Beam projector works in bootcamp, but do not work in macos

The HDMI beam projector in my classroom works fine when I boot with Bootcamp (win 10), but it shows "no signal" when I boot with macOS (10.14.6)

I have changed all the available screen resolutions, and tried rebooting, but it was useless.

But I think there should be a way to resolve this problem.

MBP 15" mid-2014.

Any ideas to solve my problem?

Solution 1:

HDMI on Macs is a curse, because Apple decided to take the HDMI spec more than just literally – not only do they rigorously enforce HDCP, but they take the unusual move of letting the display set the rules, not the host machine. Nor do Apple stick completely to the DisplayPort spec; getting 4K out of a 2013/2014 machine requires one part luck and one part voodoo – and you can forget about display daisychain :)

macOS is also extremely fussy about the output device resolutions that it will respond do – if the display signals (via EDID) to the Mac a resolution that doesn't exist in its lookup table, it goes all "talk to the hand, la la la …". To get macOS working with something it otherwise turns it's nose up at, you can either phone Apple Support and ask for an EDID Override file for that specific display device, or you can buy a copy of SwitchResX which will let you edit in whatever display resolutions you like.