Hi Petter,

I have a system that uses both decklink duos and intensity pros like you. My problems were mainly with the intensity cards getting a proper HDMI signal into them from another computer. The decklink duos have been very easy for me maybe because I am using Blackmagic component to SDI converters with my Canon XH-A1 cameras.

It seems that your problem may be that you do not have the card set for the proper signal that your camera is providing.

You can test the decklink duo to prove that it is working properly. Since it is acting like 2 decklink cards, you can use one of the cards as an output and the other as an input.
Just set up your External Output to drive the output of your first Decklink. Next, connect a BNC from its output to the input of your second Decklink. Then add an input using this second Decklink as the source. Start the External Output. When you play back a video file and put it on the program buss, you should see it on the Input you have set up with the second Decklink. If you remove the BNC, this Input should go blank.

Some things to keep in mind when doing this test:

The settings for output and input must match precisely, anything less and you will get a black screen just like with your JVC cameras.

The Decklinks can be used as an input or an output, but not both at the same time.

Let us know how you get this worked out.

Hope this helps,
Tony