Here is a video grabber that lets you capture 4K video from any video source (DVI-D and HDMI). AV.io 4K has a portable design and supports Mac, Windows, and Linux machines. The device is compatible with various video encoders.
To use AV.io 4K, simply connect it to your video source and connect the output to your computer’s USB port. Editing at resolutions 4096×2160 or 3840×2160 is supported. This 4K video capture tool is available for under $400 at this time.