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The future of MPEG video transport over QAM

Fri, 01/04/2013 - 11:52am
Conrad Clemson, director of strategy and product management for Cisco’s Service Provider Video Technology Group

A plausible first step is to take a top-down look at everything.

In this age, with every point in the distribution line being threaded through and through with IP-based technologies, it is important to consider the near-, mid- and long-term future of the MPEG video transport architecture this industry invented and built in the 1990s.

In engineering forums, strategy departments and throughout the industry, we are again on the cusp of the next wave in technological advancement – because technologies tend to arrive in a series of waves. The most recent one was the shift from analog to digital transport streams over QAM modulation, led by set-top boxes and linear digital video delivery. After that, there was DOCSIS and the careful apportioning of more carriers, underlying technologies and services toward IP delivery.

But MPEG and IP transport are innately different. The former was built by “video people,” and the latter by “data people.” Further, MPEG video transport is connectionless – it was purpose-built for broadcast video. IP is specifically connection-oriented.

And, as the OSI stack goes, QAM modulation is a Layer 1 technology. MPEG and IP are Layer 2. In legacy video environments, MPEG transport is aware of QAM – it’s a highly integrated pairing – while in IP, what’s happening in other layers of the stack is irrelevant. It doesn’t matter who’s moving what. It just goes.

The cusp toward all-IP is upon us now. As engineers and as an industry, we are just lifting a foot into what will be a big, straddling lunge. Where the lunge ends depends on how one defines the endgame. For the purposes of this article, let’s say the endpoint is when the network is 100 percent IP transport, 0 percent legacy MPEG transport.

Which is not to say that one is right and the other wrong. New technologies come into play for specific reasons: cheaper, faster, better, whatever it is. But analog technologies are still with us, even after 20 years of digital. What did MPEG transport over QAM bring? More channels. Better picture quality. The entry into all that digital brings, including VOD and SDV.

IP isn’t necessarily a standout protocol, but rather a useful common denominator for many paths – to gateways, iPads, iPhones, PCs and the like. MPEG transport gets the signal efficiently to the digital cable set-top; IP gets it to all the other devices. Plus, it’s the stepping stone into the R&D and other advancements that are coming – because the rest of the world is IP, not MPEG transport.

Cisco Figure 1
The breadth of IP
Think of it in terms of signal flow, left to right, content creation to end screen: Content creators are modifying their workflows to plumb in IP-based distribution; content distributors are responding with content delivery networks (CDNs).

Hierarchical storage teamed with adaptive bit rate encoding is at hand – whether in the cloud or in gateways – to solve the riddle of serving subscription and on-demand video to screens not connected via the traditional set-top box.

At the bandwidth level, more and more 6 MHz channels are being allocated toward DOCSIS 3.0-based channel bonds, necessary to stay ahead of the scores of IP-connectable, video-capable screens entering the networks from the hands of consumers and businesses. CCAP, the Converged Cable Access Platform, will go far in that department.

At the consumer end of the flow, we see the rising use of tablets, laptops, PCs and smartphones to view video content, dovetailed with efforts inside the service provider community to break free of limitations posed by the traditional “up-down-left-right” remote controls, which controlled grid-based, clunky guides.

That body of work – to expand navigation to other devices beyond the handheld remote, and to broaden the capabilities of search and navigation – is already in-market and gaining rapid consumer adoption.

Cisco Figure 2
The installed base
But wait. What about that installed base? Right now, by our back-of-the-envelope calculations, nearly 100 percent of the fielded base of set-top boxes and DTAs are served signals primarily over MPEG transport.

This year and onward, MSOs will start rolling out hybrid IP/QAM devices, followed by IP-based soft clients or virtual set-top boxes. Sometime after 2015 – again, this is an educated guess only – the volume of IP-based, MSO-provided CPE will begin to outrank the hybrid devices.

Even as IP channelization really takes hold, we don’t see a crossover point between MPEG transport and IP until the year 2020.

So, not only is the body of work that is MPEG transport of video not going away, it cannot be ignored. It’s the majority. MPEG transport of video over QAM will be a significant part of the industry’s digital life for at least another decade.

By that measure, it is simultaneously true that the feature base for video over IP is still immature. That indicates a significant amount of migration work to emulate, say, the various properties and requirements associated with Title 6 video – from MPEG transport to IP.

Why does Title 6 video matter? Title 6 is the chapter of the FCC’s Communications Act that applies to cable television. It dates back to 1984 and mandates all of the federal requirements for being a multichannel video provider, from franchising to emergency alerts, blackouts, program access, closed captions and navigation devices.

One reason why “more, better” video content is available via traditional set-top box than over IP is because the “better” stuff was negotiated for distribution under Title 6 rules. Which means that to get the “more, better” video content onto IP-based devices, the rules either need to be updated, or the component technical pieces need to be emulated in IP.

Cisco Figure 3
MPEG innovation
That raises a question: Do we continue innovating on the installed base of MPEG video transport over QAM? Do the innovations being harnessed for IP, along with all of the problems that can be fixed with IP, need to be considered as mechanisms to likewise extend the capabilities of the MPEG video transport architecture?

This has long been a question in various product development circles – how long (for crying out loud!) do we need to support the capabilities of the “lowest common denominator boxes,” while so much processing power, graphics capabilities and memory are available on contemporary devices?

Obviously, the move to video over IP, from MPEG transport, is happening in part to fix legacy issues, proprietary tetherings and back office lethargy. Still, some of the fixtures of the all-IP world seem highly applicable to MPEG transport.

Among them: moving software from the edge to the cloud; moving from legacy, monolithic software to modular, agile approaches; and driving features associated with HTML5 into hybrid, and perhaps even legacy, devices.

If video itself is the lowest common denominator, then it’s safe to say that the MPEG and IP transport worlds have more in common than not.

As video becomes an app, distributed in some cases over MPEG, and in other cases over IP, it becomes a question of how to build an evolutionary path from one to the next for the sake of the golden child: video.

How do we manage the coexistence while dialing up the volume on IP and dialing down the existence of MPEG video transport? (And how do we do that in a way that doesn’t require operators to incur huge capital investments? Also a biggie.)

The transition
At this point in the MPEG-to-IP transition, a plausible first step is to take a top-down look at everything – every point in the network, from content reception to headend to hub to node to CPE, including navigation. What is common? Fundamentally, video is common, but the transports are different.

Anything with software on it needs to be closely examined, with this question in mind: Why does it need to be here? Can it go in the cloud?

And likewise for conditional access, QoS, unicast vs. multiscast, in-band and out-of-band signaling, and navigation. It’s a matter of identifying how to get from old world to new world, seamlessly. Wouldn’t it be nice, for instance, to have a common, uniform user experience, whether over MPEG transport to set-tops or to IP devices, like iPads?

With headends and the racks and racks of servers and computers within them: What needs to stay? What can go higher up in the network?

In the home, DLNA (Digital Living Network Alliance) is already making headway in making existing, IP-based CPE able to share resources with other devices. PCs will be able to act as generic set-top terminals by a software load that essentially determines the personality of connected devices.

All in all, it’s safe to say that yes, MPEG video transport will recede, not unlike how analog is receding. It did and does its job well. Our work now is to find a cost-effective, efficient way to go from connectionless to connection-oriented, from conditional access to digital rights management, from satellite delivery to CDNs, from broadcast to adaptive streaming. May we live in interesting times.

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