MPEG-DASH: Adaptive streaming for multiple platforms

The need to reach multiple platforms and consumer electronics devices has long presented a technical and business headache, not to mention a cost for service providers looking to deliver online video. Creating a common file format had become very essential.

MPEG-DASH, a technology with the scope to significantly improve the way content is delivered to any device by cutting complexity and providing a common ecosystem of content and services was created for this purpose. The MPEG-DASH standard was ratified in December 2011 and tested in 2012, with deployments across the world now underway. MPEG-DASH is poised to become a universal point for interoperable OTT delivery. However, slower-than-expected initial uptake may dampen wider adoption.

A Brief History of DASH

The early days of video streaming, reaching back to the mid-1990s, were characterised by battles between the different technologies of RealNetworks, Inc. and Microsoft, and then Adobe. By the mid-2000s, the vast majority of internet traffic was HTTP-based, and content delivery networks (CDNs) were increasingly being used to ensure delivery of popular content to large audiences.

All proprietary protocols -- mostly based on the far less popular UDP -- suddenly found itself struggling to keep up with demand that changed in 2007 when Move Networks, Inc. introduced HTTP-based adaptive streaming, adjusting the quality of a video stream according to the user’s bandwidth and CPU capacity. “Instead of relying on proprietary streaming protocols and leaving users at the mercy of the internet bandwidth gods, Move Networks used the dominant HTTP protocol to deliver media in small file chunks while utilising the player application to monitor download speeds and request chunks of varying quality (size) in response to changing network conditions.  The technology had a huge impact because it allowed streaming media to be distributed ... using CDNs (over standard HTTP) and cached for efficiency, while at the same time eliminating annoying buffering and connectivity issues for customers.

Other HTTP-based adaptive streaming solutions followed: Microsoft launched Smooth Streaming in 2008, Apple debuted HTTP Live Streaming (HLS) for delivery to iOS devices a year later, and Adobe joined the party in 2010 with HTTP Dynamic Streaming (HDS).

HTTP-based adaptive streaming quickly became the weapon of choice for high-profile live streaming events from the Vancouver Winter Olympics 2010 to Felix Baumgartner’s record breaking 2012 Red Bull Stratos jump (watched live online by 8 million people).

These and other competing protocols created fresh market fragmentation in tandem with multiple DRM providers and encryption systems, all of which contributed to a barrier to further growth of the online video ecosystem.

In 2009, efforts began among telecommunications group 3rd Generation Partnership Project (3GPP) to establish an industry standard for adaptive streaming. More than 50 companies were involved -- Microsoft, Netflix, and Adobe included -- and the effort was coordinated at ISO level with other industry organisations such as studio-backed digital locker initiator Digital Entertainment Content Ecosystem, LLC (DECE), OIPF, and World Wide Web Consortium (W3C).

MPEG Dynamic Adaptive Streaming over HTTP (MPEG-DASH, or DASH for short) was ratified as an international standard late in 2011. It was published as ISO/IEC 23009-1 the following April and was immediately heralded as a breakthrough because of its potential to embrace and replace existing proprietary ABR technologies and its ability to run on any device.

It was expected that the agreement on a single protocol would decrease the cost of production, encoding, storage, and transport enabling operators to scale their OTT business.

The Benefits of DASH

The technical and commercial benefits outlined for MPEG-DASH on launch included the following:

• It decouples the technical issues of delivery formats and video compression from the more typically proprietary issues of a protection regime. No longer does the technology of delivery have to develop in lockstep with the release cycle of a presentation engine or security vendor.

• It is not blue sky technology -- the standard acknowledged adoption of existing commercial offerings in its profiles and was designed to represent a superset of all existing solutions.

• It represented a drive for a vendor-neutral, single-delivery protocol to reduce balkanisation of streaming support in CE devices. This would reduce technical headaches and transcoding costs. It meant content publishers could generate a single set of files for encoding and streaming that should be compatible with as many devices as possible from mobile to OTT, and also to the desktop via plug-ins or HTML5; in addition, it meant consumers would not have to worry about whether their devices would be able to play the content they want to watch.

Perhaps the biggest plus was that unlike previous attempts to create a truly interoperable file format, without exception all the major players participated in its development. Microsoft, Adobe, and Apple -- as well as Netflix; QUALCOMM, Inc.; and Cisco -- were integral to the DASH working group.

These companies, minus Apple, formed a DASH Promoters Group (DASH-PG), which eventually boasted nearly 60 members and would be formalised as the DASH Industry Forum (DASH-IF), to develop DASH across mobile, broadcast, and internet and to enable interoperability between DASH profiles and connected devices -- exactly what was missing in the legacy adaptive streaming protocols.

The European Broadcasting Union (EBU) was the first broadcast organisation to join DASH-IF, helping recommend and adopt DASH in version 1.5 of European hybrid internet-TV platform HbbTV. Other members have since boarded, including France and Spain, which have already begun deploying DASH for connected TVs, with Germany and Italy expected to follow. In the U.S., DASH is attracting mobile operators, such as Verizon, wanting to deploy eMBMS for mobile TV broadcast over LTE.

DASH still needs more support 

The format for DASH is similar to Apple’s HLS, using index files and segmented content to stream to a device where the index file indicates the order in which segments are played. But even though representatives from Apple participated in drawing up DASH, Apple is holding fast to HLS and hasn’t yet publicly expressed its support for DASH.

Neither has Google, though it has confirmed that the standard is being tested in Google Chrome. Some believe that until DASH is explicitly backed by these major players, it will struggle to gain traction in the market.

Adobe has encouragingly adopted the emerging video standard across its entire range of video streaming, playback, protection, and monetisation technologies. Its backing will greatly reduce fragmentation and costs caused by having to support multiple video formats.

While Apple HLS has considerable momentum, other adaptive streaming protocols are being dropped in favor of DASH. Ultimately there will only be two mainstream protcols in use for the vast majority of streaming services: HLS and DASH.

HLS  from Apple doesn’t have support for multi-DRM solutions -- DASH does, which is why most major studio houses have given it their endorsement.

Roadblocks to DASH Adoption

Experts feel that  DASH adoption won’t be a straight one.In particular the challenge of intellectual property and royalties, an issue which will need to be addressed before DASH can achieve widespread adoption.

 DASH participants such as Microsoft and Qualcomm have consented to collate patents for a royalty free solution, but the likes of Adobe have not agreed. A potential obstacle to standardisation is video codecs -- namely, the need for a standard codec for HTML5 video. Even with universal adoption of DASH by HTML5 browsers, content would still need to be encoded in multiple codecs.

There are also concerns about the way in which DASH is being implemented particularly in the area of time synchronisation. It is hoped that as adoption becomes wider, there will be industry consensus on the implementation details; the best practise guidelines being created by DASH-IF will further accelerate adoption.

There are further warnings that delays in implementing DASH could harm its success as a unifying format. A standards effort necessarily involves compromises, and probably the biggest compromises get hidden in the profile support in the overall standards effort. MPEG-DASH in its original specification arguably tried to be everything to everyone and perhaps suffered from excessive ambiguity.

Unless there is some operational agreement on how to use the standard between different platform operators it might become yet another format to support.

“DASH has taken quite a while to gather a following among consumer electronics and software technology vendors, delaying its adoption,” reportsRGB Networks’ senior director of product marketing Nabil Kanaan. “The various profiles defined by DASH have added too much flexibility in the ecosystem, at the cost of quick standardisation. We still believe it’s a viable industry initiative and are supporting it from a network standpoint and working with ecosystem partners to make it a deployable technology.”

“MPEG-DASH isn’t in a position where people are thinking that it will be the only spec they’ll need to support in the near to mid-term,” says Digital Rapids marketing director Mike Nann, “but most believe that it will reduce the number of adaptive streaming specifications that they’ll need to prepare their content for.”

DASH-AVC/264

To address this, the DASH-IF has been hard at work defining a subset of the standard to serve as a base profile that all implementations have to include. This is driven by the decision to focus on H.264/MPEG-4 encoding rather than MPEG-2 (initially both were supported). The result, DASH-AVC/264, was announced in May and is widely tipped to achieve broad adoption by speeding up the development of common profiles that can be used as the basis for interoperability testing.

DASH-AVC/264 is a means of doing the same for MPEG-DASH what MPEG 2 did to Transport Streaming (TS), providing a constrained set of requirements for supporting DASH across the devices that support it, and giving vendors interoperable targets. Aside from requiring support for H.264, the DASH-AVC/264 guidelines define other essential interoperability requirements such as support for the HE-AAC v2 audio codec, ISO base media file format, SMPTE-TT subtitle format, and MPEG Common Encryption for content protection (DRM).

The Common Encryption element enables competing DRM technologies such as Microsoft PlayReady, Adobe Access, and Widevine to be used inclusively without locking customers into a particular digital store. DASH-AVC/264 provides the details desperately needed by the industry to adopt MPEG-DASH and is expected to gain significant traction over the next one to two years.

Telestream, Inc. product marketing director John Pallett says,  “The primary driver for adoption will be the player technology to support it. The companies that develop players are generally working to support MPEG-DASH alongside their legacy formats. Most of the major player companies want to migrate to DASH, but real adoption will come when a major consumer product supports DASH natively. This has not yet happened, but we anticipate that it will change over the next year.”

The number of trials are growing and already include the world’s first large-scale test of MPEG-DASH OTT multiscreen at the 2012 London Olympics with Belgian broadcaster VRT, and the first commercial MPEG-DASH OTT multiscreen service with NAGRA and Abertis Telecom in 2012 -- both powered by Harmonic. 

In an interview with Streaming Media, Kevin Towes, senior product manager at Adobe, declared 2012 as the year of DASH awareness and 2013 as the year of discovery.

Given the number of elements of the value chain that need to line up for full commercialisation -- encoders, servers, CDNs, security systems, and clients as a minimum -- significant commercial rollouts were always likely to take time.

In conclusion, while there are still hurdles to clear, DASH is clearly on the path toward widespread adoption, especially now that DASH-AVC/264 has been approved. DASH has all the potential to become the standard for online video delivery  adopted by the Industry and enable cable and satellite providers to deliver video to all devices- including set-top-boxes- for a true TV Everywhere experience.

(This article is based on an article by Adrian Pennington published in Streaming Media magazine in Autumn 2013 edition)

Source: http://cablequest.org/articles/broadcast-technology/item/3784-mpeg-dash-adaptive-streaming-for-multiple-platforms.html
Source: http://cablequest.org/articles/broadcast-technology/item/3784-mpeg-dash-adaptive-streaming-for-multiple-platforms.html