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I have a LCD tv hooked up to an HDMI switcher flipping between a Mac Mini (2006 snow leopard using a DVI - HDMI cable), cable tv and dvd player.

Trouble is, whenever the switch goes away from mac the picture is blank when coming back.

Having looked into it extensively it seems that the mac polls for edid data from the screen once only. Once the screen is disconnected, the mac won't poll for it again and doesn't "see" the edid from the tv anymore - hence no output from the mac. To double check, when I vnc into the mac it goes to a default 4:3 screen not the widescreen.

There is a supposed hardware solution that buffers the edid and keeps it live - effectively fooling the mac to think the display is there all the time, even when switched to another source. This is a crazy solution requiring an extra box, extra power consumption and anywhere between £50 and £100 (upto $150).

Then I found a little script called HDMI reviver, but that didn't work for me either.

Can anyone explain (to an idiot) how to get the Mac to read, keep and store the EDID and always broadcast a signal, even when the HDMI switch isn't looking for it?

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What happens when you switch back to the blank screen, then power cycle the monitor? –  stuffe Nov 1 '11 at 16:27
    
I've been through this sort of EDID purgatory with HDMI switchers (e.g. AV receivers) and splitters alike. The simple answer is that real-world HDMI devices do not renegotiate EDID reliably when their counterpart source or sink is changed. It seems the only conclusively reliable way to acheive switching is for the switch to keep the negotiated connection active with all the sources and sinks at all times. That is what these HMDI over IP matrix switch modules do. –  alx9r Jan 3 '13 at 4:11
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1 Answer

I've noticed the same thing. I have not come up with an elegant solution (and in fact, you sound better educated on the problem than I am).

This definitely falls under the category of "kludge" but it does work. Access the TV-connected Mac from another Mac on the same network using Screen Sharing (technically this would work under any VNC connection). Go into System Preferences: Displays and click the "Detect Displays" button. You could speed this up a little by adding a Displays menu to the menubar--"detect displays" is right there, and easier to get at.

This suggests that it should be possible to script the interaction so that with a combination of a programmable remote, Remote Buddy, and a suitable macro, you could force the Mac to re-recognize the screen. Still not ideal, but it should be workable.

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Adam, I'd love to say that works, but it didn't for me. Thanks anyway. Andrew –  andrewfd Nov 17 '11 at 16:10
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