January 2007 - HowTo - Choosing The Right Video Connections On Your HDTV - page 2
DVI
 DVI, or the digital visual interface, was born in the computer realm, as a way to pass video signals from computer to monitor – hence its bulky, computer-like appearance. In its home entertainment form, DVI allows you to send a completely digital, uncompressed video signal between source and TV. When you use an analog connection like component video, the digital video signal has to pass through digital-to-analog and analog-to-digital converters en route to the TV, which can potentially degrade the signal’s quality. A digital connection like DVI removes the need for these converters and thus allows for an improved image, at least in theory. One potential tradeoff is that a DVI signal may suffer when traveling over a long distance; if your cable run is longer than 20 feet, you may want to stick with component video. Another more expensive solution is to look at fiber optic cables, which send up to 1080p video over longer runs (as long as 300 feet) without loss.
The DVI signal’s uncompressed nature allows for a high-quality HDTV image, but it also means that the signal is much too large to be recorded. To further prevent the illegal passing and copying of the digital signal, most current home theater components incorporate HDCP copy protection into their DVI connections. A DVI connector that lacks HDCP protection won’t communicate properly with one that has it. If you bought one of the first HDTVs or projectors to use DVI, it probably lacks HDCP and thus won’t work with one of the many new DVI-equipped DVD players and set-top boxes on the market. DVI was essentially a stopgap between analog component video and digital HDMI, and it’s appearing on fewer new HDTVs, as manufacturers embrace HDMI instead.
HDMI
 HDMI (High Definition Multimedia Interface) has the potential to someday replace all of the other connections on your TV, receiver, DVD player and set-top box. That’s because this all-digital connector can carry both high-definition video and uncompressed, multi-channel digital audio over one cable. It also enables devices to communicate intelligently with one another, relaying power status and other information back and forth to make sure every device in the loop is on the same page. Okay, it may not replace every connection. Like DVI, the HDMI signal is too big to be recorded, so we must rely on a connection like FireWire (see below) for that. I don’t know about you, but I could live quite happily with a rack full of equipment that uses just HDMI and FireWire connections.
Thus far, HDMI has been used primarily as a video-only connection linking HDTVs to DVD players and set-top boxes. As a video connector, it’s compatible with DVI and uses HDCP copy protection, so you can connect a DVI-equipped DVD player to an HDMI-equipped HDTV (as long as the DVI device has HDCP). You can purchase cables that offer DVI on one end and HDMI on the other, or you can buy a simple DVI-to-HDMI (or vice versa) adapter. HDMI has a much slimmer form factor than DVI and can travel over longer cable runs with less signal degradation, although degradation is still a concern.
Slowly but surely, devices are emerging that make use of HDMI’s audio and control capabilities. Panasonic recently released its EZ Sync product line, which utilizes HDMI’s full potential to reduce cable clutter and improve communication between the company’s flat panels, receivers and DVD players. At the recent CEDIA show, many electronics manufacturers were touting receivers that let you pass both video and audio over HDMI to reduce the number of cables you need when routing everything through a receiver. One reason these products have been slow in coming is because the HDMI spec is still evolving to incorporate greater functionality. We’re now at HDMI version 1.3, and we all know what that means: multiples specs usually equals mass confusion. In the video realm, each HDMI spec is backwards-compatible, so you should be able to pass a high-definition signal from any HDMI connection to any other HDMI connection, including 1080p. Communication errors and inconsistencies abound, however, so HDMI has a way to go before it becomes the model of smart, simple connection we all hope it can be.
Honorable Mention: For You Over-the-Air Types
 As hard as it may be to believe, I still own a television that has just one lone RF input on its backside. Since the golden days of yore, broadcasters have modulated their TV signal onto a radio frequency signal, which enters the TV through a single coaxial cable and gets demodulated by the TV’s internal tuner. If your new TV has any type of internal tuner, it will have RF inputs. Unless you only watch over-the-air signals, it’s best not to use the RF input associated with standard-definition TV, as it will render the poorest-quality image. However, if you’ve purchased a dedicated HDTV with an internal ATSC tuner, you can tune in free, over-the-air high-definition signals, which may look better than the high-def feed from your cable or satellite provider if it’s not as compressed. Just feed the coaxial cable coming from your indoor or outdoor HDTV antenna directly into the correct RF input on the TV, the one labeled HDTV or ATSC. This set-up method only gives you access to the nationally broadcast channels: CBS, NBC, ABC, Fox, PBS, and the CW, plus any local HD broadcasts. For premium HD channels like ESPN, TNT in HD and Discovery HD, you have to go through a cable or satellite provider.
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