Previous 1 2 3 Next 39 Replies Latest reply: Apr 13, 2014 7:06 AM by avantronica
keysthatclick Level 1 Level 1 (10 points)

I was running into an issue with my Mac mini (2011) running Mountain Lion when trying to run AirPlay mirroring to Apple TV. I figure I should share this in case people are having similar issues.

 

The Mac mini is a headless unit that I Share Screen into from my MBP or iOS devices. When I tried to run AirPlay mirroring to the Apple TV after installing Mountain Lion, the mirrored image would result in a garbled pink screen. It seemed like no matter what I did (changed network settings, display settings) the same thing kept happening. It wasn't until I tried plugging a monitor into the headless Mac mini that AirPlay mirroring suddenly worked. Unfortunately - I have to keep the monitor plugged in for this to work, thus negating the whole benefit of running a headless machine. Hopefully this is something that can be taken note of and perhaps fixed in a future version of ML. Anyone know how I might be able to submit this as a proper bug report?

 

I tried this on both a 2nd and 3rd gen Apple TV with the same results.


Mac mini, OS X Mountain Lion, running with Apple TV (2nd and 3rd)
  • Christopher Collins Level 1 Level 1 (50 points)

    This has often been an issue in the past going back a long time for other services that require the graphics card to be completely "available" for lack of a better word. On Mac Pros that we needed to run headless for some video encoding that requiered Quartz Extreme compatible video cards, well the graphics card in the Mac pro wouldn't show up as Quartz Extreme enabled unless a monitor was plugged in on the other end. In this case I actually built a little dongle that had the right pins to make the video card think there was a monitor on the other end. Unfortunately, I think this is always going to be an issue. Since all AirPlay video encoding is happening on the graphics chipset, I bet this is why you are seeing weirdness.

     

    One way you could potentially verify is with a monitor plugged in, go into System Info and look at what it says for your graphics and displays, then compare when its unplugged. I wouldn't be surprised if it looks different.

  • billmar Level 1 Level 1 (0 points)

    I'm having the same problem.   As long as an external display is attached when I start AirPlay it works.   I can then unplug the screen and it will still work until the system realizes the external display is gone.

     

    Hopefully Apple will come up with a solution as this was a great way to watch the streaming video on NBCOlympics.

     

    Use my ipad to connect to the mac mini and manipulate the browser and the output on a big screen tv.

  • ScutterOz Level 1 Level 1 (0 points)

    I'm having exactly the same problem here too. I can airplay from itunes without any issues, but airplay mirroring produces a garbled screen on the ATV.

     

    I guess we just sit and wait? Come on apple! Hopefully 10.8.2 will fix this?

  • ScutterOz Level 1 Level 1 (0 points)

    "Hopefully 10.8.2 will fix this?"

     

    ...no it didn't.

  • Don Morris Level 1 Level 1 (35 points)

    Christopher Collins wrote:

     

    ...unless a monitor was plugged in on the other end. In this case I actually built a little dongle that had the right pins to make the video card think there was a monitor on the other end. Unfortunately, I think this is always going to be an issue. Since all AirPlay video encoding is happening on the graphics chipset, I bet this is why you are seeing weirdness.

    This was exactly the cause of the problem for me. New Mac Mini (headless), new AppleTV. Plugging in a monitor solved the problem. I don't suppose I could buy a dongle from you? I'm not interested in wiring my own.

  • ScutterOz Level 1 Level 1 (0 points)

    Hi Don,

     

    I'm currently investigating the options of making one. If i work it out i'll share the experience!

     

    I have an idea of what is needed but i've done any electronics before: a thunderbolt/hmdi/DVI to VGA adaptor(s) of some sorts then 1 (or possibly 3) 75ohm 1/4W resistors (?) wired acorss the G or RGB pins. i still need to work out which pins need to be wired up but i've seen diagrams showing this online. I'll work that out once i have all the parts.

     

    My problem is i'm reluctant to buy the converters for them not to work and waste the $s, so i'm trying to find them as i'm sure i have what i need somewhere!

     

    If anyone has made one i'd appreciate you confirming what you used and how. as what i've stated above is unconfirmed.

  • ebcase Level 1 Level 1 (0 points)

    We're experiencing this as well — anybody find a workaround yet? Maybe even plug in an old/cheap display somehow?

  • Don Morris Level 1 Level 1 (35 points)

    Well, sure, you could plug in a display to get it to work. But that defeats the purpose of running it headless.

  • ScutterOz Level 1 Level 1 (0 points)

    Yeah I have mine working.

     

    I bought a mini display port to vga adaptor, and a pack of 91R .5w metal film resistors.

     

    Then followed the instructions on this website.

     

    http://www.overclock.net/t/384733/the-30-second-dummy-plug

     

    The adaptor cost $20 aud, but the resistors were dirt cheap.

     

    It was really easy and works like a dream!

     

    :)

  • hueysds Level 1 Level 1 (0 points)

    This is exactly what I was looking for! Thanks for the tip!

     

    Any reason you picked the 91R .5w metal film resistors over the ones suggested in the link (or are these the same thing? I'm a little rusty on resistors, haven't touched them since college)

     

    EDIT: what does 91R even mean, having difficulties finding these resistors online, can find plenty of the 68 ohm resisters that are suggested in the link, just want to make sure I'm not going to blow up my displayport or something. Also, would this work with a HDMI to VGA adapter as I would like to keep my thunderbolt port open for peripherals

  • hueysds Level 1 Level 1 (0 points)

    Ok, I think I've got it (correct me if I'm wrong) 91R is equal to 91 ohm (duh!)

     

    Ok, so why did you choose 91 ohm over the 68 ohm suggested in the link?

  • hueysds Level 1 Level 1 (0 points)

    Nevermind, found another tutorial that says you can use any resistor between 50 and 150 ohms...

     

    http://www.geeks3d.com/20091230/vga-hack-how-to-make-a-vga-dummy-plug/

     

    Thanks for pointing me in the right direction! I will post back here if the HDMI to VGA dummy plug works!

  • ScutterOz Level 1 Level 1 (0 points)

    Hi

     

    No real reason for the resistor choice apart from I was aiming at getting 75ohm resistor but couldn't find any in the shop I went to. So went with the next size up.

     

    If you try with hdmi let me know if it works as I'd be interested in freeing up the thunderbolt port. :)

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