wide support area. HLS is currently the most used streaming protocol. However, the HLS protocol offers a latency of 5-20 seconds.

HLS’s adaptive-bitrate capabilities ensure that broadcasters deliver the optimal user experience and minimize buffering events by adapting the video quality to the viewer’s device and connection.

Players can automatically adapt and adjust for changes in network speed, preventing stalls when the local connection is unstable.

Devices and Browsers that Support HLS

As we said, the HLS streaming protocol is supported by a wide range of devices and browsers.

Once limited to iOS devices such as iPhones, iPads, and iPod Touch at the time of its release, HLS is now supported by the following devices and browsers:

  • All Google Chrome browsers
  • Safari
  • Microsoft Edge
  • iOS devices
  • Android devices
  • Linux devices
  • Microsoft devices
  • macOS platforms

When to use HLS?

As we said, HLS is currently the most used streaming protocol. Which is why live broadcasters have definitely heard of HLS. HLS can be used in streams where video quality is important but latency is not much more important. Examples include Sports Competitions and event broadcasts.

When not to use HLS?

If you care about delay and interaction in your broadcasts, HLS is not for you. If you are looking for a solution in a field such as video conferencing and game shows, the best and only solution for you is WebRTC

HLS vs RTMP

RTMP is a protocol, created by Macromedia and now owned by Adobe, that provides high-performance transmission of video, audio, and data between dedicated streaming servers and Adobe Flash Player across the internet. RTMP is created for high-performance transmission of media such as audio and video data.

However we left 2020 in the past, so this is the death time of Flash Player and also RTMP. Adobe will stop updating and distributing the Flash Player. We said above that HLS is the most popular protocol. With the fall of RTMP, this popularity seems to increase even more. 

It is time to move from RTMP to HTML5 solutions.

HLS vs WebRTC

We answered the question of what is HLS streaming and talked about HLS enough and learned its positive aspects. The worst feature of HLS is that it provides high latency. If latency is important to you, WebRTC is the right choice.

WebRTC(Web Real-Time Communication protocol) is an open-source standard for real-time communication supported by almost every modern browser, including Safari, Google Chrome, Firefox, Opera, and others. That support ensures that the WebRTC standard remains up to date and functional for the foreseeable future.

Thanks to WebRTC video streaming technology, you can embed the real-time video directly into your browser-based solution to create an engaging and interactive streaming experience for your audience without worrying about the delay. WebRTC provides sub-second delay – 0.5 seconds.

One of the other most important features of HLS was its scalability. On the other hand, WebRTC successfully responds to the need for scaling. Here’s our blog post on scaling WebRTC to 70k viewers.

As a result, the HLS streaming protocol is a protocol that every broadcaster should have on one side of his/her mind. 

Previously published at https://antmedia.io/what-is-hls-streaming/

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