Capturing from video source

I've a Blackmagic DeckLink SDI 4k card and I would like to be able to send a video stream (assume MP4 video) to the card, so another software can capture this video stream. There is usually an SDI cable connected to the card, but in this case I want to be able to send a very specific stream of images so, that the piece of software that captures from the card, behaves in a very specific way.

Can this be done through software or do I need some sort of physical setup (I'm thinking HDMI/SDI converters)?

Any ideas?

Best,

Yoanis.