AVCaptureSession.Preset 4K for OS-X

I'm trying to capture 4K video in an OS-X application using an av.io 4k hdmi to USB adaptor. When I connect the adaptor it scales the output to a lower resolution. The output from the camera is 4k. The supplier of the device says I have to set the resolution to 4K in my capture session. However there does not seem to be a 4k option for OS-X


For iOS there is

public static let hd4K3840x2160: AVCaptureSession.Preset


XCode tells me that this is not available for OS-X


There are apps that can capture 4K input so there must be a way to do this.


Can anyone help?