Device Shifting

The San Diego TV-to-PC Trial

By Kenneth Gould, Time Warner Cable

Two key ways for cable companies to demonstrate that network functionality is evolving to accommodate their subscribers’ busy, changing lifestyles are time shifting and device shifting.

Time shifting refers to the ability for viewers to have some degree of control over when they begin watching programs. Time Warner Cable launched its version of time shifting, called Start Over, in November 2005. By the end of 2006, TWC had seven markets in play with this capability, with plans to expand the number of markets significantly in 2007 and 2008.*

Device shifting, on the other hand, provides subscribers with the opportunity to watch TV programming on PCs, cell phones and other devices, not just immobile TV sets. In July 2005, TWC launched a broadband TV (BBTV) trial in San Diego that allowed some customers to watch TV programming on PCs inside subscribers’ homes.

What follows is an overview of the TV-to-PC trial, a summary of lessons learned and a look at some of the related capabilities that TWC would like to explore going forward. While the particular implementation used for the trial will likely not be replicated elsewhere within TWC’s footprint in the near term, the information gleaned from it is worth many times more than the cost of its implementation.

TV-to-PC overview

TWC’s BBTV trial was set up to deliver approximately 80 broadcast channels to subscribers over a high-speed data network using DOCSIS. The goals of the trial included exploring technical implementation issues, policy topics and marketing strategies.

In order to receive the BBTV service, the customers had to be subscribed to one of the basic or expanded basic video tiers and to TWC’s Roadrunner high-speed data service. The trial was accessible to customers residing in an area served by several hubs in TWC’s San Diego division.

The 80 channels of broadcast video are identical to those found on the San Diego division’s basic or extended basic video tiers. The channels on the BBTV service are on parity to those that customers can access on their TV sets, meaning that if they subscribe to the basic video tier, they cannot access the extended basic video tier on their PCs.

Figure 1 shows the network architecture used to support the BBTV trial.

FIGURE 1: Network topology engineered to support TWC’s TV-to PC trial in San Diego

The real-time encoders (RTEs) are approximately 40 general purpose PCs with high-end encoder cards. Each RTE is capable of encoding two video channels simultaneously. A subset of the channels consists of programming containing secondary audio feeds. For this subset, a single encoder is typically used to encode the video and both audio feeds. The RTEs also run the “producer” program that encrypts the video and synchronizes the digital rights management keys with the Storefront server. The video client on the PC must receive an encrypted license from the Storefront that allows that unique client to first decrypt the license and then use the license to decrypt the video. Different licenses are used to protect the individual channels in the different video tiers. The license is unique per video client and cannot be successfully moved from one PC to another.

The video codec, video servers and video player were provided by Real Networks, and the video/audio data rates for a single channel are less than 1 Mbps.

The user interface used to navigate between channels and to control the video playback is a series of Web pages served to the users’ browsers from the BBTV Storefront. The Storefront verifies that the user is entitled to access the BBTV service (via the BBTV Authentication Server), determines to which video tier the user is subscribed, and provides an encrypted license to the RealVideo player that is embedded within the Web page. (See Figure 2.)

FIGURE 2: Example of programming viewed on a PC by a subscriber in TWC’s BBTV trial

The BBTV Authentication Server works in conjunction with several cable-modem provisioning servers to ensure that the user is accessing the video service through a cable modem associated with the subscriber account that is also associated with an appropriate video service tier.

Each video channel is requested via a unique Web URL. In fact, the URL for each channel is specific to an individual instance of the video client running on a PC. A user cannot “skip” the authentication process by sharing one of the video URLs with another person.

The Real Helix video servers receive the requests for video from the video client and stream the video to the appropriate PC. If a particular channel proves to be extremely popular, multiple video servers are able to serve the same video channel to multiple video clients. The video is only delivered from an RTE to the appropriate video server if a user has requested the channel. When a channel is unwatched, no video traffic is transported from the RTE to the video server. Usage statistics are pushed from the video servers to the reporting server for correlation.

Project goals

One driving goal of the project was to take the video content accessible via the TV set and demonstrate that the same service could be replicated and delivered over an Internet protocol (IP) network (in this case, DOCSIS) to a PC. The BBTV service really is a replication of the analog TV viewing experience—the emergency alert system (EAS) messaging, closed captioning, secondary audio controls, parental controls and channel navigation found on the TV set were replicated onto the PC platform. The service does allow for full-screen mode, mute and volume control, but does not allow personal video recorder (PVR)-like capabilities such as live pause, rewind, fast-forward, etc., nor does it support Start Over capabilities.

One goal of the project was to determine if the PC could viably be considered as just another video outlet in the home.

Because the goal was to demonstrate device shifting, and not place shifting, checks were put in place to ensure that the user was accessing the service from behind the cable modem associated with their high-speed data account. The customer could not provide access to the service to someone served by a digital subscriber line (DSL) modem, nor behind a cable modem associated with an account that did not also subscribe to one of the appropriate video tiers.

While we will not go into all of the content protection details here, we can also state that the content is encrypted, digital rights management (DRM) protected, and that the licenses handed out to the PC to decrypt the video stream could not be used on another PC, nor could the license be used by the PC were it to be moved to another cable modem.

Insights gained

Why demonstrate device shifting? Better yet, why not put an RF tuner into a subscriber’s PC and continue to deliver analog video to every device in the household? The short answer is that while we continue to launch interesting and customer-rewarding products over the “classic” MPEG video plant, TWC wanted to identify potential pitfalls and triumphs that could come from delivery of video over a high-speed IP network.

Here are some of the insights gained from the BBTV trial:

• TWC spent quite a bit of time determining the least intrusive methods for authenticating the users, verifying their physical location, and authorizing the subscribers’ video client to allow the display of the appropriate video tier. Obviously this required a high degree of integration with the high-speed data provisioning systems and with the cable billing system. All of these checks can be performed quickly enough that they do not adversely affect the consumer experience.
• While the coordination of the Web-based navigation and video display client with the DRM-specific parts of the backend system are complex, to the end user it is seamless and nonintrusive.
• There are fundamental features of the traditional cable video service that have existed for decades that can be quite complicated to replicate in a PC video environment. For example, TWC developed a system for delivering closed captioning data to the PC outside of the video stream, yet still keeping that data synchronized with the audio. This was largely because of the fact that for the trial we elected to use a video codec that is not capable of accommodating the closed captioning data within the video stream.
• TWC chose to encode and encrypt the video after the EAS messages were overlaid on the video and after video advertisements were inserted. This was acceptable for a field trial because the limited geographic area served by the trial was contained within a single ad zone and EAS zone.
• TWC constantly monitors the DOCSIS cable modem termination system (CMTS) utilization to project when additional capacity will be required. As with the introduction of cable telephony services, the mechanisms that trigger activities to add more capacity were also used for the BBTV trial. We should point out that for our trial purposes, unicast video streams served each video customer. We developed the ability to multicast the streams, but elected not to implement it for the BBTV trial and instead considered the unicast traffic to model the “worst case” traffic pattern.
• Usage reporting systems can be made very robust and will keep the marketing and product development teams busy forever.

Future capabilities

Although the momentum within TWC for Start Over has created a long list of related, time-shifting capabilities that TWC wants to explore (including program guides, real-time acquisition, storage, scheduling, distribution, etc.) some items overlap with device shifting.

Just as time-shifting introduces new advertising opportunities, for instance, the real-time insertion of ads into IP video streams being delivered over DOCSIS to nontraditional video devices, such as PCs, promises significant benefits. Advertising in a BBTV scenario would pose challenges initially to implement, but here are some points to consider:

• Cable companies can increase ad revenues by catering to marketers increasingly interested in using the Internet as an advertising vehicle.
• The concept of “targeted advertising” can be utilized to deliver to subscribers ads that more closely match their interests, resulting in higher response rates and leading to marketers willing to pay more to leverage this type of advertising.
• The additional revenues obtained from inserting ads into BBTV streams can help fund broader device-shifting deployments.

Device shifting also requires that the conditional access (CA) systems used on traditional cable infrastructures be replicated to protect content delivered over IP networks and augmented with DRM to a degree that satisfies content owners and is transparent to subscribers.

Network advantage

Experience has shown that consumers positively receive network-based functionalities. Beyond services such as Start Over and BBTV, for instance, other examples include:

• Virtual private network (VPN) services supported on platforms in a service provider’s networks replacing VPNs run on enterprise equipment
• Residential voice mail systems managed by service providers becoming preferable to telephone answering machines in the home
• The growing popularity of on-demand movies vs. rentals from brick-and-mortar video chains
• Increasing amounts of music and video being downloaded via paid services, at the expense of peer-to-peer swapping

For its part, BBTV provides subscribers with the ability to view broadcast-quality TV programming on their PCs, offering them the added convenience of, say, watching their favorite TV shows while checking email.

Future investments by cable operators in their DOCSIS infrastructures, and by computer manufacturers in PC technology, will enable the quality of the picture and audio experienced by viewers to evolve to the point where broadband TV viewed on a PC will be equivalent to what traditional TV sets offer.

Many additional technical challenges remain for both time shifting and device shifting, especially in the areas of storage formats and encryption techniques. But given continued innovation, the prospect of not just providing “everything on demand,” but also moving closer to making “television more like the Internet and the Internet more like television” appears bright.

Kenneth Gould is senior director, consumer technology development, at Time Warner Cable.
Reach him at Kenneth.Gould@twcable.com.