MPEG-DASH (Dynamic Adaptive Streaming over HTTP) Explained

Apple’s HTTP Live Streaming (HLS) is probably the most popular protocol. BUT, the up-and-coming, open-source MPEG-DASH streaming technique (it’s actually not a protocol, more below) is well on its way to kicking HLS off its throne!

While both types of streaming offer closely similar features, MPEG-DASH has gained momentum as the newest streaming solution available, providing some strong competition preventing HLS from completely dominating the streaming world. And while it was at first an unknown quantity, DASH has been steadily gaining native support from electronics and technology companies as well as from popular video streaming platforms. Head down below for in-depth details about what MPEG-DASH does and whether it would be a good fit for you to use it.

Jump to:

• What is MPEG-DASH (Dynamic Adaptive Streaming over HTTP)?
• How does MPEG-DASH Technology Work?
• MPEG-DASH HLS: Pros & Cons
• Who is Currently Using MPEG-DASH?
• Private or Commercial Use?
• Key MPEG-DASH Players & Devices
• Is MPEG-DASH Patent Protected?
• Meet Kaltura’s Streaming Solutions
• Final Thoughts

What is MPEG Dash (Dynamic Adaptive Streaming over HTTP)?

As the header indicates, MPEG-DASH is short for “Dynamic Adaptive Streaming over HTTP”, the MPEG part refers to the Moving Picture Experts Group, comprised of experts from industries, universities, and research institutes, who set standards for media coding, transmission, and file formats for varied applications. (Yes, this is where the .mpeg / .mpg video file format also originated.)

Sometimes called just DASH, it’s one of the newest streaming techniques. Note here that strictly speaking MPEG-DASH is not an actual protocol. The transport protocol that DASH uses is TCP, and the solution leverages the existing HTTP web server infrastructure that is used for the delivery of “essentially all World Wide Web content.”

DASH was developed on the heels of HLS in 2010-2011 and first published as a standard in 2012. The MPEG group developed the format during the rising years of video streaming when several different protocols were still competing on the market. It was unknown which, if any, would end up the most widely preferred and adopted. In response to the cluttered streaming market, DASH was developed by international standards organizations to provide an alternative, unifying streaming standard that would not be exclusively controlled by any company and was based on open-source technology. Additionally, MPEG-DASH is a “codec-agnostic” streaming solution meaning it can use content that is encoded in any format.

How does MPEG-DASH Technology Work?

MPEG-DASH streaming has 3 primary steps

Encoding and Segmentation: The video server where the file originates divides a video file into smaller pieces for streaming (i.e. “segments”) which are a few seconds in length. Also, the server creates an index file for the video segments, something similar to a table of contents for a book or site. The segments are encoded, a process that formats them in a way suitable for multiple devices to playback. As mentioned, DASH is an “agnostic” format that can be used with any encoding standard.

• • This will include an MPD file describing how the video is split and segmented, arranged, and will be delivered (i.e. the index file).
  • The packaged video is stored on a server and usually served through a CDN.

Delivery: Encoded videos are sent out to client devices over the Internet. Per the Step 1 encoding process, when users decide to watch a stream, their player is making a request to a server, which then sends out the encoded video segments to be interpreted and played back by the device. In most cases, the stream travels through a content delivery network (CDN) that more efficiently distributes video content.

• • The player downloads the index file first to determine the mechanics of serving the video, checks available bandwidth, and then begins a playback session.

Decoding and Playback: User devices receive streamed data, decode it, and play back video. DASH uses adaptive bitrate, allowing the video player to automatically adjust to network conditions and switch to lower or higher quality resolution. For example, when a user’s bandwidth is low, streamed video will play at a lower quality level to use less bandwidth. However, while technically a “lower quality” picture, the adaptive streaming experience still delivers a good quality video free of blurring and pixelation and/or sudden starts and stops. It’s simply played at a lower resolution; for example, a 480p image (what used to be considered “standard definition”) vs. a 1080p HD image.

• • When downloading and playing, the player requests chunks/segments from one of the video’s bitrate variants depending on its buffer size and available bandwidth.
  • By continuously monitoring bandwidth and buffer levels, the player adaptively streams the content to provide a good user experience.

Additionally, MPEG-DASH leverages adaptive bitrate streaming to provide the best quality viewing experience over the widest range of devices.

“Adaptive Bitrate Streaming,” or ABR (also sometimes referred to as adaptive streaming) is the basis of today’s leading delivery formats, both HLS and DASH. ABR means that the streaming technology can detect bandwidth and CPU capacity on the device it streams to, and automatically adapts to the capabilities of the device to provide the smoothest experience possible.

Let’s look at one other more technical aspect of functionality–the ABR “bitrate ladder”. In ABR streaming videos are transcoded into multiple resolutions and bitrate combinations. Each of these is referred to as a rendition, and a collection of renditions is a bitrate ladder.

A typical bitrate ladder could look like this:

• 1080p – 5.0 Mbps
• 720p – 4.0 Mbps
• 640p – 3.2 Mbps
• 480p – 2.0 Mbps
• 270p – 1 Mbps

For example: If a player plays back a video that has been encoded on the above bitrate ladder, it senses the available bandwidth. If the example bandwidth was 20 Mbps, it’s much higher than the highest bitrate on the ladder, 5 Mbps, so the player downloads the highest bitrate for the first video chunk (which is likely 6-10 sec long, see below). The player will then check the bandwidth again–if it is still high, it will ask for the highest bandwidth again.

If the bandwidth were to drop to around 4 Mbps, though, the player’s next request would be for the 3.2 Mbps (640p) chunk from the server–it would be risky to ask for the chunks encoded at 4 Mbps or 5 Mbps, there could be playback issues. It then plays the segment back, checks bandwidth again, and so forth. Now you have a sense of how ABR does its job.

Since ABR is a key feature for both HLS and MPEG-DASH, we’ll delve a little deeper into the distinctions between the two below.

MPEG-DASH vs. HLS: Pros & Cons

Both types of streaming are similar in several ways:

Both HLS and MPEG-DASH run over HTTP and use TCP as a base for their transport protocol (or in the case of DASH, as its actual transport protocol). They compress and segment video into small chunks and an accompanying index file and use ABR streaming to send them sequentially to a device. They both optimize for the speed of your hardware and data connection to minimize playback problems

However, there are outstanding differences. To begin with, HLS is a proprietary protocol developed by Apple and while it has wide support, has not been published as an international standard. DASH on the other hand was conceived to be an international standard and doesn’t belong specifically to one company or organization.

Related to this, MPEG-DASH allows the use of any encoding standard, while HLS is limited to using Apple’s H.264 or H.265 encoding.

As you might guess, HLS’s proprietary nature means that it’s also the only format natively supported on Apple devices. If you use an iPhone, MacBook, or other Apple products there is no support for video delivered over MPEG-DASH in the default Safari browser. This is easily remedied on Mac computers by downloading an alternative browser, but users dependent on the mobile version of the Safari browser (iPhone, iPad) or using AppleTV have an obstacle.

On a slightly more technical level, the two technologies also have a slightly different default video segmenting length. HLS segments default at 6 seconds, though they can be adjusted to a different length. MPEG-DASH segments between 2 and 10 seconds; optimal length is usually considered to be 2-4 seconds.

In general, HLS has gained a certain amount of popularity and market share and DASH is a newer streaming method that’s still unproven in some areas. However overall DASH is an equally powerful alternative to HLS should you decide to use it.

Who is Currently Using MPEG-DASH?

As online video streaming has exploded over the past few years, the popularity of MPEG-DASH has also expanded. DASH is now widely used to deliver media through VOD or live streaming to a variety of end-user devices including TVs, consoles, PCs/laptops, smartphones, and more. As mentioned, Apple devices put up a barrier to use and adoption, but it’s widely supported across other devices and therefore by other companies. Examples of compatible players include JWPlayer, Android Exoplayer, and Roku.

There is additionally a DASH Industry Forum that consists of major streaming and media companies including Microsoft, Netflix, Google, Samsung, Adobe, and numerous others who are guiding the adoption of DASH and creating guidelines for different use cases. Finally, broadcasters and other hardware manufacturers have been adopting support for MPEG-DASH in a variety of devices used in streaming workflows as well as end-user viewing devices: the TVs, consoles, and other consumer electronics mentioned above. Very popular streaming platforms such as YouTube and Netflix also support MPEG-DASH.

Private or Commercial Use?

As demonstrated in the above section, commercial use of MPEG-DASH is already widely adopted. Its utility over streaming networks, players, and end-user devices has been proven. Additionally, its (for the most part) open-source and typically cost- and royalty-free implementation has made it popular for many commercial uses.

Depending on your private use case MPEG-DASH also could be invaluable; inward-facing streaming videos such as live events, conferencing, virtual events or courses, and other streaming videos will perform well using DASH. One key evaluation is, subject to DASH’s limitations, will many of your users be accessing video through Apple devices? If so, it might be wise to default to HLS, though you can encode in both if you choose.

Key MPEG-DASH Players & Devices

MPEG-DASH is widely supported by player companies, many popular streaming platforms, and several hardware and electronics companies.

As noted above, YouTube and Netflix support DASH, as does the Roku player and Chromecast. It’s also supported as a part of the Android ecosystem: phones, TVs, and other devices. Since Apple products can be prohibitively expensive in many parts of the world, this is still an important segment of the global consumer market.

Some of the more well-known and well-used media players supporting MPEG-DASH also include:

• VLC Media Player
• Android Exoplayer
• js
• Bitmovin

Devices supporting DASH include a list of consumer electronics from some very prestigious companies:

• Samsung Smart TVs from 2012-forward
• LG Smart TV from 2012 onward,
• Sony TV, 2012 and onward
• Philips NetTV 4.1 and forward
• Panasonic Viera, 2013 onward

And of course, a large number of servers and services, including:

• Kaltura
• Akamai CDN
• Amazon Cloudfront CDN/Amazon Web Services Elastic Transcoder
• Cloudflare
• … and many more!

Is MPEG-DASH Patent Protected?

DASH has been marketed as open-source, and for the most part, this is the case, however a “DASH patent pool” did exist as of 2019. However, the latest website content from licensing company MPEG-LA seems to indicate a “patent portfolio license” is no longer offered to new licensees. Check the links for additional details, however, it seems most likely that DASH can be used freely at this point without issues of royalties arising.

If you have further questions or are looking for a more in-depth resource regarding whether there would be any issues of infringement regarding your implementation of MPEG-DASH, we’d also recommend visiting the previously mentioned DASH Industry Forum website and checking for updates on patent status.

DASH-IF, as it’s called, is dedicated to the standard and works to promote and catalyze DASH. Their goals include facilitating deployments, recommending baselines for interoperability, and generally promoting the growth of a single industry-defined open standard. Therefore, they have a stake in barriers to the use and adoption of DASH, and keep up to date on patent, licensing, and legal issues.

Meet Kaltura’s Streaming Solutions

If you’re looking for a streaming solution with a technology stack that includes ABR and MPEG-DASH capabilities, we’d also recommend checking out our suite of Kaltura products; we feel confident one of our industry-leading solutions will be right for your needs.

We leverage the most current streaming technologies to provide excellent playback across devices and unreliable network conditions while providing top-tier content security and user access to content. Our video streaming solutions guarantee a flawless viewing experience for your users on any device, via any connection, anyplace. If you want to take a deep dive into our technical processes, you’ll find we also support MPEG-DASH among many other streaming techniques and technologies, to provide a variety of options for seamless streaming and video viewing.

If you’re looking for best-in-class streaming options we recommend checking out our video portal, even signing up for a free trial. We give you the means to provide your users with the best viewing experience possible! Wherever the viewer is, whichever device they’re using, we can deliver the highest quality video live or on-demand.

Company webcasts to real-time media events–Kaltura will enable you to provide the excitement of a live video stream. Kaltura streaming is also optimized for cross-device delivery including mobile devices, laptops, and even set-top boxes. Our solutions use ABR delivery and multiple options for transcoding, guaranteeing the best results for viewers, including for HD streaming. We support MPEG-DASH, HLS, and other popular and versatile streaming technologies to leave no stone unturned.

Our live streaming options take advantage of cloud transcoding, DVR, ad-stitching, and real-time analytics delivered to any device. We facilitate easily and quickly creating new live events; the process can run less than five minutes from live stream set up to broadcast.

Livestream capability can also be scaled from just a few events to 24/7 live broadcasts, and event value can be further extended with instant archiving. You can publish an event to Kaltura Video Portal or our other pre-integrated applications or your own website and have fine-grained control over when the livestream and VOD are available to your audience.

We also provide CDN and CDN integration options: Kaltura provides scalable and secure video delivery behind the firewall, either with our services or integrate our services with a wide range of industry CDNs.

Final Thoughts

MPEG-DASH is a powerful tool in a streaming toolkit, however, it’s dependent on the use case whether it’s the best choice or not. Which methods, formats, and protocols to use are always dependent on your choices and needs for your streaming content, so your best bet is to make sure to use streaming solutions that support multiple options.