The Two Dominant Delivery Formats For Low Latency: HLS and DASH

Video consumption has massively increased in the past decade, thanks to younger demographics spending considerable time online watching video-based content. 

According to industry estimates, one-third of all online activity entails watching a video. More and more companies are competing to grab a slice of this lucrative video market, and the demand to deliver lower latency and improved playback has become higher than ever. Conversely, poor streaming quality will result in bad user experience and negatively impact a brand. As a result, companies have been upgrading their infrastructure to cope with the demand. 

This is where choosing a suitable streaming service plays an important role. 

What are Video Streaming Services? 

Delivering video over the internet happens over a set of protocols — and this is where streaming protocols come into the picture. With streaming protocols, rules are defined to govern how data travels from one communicating system to another, so that data can be delivered over the internet reliably and effectively. Online video delivery relies on both streaming protocols, as well as HTTP-based protocols.

In the past, the online video used to be delivered via RTMP (a flash-based standard) as a reliable streaming service. However, with the advent of the HTML5 standard for web applications, which support inbuilt video playback, the use of Flash for video streaming has been in decline. In 2017, Adobe announced it was pulling the plug on Flash,  one of the oldest formats used to deliver video content, in preference of HTML5. 

Video streaming is delivered by multiple technologies, all of which need to work together to deliver high-quality live streaming and video-on-demand to viewers.

Streaming protocols are similar to Real-Time Messaging Protocol (RTMP): both help in speedy video delivery. While RTMP uses dedicated streaming servers, HTTP-based protocols use regular web servers to optimize the viewing experience for users.

What is HLS?

Apple announced the launch of HLS (short for HTTP Live Streaming) at its annual Worldwide Developer Conference, as a protocol used to stream live video over the internet. In the beginning, HLS was only supported by iOS. However, HLS has now become a proprietary format with almost every device supporting it. As the name suggests, the HLS protocol delivers content via standard HTTP web servers. Hence, no unique infrastructure is needed to deliver HLS content. 

The initial disadvantage with HLS was that HLS support was limited to iOS devices, such as iPhones and iPads. However, native support has since been added. Since this was announced, a range of platforms — including Google Chrome browsers, Android, Linux, Microsoft, as well as macOS devices — now support streaming delivered using HLS.

Any standard web server or CDN can be used to deliver content over the HLS protocol. The advantage that HLS offers is that content is less likely to be blocked by firewalls when streamed over HLS. HLS can also play video encoded with H.264 or HEVC/H.265 codecs. In addition, HLS is an adaptive bitrate protocol. This means the client device and server can dynamically adjust the video quality in response to the internet speed of the user.

HLS provides excellent support for advertising standards (VPAID and VAST). Other HLS advantages include features such as embedded closed captions and synchronized playback of multiple streams.

What is MPEG-DASH?

DASH was developed between 2009 and 2012. It was created to present an alternative streaming protocol to Apple’s HLS. Before DASH, the streaming market had become fragmented and there were several streaming protocols competing with Apple’s HLS. The Moving Pictures Expert Group (MPEG) is an international authority on digital audio and video standards. It was pivotal in developing the Dynamic Adaptive Streaming over HTTP (DASH) as an open-source, vendor-independent, and global standard for adaptive bitrate.

The advantages of MPEG DASH are multifold — it supports DRM, HTTP delivery, lower-latency streaming, and several other features. MPEG-DASH is codec agnostic. So, it can support HEVC/H.265, H.264, VP9, and any other codec that you choose to use. 

Which streaming protocol is better and more reliable?

When choosing a streaming protocol, the following points are essential to consider: 

• What is the scalability offered? 
• How much latency is acceptable to your users?
• Quality of experience (i.e. Does your content delivery need to enable adaptive bitrate streaming?)
• Are you looking for proprietary or open-source technology?
• Any codecs requirements?

By defining what you are trying to achieve, you will be able to select the right protocol that suits your requirements. Latency, playback compatibility, and viewing experience can all be impacted by your choice of technology. Sometimes, content distributors don’t use the same protocol from capture to playback. For example, a number of broadcasters use RTMP to get from the encoder to the server and then transcode the stream into an adaptive HTTP-based format.

Apple’s HLS and MPEG DASH both are dominant technologies in the streaming market, and there is little difference in terms of the quality offered by both. HLS prioritizes the quality of experience over low latency. Also, HLS supports video codecs H.265, H.264, but MPEG DASH is codecs agnostic and can support whatever codecs you choose. 

The most significant advantage enjoyed by HLS over MPEG DASH is the range of supported devices. HLS should be supported on Windows, iOS, Android, Mac, Linux, Chrome OS, and other modern devices, like smart TVs, game consoles, and set-top boxes. 

However, the Safari browser, which is the default browser on most iPhone, iPad, AppleTV, and macOS devices, does not support MPEG-DASH. Hence, there are over a billion iOS users globally who don’t use MPEG DASH unless they are using a third-party browser. 

At Medianova, we provide global CDN solutions in streaming, encoding, caching, micro caching, hybrid CDN, and website acceleration. We have delivered and managed CDNs for leading enterprises and our state-of-art solutions are benchmarked against industry-leading quality parameters. 

Get in touch with us to learn more about how Medianova can build and manage a dedicated CDN for you.