HDTV Forum

Originally published 11/12/2004, HDTV Magazine, editor Dale Cripps

Updated 09/21/05

By Richard Fisher

DVI/HDCP and HDMI are the new digital video connections used by the industry. It is recommended that if you are buying a new display that it comes with one of these connections.

DVI comes in 3 different connector/cable versions. DVI-A is PC analog video just like VGA using a DVI-A or DVI-I connector and is not what we are looking for. DVI -I handles both digital and analog DVI and is not necessary for our application. The other is DVI-D which is the right connector /cable we are looking for. Unfortunately, there are a number of HD displays with that type of connector and they will be shut out of the high performance digital future because they do not have HDCP. DVI-D with HDCP is the one we care about and the consumer should avoid any new display that does not have this type of input, period! A new version of this is HDMI, which adds digital audio and control interface to control other components.

DVI HDCP and HDMI are considered 100% compatible for video. You can buy cables with DVI-D on one end and HDMI on the other or an adapter if your cable has both connections. Note that when using this cable or an adapter you will lose the digital audio and control interface. Using an adapter is not recommend for long runs that are near the maximum distance, about 30 feet. For this and longer runs there are special DVI/HDMI cables that increase the distance and also repeaters with standard cables. HDCP stands for Hi Definition Copyright Protection and is part of the DVI or HDMI application for HDTV. DVI is an uncompressed digital stream and of extremely high bandwidth. While it is encoded using HDCP this is hardly the problem with recording it. If you can crack the HDCP then you have to find some way to capture it and this is considered highly unlikely for the next 5-10 years. The content providers are counting on a more robust encoding system within this time frame. The biggest problem with DVI is that big chunky connector, which is why HDMI was necessary. Most displays (if not all) are limited to one DVI input so if you have multiple DVI or HDMI sources you need switching. Some of the new receivers offer HDMI and there are numerous external switchers on the market.

Firewire or 1394 on the other hand is the raw compressed digital stream and also has DTCP, another form of HDCP. This digital video interface was promoted by Mitsubishi and Panasonic for it

Richard,
I am concerned that the comment "DVI HDCP and HDMI are 100% compatible
for video--no conversion required." may not be totally correct. It is
my understanding that since DVI was originally designed for the computer
world, it was designed to work with RGB video, while HDMI was designed
for component video. In our high end projectors, we give you the
ability to select between Component/RGB PC/RGB TV for the DVI input,
which many other TV's and Plasma's do not offer this selectabilty. I
also understand that if a display (HD Plasma or TV) has a DVI input, it
may not be able to properly display an up converted DVD for example that
is output HDMI and then adapted to DVI to connect to the display. So I
guess, what I am looking for is clarity that if your readers output a
signal that is up converted from a DVD player through it's HDMI
connector, are you completely sure that it will play back properly on a
TV or Plasma through its DVI input. My understanding is that it may
not! Thanks!

Bart Greenberg
National Sales Manager
Yamaha Electronics Corporation
Tel: (714) 522-9336
Fax: (714) 670-0108

DVI was originally designed for the computer world, it was designed to work with RGB video, while HDMI was designed for component video.

My understanding is DVI is digital and was designed for digital displays. For compatibility they designed the DVI-I connector that handles both formats. This was something you had to be careful of in the PC world early on as there were a number of digital displays that had a DVI input but was using the analog portion only. The point being that one could not buy a DVI display for the intent of a digital stream just based on the fact that it had a DVI connector. HDMI is a digital only format so component only plays a role in that this is the format being sent down that pipe in a digital form for HDTV applications.

In our high end projectors, we give you the ability to select between Component/RGB PC/RGB TV for the DVI input, which many other TV's and Plasma's do not offer this selectabilty.

All true and I had no idea your product had that kind of DVI support. If our readers wish to fully exercise this capability then you will need a DVI-I cable.

I also understand that if a display (HD Plasma or TV) has a DVI input, it may not be able to properly display an up converted DVD for example that is output HDMI and then adapted to DVI to connect to the display.

Based upon everything I have read and my own HD pattern generator the use of a DVI to HDMI adaptor is not an issue. All you lose is the digital audio and the digital control interface for other components in your system. The video should work just fine provided the display supports the HDCP protocol.

are you completely sure that it will play back properly on a TV or Plasma through its DVI input. My understanding is that it may not! Thanks!

Your concerns are well founded. The display DVI input must be HDCP compatible or it will not work and there are a number of displays that were sold with a digital DVI input without the HDCP protocol on board. There is nothing those folks can do about this except replace the display if they want the form of DVI used for HDTV content. I should also note that the big accuracy key here is not so much the connection type, digital versus analog, as much as getting the source to match the native scan rate of the display so you can bypass the internal scaler which is still necessary for the most part but they are getting real close now.