You need a special software device driver if you want to use several instances or apps with one capture device. Osprey offers this known as 'Simulstream' for $ or you have to look for a virtual video device driver. I knew there are such projects out there but they usually lack of functions or configuration features which i.e. an Osprey drivers brings (hw deinterlacing, hw cropping, resizing,...).
Buy Osprey cards with Simulstream or cards with multiple inputs.