Everything 'Technical' about AirPlay to Mac

[helix21]

I'm having some difficulty using Airplay to Mac as an extended display smoothly. It seems like, when connecting from one Mac to another, either the interface scaling/dpi settings or the limited display resolutions fail to create a seamless experience on the airplay display and isn't quite comfortable to work with. Also, the aspect ratio seems to be limited to one option, which can lead to undesirable black bars depending on your devices.

The only available output resolutions to an extended AirPlay display seem to be as follows, regardless of what device you connect to. There is a "Show All Resolutions" checkbox, but it only provides "low resolution" versions of the two lower resolutions already in the list.

3840 x 2160 2560 x 1440 (low resolution) 1920 x 1080 1280 x 720

When I extend my display from my M1 MacBook Pro to my M1 iMac, it uses the correct 1.78 aspect ratio and the image fills the iMac display from edge-to-edge, however there is not a resolution option that matches the "Default" scale options that the iMac traditionally uses (2240x2160). The "More Space" scale option is there (2560 x 1440), but only as a "low resolution" version that results in the UI looking slightly blurry. The 4k option (3840 x 2160) looks sharp, but the UI becomes impossibly tiny on the iMac display. It actually does look native and great if I swap the AirPlay image over to my external 4k Samsung display that is attached to the iMac.

The situation is even more sad if I try to extend the display from the M1 iMac over to the M1 MacBook Pro. Since the MacBook display's aspect ratio is 1.6, all of the available resolution options result in black bars at the top and bottom of the display. On top of that, none of them are close to the comfortable options for that display (1440x900 or 1680x1050).

Here are some examples:
M1 MacBook Pro Airplay Extended out to M1 iMac
3840 x 2160 - Tiny UI
View attachment 1806595

2560 x 1440 (low resolution) - The UI looks a bit blurry, but it's hard to see in the photo
View attachment 1806596

1920x1080 - Looks decent, but UI is a bit larger than what would feel natural
View attachment 1806597


M1 iMac Airplay Extended out to M1 MacBook Pro
3840 x 2160 - Tiny UI and Black Bars
View attachment 1806598View attachment 1806599

2560 x 1440 (low resolution) - Small UI, slightly blurry, and Black Bars
View attachment 1806600

1920 x 1280 - Decent UI Size, but Black Bars
View attachment 1806601

1280 x 720 - Large UI and Black Bars
View attachment 1806602

Thank you for doing this. I am really thinking of installing Monterey on my 27" 5k iMac just so I can use this feature, but that's my work computer and I am hesitant too.

From what you've said, it looks like then that there is no good 'Retina' HDPI option? Is the 4K 3840 x 2160 a retina HDPi? Is there no 2560 x 1440 HiDPI option? That would be perfect for the 27" 5K iMac

 

[RossGGG]

Thank you for doing this. I am really thinking of installing Monterey on my 27" 5k iMac just so I can use this feature, but that's my work computer and I am hesitant too.

From what you've said, it looks like then that there is no good 'Retina' HDPI option? Is the 4K 3840 x 2160 a retina HDPi? Is there no 2560 x 1440 HiDPI option? That would be perfect for the 27" 5K iMac

I'm not entirely sure what a "Retina" option would be exactly since later versions of macOS seem to obfuscate this, but in my testing, it didn't seem like it was scaling the UI up at all to compensate for higher resolutions.

I actually can't do any follow-up testing because I removed the betas due to them not working with the VPN client I use for work (VIA).

 

[RossGGG]

@RossGGG, this is great investigative work.

It upsets me a bit Apple only offers very limited resolutions (& aspect ratios) in "extend" mode: 4K, 2K (non-HiDPI), 1080p and 720p. The black bars are particularly upsetting when used between Mac to Mac. I don't understand why Apple can't create a virtual frame buffer that matches the target display's perceived resolution (& aspect ratio). Hopefully with more time next year's version will bring improvement and be up to Apple standard.

In "mirror" mode, if you select the primary Mac's resolution/aspect ratio to match the target display's, do you still see black bars? I would guess Apple might have "mirror" mode in mind as primary usage when they do the Mac to Mac scenario.

I didn't test mirror mode, and I'm no longer running the betas, for now, due to issues with my work VPN, but hopefully someone else can find and post examples.

 

[Gregintosh]

Without HiDPI it seems this is going to really cripple the feature and prevent it from being used truly as a monitor for a Mac. Hopefully this will be added in a future release (maybe a point update after Mac OS Monterrey comes out) or someone will make a hack for it. This is a major omission!

 

[Bobs1]

I'm having some difficulty using Airplay to Mac as an extended display smoothly. It seems like, when connecting from one Mac to another, either the interface scaling/dpi settings or the limited display resolutions fail to create a seamless experience on the airplay display and isn't quite comfortable to work with. Also, the aspect ratio seems to be limited to one option, which can lead to undesirable black bars depending on your devices.

The only available output resolutions to an extended AirPlay display seem to be as follows, regardless of what device you connect to. There is a "Show All Resolutions" checkbox, but it only provides "low resolution" versions of the two lower resolutions already in the list.

3840 x 2160 2560 x 1440 (low resolution) 1920 x 1080 1280 x 720

When I extend my display from my M1 MacBook Pro to my M1 iMac, it uses the correct 1.78 aspect ratio and the image fills the iMac display from edge-to-edge, however there is not a resolution option that matches the "Default" scale options that the iMac traditionally uses (2240x2160). The "More Space" scale option is there (2560 x 1440), but only as a "low resolution" version that results in the UI looking slightly blurry. The 4k option (3840 x 2160) looks sharp, but the UI becomes impossibly tiny on the iMac display. It actually does look native and great if I swap the AirPlay image over to my external 4k Samsung display that is attached to the iMac.

The situation is even more sad if I try to extend the display from the M1 iMac over to the M1 MacBook Pro. Since the MacBook display's aspect ratio is 1.6, all of the available resolution options result in black bars at the top and bottom of the display. On top of that, none of them are close to the comfortable options for that display (1440x900 or 1680x1050).

Here are some examples:
M1 MacBook Pro Airplay Extended out to M1 iMac
3840 x 2160 - Tiny UI
View attachment 1806595

2560 x 1440 (low resolution) - The UI looks a bit blurry, but it's hard to see in the photo
View attachment 1806596

1920x1080 - Looks decent, but UI is a bit larger than what would feel natural
View attachment 1806597


M1 iMac Airplay Extended out to M1 MacBook Pro
3840 x 2160 - Tiny UI and Black Bars
View attachment 1806598View attachment 1806599

2560 x 1440 (low resolution) - Small UI, slightly blurry, and Black Bars
View attachment 1806600

1920 x 1280 - Decent UI Size, but Black Bars
View attachment 1806601

1280 x 720 - Large UI and Black Bars
View attachment 1806602

@RossGGG Sorry this is an old thread, but I’m assuming the conclusion is that don’t count on using the iMac as an extended display from MBP reliably?

 

[RossGGG]

@RossGGG Sorry this is an old thread, but I’m assuming the conclusion is that don’t count on using the iMac as an extended display from MBP reliably?

I didn't really focus on reliability in my tests, but I do remember it being pretty stable and the lag being reasonably low. What I would say is don't expect it to feel like a native experience because of the limited resolutions and UI Scaling limitations. It's serviceable, but disappointing.

 

[Bobs1]

I didn't really focus on reliability in my tests, but I do remember it being pretty stable and the lag being reasonably low. What I would say is don't expect it to feel like a native experience because of the limited resolutions and UI Scaling limitations. It's serviceable, but disappointing.

right I see thanks. I’m hoping it will be addressed before the official release.

 

[solinari6]

I find this feature quite useful, though I wish it had a windowed mode, don't really like the fullscreen look.

If you have any iOS apps that prevent you from screen recording, you can use this to cast the screen to your Mac, and then use Quicktime screen recorder to save it. Even works with sound if you use the blackhole audio re-router.

 

[Charmandrigo]

has anybody figured out a way of make this feature not black out additional displays connected to the mac working as airplay receiver? I actually wanted to have my ipad in one of my monitors while my other ones still showed my mac windows, but all of them go black when the receiver is working.

 

[josduc]

iMac 2017 27" with 21A5552a beta and not a sign of Airplay yet. Airplay settings in Sharing just doesn't appear.

 

[nopster]

Hello, same here: my MacPro 2019 is seen by my MacBookPro 2017 as a receiver, but on this MBP cannot set airplay receiver on system preferences > display.
I watched on YouTube how to install OpenCore, but this method will install an entire fresh install of Monterey.
I wish I could patch AirPlay sharing on MBP with a patch, without reinstalling a new system.

 

[tomswift99]

Is anyone else just using the standard screen sharing feature? I have my MBP 14 connected to my 2017 iMac 27 over thunderbolt bridge, and just screen share the MBP screen to the iMac. Works amazingly. No need for airplay.

 

[nopster]

Is anyone else just using the standard screen sharing feature? I have my MBP 14 connected to my 2017 iMac 27 over thunderbolt bridge, and just screen share the MBP screen to the iMac. Works amazingly. No need for airplay.

you can use screen sharing to watch the MBP in your iMac, but what is cool about airplay is that you can use MBP as an extended monitor for another Mac. Apple has dropped support for old macs, even MBP 2017.
Something like Sidecar for iPad or Luna Display from Astropad.

 

[tomswift99]

you can use screen sharing to watch the MBP in your iMac, but what is cool about airplay is that you can use MBP as an extended monitor for another Mac. Apple has dropped support for old macs, even MBP 2017.
Something like Sidecar for iPad or Luna Display from Astropad.

That makes sense. Screen share is just for mirroring unfortunately. Still, a workaround for those with older iMacs who want to use it as a main display.

 

[PatriotInvasion]

Really hoping they add HiDPI and native 16:9 and 16:10 aspect ratios for Mac-to-Mac AirPlay. If it's particularly data intensive could they not specify that some resolutions require a wired connection over USB-C? I just want an iMac to be able to be the primary Mac and a MacBook Air the secondary display all in native resolution.

Universal Control will solve half of this, but both OS's will be independent with independent app instances. I suppose I could live with that for the native resolution.

 

[fyun89]

Really hoping they add HiDPI and native 16:9 and 16:10 aspect ratios for Mac-to-Mac AirPlay. If it's particularly data intensive could they not specify that some resolutions require a wired connection over USB-C? I just want an iMac to be able to be the primary Mac and a MacBook Air the secondary display all in native resolution.

Universal Control will solve half of this, but both OS's will be independent with independent app instances. I suppose I could live with that for the native resolution.

Are you also having the issue of unable to set secondary Mac to display airplay in 16:10 aspect ratio?
I can only set to 16:9 ratio resolution and see huge black letterboxes at top and bottom...

Is there any alternative way to fix this?

 

[PatriotInvasion]

Are you also having the issue of unable to set secondary Mac to display airplay in 16:10 aspect ratio?
I can only set to 16:9 ratio resolution and see huge black letterboxes at top and bottom...

Is there any alternative way to fix this?

There's no alternative. AirPlay is 16:9 only. This probably stems from its original use case being to play 16:9 video from an Apple device to a TV.

Apple would have to update its capabilities to handle more resolutions, and Mac-to-Mac AirPlay isn't likely to be high on the priority list given the small number of people that would actually do this.

Ultimately, this could all be solved if a Mac could just be an external display for any other Mac over USB-C/Thunderbolt. They can't either because Apple hasn't bothered to enable this, or there are HDCP limitations that prevent this over DisplayPort.

 

[the[V]oid]

Really hoping they add HiDPI and native 16:9 and 16:10 aspect ratios for Mac-to-Mac AirPlay. If it's particularly data intensive could they not specify that some resolutions require a wired connection over USB-C? I just want an iMac to be able to be the primary Mac and a MacBook Air the secondary display all in native resolution.

Universal Control will solve half of this, but both OS's will be independent with independent app instances. I suppose I could live with that for the native resolution.

Are there any updates on this? I'm struggling to use my MacBook Air M1 display as second screen for M1 iMac, so both are of the same generation, and I do not understand how this feature wasn't tested for these two devices before release (after all, both are newest generation). Everything on the AirPlay display is far too small and totally unreadable. In this state, this feature is just not usable.

 

[PatriotInvasion]

Are there any updates on this? I'm struggling to use my MacBook Air M1 display as second screen for M1 iMac, so both are of the same generation, and I do not understand how this feature wasn't tested for these two devices before release (after all, both are newest generation). Everything on the AirPlay display is far too small and totally unreadable. In this state, this feature is just not usable.

You can edit the resolution settings so that the MacBook Air uses something closer to 720p or 1080p. It will be 16:9 with back bars on the top and bottom, but the UI elements will be much bigger and more usable. This is the bare minimum of acceptable as a separate monitor to toss a random app or two on, but the latency is annoying and the non-native, non-hiDPI resolution is just not pleasant to look at.

I'm afraid Mac-to-Mac AirPlay for extended display mode is a dud of a feature until they support native resolutions.

 

[Alexander5673]

I was looking into this topic again. - I like to project from my M1 MBP to my 27" iMac, and I agree to everybody who says that 2560 x 1440 (HiRes) would be perfect, but the M1 has at least a 2056 x 1329 (HiRes) resolution which still works with AirPlay.

The only thing I'm missing there: The iMac scales up the 2056 x 1329 by about 10% to (almost) full screen, which adds unacceptable blur to the text. - I'd much prefer to have a pixel perfect 2056 x 1329 projection to my iMac ("actual size", "1:1", however you like to call it), even if it's 10% smaller.

Does anybody know a way to scale down the projection on the receiving side? - The underscan slider is not offered with airplay mirroring to my iMac (which could be used to address the scaling issue), and modifying /var/db/.com.apple.iokit.graphics doesn't seem to work in newer macOS versions anymore.

Any other hints?

Thank you,
Alex