DVI interoperability

Derek writes:

I have recently purchased a Hitachi 42 pd 5000ta plasma screen which has a DVI input. I have also recently purchased the Samsung HD DVD-937. My question is in regards to compatability, I have been told by Hitachi that this plasma does not support HDCP copy protection, however when I hooked this dvd player up using the DVI connection, it became clear that it was working to a certain extent. It would work in 576p & 1080i, but would be scrambled in 720p. This would also change, as on this plasma, the DVI connection on RGB 1 has 2 modes, one for PC, the other for STB. It was only scrambled in 720p when in STB mode, however in PC mode the picture was visible, but extremely large & off centre.

I am wondering if this is normal, or for some reason the Samsung dvd player is overcoming any related problems with HDCP encryption. I am also wondering if the dvd player is working to it’s full ability?

Any help would be appreciated!

Interesting questions, so let’s break it up into two parts. First, the HDCP issue. There are two possibilities here: either Hitachi is in error, or Samsung is supplying machines that do non-HDCP protected DVI output. I suspect the former. The copy protection community are far more concerned about source devices than display devices. Sources (such as DVD players) became available with DVI outputs only late last year because each device has to be approved before it can be make available. However displays supporting DVI/HDCP have been around for a while. It could be that Hitachi put it in but the information never made it from the engineers to the marketing types, or it was an early version that it didn’t consider fully reliable.

If Samsung is bypassing the HDCP encryption, the company will be in big, big trouble. So that’s not likely.

Regarding the problem with 720p, that isn’t too surprising. There are a lot of display devices that support 720p at 60 hertz, but not at 50 hertz. The (PDF)specifications for this Hitachi display show support for ‘480i/p / 575i/p / 720p(60) / 1080i(50/60) / 1035i(60)’. Note, no ’50’ after 720p while there is after 1080i.

As it happens, 720p is not an especially useful display format for this display anyway. The vertical resolution of the Hitachi panel is 1,024, so it is as well to go for either 1080i or 576p from the DVI output. Experiment. Offhand, I’d say that it would be best to provide the signal at native resolution (576) and let the Hitachi scale it to its native resolution, because that avoids double-processing the signal. But the Samsung has excellent (Faroudja DCDi) scaling circuitry, so it’s worth trying both the 576 and 1080 settings to see which works the best.

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