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June 7, 2013
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Device and content prioritization among next steps for CDN

Service providers are telling Alcatel-Lucent that they expect unicast video streaming to multi-screen and connected TV devices to increase dramatically over the next 3-5 years as consumers get used to services like time-shift TV and cloud DVR on various devices. This means there is continued pressure to reduce the cost of delivering unicast video, which requires further optimization in CDN technology.

However, there is a parallel requirement to support advanced TV features like digital advertising insertion (especially in North America), regional black-outs, and emergency alert systems. More personalization is needed, so people can prioritize a living room Smart TV over a bedroom Xbox 360, for example. And with more linear streaming, there is a need to reduce channel start-up and channel-change times. These are some of the things on service provider shopping lists when it comes to next-generation CDN technology.

According to Roland Mestric, Solution Marketing for IP Video at Alcatel-Lucent, whose Velocix solutions provide advanced on-net CDN solutions for service providers, repackaging (or on-the-fly packaging) is one of the features that characterizes next-generation CDN architectures. Instead of packaging video into the various adaptive bitrate formats centrally (Apple, Microsoft, Adobe and soon MPEG-DASH, among others) and then transporting video in these multiple formats to the edge of the network, service providers can send video in a single format to the edge and then repackage it there into the formats needed for different devices, depending on which devices are requesting it at the time. “This is a simple way to further optimize the delivery,” Mestric says.

Edge processing of the unicast streaming sessions is how you efficiently introduce personalized advertising, too, Mestric believes. If you insert different advertising into video streams at the edge, making the streams more personal, you can still make use of edge caching for the original video stream.

The next-generation of CDN needs to give service providers much greater control over bandwidth priorities in the home, Alcatel-Lucent believes. If there are multiple devices competing for bandwidth, you need to be able to say that a connected television needs priority for streaming and that a smartphone should be given a lower bitrate stream, for example.

“Service providers need a way to control the quality that is delivered to every screen and that is not possible today with adaptive bitrate streaming,” Mestric explains. “So in the CDN we will include a session manager that makes the CDN aware of all the different devices and session requests so that if you start to watch video on an iPhone and there is no congestion in the access network you will get the highest bitrate possible, but if someone else in the family turns on a connected TV device the service provider can then limit the bitrate profiles that can be accessed by the iPhone, for instance.”

This ABR session management happens dynamically and can be based on the type of device that is requesting the content or the kind of content being requested or currently watched. So if someone is watching the news and someone else wants to see the Roland Garros French Open then the tennis can be given priority because sports needs higher bitrates to look good.

The aim is to provide the best experience for a family as a whole, which means balancing the demands of different client devices. ABR clients do not limit themselves to 0.5Mbps if they can grab 1.0Mbps, even if the video quality tops out at 0.5Mbps on that screen and there is no actual QoE gain by taking more. With this dynamic session management, that 0.5Mbps can be better employed somewhere else.

Mestric points out that session prioritization could be useful if there is contention on mobile networks. Then a content provider could prioritize a premium subscriber over a basic subscriber so they get the higher bitrate if there is no chance to provide them both with the best possible experience.

All the policies that determine the prioritization actions for ABR streaming are set in advance by the service providers and that could, of course, involve consumers pre-selecting the actions they want in the home if there is contention, maybe through settings on a User Interface.

These next generation CDN features are being offered to Alcatel-Lucent’s Velocix customers today as part of the Velocix Enhanced Video Experience (EVE). The edge repackaging uses a proprietary Velocix technology called rule-based transformation (RBT). With this approach the content, delivered once in a common format, also comes with a rule that describes how to process this content to transform it into other output formats.

So if the common format is HLS (Apple HTTP Live Streaming) it comes with a rule for how to adapt the video into Adobe HDS (HTTP Dynamic Streaming) format. If required, the rule can be cached locally for future use. Alcatel-Lucent claims its unique approach needs less processing power than just-in-time packaging techniques that need to analyze the incoming format before converting it to the target output formats.

Rule-based transformation can also be used for subtle transformations to the video so that you can introduce trick-play on adaptive bitrate streams, like fast-forward, rewind and jumping to a future frame. RBT can also be used for denting, where you dynamically reduce the bit rate by removing video frames from segments to create a lower frame rate. Denting can be used for trick-modes but also for fast channel start-up.

With Velocix EVE you can dynamically shorten the first few segments of an HLS stream so that initial buffering time is reduced (three segments are buffered before playout). This is particularly important when switching between linear channels that are being streamed, as consumers are less tolerant of channel-change delay than start-up delays for on-demand content. The company was highlighting many of these features at the recent ANGA COM exhibition in Germany.