Must-carry, Firewire and PSIP

Mon, 08/31/1998 - 8:00pm
Jeffrey Krauss, Must-Carry Maven and President of Telecommunications and Technology Policy
By Jeffrey Krauss, must-carry maven and President of Telecommunications and Technology Policy

The FCC has proposed seven alternatives for must-carry policies during the transition from today's analog broadcasting to digital broadcasting. These range from requiring cable systems to start carrying all digital TV broadcasts as soon as they begin, to not requiring any digital carriage until all analog broadcasts have terminated, and a variety of intermediate alternatives. This issue will eventually boil down to a negotiated compromise between the broadcast and cable industries, after there have been some contracts negotiated between individual MSOs and broadcast networks.


The first major technical issue that the FCC has highlighted is the absence of an industry standard for connecting cable boxes to TV sets. While there is widespread agreement that the IEEE 1394 ("Firewire") high-speed data bus should be the physical layer, there is a fight between TV makers Thomson and Sony over the command language to be used on the bus.

Not only has the FCC figured out that this is a serious problem, but so has Congress. On July 15, Sen. John McCain sent a letter to the Consumer Electronics Manufacturers Association (CEMA), blaming it for creating a major obstacle to the public's acceptance of digital television. And indeed, CEMA deserves this blame, because CEMA created two separate standards subcommittees, one to standardize the Thomson approach, and one to standardize the Sony approach, rather than forcing the two sides to reach a compromise. TCI recently announced that its cable boxes will use the Sony approach, so maybe the cable industry will be the one to pick a winner.

Copy protection

The FCC recognized that even when that dispute is ended, there is still the question of copy protection. The Firewire link between the cable box and the TV set can also connect to a digital VCR, and the movie industry has said that it wants some kind of copy protection on that link to prevent unrestricted copying. The FCC noted that a group of five companies has presented a proposal to add a form of encryption to the Firewire link as a way to accomplish copy protection, but some industry observers think this proposal will be too expensive to implement.

What about multiplexed programming? If a broadcaster carries (say) six standard definition movies on its digital channel, and if the FCC decides that only one of those is entitled to must-carry status, then the cable operator would presumably demultiplex the channel, select the one program, and remultiplex it into a bundle with other programs. But that's hard to do if the broadcaster uses statistical multiplexing, because the data rate of the selected program keeps varying. So multiplexing it into a bundle with other programming becomes difficult, because the cable operator has no control over the amount of channel capacity that a program needs at any time. And what happens when the broadcaster switches from an SDTV multiplex to a single HDTV program? The cable operator will have to know in advance when this is scheduled, and will have to make sufficient channel capacity available.

The Program and System Information Protocol (PSIP) is a standard that defines a data channel carried along with digital broadcasts. The PSIP data is ancillary data, just like the ancillary data that is carried in the vertical blanking interval of analog television signals. Except for the ancillary data that carries closed captioning information in analog channels, cable operators are free to strip out the broadcasters' ancillary data and replace it with their own. And that policy applies to digital must-carry as well.

But PSIP contains channel navigating and numbering data. PSIP creates the idea of two-part channel numbers, to allow viewers to select among multiple programs within the 6 MHz digital channel. And it allows a TV station to retain the "brand name" of the analog channel number. In this way, while WNBC (channel 4) has been assigned channel 28 for digital broadcasts, the PSIP data will tell the TV set that when the viewer selects channel 4-1, the TV set should tune to channel 28 and display the first movie in the multiplex. The viewer need never know that it is being carried on channel 28. But PSIP is a brand-new standard, so existing digital cable systems (and cable boxes) won't support PSIP, at least not yet, and neither will most of the digital TV sets on the market this year. So the FCC has asked whether it should have rules that require support for PSIP.

The FCC notice does not propose any rules; it simply contains a list of alternatives and asks for industry comments. It isn't a process geared to speed, but that should suit the cable industry.


Share This Story

You may login with either your assigned username or your e-mail address.
The password field is case sensitive.