Coping With Cable’s “Switched Digital Video” Technology: TiVo and CableCARD Users Take Note
The transition to digital high definition television continues on cable and satellite as providers rush to add new “HD” versions of cable networks that have been available in standard definition for years. Your cable or satellite provider is probably already pelting you with mailers and promotional announcements talking about new channels coming to your lineup. Most of the new channels turn up on those very high channel numbers accessible on your set top box. Time Warner Cable loves to put a lot of their HD channels on channels starting at 1000, others put them on channel numbers above 100. Satellite providers already offer dozens of HD channels, and have for sometime now, a point they routinely raise in their advertising. So cable systems are in a hurry to catch up.
But for some cable systems, there is a capacity problem. Carrying those high definition signals requires a lot more “bandwidth” (or space) on the cable coming into your home. Most cable systems in the United States were last upgraded in the early 1990s to accommodate the launch of “digital cable,” which actually has nothing to do with the recent digital TV transition, or HD for that matter. Digital cable channels are simply compressed, allowing more channels (often up to six or more) to fit in the amount of space it takes to provide one analog channel (such as those you watch on television sets around your home that do not have those big set top boxes attached to them).
In the 1990s, we suddenly saw hundreds of new channels arrive on digital cable, from niche cable networks like Current and History International, to premium movie channels which suddenly had six to eight extra channels, to a myriad of pay per view and on demand channels. We even got cable radio like Music Choice.
But the challenge of trying to provide 100 or more digital HD channels on today’s cable systems has resulted in some creative thinking by the nation’s cable operators to fit everything into the space they have today, without spending millions of dollars to once again upgrade their cable systems.
Some cable systems like Comcast, the nation’s largest, have been dropping a dozen or more analog channels (which use a lot of space) and moving them to the digital cable tier. Others, like Time Warner Cable and Bright House, are using a new technology called Switched Digital Video (SDV). Simplified, SDV only sends the digital channels people in your neighborhood are watching down the cable line. The cable operator assumes not everyone on your street will watch every digital channel at the same time, so why waste space sending Fox Business News or C-SPAN 3 down the cable if nobody nearby is watching it?
Motorola released a short video which explains how the system works:
The trick, of course, is to make the system as transparent as possible for cable subscribers. Who wants to wait around for a channel to appear as you flip through them with your remote control. The technology is designed to make it look like those “switched video” channels are no different than any others. For subscribers using set top boxes, it has not been difficult to make the whole thing transparent to consumers. The only time a problem can pop up is if the cable company runs out of room because lots of people are watching lots of different channels. Sometimes the cable company makes the “party line” too big, and that increases the chances the system will run out of room at peak viewing times, and someone gets a black screen with a message saying the channel they want to watch is “temporarily unavailable.” When someone down the street switches channels or turns the set off, there is once again room to show more channels.
If you do not watch digital cable, or have a basic cable subscription that does not have a set top box, none of this will matter to you. Analog cable channels are not provided to you this way.

If there is no room in your neighborhood to show additional SDV channels, or if the cable system thinks you are no longer watching the channel, you may see this message on your television.
If you use a “CableCARD” provided by the cable company to plug into your HD television, or if you use an HD TiVo Digital Video Recorder without a cable box, you could run into another problem. The current generation of CableCARDs often cannot communicate with the cable company’s SDV system.
That means when you try to tune a channel provided using SDV, you end up with an error message saying the channel is not available. Those CableCARDs that can successfully request an SDV-provided channel may not be able to respond to the cable company when its software periodically asks (in the background) whether your TV set is still watching an SDV channel. If the equipment cannot respond that you are, the system will assume you are not and the channel will go blank.
Sometimes, the cable system will display a message and let you press a key on your remote to let the system know you are still watching the channel, and do not want it to go away. Unfortunately, without the two way communication that the cable company-provided set top box or add-on equipment provides, there may not be a way to get your request back to the cable company.
The cable industry will ultimately need to release a new generation of CableCARDs that are fully capable of two-way communications. Until that happens, some cable companies are loaning out, often at no charge for at least a year, special add on equipment to deal with this problem.
A Tuning Adapter is a small set top box that adds two-way capability to your existing equipment, so it can “talk” back and forth with the cable system. Some cable companies, like Bright House, will provide up to two of these devices for no charge for 12 months. After that (and for each additional box), the rental fee is $3.80 per month for each Adapter. Time Warner Cable provides them for free.

Uh Oh... the cable system wants to doublecheck you are still watching this channel. If your equipment can't communicate with the cable system, it will assume you are no longer watching, and turn it off.
It’s unfortunate existing CableCARDs can’t work properly without requiring the extra equipment, but when the original CableCARD specifications were developed, SDV wasn’t available.
Eventually, most cable systems will either upgrade systems to handle more channels and services, or will slowly move more and more analog cable channels to digital, opening up lots of additional space for high definition cable and broadcast signals, as well as on-demand and broadband services.
The newest generation systems from Verizon (FiOS) and AT&T’s U-verse use fiber optic cable, which has tons of capacity to handle everything. Verizon installs the fiber cables right to your home. AT&T installs it on the poles in your neighborhood, and then sends only the individual channel(s) you are watching across the copper wire phone cable already in your home. Since AT&T doesn’t send any channels you are not watching across your phone cable, capacity isn’t much of an issue with U-verse.

There are two Tuning Adapter brands, Motorola and Cisco. Your cable system will send you the one that will work for you.
Satellite television relies on a fleet on satellites to deliver channels to subscribers, either on a national “beam” which reaches every home, or a focused narrow “beam” which only reaches small regions of the country (which is used to deliver local television channels). To add capacity, satellite providers launch additional satellites, or find new ways to compress their existing channels to make room for additional programming.













