The acronym HLS stands for HTTP live streaming. Before Apple introduced HLS, the main method of delivering video over the internet was Adobe’s Flash video technology. In 2009 with the debut of the iPhone 3, Apple launched the HLS media streaming protocol. Soon after that it replaced Adobe flash protocol in many online OTT platforms. So let’s know what exactly HLS is and what bigger advantage it has.
What is HLS
HLS (HTTP Live Streaming) is an HTTP-based streaming communication protocol created by Apple for live and on-demand streaming. It enables a receiver to adjust the bit rate of the media to the current network conditions in order to ensure uninterrupted playback at the highest quality feasible.
Your video will be compressed, divided into chunks, and sent over HTTP if you use the HLS protocol. All of those pieces will be reassembled into a playlist by HLS, and your viewer will only see a consistent stream of content.
Unlike UDP protocols like RTP, HTTP can pass over firewalls and proxy servers. It makes the content available in different HTTP based networks which is taken from the typical HTTP servers. With the use of HTTPS conventional encryption mechanism and secure-key distribution is offered as a DRM system for legal access to the digital content .
How does HLS work
At a high level, HLS works like all adaptive streaming technologies; it creates multiple files for distribution to players, which can adaptively change streams to optimize the playback experience. As an HTTP-based technology, no streaming service is required, so all the switching logic recedes on the player.
To distribute to an HLS client, it encodes the source into multiple files at different data rates and divides them into short chunks, usually between 5-20 seconds long. HLS uses this chunk based data transfer method that enables smooth streaming even over unreliable networks. These are uploaded onto HTTP server with text based manifest files which have M3U8 extension so that the player could avail extra manifest files in each of the encoded streams.
The playlist file, containing M3U8 file extension, has a minimum of three chunks of TS files in MPEG-2 media format. The user downloads a M3U8 playlist that contains many URIs.In order to get an uninterrupted stream, the playlist must be updated with the production of MPEG-2 files along with product URIs.
This process creates a seamless experience for users even at different bandwidth levels.
A Direct comparison between HLS and other protocols
HLS vs MPEG-DASH
MPEG-DASH is a method of streaming. DASH is an acronym that stands for “Dynamic Adaptive Streaming over HTTP.” Because it is HTTP-based, any origin server can be configured to serve MPEG-DASH streams.
MPEG-DASH, like HTTP Live Streaming (HLS), is a streaming protocol that divides videos into smaller chunks and encodes those chunks at various quality levels. This allows you to stream videos at different quality levels and switch from one to another in the middle of a video.
HLS and MPEG-DASH, both follow adaptive bit-rate protocols to deliver the content. And in most of the cases they are proved to be reliable, with little to no difference between them.
Such as, both support 4k resolution, HDR ( High Dynamic Range), which can deliver a wider color gamut and better tonal rendition.
HLS has undergone many changes to eliminate the gap and sometimes proved to be a better protocol. But one thing HLS beats DASH is MPEG-DASH does not support mobile safari browsers. And with a billion of audience using ios devices, one cannot afford to avoid them.
HLS vs RTMP
Adobe’s Real Time Messaging Protocol (RTMP) is a bidirectional message multiplex service that uses a reliable stream transport protocol like TCP [RFC0793] to convey concurrent streams of video, audio, and data messages, as well as associated timing information, between two interacting peers.”
RTMP is ideal for low latency, but it has become outdated in recent years, and because it is based on Flash, it may be incompatible with some browsers and devices.
It has many disadvantages which are being covered by HLS, and thus proving it a much better protocol than RTMP.
Such as, It does not have native iOS support. RTMP does not work in HTML5, it differs from the HTTP Protocol, and video delivery security is minimal. Whereas, HLS is a pocket-friendly protocol which is Compatible on all the platforms and supports HTML5 video player.The most significant advantage of HLS is its ability to deliver adaptive bitrate streaming, which allows for high pixel-rate content quality.
HLS vs MSS ( Microsoft Smooth Streaming )
Another example of HTTP-based streaming is Microsoft’s Smooth Streaming, which enables adaptive streaming of on-demand and live media over HTTP to clients such as Silverlight. Smooth Streaming optimizes content playback by switching video quality in real-time by dynamically monitoring available bandwidth and video rendering performance. Users with high bandwidth connections and the latest computers, for example, can enjoy full HD 1080p quality streaming, whereas users with lower bandwidth or older computers receive a stream that is more appropriate for their capabilities. Despite being backed by such a huge industry leader it has miserably failed to compete with protocols like HLS and DASH due to many limitations.Microsoft announced the end of Silverlight support in October 2021, limiting browser support for Microsoft Smooth Streaming streams.
HLS vs RTSP
RTSP is an application-layer protocol that is used to control streaming media servers via pause and play functions. It does not transmit data, rather it communicates with the server to establish real-time control over streaming media. To move the actual streaming data, RTSP servers frequently use the Real-Time Transport Protocol (RTP) in conjunction with the Real-Time Control Protocol (RTCP).
In this comparison HLS stands far more above RTCP. This is because RTCP has a lot of drawbacks and is not compatible with modern era platforms. Such as, It lacks application-level error correction (and frequently runs over UDP, which lacks transport layer error correction), so any network instability results in dropped frames, macroblocking, or other visual artifacts. It works with the video bitrate.
RTSP is also difficult to cache for widespread distribution. As a result, it is rarely used for internet-based streaming. It works best in networks where the operator has complete control over the network environment.
HLS, on the other hand, is extremely resilient to network variability. HLS is also capable of adapting to changing bitrates. Because it is an HTTP transfer, browsers and existing caching and content delivery networks support it well.
In today’s growing demand for on-demand and live streaming platforms, it is crucial to have a robust infrastructure and strong streaming protocol. HLS has proved to be the one to meet all the demand by constantly updating itself and eliminating the gaps. With this it can be considered as the most compatible streaming protocol of all.
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