Although recent versions of macOS have been opening the door to high-quality 4K streaming on Apple’s desktop and laptop computers, it would appear that users of older MacBooks and iMacs are going to continue to be left out of the party.
In fact, the addition of 4K content to the Mac has already been a strange and winding road. Even though Apple released its Apple TV 4K over three years ago, bringing 4K movies to the iTunes Store along with it, it wasn’t until last year’s release of macOS Catalina that customers were actually able to enjoy their 4K iTunes flicks on their Mac.
In other words, even if you had splurged for the most expensive 27-inch 5K Retina iMac or iMac Pro, you were still limited to watching your movies in 1080p HD, even if you had purchased them in 4K from iTunes, and the same limitations applied to streaming services like Netflix and even YouTube.
It wasn’t until Apple split up iTunes with macOS Catalina last year that 4K streaming came to the Mac through Apple’s own TV app. This was no doubt at least partly so that users could enjoy new Apple TV+ content in all of its 4K glory, but with it also came support for watching iTunes purchased and rented movies and TV shows in the higher resolution as well — as long as you were running a more recent model of Mac.
However, since only Apple’s own TV app gained the ability to handle 4K content, every other streaming service continued to be stuck at 1080p, leaving users to turn to an Apple TV, smart TV, or other set-top streaming boxes if they wanted to get full 4K HDR quality.
Enter Big Sur
The good news is that Apple has finally decided to address this in macOS Big Sur, which will introduce 4K support in Safari 14 and Apple’s WebKit frameworks, but sadly it looks like there’s still going to be a catch, at least when it comes to streaming services like Netflix.
As noted under “Netflix in Ultra HD” on Netflix’s support page, along with macOS 11 Big Sur and other expected requirements such as a 4K display, playing back content in full 4K resolution also requires a “Select 2018 or later Mac computer with an Apple T2 Security chip“
If you have a recent MacBook Air or MacBook Pro, this isn’t a huge problem, as Apple has been included the T2 chip in those models since at least 2018, and the same is also even true for Apple’s Mac mini.
Unfortunately, however, a great many of the only Macs that actually have built-in 4K (or 5K) displays — Apple’s iMacs — are not included on this list.
While Apple did add the T2 chip to the high-end iMac Pro released back in late 2017, the T2 chip didn’t come to the standard iMac lineup until two months ago.
In other words, the vast majority of iMac users are still not going to be able to enjoy 4K UHD video content, even with Big Sur.
Why Is a T2 Chip Required?
While there’s a fair bit of speculation as to why this restriction exists, it actually shouldn’t be a big surprise when you consider that Apple has listed the exact same requirements for 4K iTunes content since macOS Catalina was released last year.
Although Apple doesn’t specifically call out the T2 chip as the reason, the list of Mac models that support HDR is identical to those that include the T2 chip, suggesting that Apple’s coprocessor definitely plays a role in driving 4K content.
Since the T2 chip is primarily marketed as a “Security Chip” a common theory seems to be that it’s about the movie and TV studios ensuring that strong copy-protection enforcements are in place, and while this certainly seems extremely plausible considering the clinical paranoia of many Hollywood execs, there’s actually more to the T2 chip than purely security.
In fact, there’s a very good chance this has nothing to do with DRM at all. It’s unclear exactly what the T2 chip would add to copy protection for streaming content in the first place, since the security features are primarily designed for driving things like Touch ID and encrypted storage. It’s possible that it could also be used to store and manage DRM keys in the Secure Enclave to help harden them against reverse engineering by hackers, but the fact that such a requirement doesn’t exist on any other platform would seem to rule that out.
However, the T2 chip also incorporates an image signal processor that’s already known to assist the FaceTime HD camera with enhanced tone mapping and exposure control, as well as built-in H.265 HEVC hardware decoder, so it wouldn’t be at all unreasonable to assume that Apple’s 4K HDR rendering engine in macOS Catalina and Big Sur simply requires the T2 chip to handle the heavy lifting and that it actually has nothing to do with DRM at all.
It’s also worth noting that users of Windows PCs don’t require any special security hardware to stream Netflix in 4K, although they do still need to be using a relatively recent CPU — a 7th-generation Intel Kaby Lake or later. While some have suggested that this also has to do with hardware-based DRM encryption, the reality is that it was the Kaby Lake series that first introduced built-in support for hardware-based H.265 HEVC decoding used by most 4K HDR content.
It’s not clear yet whether Big Sur users will face similar requirements to stream YouTube videos in 4K. Since copy protection isn’t an issue for YouTube videos, a T2 chip requirement would speak to it assuredly being needed for accelerated video decoding, however it’s also worth keeping in mind that YouTube uses an entirely different codec for its 4K videos which may not be able to take advantage of the T2’s H.265/HEVC hardware decoder anyway.