SQUARE PEGS AND ROUND HOLES
Don’t Look Now, but the
Interfaces to Your
Projectors and Monitors are Changing…
The transition to digital media has been a good thing in many ways. It’s brought the cost and complexity of video acquisition and editing equipment down much faster than most would have predicted. Digital has made file storage, transport, and duplication far less complex.
Combined with high-speed pipes (broadband, SDI, 1394) it’s possible to move large media files around pretty much anywhere and anytime you wish. So it stands to reason that the displays we use to view those files should also adopt digital interfaces for the same reasons.
That’s exactly what’s been happening, except the situation is a little more turbulent thanks to the blurring of “consumer” and “pro” display technology. Hollywood and other media giants are so worried about piracy and loss of revenue from their premium content (particularly anything that is mastered and distributed in HD formats) that they are successfully pressuring display manufacturers to incorporate ‘secure’ interfaces; some of which sound downright draconian.
You’ve probably heard about DVI, the PC-based digital interface that has now migrated into the consumer realm. But do you know what DVI-HDCP is? How about HDMI? Ever salute the broadcast flag? Would you recognize an analog hole before you stepped in one?
These are all terms at the forefront of the copyright debates, and will have some effect on the work that you do – or watch. Let’s delve a little deeper into each.
PURE DIGITAL
DVI, or Digital Visual Interface, grew out of a consortium of companies known as the Digital Display Working Group (www.ddwg.org), including Intel, Fujitsu, Hewlett-Packard, IBM, NEC, and Silicon Image. The intent was to reach accord on a pure digital pipeline from a PC to the new breed of LCD and plasma monitors.
DVI has since grown and been adopted by the consumer display industry as a ‘preferred’ interface between such things as DVD players and cable/satellite/terrestrial set-top DTV receivers. DVI is available in two flavors: DVI-I, which is a combination analog/digital interface for some backwards compatibility, and DVI-D, which is 100% digital.
DVI also accommodates two different bandwidths. Dual Link DVI supports 2x165 MHz channels of bandwidth, which can handle a 2048x1536 pixel progressive-scan image at 60 Hz refresh or a 1920x1080 pixel image with progressive-scan at 85 Hz. All 24 pins on the connector are used for Dual Link.
Single Link DVI supports a maximum bandwidth of 165 MHz on a single channel, sufficient to handle a 1920x1080-interlaced signal at 60 Hz or a 1280x1024 image with an 85Hz refresh. A single link implementation utilizes 12 of the 24 available pins.
The consumer world adds another layer of complexity by incorporating High Definition Copy Protection (HDCP). HDCP encrypts each pixel as it moves from the player or set-top to the display, using an asymmetric system that calls for periodic reauthorization from the source. In other words, it’s dynamic.
You can take it for granted that every plasma or LCD TV, every rear-projection TV, and every set-top receiver that uses DVI is set up for HDCP. That means certain industrial displays may not work with set-tops or DVD players, unless those devices ignore the HDCP protocol.
In a test I conducted last summer, I was unable to drive an NEC 42-inch plasma through its DVI input from my Samsung SIRT-165 set-top DTV receiver. The NEC plasma simply displayed “Illegal Signal” and nothing more. Other products used in that test, including a 46-inch plasma from Vizio and a 40-inch LCD monitor from NEC-Mitsubishi, weren’t as fussy with the DVI connection.
The fervent hope of content providers is that DVI-HDCP will become the standard and that analog component video display connections will go away. (For good. Completely. Never to be seen again!)
That’s because those content providers are worried about the so-called ‘analog hole’, or the ability of anyone to digitize and copy the video signals coming from a three-wire component connection. Never mind that it would require quite a bit of bandwidth to send such files over the Internet – a one-hour HD program requires about 9 GB of hard drive space when delivered in the ATSC format (about 18 Mb/s).
WAIT! WE WANT A DO-OVER
The move to DVI would be okay for a lot of reasons, not the least of which is the ability of the display and the video source to communicate and set up the optimum pixel count and picture refresh rate for your viewing pleasure. The problem is that now another interface is being proposed (and even adopted), and it will replace DVI down the road.
That interface is HDMI, which stands for (maybe you guessed it) High Definition Multimedia Interface. HDMI is intended to be a one-plug “do-it-all” connection that can carry not only video and display information, but also audio and even text. The companies behind HDMI include Pioneer, Panasonic, Hitachi, Thomson (RCA), Sony, Silicon Image (again), Philips, and Toshiba.
According to the HDMI web site (www.hdmi.org), “HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable. It transmits all ATSC HDTV standards and supports 8-channel digital audio, with bandwidth to spare to accommodate future enhancements and requirements.”
HDMI also has a lot more bandwidth than DVI – about 5 Gb/s, to be exact. It’s also supposed to work with longer cable lengths than DVI, although some folks have found DVI is fine with cables up to 15 feet. Of course, it goes without saying that the HDMI connector looks nothing like a DVI connector and that both are physically incompatible without an adapter. That means a good business for companies who manufacture adapters, at least for a few years!
The big selling point for HDMI is that it is the ONLY cable you would need to connect between components in a home theater system, including DVD players, set-top boxes, TVs, and AV receivers. (You’ll still need speaker wires, unfortunately…)
At this year’s Consumer Electronics Show, Pioneer showed a complete AV system with all components interconnected by HDMI cables. I can say that it sure does eliminate the old “rat’s nest” of wiring, and it appears to be a true plug-and-play system – the Pioneer DVD player connected in the system set up its video output automatically to best match the plasma monitor it was driving.
IT’S A GRAND OLD FLAG, AND YOU’D BETTER NOT COPY IT
Our discussion of secure visual interfaces wouldn’t be complete without touching on the controversial broadcast flag. This seemingly innocuous collection of bits is designed to “prevent distribution of HDTV shows on the Internet”, according to CBS/Viacom. In theory, a TV program encoded with the flag couldn’t be copied and “Napstered”.
The problem is, such a scheme only works if the equipment that receives the flag bits responds accordingly. That means all of the legacy set-top TV tuners out there will just pass it through like a watermelon seed, as will the home theater PC systems that are capable of tuning in and recording (time-shifting) HD programs.
The FCC gave the broadcast flag further momentum last November when it was green-lighted for implementation in consumer integrated digital TVs and set-top receivers. Not surprisingly, advocacy groups like the Electronic Frontier Foundation (www.eff.com) and Public Knowledge (www.publicknowledge.org) have filed suit against the FCC, seeking to overturn this mandate.
There are real concerns with the broadcast flag and any copy-protection systems, mostly that pertain to First Amendment rights to free speech and an individual’s ability to make copies of programs for their own use. With the flag, bits could be sent to the receiver or TV that set any of these copying conditions and/or restrictions – (1) Okay once, (2) Okay many times, (3) Never okay, (4) Not possible on Internet. (What do you want to bet that #4 shows up every time?)
The broadcast flag is not in itself an interface standard. But it can and will ride along on the back of HDCP content, as well as programs you receive over the air, off digital cable, or off satellite. Combined with a secure interface, it would seem that protection of premium digital video content might be bullet-proof, except we all know the DeCSS DVD encryption system was broken by a 15-year old a few years back.
YOU LOOK FUZZY, SOMEHOW
One concern that has arisen out of all these discussions and standards is the threat of ‘down-rezzing’—a technique whereby the content provider would signal your set-top receiver or integrated digital TV not to show HD content at high resolution.
At first glance, this would seem to be oxymoronic. Why would anyone go to the trouble of producing HD programming for delivery to customers with HDTV sets, then down-convert that content in resolution so (supposedly) it can’t be copied and illegally distributed- particularly if those viewers paid good money for the service?
It’s a good example of legal departments run amuck. In fact, most DirecTV set-top HDTV receivers sold in the past three years have the capability to shut off the HD analog outputs remotely, but to my knowledge it has never been done.
At the recent CEA HDTV Summit in Washington, Rick Chessen, chairman of the FCC’s Digital Television task force, stated that while the FCC feels confident the broadcast flag ruling will be upheld in court, they have prohibited what is called ‘selectable output controls’ on set-top receivers and in integrated digital TV sets.
IT’S NOT JUST A PLUG ANYMORE
Could you ever conceive such a fuss arising over a simple video display interface? Most people couldn’t prior to the “HD Age”. But those simple plugs are taking on far more importance these days as the next wave of digital TVs, digital monitors, DVD players (including the new Blu-Ray models) and set-top receivers come to market.
How will things turn out? No one can say for sure, although a few things are certain. (1) DVI will give way to HDMI, now that several movie studios have endorsed it. (2) The broadcast flag is here to stay. (3) Cabling will become easier in the future. (4) Court dockets will remain full for some time as First Amendment and intellectual property rights continue to clash behind your TV screen.