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Mac Mini TV underscan issue

Hello, I recently bought myself a late 2012 Mac mini running High Sierra to use with an oldish Samsung TV. Like so many other users I have a problem with the screen size underscan not functioning correctly with the telly. Whenever the Mac mini goes to sleep or if it is restarted the display underscan setting are ignored upon wake-up and I need to reopen the display preferences click on the slider (which is in the correct position) and the screen will snap back to the correct dimensions. I can also reset the screen dimensions by physically detaching the HDMI cable and reinserting it.

Like everyone else who has this problem I find it extremely frustrating to have to keep resetting it constantly. I am even more frustrated that Apple don't seem to have offered a solution!


I think other users with this problem might like to know that I also own a mid 2011 Mac mini running Sierra, that I have attached to another old Samsung TV. This computer doesn't have the underscan problem with either TV. It is only the late 2012 which runs High Sierra. Is the problem a software issue or a hardware issue? If there's anybody out there who can point me to a solution I'd be grateful.


Thanks, Chas


Posted on Jul 27, 2021 12:26 PM

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9 replies

Jul 28, 2021 3:34 PM in response to Malcolm J. Rayfield

I understand that you are trying to provide a solution, for which I am grateful. However, I would prefer not to make adjustments to the TV because I don't want to disturb the actual tv settings when it's clear that the mac mini is at fault. BTW I cannot see any way to adjust the underscan or overscan in the TV settings.

If my Mac mini 2011 can do it perfectly, why can't the more recent 2012 model running a more recent MacOS do it?

I think I first need to downgrade the OS to Sierra first before struggling with the tv.

I think Apple have slipped badly and I think less of them. They make errors that impact their customers but don't seem to care.

Aug 2, 2021 2:57 AM in response to Malcolm J. Rayfield

Hello again Malcolm, this is simply a response to let you know that your advice has led to the solution of my underscan issue, so thank you. I had planned to downgrade to Sierra as that OS works well on my other, older Mac mini. I parked the whole issue for a week as I didn't have time. Today before going down that route I decided to thoroughly go through the Samsung TV settings again and this time found a "picture size" setting with an array of choices. I have to confess some of the choices seemed odd to me but there was one called "screen fit" that fixed the problem. On the Mac mini it was necessary to turn off underscan setting.

I do remain confused as to why there is this, presumably firmware difference, between the behaviour of two Mac minis built only a year apart?

Thanks, Charlie

Aug 3, 2021 1:12 AM in response to Chasdemont

I'm glad you finally found the TV's size setting. They don't make it easy. With Underscan off you should now have a sharper display for two reasons:


1) The computer can use more pixels since it can now go all the way to the edges.


2) The TV can put each pixel on its own dot on the screen. When the TV's Overscan was on it was enlarging the picture, which meant the computer's pixels did not match the spacing of the dots on the screen. This caused some blurring.

Aug 9, 2021 12:40 AM in response to ronaldfromsunset valley

I reckon that this issue will continue to crop up as I suspect more people decide to attach Mac Minis to their old TV sets. My Samsung "smart" TV stopped being so smart as it got older. Various apps such as YouTube ceased to function. I needed a way to revive these services without buying a new TV. First I used a video cast dongle, which was good for a while but then it dawned on me that a small dedicated computer would be the best solution.

With the mouse, icons and text enlarged where possible the mini can be controlled from a distance with a Bluetooth trackpad and keyboard. And with the fibre optic sound connected to my old 5.1 sound system it provides one of the best ways to enjoy music I can think of.

Aug 9, 2021 12:58 AM in response to Malcolm J. Rayfield

That is interesting Malcolm and I understand your logic. I have now reset my earlier Mac Mini in the same way and again everything seems to be working well. That said I cannot say I have noticed any improvement in the sharpness of the picture. I previously used my 2011 version mini with underscan on since 2011 and have never considered the picture to be even slightly blurred. I have only noticed blurring if the picture scaling option is used.

Aug 12, 2021 1:21 PM in response to Malcolm J. Rayfield

Thanks Malcolm for taking the time to show me this. Alas I am still unable to detect any noticeable degrading of test image quality, whether the Mac mini underscan setting is on or alternatively with it off and the TVs picture setting is set to Fit Screen, rather than 16:9 (which was how the TV was set when I bought it.)

My Samsung TV has a screen size of 1920x1080 so I scaled the image you supplied to fit as a desktop wallpaper. I then took screen grabs of the desktop whilst using both setups and compared the two images layered in a popular graphic application. Switching on and off the top layer would reveal any slight change in pixel position if there was any. The only movement I could see was the different position of the system prefs window which I had moved out to the edge when taking the screen grabs.

Mac Mini TV underscan issue

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