Mission Planner USB video receiver low frame rate

I am using a USB video capture device to get the HDMI from a walksnail VRX and then put that on the mission planner data page under the hud.

I have not flown with this yet, Just got the HDMI to USB device. When I set it up in mission planner it works and I get picture but the highest frame rate it seems to want to support is just 10fps.

Using this device in the webcam preview looks a lot smoother and is clearly running at a higher frame rate.

How do I get mission planner to see higher FPS modes for this device? I tired on 2 different computers and have the same issue.