Built for speed: Comcast RDK
Comcast’s Reference Development Kit shortens development cycles.
In today’s competitive market, cable operators need to be both nimble and thrifty when it comes to developing new products and services.
Currently, it takes about two years to deliver a new set-top box from the design stage into a customer’s home, but over the past few years, Comcast has been developing its Comcast Reference Development Kit to cut that innovation cycle in half.
In May, during a panel session at The Cable Show in Boston, Comcast’s Steve Reynolds, senior vice president of CPE and home networking, outlined the elements of the Comcast RDK and why it’s important to the cable operator industry.
“The typical set-top box development cycle was taking about 24 months when we launched this project, and that’s just a long time to go through the whole process of building the box, building the software, and getting everything up and running,” Reynolds said. “So we had this notion of building a reference design for software that would bring all of the modules together in a pre-integrated kit, where we could take that kit and work directly with the SoC manufacturers to get the RDK up and running on those chip platforms before they even started building the box around that chip.
“By working directly with the SoC manufacturers to do that porting, we really make all of the software that we need for a box OEM available essentially when that chip comes back from samples, and our hope is that by launching this software platform and doing all of this advance work with the SoC manufacturers, we'll be able to cut that development cycle to a year, or even under a year, to launch a brand new set-top box.”
The Comcast RDK was developed internally using open-source components and by working with various vendors. The RDK is a community-based project that allows developers, vendors and cable operators to use a defined stack of software on one layer in order to provision set-top boxes and gateways. Reynolds compared the RDK to the community of handset developers that have rallied around the Android operating system in order to accelerate the speed to market of new devices.
The RDK allows all of the interested parties to develop once and then scale across multiple environments – in the CableCard/QAM/MEPG-2 world of today, as well as in the IP environment of tomorrow. While Comcast doesn’t provide a full list of licensees, it has publicly licensed the RDK to itaas, Entropic and Broadcom.
Cable operators that have openly embraced the RDK to date include, in addition to Comcast, Charter Communications, Time Warner Cable and Liberty Global.
“I think from a cable operator perspective, the advantage of having a single software platform is pretty clear in the sense that they get the advantage of scale, and third-party application developers can develop to a single set of functions and capabilities,” said Jatin Desai, chief technology officer at itaas. “What the RDK brings is having the standard interfaces and a shared source code model so you can reasonably guarantee that the interfaces and functionality are going to work on the various platforms that are going to be supported by it. By selecting to work with specific SoCs, you can optimize the RDK to a specific SoC vendor once, and the benefits can be realized across multiple MSOs.
“In terms of vendors, SoC or OEM vendors, what it does provide is the ability to go to market with a single platform and a single-source code base across the MSOs that are licensing the RDK.”
While CableLabs’ OCAP/tru2way specifications sought to unify a technology across MSOs, some cable operators had their own versions that each needed their own support from the vendors, which instead led to fragmentation.
“We’re looking at the RDK for our IP set-top initiative that we’re working on deploying toward the end of this year and early next year,” said Chris Cholas, director of subscriber equipment for Time Warner Cable. “We’re excited about the RDK for a number of reasons. One of them is mostly on the integration side. We see a very large benefit in implementing a single stack across multiple vendors, which we hope the RDK will offer us.
“We’ve spent a lot of time in that portion of the development cycle when we did OCAP maintaining three different OCAP stacks. There were a lot of differences, and it took a lot of coordination to make that happen. So the benefit from running the RDK is that you keep everything simple in the stack down inside of the IP set-top. We did a lot of modifications above the stack or above the browser in the HTML5 world to get it out as quickly as possible.”
In June, Time Warner Cable started rolling out an updated OCAP guide that included cloud-based functionalities in VOD. The VOD cloud capabilities, which feature richer graphics and better search functionalities, will be tied into cloud-based navigation on a new guide that will work with the RDK-based IP set-top boxes.
Building the RDK
At the base layer of the RDK stack are the SoC companies, such as Broadcom and Entropic, which do the basic porting to make it work on their platforms (see Figure 1).
On top of the SoC layer are the OEM manufacturers, which include the likes of Pace, Cisco and Motorola, that put the SoC baseboards into their boxes. The actual RDK layer is next, and Reynolds said this is where most of the development work is being done, with the goal of keeping as much of it common as possible.
The traditional, or current, implementation of the RDK includes CableLabs’ “Reference Implementation” for OCAP and tru2way, as well as the Java Virtual Machine (JVM).
Open-source components of the RDK include GStreamer, QT and WebKit, which are execution environments that can be tailored to each MSO. There are also optional plug-ins, such as Adobe Flash and Smooth HD, the latter of which is part of Microsoft’s PlayReady system.
QT is a windowing framework that allows cable operators to do multiple applications within the same runtime environment, according to Reynolds. GStreamer is a media management framework that enables cable operators to do manipulation of the video streams. It was originally developed for Web-based content, and Comcast has adopted it for its own IP boxes.
Speaking at The Cable Show, Charter Communications’ David Colter, vice president of architecture and technology, said his company has been looking at several transitional paths to all-digital and migrating to IP.
“We’re kind of taking a slightly different step than Comcast, where we’re actually doing an HTML5 user interface on top of it, whereas Comcast has started with XRE,” Colter said. “Because Charter had not done an OCAP guide previously, [the RDK] really gives us a chance to move forward with a different UI experience, and we’ll probably see a field trial from Charter toward the middle of next year.”
One key area is that the RDK has the ability to support multiple execution environments, which lets cable operators develop their own guides and specific applications. Reynolds said Comcast is using an XRE (cross-platform runtime environment) receiver built in QT, which is a Nokia-developed platform that lets it do portable apps in essentially a native layer.
“Other operators have chosen to use the WebKit implementation of HTML5 to build their user interface on top of, but at the lower layers of the RDK, it’s still the same portable code. So all of that work that is being done by Time Warner, Charter and Comcast to optimize the lower layers of the stack is of benefit to all of us,” Reynolds said.
RDK in the field and abroad
Comcast used the RDK to develop its Pace-made “Parker” boxes that are being used for its X1 service, which was formerly called Xcalibur. After a trial in Augusta, Ga., last year, Comcast is rolling out the cloud- and IP-based X1 platform first in Boston, and then to other areas of its footprint this year.
The RDK is also the basis for Comcast’s IP XI3 client device that will work in conjunction with the cable operator’s XG1 hybrid gateways.
Itaas’ Desai said his company is working with cable operators and vendors to define validation criteria architecture for the RDK. As a licensee, itaas can also sub-license the RDK to other cable operators.
“I can’t name names, but we are having discussions about the RDK with international MSOs,” he said. “We’re trying to educate them, and there’s definitely interest. We’ve heard from Comcast that international MSOs are interested, as well.
“There’s really nothing in the RDK that is specific to American standards, per se. One of the things that the cable industry in general is trying to do is go with worldwide standards, and not cable-specific standards. That’s why the RDK is based on things like HTML, QT, Flash, and other things more or less accepted worldwide instead of just by the cable silos.”