MPEG-DASH: ABS, but Without Reinventing the Wheel

The complex world of streaming video to PCs, mobile devices and an emerging generation of IP-enabled TV sets offers cable operators huge potential opportunities. At the same time, the industry is struggling to create the infrastructure necessary to deliver these services in an efficient manner.Clearly, one area in which more efficient processes are necessary is adaptive bitrate streaming. The goal of ABS is to send the optimum number of bits to an end point device based on a number of variables, such as congestion in the network, the nature of the content and demands of that device. To date, it's been a bit of a free-for-all, with systems from Microsoft (Smooth Streaming, a part of the Silverlight Web development environment), Apple's HTTP Live Streaming (HLS), a couple of versions of Adobe Flash, WebM and Rovi's DivX Streaming.In a very general sense, the technologies work in a similar way. Indeed, from a technical perspective, it would be possible for all mobile devices to settle on one approach. The problems are that while similar, the systems aren't the same. A second challenge is that there are significant licensing issues that would have to be hashed out among the competing companies for one to predominate. Finally, ongoing elements of the ABS stack -- digital rights management (DRM) is mentioned by many observers -- are still unsettled.Service providers, vendors, content owners and others are trying to wring out as much of the confusion as possible with an open standard. In December, the MPEG (the Moving Picture Experts Group) -- which is run by the Organization for Standardization (the ISO) and the International Electrotechnical Commission -- passed ISO/IEC 23009. The standard is called Dynamic Adaptive Streaming over HTTP or MPEG-DASH.MPEG-DASH is all about expediency and efficiency. "Vendor neutrality allows operators a greater landscape to target," said Digital Rapids President Brick Eksten. "Today, [service providers] have to do a little of everything. In the future, they can use DASH because of support from the consumer electronics companies and lower level support from chip makers like Qualcomm."This could be an especially good thing for cable operators, who are betting a lot on their own TV everywhere services and who are obligated to support third-party OTT initiatives. "This is a situation where something like DASH would help them," said Jan Ozer, the author of Video Compression for Flash, Apple Devices and HTML 5. "It could create one set of files that could serve all those platforms."Ozer said the conceptual innovations in MPEG-DASH -- things that truly are new -- are minimal. He said that all the HTTP formats use the same essential approach: There are manifest files and content files. The manifest files, as the name implies, carry information that the end user device -- the laptop, the tablet or anything else -- uses to determine what version, or profile, of the content is used.Ozer said that the manifest files are decoded by the end device and don't rely on a server. Ozer said that the manifest file in MPEG-DASH is in the XML format, which enables inclusion of a great deal more information. The goal of MPEG-DASH, however, isn't reinventing the wheel -- it's getting the cart rolling. "There is not a lot of innovation in DASH," Ozer said. "It's, 'Hey, pick an approach we can all buy into.'"Arnaud Perrier, the Vice President of Solutions for Envivio, wrote in response to emailed questions that the advantages of MPEG-DASH are that it is codec agnostic and supports two file formats, MPEG 2 TS and MP4. "This gives developers and operators flexibility," he wrote. "It can prevent operators from having to choose or lock themselves into a specific workflow."MPEG-DASH will be in the news during the next several months. Tony Huang, a senior product manager at Digital Rapids, said a final vote on the spec is likely during the first quarter, the start of proof-of-concept trials in the February and March timeframe, and product availability at the NAB show in the middle of April.The good news for operators, according to experts, is that the streaming infrastructures they are building now won't be stranded investments. Nobody suggests that operators slow down deployments today in anticipation of MPEG-DASH.Thierry Fautier, Harmonic's senior director of convergence solutions, said the move to MPEG-DASH is important for a number of reasons. On one level, it is an important scene-setter for the next generation of encoding schemes, which include the MPEG-4 and H.265 (which also is known as the High Efficiency Video Coding, or HEVC) approaches. "MPEG-DASH can use other codecs," he said. "It is an investment in the future." He said HEVC may be completed this year, and products could become available in 2014.Harmonic said that a group to promote the standard, The DASH Promoters Group, has been formed. Members include Harmonic, Adobe, Microsoft, Akamai, Samsung and Qualcomm.MPEG-DASH also sets up an organized and efficient process by which DRM -- the processes by which content is secured -- can be implemented. This part of the initiative is close to the hearts of content owners and is considered the most important unsettled issue in the world of streaming. Fautier pointed out that there is no single approach to DRM in streaming. Thus, a platform in which various approaches can be interchangeably swapped in and out is vital.A final advantage of MPEG-DASH is that, according to Perrier, it provides "a standardized framework for ad insertion over HTTP. "This is great news," he wrote.The next steps are for various industry groups -- including CableLabs -- to create the profiles that fit best for their industries and for owners of intellectual property to take the necessary steps to create a royalty-free environment. This may take a while. It will happen, however, Fautier said. "It is what everyone is dreaming of," he said. "But it may take a few years for everyone to get their act together."Carl Weinschenk is the Senior Editor of Broadband Technology Report. Reach him at [email protected].