Sync cv2.VideoCapture(0) frames with Capture Card?

edit

Hi all,

I'm running into a problem with my current setup. I have a video (let's say .mp4, not too important) that is 60FPS where each frame is a different QR code encoded with some string. I want to test the capabilities of a player software using a capture card (currently an Elgato HD60 Pro), and using OpenCV's VideoCapture() object to grab each frame and decode the QR code.

I made sure my monitor refresh rate, Capture Card and VideoCapture() object were set to capture at 60FPS, however there are still a lot of frames missing with OpenCV. Is this a latency issue with the capture card or is there something I can do to improve the frame reading with OpenCV's read method?