Review on SIIG 1x2 HDMI 2.0 Splitter 4K 60Hz with HDMI Audio Extractor - Auto Downscaling (4K and 1080p Mixed Output) - HDCP 2.2, 18Gbps, YUV 4:4:4, 3D, EDID - Supports Various Audio Formats - 1 Input 2 Output (CE-H24X11-S1) by Justin Webb

I had a situation where I used an HDMI splitter to send a 4K UHD 3840 x 2160 stream to a pair of 4K wall monitors and also to one as a 'confidence monitor' to distribute a small 12-inch desktop monitor. However, a 12-inch monitor only has a resolution of 1080 and only displays a 4K image for a brief second, and then "Invalid format" flashes. So I figured it must be a scaling issue that the monitor can't handle. This device has completely solved this problem! I toggled the S1 and S2 "down" switches to "force resolution" and BAM! Perfect 4K feed upscaling up to 1080. Super easy to use and a great problem solver.