CEMA announced publication of a voluntary standard (EIA-761) for the interface between digital set-top boxes and digital television receivers using the U.S. digital-modulation system, vestigial sideband (VSB). The VSB digital-TV interface, also called an RF remodulator standard, translates quadrature amplitude modulation, widely used by the cable industry, into VSB. The spec, which also includes enhanced on-screen display capability, can be used to connect decoder boxes, satellite receivers, digital VCRs or a computer to a digital-TV receiver.

CEMA's RF remodulator spec will complement a 1394 standard and two other technical specs for linking digital set-tops and receivers. The other CEMA interface specs include a component video interface and the National Renewable Security Standard (NRSS) interface.

CEMA said in November that it had reached an agreement with the cable industry on extensions to the baseline IEEE-1394 interface spec to link digital set-tops and digital TVs. The spec followed regulatory pressure to develop a cable-DTV link in time for the start of U.S. digital-TV broadcasts last November.

The group's latest move to approve the DTV remodulator spec adds a new wrinkle to yet-to-be-resolved discussions over interfaces as well as the copy-protection issue between a cable set-top and a digital-TV receiver.

With the VSB digital-TV-interface standard, some in the consumer industry now say an IEEE-1394 interface is not the only digital-interface solution. They also stress that the Digital Transmission Content Protection Method (DTCP) — a copy-protection scheme for 1394 — is not the sole digital copy-protection scheme to be used for the cable-DTV receiver interface.

"Neither Sony-led 1394 nor its DTCP copy-protection scheme is a done deal yet," said Ed Milbourn, manager of advanced TV product planning at Thomson Consumer Electronics.

The crux of the issue is not only the choice of an interface for digital consumer systems, but also the copy-protection method for signals moving from one device to another. Two camps have been promoting separate copy-protected digital interfaces for linking digital cable or satellite set-tops, VCRs, DVD players and PCs to digital-TV sets. The interfaces would prevent unauthorized copying of digital programming.

CEMA said the four standards will ensure that future DTV sets can receive digital cable signals and can be used with digital-video services and devices.

George Hanover, vice president for technology at CEMA, said the association's digital-interface specs let manufacturers pick the one best-suited to a particular application. "They're actually [designed] for different applications," he said. "They're all interfaces, but they do have very specific applications. There is a little overlap."

Asked whether each would require separate copy-protection schemes, Hanover said they would for some applications using either one- or two-way communications. However, the 1394 and NRSS interfaces could probably use the same scheme.

Zenith Electronics Corp. and Thomson Consumer Electronics head a manufacturers group that favors a smart-card-based renewable encryption scheme called Extended Conditional Access, or XCA. A second group, led by Sony Corp., favors the encryption-based DTCP. The Sony group, known as 5C, includes Hitachi, Intel, Matsushita and Toshiba.

At the Consumer Electronics Show in Las Vegas, Thomson unveiled what the company touted as the industry's first, secure high-definition DVD. The technology was jointly developed by Thomson and Digital Video Express (Divx). This is the first digital consumer product designed to deploy the VSB digital-TV interface, to connect a DVD player and an HDTV receiver.

According to the scenario, by connecting a DVD player to an HDTV via an RF cable, signals will travel from the DVD player to the HD receiver, without being demodulated, de-encrypted or decoded inside the new DVD player. From the HDTV receiver, the 8VSB modulated HD signals — encrypted — coming off the HD-DVD player look just like those transmitted from an HDTV channel. The smart card inside the HDTV receiver will decrypt the signal, while the HD receiver also takes care of VSB demodulation and HD decoding.

Zenith's Wayne Luplow, executive director for business development, said CEMA is offering "a series of menus with different virtues." Referring to CEMA's inclusion of both the 1394 and VSB remodulator approaches, Luplow added, "The marketplace will eventually go in one direction or the other."

Many consumer electronics manufacturers say privately that they are still not sure which digital interface they plan to use. Their main concern is that featuring either a 1394 or RF remodulator interface, in addition to the copy-protection schemes associated with them, means additional cost. For instance, Apple Computer Inc. is seeking royalties of $1 per port for every IEEE-1394, or Firewire, interface.

Most manufacturers are using an analog-component video interface to connect set-tops to digital-TV receivers. No manufacturer has yet launched a DTV system with a digital interface.

An industry source said, "I do think that 1394 is a good solution for certain applications such as a connection between a digital VCR and a TV, or home networks further in the future. But it is not a solution fit for a set-top and a digital TV today." In his view, that copy-protected digital interface is still "cumbersome, extremely impractical and adds new cost and complication."

Pressure to resolve the digital-encryption debate is growing as regulators seek to jump-start digital-TV services." Consumers want complete solutions and, quite frankly, most don't want to know the details," FCC Commissioner Susan Ness said at CES. "They just want sets that work, that are easy to use, that are affordable and that are compatible with current and future choices in video."

Industry sources said the copy-protection debate is being driven largely by Hollywood studios. The studios' lobbying arm, the Washington-based Motion Picture Association of America (MPAA), said behind-the-scenes negotiations on copy protection are ongoing.

An MPAA spokesman also downplayed the impact of the latest CEMA spec on the copy-protection debate. "This is not something that would help consumers who would like to access copy-protected material," he said.