January 12, 2011 – New developments facilitating use of adaptive streaming for delivering premium TV content over broadband connections could go a long way toward accelerating the emergence of IP-based multi-device services.
While adaptive streaming (AS) is becoming a mainstay in over-the-top video distribution through outlets like Apple, Google, Netflix and many other Web-based aggregators, its viability as a support mechanism for subscription TV service is at issue. Service providers are impeded by uncertainties as to what the quality-of-service ramifications are and by the difficulties of putting together an easy-to-manage delivery platform suited to securing and formatting content for all types of devices.
But all that might be about to change. Indeed, one MSO customer of Motorola’s SecureMedia unit has been in trial and is about to go commercial with a multi-screen service solution combining the SecureMedia premium content protection platform with HLS (HTTP Live Streaming), notes Whit Jackson, vice president for business development and studio relations at SecureMedia.
“This is a traditional cable customer that delivers subscription TV to Motorola set-tops with cable cards,” Jackson says. “They’re starting out delivering a subset of their content to the PC, but they’ve given us our marching orders for delivering video to Droid handsets, iPhones and iPads and soon after that Android tablets, game consoles and connected TVs.”
As explained by Jackson, the SecureMedia solution takes many of the hassles out of delivering premium services to different classes of devices by providing a level of protection suited to premium content that has been pre-integrated with HLS so as to eliminate the need to support multiple AS modes. The company chose to work with HLS, now under consideration as a potential standard at the Internet Engineering Task Force, because the AS system is already approaching de facto standard status on the Web, driven in part by wide adoption of the iPhone and iPad as video viewing platforms.
Along with reducing the ingestion hassles, he says, the new solution allows the unnamed MSO to continually add content with assurance that content will reach all targeted devices. “Right now they’re working with their own content,” he says. “When they turn the service on they’ll have 15 channels, then go to 20. They’re working with content suppliers to extend their licensing agreements as fast as they can. And they may also expand the range of affiliations to include OTT providers like Netflix or Amazon.”
SecureMedia’s Encryptonite ONE platform consists of a suite of functions required for subscriber authentication, digital rights management (DRM) protection and much else on the security side, Jackson says. This is integrated with HLS into client software that service providers can download to their subscribers’ devices. When a play request is sent from the device, rather than going to the source media server to retrieve the native DRM encryption key, the message is intercepted and redirected to the SecureMedia key delivery process.
The Cisco Approach
Taking a somewhat different approach in its new Videoscape initiative, Cisco Systems has developed a distribution framework in conjunction with its Content Delivery System (CDS) infrastructure solution that similarly is meant to enable use of high-security DRMs that may not be native to a particular adaptive streaming platform. This is essential to the Videoscape mandate, which is to provide an easy-to-operate, unified framework for everything associated with multi-device video services, from subscriber authentication to formatting to security and distribution.
“If you’re embracing the idea of delivering video to a whole range of unmanaged devices, then, number one, adaptive bit rate is non-negotiable,” says Ken Morse, CTO for Cisco’s service provider technology group. “You need adaptive bit rate streaming.”
All the major AS systems have been incorporated into CDS, he says. The Videoscape framework allows service providers and content suppliers to use non-native DRMs with those AS modes in instances where they feel the native security is not sufficient to their requirements and/or they want to avoid having to use multiple DRMs. With the intelligence built into CDS, the system can read the AS mechanisms associated with generating encryption key delivery and perform “late binding” of keys from a different DRM, Morse explains.
AS only recently came into its own as video became a big component of consumer usage. With AS, content continues streaming even as bandwidth fluctuates, thereby avoiding the annoying buffering process, which would be completely unacceptable for a TV service. But to be of use to service providers the changes in quality resulting from adjustments in the bit rate must be barely noticeable to the average viewer, if at all. This means a low-end bit-rate threshold must be set to avoid unacceptable quality deterioration, and the transition from one bit rate to another must be made without any hiccups in the stream.
The technology assigns content multiple profiles for bit rates, resolutions and formatting dimensions for each type of device to be served by an HTTP (Hypertext Transfer Protocol) or streaming server. During a video streaming session the device signals which profile should be streamed based on what the available access data rate is on the network and on how much processing power is available to handle the video stream.
The most commonly used AS modes, Apple’s HLS, Adobe’s Access and Microsoft’s Smooth, and others tied to various security platforms, are all incompatible with each other. For example, the duration of the “chunks” or file segments that are streamed at a given rate based on which profile the device has asked for differ from one AS mode to the next. And each one comes integrated with a different DRM.
Indeed, Jackson notes, out-of-the-box solutions designed for run-of-the-mill over-the-top applications have fallen short of service providers’ premium content requirements on many counts. First and foremost, all these incompatibilities create a costly, hard-to-manage ingestion and transcoding process that limits flexibility to maximize content options that might be available to users on any given type of device.
“Service providers want to deliver the same branded experience on all the different devices,” Jackson says. “And they want to deliver it live as well as on demand. In the trial I mentioned we’re streaming live broadcast along with VOD.”
New Security Requirements
Another big issue service providers must deal with to enable such multi-device services is the rigorous security and quality-of-service requirements set by content owners for licensing premium content, especially as OTT delivery enters the connected TV domain with the need to deliver 1080p HDTV. Neither HLS nor any of the other commonly used DRMs integrated with AS systems are designed for this environment, insofar as they lack means of authentication, securing encryption keys, protecting metadata tied to a particular subscriber on a given device and protecting content at in-the-clear points of vulnerability in the internal workings of each device.
Alternatively, more rigorous DRMs designed for premium content that come with their own proprietary AS systems don’t have a wide-scale AS market base to work with, which means the service provider must provide every device with the proprietary player. And such AS systems tend to be less reliable than one that’s been hardened through multiple iterations across millions of devices.
In fact, AS performance in general has proved to be an issue requiring careful attention to detail even in the case of HLS, Jackson notes. “Early on we found that in switching from one bit rate to another AS had some transition issues,” he says. “At the demonstration we ran at Media Innovations Summit [in September] we were getting some black frames. Now we’re getting what we want.”
Another issue requiring careful attention is the encoding that takes place across all the profiles in the transcoding process. SecureMedia is putting many encoding platforms through their paces at Motorola’s facilities with the goal of choosing a couple to recommend for use with the new integrated HLS/SecureMedia solution. “We’re discovering there are no silver bullets,” Jackson says. “The basic issues are frame drops where some are better than others. Plus there’s the overall encoder output quality, which varies.”
Also unsettled in service provider applications of AS is how many profiles to support. The narrower the gradations from one bit rate to the next within a given range of throughput speeds, the better the consumer experience will be. But the costs of encoding and processing go up with more profiles. SecureMedia is recommending eight profiles, Jackson says.
“We’ve seen as many as 13 in use by one MSO, which I think they now agree is going too far,” Jackson says. “We’ve found that four doesn’t give you the range you need. An eight-profile setup launches quickly and covers a pretty wide range, so that’s what we’re recommending.”
Matching AS to Quality Expectations
In another move essential to making AS a service provider-friendly tool, RGB Networks, working with video analytics device supplier Tektronics, is developing a quality assessment method which will help service providers determine acceptable AS data rate settings for premium services on various devices, including the requirements for delivering HDTV 1080p video over broadband connections to TV sets. Getting comfortable with bit-rate ranges for premium content is crucial to operators’ being able to move ahead with new multi-device service strategies, says Nabil Kanaan, senior director of product marketing at RGB.
“There are folks operating traditional video IPTV or cable TV networks who are looking at using adaptive streaming to deliver content to the TV screen, but they need to better understand where the threshold is for acceptable quality,” Kanaan says. “That’s where video quality matters the most, as opposed to having something get to your phone.”
For service providers to confidently set the AS profile parameters for delivering acceptable quality to TVs and other devices requires that operators be able to quantify measured video quality in a way that accurately correlates with subjectively perceived quality in the viewing experience. If operators can do this, they can determine what the minimum bandwidth requirements will be for any bandwidth contention level across multiple types of devices, thereby avoiding excessive spending on network capacity.
So far, RGB and Tektronics, using a technique refined by Tektronics to quantify human perception of quality variations, have shown operators have great latitude in setting AS bit rates without compromising on the consumer experience. Tektronics has adapted the intensely manual Mean Opinion Score process, which calibrates video metrics to the responses of the human vision system, to an automated DMOS (Differential MOS) analysis performed on its PQA 500 VQ device. The tool immediately delivers reliable measures of viewing quality experience that once took days or weeks of work to compile, Kanaan says.
The companies found that bit rates significantly below the threshold that would be set using traditional peak signal-to-noise-ratio (PSNR) measurements register within an acceptable range of good experience on the DMOS analysis. Consequently, Kanaan says, operators can use AS to accommodate less-than-optimal conditions that might occur with allocation of less bandwidth than would be required if one were to rely on PSNR.
The methodology is not ready for prime time, Kanann acknowledges. So far the tool only performs its gauge of changes to quality in the progressive display domain, which fails to accommodate any quality impact caused from the conversion of interlaced TV content to progressive scan. The measurement process will also have to be adjusted to look at the impact of pixel scaling as the number of pixels in a TV display is reduced for display on smaller screen devices. And the test results will have to include a measurement of the overall experience across the viewing time as AS shifts from one rate to the next.
All of these challenges are being address, Kanann says. “We will be refining the measuring technique as we go forward,” he adds. “But we are confident we’ve identified an approach that could become a common method of setting AS parameters for premium service delivery.”