There are two type of DVR cards generally found:
1 - 1 X BT878 chip - used in a round-robin-access setup between the inputs
2 - 4 X BT878 chips - used in either 1-chip-per-input or round-robin setup, good for 4-16 inputs (or sometimes even more)
I have found that a number of DVR programs will not access the first type of card properly - they are not written to cycle through the inputs, so they either won't touch the card at all, or only read input 1.
Most DVR programs will access the second type of card with no problems - each input (1-4) has its own capture device installed in Device Manager, so the software can access each of the 4 inputs simultaneously. But if the card had say 16 inputs with 4 chips, then you are back to square one again...Stuck with 4 inputs only.
I would venture a guess that EyeLine falls into the first category - not polling each input in turn. I will test this out in a couple of days - I have access to both types of cards at my workplace, so after the weekend I'll see what I can find out.
From what I have seen so far on these forums, NCH tech support don't really provide any feedback so to speak as to how their software works - as their income model is based on support, they don't seem to believe that they should provide feedback...(disclaimer: I can't speak from a first-hand viewpoint in regards to NCH and am not passing judgement with my preceding comment)
While I have no problem with their chosen model, there is a place for providing basic feedback to users of the system - users whether they pay or not need enough information to be able to go away and nut things out for themselves, to a point. Otherwise they just walk away and find another package, either a free one or one they can buy outright and access useful online support information including forums with active developer input.
How NCH find that balance I have no idea! I'm glad I don't have to work that out!
I would suggest to the EyeLine developers they maybe look at some source code from say ZoneMinder to get an idea of how to access the multiple inputs - just don't steal the code guys, it's under the GPL! But there's nothing wrong with trying to get some pointers - GPLed code is all about free speech... 
