MPEG Dynamic Adaptive Streaming over HTTP (MPEG-DASH) picked up steam last week when Microsoft publicly backed the standard.
Specifically, the company blogged that, later this year, Windows Azure Media Services and certain client development kits will support MPEG-DASH as part of what it calls an industry-wide effort to "establish reliable video delivery to Internet-connected devices".
While HTTP streaming has emerged as the approach of choice for addressing growth in Internet video and for delivering content to multiple devices, three competing solutions —Microsoft’s Smooth Streaming, Adobe’s HTTP Dynamic Streaming (HDS) and Apple’s HTTP Live Streaming (HLS) — have fragmented the market, making it more expensive and complicated to meet consumer demand.
Each platform requires different manifest and segment formats, requiring a device to support three client protocols in order to receive content from three corresponding servers. MPEG-DASH seeks to solve this challenge, in part, by defining a common format called a Media Presentation Description (MPD) — essentially a unified manifest file listing the metadata a device uses to self-select the best variances for its capabilities.
"With a single DASH player, you would be able to stream content that is packaged in different ways (HLS, HDS, Smooth Streaming),” says Arnaud Perrier, vice president/Solutions at Envivio. “It is about packaging and streaming technology. It is not changing any of the codec layer. It is designed to be codec agnostic.”
In other words, MPEG-DASH is more of an umbrella or an amalgamation of existing protocols. Notes Andy Salo, director/Marketing at RGB Networks, "You would have a client that could access an MPD file that describes the metadata. Clients would be able to reference that and pull the content, no matter what format it is in.”
Jumping The Hurdles
In addition to allowing interoperability between servers and clients, MPEG-DASH could solve other thorny issues, including how to switch audio streams so that the proper language file is chosen, for example, with a single protocol instead of three.
And although each of the three protocols currently defines different ways to perform encryption, MPEG-DASH would make the client player agnostic to the DRM technology used. "It helps vendors and MSOs to streamline implementation because we only have to worry about doing encryption once in a common manner," Perrier explains.
For operators, while MPEG-DASH is an adaptive-streaming construct for delivering multi-variant content to different devices, it also can serve as a wholesale distribution method. "It can be used as a common means of providing all the necessary information to encapsulate a high quality distribution asset from the studio to someone turning it into a final distribution format," comments Comcast Fellow Mark Francisco.
Moving forward, work has to be done to make DASH compatible with the three ecosystems, but it is a fairly straightforward specification, Francisco adds.
Like Microsoft, Adobe has announced its intent to support the standard. Apple, however, has not yet stated its plans. "If Apple were to do things that preclude MPEG-DASH, it can only go so far," Francisco says.
There also could be intellectual-property-rights issues with MPEG-DASH, Salo notes: "Will somebody stake a patent claim on a component of DASH? That would certainly affect how people will want to deploy the technology."
Yet, as evidenced by demonstrations at last week’s NAB Show in Las Vegas, plans for MPEG-DASH are moving forward. RGB and Envivio both plan to showcase new MPEG-DASH capabilities in conjunction with a selection of client-side vendors. And, after being ratified by 24 national bodies in November 2011, MPEG-DASH — also known as ISO/IEC 23009-1 — is expected to be published by the International Standards Organization soon.
— Monta Monaco Hernon