4 colours from a 3-colour signal?
Can anyone tell us how they are doing this? The Sharp website refuses to say anything except "there are 4 colours".
But thinking mathematically, the incoming signal has only three degrees of freedom and the output (controlling the pixels) must have four, so are they just using heuristics to (for example) use the yellow emitter to supply the fraction where R=G? That probably moves the gamut around a bit, presumably to cover an area more useful to human observers, but probably doesn't increase that area at all.
It's an interesting development though because the raw hardware probably DOES have a much wider gamut than the signals it is asked to display, and THAT breaks the log-jam on extending the gamut of TV.
Previously, there were no devices capable of displaying a higher gamut signal, so there was no incentive to create broadcast or disc-based content that had a higher gamut, so there was no incentive to create a device that could display it. Deadlock.
If this device delivers a better picture quality on existing signals AND could display a higher gamut, it breaks that deadlock.