1080i 50hz outputting as 1080p 25hz

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1080i 50hz outputting as 1080p 25hz

Hi There,

My iMac (Retina 5K, 27-inch, 2020) running Catalina 10.15.7 has an external display set to 1080i 50hz, but the monitor reports it as 1080p 50hz. Also, when the iMac is set to 1080i 60hz, the monitor reports it as 1080p 30hz.

I have a MacBook Pro which can connect to the same display via the same cable. When 1080i 50hz is selected, the monitor reports that it is receiving and showing a 1080i 50hz image. This is how I know that neither the cable nor the monitor are the issue.

Here is an image showing the iMac set to 1080i 50hz, but only sending a 1080p 25hz signal.

It's odd to me that it works through the Macbook but not through my brand new 27" iMac. Any help appreciated.

iMac Line (2012 and Later)

Posted on Nov 9, 2020 9:52 PM

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Answer 1

mslater92 Author

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Nov 19, 2020 8:47 PM in response to Malcolm J. Rayfield

I am using broadcast hardware that needs to receive all inputs at 1080i 50hz. I wish I was not as restricted with the hardware but that's what I'm working with.

If the iMac didn't list 1080i 50hz it as a supported resolution, I would say "fair enough" and purchase hardware or a different Mac that suits my needs. However with this resolution listed as a supported resolution, I felt confident to purchase this iMac and now it does not deliver on what it promised, hence me looking for a solution here

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Answer 2

Dec 16, 2020 8:08 AM in response to Dylan-DDCProAV

I am having the same exact issue with my brand new 2019 Mac tower. Apple support has said that Radeon is the reason why they don't support 1080i. In fact I upgraded to the new OS big Sur and 1080i is no longer even an option which prompted my discussion with support.

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Answer 3

mslater92 Author

Level 1

5 points

Nov 10, 2020 3:51 PM in response to mslater92

Whoops, slight typo. I meant to say the iMac is set to 1080i 50hz, and the monitor reports 1080p 25hz.

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Answer 4

Nov 19, 2020 1:32 AM in response to mslater92

I have a 3 week old from the apple store 2019 MBP, and have the exact same issue. What is the fix apple??

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Answer 5

Nov 19, 2020 5:57 PM in response to mslater92

Why don't you want to use 1080p 50hz?

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Answer 6

Nov 19, 2020 6:15 PM in response to Malcolm J. Rayfield

Because i need to use 1080i 50hz. Why is irrelavent. that fact that it doesnt work is the issue. if it say 1080i 50Hz then it shoud outout that.. not output 1080i 25Hz.

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Answer 7

Nov 19, 2020 9:06 PM in response to mslater92

Maybe SwitchResX would help.

https://www.madrau.com/

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Answer 8

Nov 19, 2020 9:08 PM in response to mslater92

Yeah.. Its something to do with the iOs.. for me, it was working, then stopped working putting out 25Hz.. So i think its something apple need to fix

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Answer 9

Nov 19, 2020 9:09 PM in response to Malcolm J. Rayfield

i dont think the broadcast world want to have to add gear for a native resolution & frame rate.

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1080i 50hz outputting as 1080p 25hz

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