HDCP VS. DVI

What is DVI?

DVI, an acronym for Digital Visual Interface, is a technology developed in 1999 to enable digital-to-digital high bandwidth data transfer from a computer to a monitor.

What is HDCP?

As we mentioned earlier, DVI delivers exceptionally high quality video. In fact, the quality is nearly as good the original or master content. This previously unattainable quality has raised concern from Hollywood executives who fear video could be mass produced and illegally distributed, much like what has happened within the music industry. In an effort to protect this high definition home video content from being copied and illegally distributed, Hollywood studios employed tech companies Intel and Silicon Image to develop a method of security encryption. The standard they created is called High bandwidth Digital Content Protection or HDCP.

HDCP works by adding circuitry within the DVI connection on both transmitter (DVD player, cable box, etc.) and the receiver (projector, LCD TV, etc.) that encrypts video content. Software such as DVDs will not be affected as was the case with tapes for your VCR. Instead, the source players and the display device will be responsible for the encryption.

Why use DVI?

DVI is the fastest way to transfer data or video. It beats every other connectivity standard hands down. DVI is a 24-bit digital RGB interface that can support computer resolutions as high as 1600 x 1200 (UXGA), and the cinematic-apex, 1080 progressive high definition format. In fact, it is capable of supporting even higher bandwidth using a Dual Link. Dual link DVI connections can produce double UXGA bandwidth, but almost no one is using dual link today.

Using DVI with a digital display device, such as a projector or flat screen monitor, will create an entirely digital-to-digital connection. With a VGA cable the information from a digital source like a computer has to be converted from digital to analog . If you were using a projector there was an additional conversion back to digital. Each conversion slightly degrades the quality of the final image. Theoretically a DVI connection will therefore provide the least number of conversions, providing the consumer with the best quality image.

Why wouldn't I want to use DVI?

Although it is a high-bandwidth connection, DVI does have some limitations. If your home theater setup requires that you run cables longer than 6 feet from source to projector, DVI may not be the best choice for you. Signal degradation in DVI is like most digital devices in that content becomes unwatchable, suffering from "sparkles" or "blue-screening" if the cable has been run too far. Signal amplifiers are available that allow for longer cable runs, but they are not cheap. A solution built in to the cable or display device is likely on the way, but is not here yet.

Because DVI is a new technology, still in version 1.0, it is not yet entirely standardized. There are some compatibility issues with chip designs, board sets, and in the interconnecting of the cable assembly. With most compatibility problems the issue is periodic video artifacts rather than complete failure.

Can I watch HDTV without a DVI connection on my projector?

Yes. Using a component video (YPbPr analog) input you can still watch HDTV content. If the video source (DVD player or cable box) is able, you can watch video as high as 1080i with this type of connection. The primary difference between the two types of connections is that component video will be a converted analog signal rather than a pure digital signal.

A high-definition analog signal still looks immensely better than a regular analog broadcast signal. Particularly when viewed on a large screen. In some cases, an analog image will often look as good (and sometimes better) than a digital signal.

Can I watch HDTV content using DVI without HDCP compatibility?

Yes, if the cable box or DVD player is capable of outputting HD quality signals and is not using the HDCP encryption yet, you will still be able to use your DVI connection to watch high-definition content. Remember you can also watch analog high-definition content via a component video connection.

Will projectors with DVI and without HDCP be made backwards compatible?
It isn't clear whether a legitimate, legal solution will be developed for those consumers who purchased DVI products before the advent of HDCP. Projectors without HDCP compatibility will not be made compatible with a simple firmware update. There is hardware required to make the conversion. However, there may be a solution using an IEEE 1394 converter that allows for digital-to-digital HDTV from legacy DVI devices.

What about DTCP and IEEE 1394 FireWire?

Digital Transmission Content Protection, or DTCP , is the encryption standard used to protect content which is sent over the IEEE 1394 of FireWire standard. The DTCP standard allows for use of a set top box which decodes the digital signal. DTCP is unlike HDCP which requires a direct link between source and display device, however, due to the bandwidth limitations of FireWire, it can output no higher than a 480p digital signal.

FireWire is not a common connection on video projectors, but is more commonly found on plasma and LCD TV digital displays.

New on the Horizon -- HDMI.

High Definition Multimedia Interface is a descendant of DVI. Like DVI, it is a digital cable and connection that supports digital data transmission. Unlike DVI which supports only video transmission, HDMI supports both high definition video and audio. HDMI will offer 'legacy' support of older DVI connections.

DirecTV, EchoStar (Dish Network), and CableLabs are supporting the new HDMI standard.