Reverse-engineering the M4 Air HDR issue: Why I have to UNPLUG my Mac to get good colors

[edhinnig]

TL;DR:The M4 MacBook Air forces dark/bad HDR on Netflix. After digging into system plists, EDID overrides, and terminal commands, I found that Apple hard-coded the only fix (HDR-to-SDR conversion) to the physical battery state. There is no software workaround.

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Hi everyone,

I wanted to share a deep technical dive regarding HDR playback on the new M4 MacBook Air.

If you watch Netflix via Safari, the system forces a Dolby Vision stream. Since non-XDR screens lack local dimming, Apple's tone mapping crushes mid-tones. The result is a dark, washed-out image compared to SDR.

I spent the last 24h attempting to bypass this to force 4K SDR while on AC power. My goal was to trigger the internal "Optimize video streaming" flag without unplugging the cable.

Here is why every software solution fails on M4:

1. The "Easy" Fixes (Failed)
Chrome/Firefox: They force SDR (great colors) but are capped at 1080p due to Widevine L3 limitations on macOS.
Color Profiles: Forcing sRGB/Rec.709 is ignored by the AVFoundation video pipeline, which queries the display hardware directly.

2. The "Power User" Fixes (Failed)
BetterDisplay / EDID Overrides: On Apple Silicon M4, the internal display's EDID seems hardware-locked against software overrides. We cannot simply uncheck "Allow HDR".
User Agent Spoofing: Forcing a Windows UA breaks the DRM handshake (Netflix expects Widevine, gets FairPlay).

3. The "Deep System" Attempts (Failed)
Terminal Manipulation: I tried `sudo pmset -c lowpowermode 1` hoping to trigger the video optimization boolean. It throttles the CPU but does NOT toggle the `kOptimizeVideoStreaming` flag, which appears hard-coded to the physical `ACPower` state in `IOKit`.

The "Nuclear" Option: Editing `/Library/Preferences/SystemConfiguration/com.apple.PowerManagement.plist` or injecting code into `CoreDisplay` would require disabling SIP (System Integrity Protection), which is too risky for a streaming fix.

The Conclusion:
Apple has tightly coupled the HDR-to-SDR conversion logic to the physical power source.
The ONLY way to get proper 4K SDR colors is to literally UNPLUG the MagSafe charger.

This immediately flips the "Optimize video streaming" state, and the image becomes perfect. Plug it back in, and the "dark" HDR returns.

Has anyone managed to spoof the `ACPower` state specifically for the `powerd` daemon without disabling SIP? We desperately need a "Prefer SDR" toggle.

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UPDATE (Dec 1):
For anyone wanting to reproduce this, here is the quick test workflow:

1. Open Netflix in Safari (it triggers HDR automatically).
2. Look for a dark scene (it will look washed out/dim).
3. Physically UNPLUG the MagSafe charger.
4. Watch the screen brighten up and colors pop instantly (as the "Optimize video streaming" flag kicks in).
5. Plug it back in -> image gets dark again.

If you have an M4 Air, please test this and let me know if you see the same behavior!

 

[Bigwaff]

**The ONLY way to get proper 4K SDR colors is to literally UNPLUG the MagSafe charger.**

Same behavior while charging via USB-C ?

 

[edhinnig]

Just tested it, great idea to check!

Confirmed: The behavior is exactly the same with USB-C charging.

I plugged in a USB-C charger (instead of MagSafe), force-reloaded Netflix, and the Stats for Nerds menu confirms the system is still forcing the HDR track:

- Video Tags: SEGMENT_MAP_HEVC_PPS_HDR10
- Playing state: Normal
- Buffer state: Normal

The image remains dark/washed out, just like with MagSafe.

This confirms the OS is checking the global power state (AC vs Battery) at the IOKit level, regardless of which physical port delivers the power. The "kOptimizeVideoStreaming" flag only flips when ACPower == 0.

So unfortunately, no workaround via port switching. The only trigger remains physically disconnecting from AC power entirely.

Thanks for suggesting this test, good to have it documented!

 

[EugW]

For Netflix I have to turn the brightness way up. Mid-tones are then more visible at expected brightness, and highlights are much brighter.

 

[okkibs]

Perhaps Netflix should stop forcing HDR on users and give them a choice. They claim that you can disable HDR when using the app but they do not offer a macOS app in the first place. I did see that there are 3rd party apps for that on the Mac App Store so perhaps that could be used as a workaround?

The Macbook Air (as well as the Studio Display) aren't advertised with HDR capable hardware, they merely support decoding HDR video to display the video correctly. On older Macbooks without that capability you'll find that HDR video will not display correctly.

The problem here seems to be more with Netflix not giving the user a choice since clearly they offer a SDR version. I wonder if this is unique to Netflix and how other streaming services deal with that? I have local HDR media that I use with my XDR Display and I appreciate that playback of the same media works on my Macbook Air on the go (which does not work on my much older Intel Macbook since it lacks HDR playback capability).

Of course it wouldn't hurt either if Apple allowed to set this manually or at least allowed for an override workaround like what you've been trying to find. But then again, it seems lazy for Netflix to offer a HDR toggle in their app but not in the browser. I am shocked they even let you access Netflix in the browser these days, which is of course a good thing because I sometimes come across interesting services only for their website to offer little more than a button to download an app I am never going to install. Sometimes these apps are merely a wrapper for a browser window anyways.

 

[edhinnig]

For Netflix I have to turn the brightness way up. Mid-tones are then more visible at expected brightness, and highlights are much brighter.

For Netflix I have to crank the brightness way up. Then the mid-tones show up at the expected brightness and the highlights get much brighter like they should.

But that creates two problems: the brightness becomes eye-searing if you're watching in a dim room or at night, and it raises the black floor (blacks look grayish), killing the contrast.

The visual of the "unplugged" workaround (SDR) is that I can keep the brightness at a comfortable level (50-60%) and the image still has punchy colors and deep blacks, without needing to blast the backlight to 100%.

 

[edhinnig]

Perhaps Netflix should stop forcing HDR on users and give them a choice. They claim that you can disable HDR when using the app but they do not offer a macOS app in the first place. I did see that there are 3rd party apps for that on the Mac App Store so perhaps that could be used as a workaround?

The Macbook Air (as well as the Studio Display) aren't advertised with HDR capable hardware, they merely support decoding HDR video to display the video correctly. On older Macbooks without that capability you'll find that HDR video will not display correctly.

The problem here seems to be more with Netflix not giving the user a choice since clearly they offer a SDR version. I wonder if this is unique to Netflix and how other streaming services deal with that? I have local HDR media that I use with my XDR Display and I appreciate that playback of the same media works on my Macbook Air on the go (which does not work on my much older Intel Macbook since it lacks HDR playback capability).

Of course it wouldn't hurt either if Apple allowed to set this manually or at least allowed for an override workaround like what you've been trying to find. But then again, it seems lazy for Netflix to offer a HDR toggle in their app but not in the browser. I am shocked they even let you access Netflix in the browser these days, which is of course a good thing because I sometimes come across interesting services only for their website to offer little more than a button to download an app I am never going to install. Sometimes these apps are merely a wrapper for a browser window anyways.

Regarding 3rd-party apps: I actually went pretty deep trying to use BetterDisplay to work around this.

On external monitors, BetterDisplay exposes HDR toggles, EDID overrides and the full virtual-display stack. But on Apple Silicon laptops, Apple has completely locked the internal panel’s pipeline. The usual “Allow HDR” switch simply does not exist for the built-in display, and BetterDisplay can’t override it because the system reports the panel as non-configurable at the EDID level.

Trying to fix this with custom Color Profiles felt like putting a band-aid on a broken bone. You can shift the look, but you can’t change the underlying fact that Safari is still receiving a full HDR signal and macOS is still tone-mapping it into a 500-nit SDR display.

I don’t think this is naïveté from Apple. It looks like intentional engineering.

From Apple’s point of view, the darker tone-mapped image is technically “correct” because it preserves highlight detail rather than clipping it to white, the way SDR would. The problem is perceptual: they compress the entire HDR range into the panel’s 500 nits to save highlight data, and that sacrifices midtones, especially faces.

It feels like Apple is prioritizing mathematical fidelity over visual usability.

If there's 3rd-party app that has actually cracked this lockdown on Apple Silicon internal displays, I’d love to hear about it. Everything I’ve tested hits the same system-level barrier.

I agree Netflix could offer a proper SDR toggle, but I also think this issue is primarily on Apple. Netflix is simply sending HDR when the OS reports HDR decoding capability. macOS treats “can decode HDR” as equivalent to “has an HDR-capable panel,” which isn’t true for the Air or the Studio Display. That mismatch is what creates the bad tone-mapping.

 

[edhinnig]

Quick update here: It’s not just the hardware, it’s the Mastering.

I spent some time A/B testing different Netflix HDR titles via Safari to isolate the variable, and the results changed my perspective a bit. I tested Alice in Borderland in HDR, and surprisingly, it looked fantastic on the Air’s panel. The brightness pop was there, the gamma was correct, and it didn't look washed out. This proves that the M4 Air actually can handle HDR tone-mapping correctly when the source metadata is solid.

However, when I switched to Breathless (also Netflix HDR), it was a disaster. It was dark and low-contrast as I described before, but I also noticed some weird brightness flickering in certain scenes. It seems that when the master is bad or the metadata is inconsistent, the Mac's tone mapping algorithm falls apart on this screen. Since macOS lacks a simple "Disable HDR" toggle, we are forced to watch these bad masters as-is. So the unplugging trick effectively acts as a manual override to force a clean SDR stream when you stumble upon a garbage master like Breathless.

 

[DaveEcc]

What about if you go into the Display settings and pick a preset without HDR? On M1 Pro I see Apple XDR Display (P3-1600 nits), and Apple Display (P3-500 nits) as options. I would imagine the 500 nit option is SDR.

 

[edhinnig]

What about if you go into the Display settings and pick a preset without HDR? On M1 Pro I see Apple XDR Display (P3-1600 nits), and Apple Display (P3-500 nits) as options. I would imagine the 500 nit option is SDR.

The logic is sound, but unfortunately, the M4 Air's internal display pipeline doesn't respect the user-selected Color Profile when a protected HDR video stream starts.

Even if I force the display to a strict "Rec. ITU-R BT.709-5" (sRGB/Gamma 2.4) profile in System Settings, the moment Safari detects the Dolby Vision/HDR flag from Netflix, macOS performs a system-level override. It bypasses the ICC profile completely for the video plane and engages the HDR tone-mapping.

It seems that on these new internal panels, the HDR handshake happens at a hardware/driver level that sits "above" the standard ColorSync profiles. So the profile stays active for the UI, but the video window forces itself into HDR mode regardless.

 

[DaveEcc]

That seems like a concrete enough example of doing it wrong and giving a bad user experience that you should be able to file a bug report (Open feedback assistant app). No idea if they'll address it, but they really should.

 

[okkibs]

Since macOS lacks a simple "Disable HDR" toggle, we are forced to watch these bad masters as-is.

You could also say: Since Netflix lacks this toggle. Nobody forces Netflix to send the Dolby Vision stream instead of the SDR version especially since this isn't a macOS app store Netflix app that needs to adhere to various arbitrary Apple rules that could say "do not confuse the user with extra toggles". Adding this toggle on the web player would not cost them anything.

That is why I suggested trying out one of the third party Netflix apps for macOS and see if they might have such a toggle. Netflix does not offer their own macOS app as far as I can see.

Still, Apple could offer their own toggle just as well.

It seems that on these new internal panels, the HDR handshake happens at a hardware/driver level that sits "above" the standard ColorSync profiles. So the profile stays active for the UI, but the video window forces itself into HDR mode regardless.

This also happens on the Studio Display and the XDR Display and it's considered a good feature because it allows to show both SDR and HDR content on the same screen. And it allows to switch the display into whichever mode is needed automatically.

It's a wanted feature because on third party HDR capable monitors this switch between SDR and HDR does not occur automatically. Apple actually offers that toggle that you want for third party monitors precisely because it does not have enough control over the monitor to handle it automatically.

This is actually the main reason I use a XDR Display as HDR monitor management with third party monitors is a horrible experience. It's just as bad on Windows except this bad experience is forced with all monitors. Because all monitors for Windows computers are by definition third party monitors. Even with Windows 11 users still report that the colors are blown out just sitting on the desktop with the HDR toggle switched on. That's borderline unusable.

The easiest fix is, and I say this half-jokingly, to switch the Macbook Air for a Pro that has actual dimming zones and HDR-suitable brightness of 1000 nits for 100% coverage and up to 1600 nits peak for smaller bright objects. Unfortunately neither these displays nor the XDR Display have enough dimming zones leading to blooming issue where bright highlights bleed into darker parts and the panels have various other problems like slow response times that make 120Hz less effective and lead to visible ghosting effects. But it's still a good choice for HDR content. And the moment Apple comes out with an OLED Macbook all current miniLED drawbacks should be resolved. I can tell from my iPad Pro M4 with Tandem OLED that HDR content looks much better. Washed out dark parts retain more detail in direct comparison with the same DV video. Ghosting and blooming issues are completely gone.

I don't know if Netflix HDR looks good on HDR capable displays though. Perhaps as you say the HDR stream Netflix sends is bad from the start.