Splitting an HDMI source to feed both a video projector and a flat panel set is an increasingly popular option in custom home theater installs. But consumer-priced splitters that can do 4K are only just starting to appear. The HDS-12i from Transformative Engineering is one of the first. It can mix output resolutions and both up- and down-scale to 4K. A typical setup might involve a 2K projector and a 4K flat screen Ultra HD TV.
The device also provides full HDCP security and will recognize different EDIDs for each display. Output 2 also can be configured for pass-through, selectable scaling, or an AVR mode which bypasses 4K and 3D to route audio to an AVR or surround pre-pro that lacks the ability to handle these formats.
The HDS-12i's main limitation is that it's only HDMI 1.4a compliant, not 2,0, but that should be adequate for today's source material. It's firmware upgradeable (though not to 2.0--that's hardware) and sells for $299.