by Brandon Butler
Dolby Vision on the new 12’s 10/20/2020

The Verge team has a great review of the two new iPhones shipping this Friday: The iPhone 12, and the iPhone 12 Pro. I love Verge video reviews, but Nilay Patel’s written review is also superb. I’m always impressed with how quickly they’re able to turn around these massive reviews, getting text and video out the same day. What a combo. That said, I was especially intrigued by Patel’s explanation of how the iPhone’s Dolby Vision works here, and I gotta say, it’s damn clever:

I’ve been saying “HDR” this whole time, not “Dolby Vision.” That’s because Dolby Vision is one kind of HDR — a format — and there are lots of HDR formats. With lots of formats come compatibility problems. And, yep, Dolby Vision on the iPhone 12 has some compatibility problems — but not as many problems as I feared. Apple and Dolby have done something very smart to ensure long-term compatibility at the cost of some short-term incompatibility.

Dolby Vision and the rival HDR10 format are what’s called perceptual quantizer (PQ) HDR systems. And PQ systems are not backwards compatible with SDR displays, meaning Dolby Vision video has only been compatible with Dolby Vision displays. (Playing a Dolby Vision video on a non-Dolby Vision display would look completely wrong.) If you wanted to watch a Dolby Vision video on a regular display, you would have to re-encode it into SDR — basically, make an entirely new video file.

But the iPhone 12 shoots video in a newer version of Dolby Vision called Profile 8.4 that’s built on a standard called HLG, or hybrid log-gamma. HLG works differently than PQ systems; it was developed by broadcasters like the BBC and NHK to be backwards compatible with SDR displays so they would only have to broadcast one video stream.

All this means that an iPhone 12 HDR video is a 10-bit HLG file with additional Dolby Vision metadata on top, and it will happily play back as SDR on SDR displays, HLG on HLG displays, and Dolby Vision on Dolby Vision displays that support Profile 8.4. And iOS 14 is smart enough to know when the apps and devices you’re sharing video to don’t support this new format, and it’ll make sure you send something that works. It is all very clever, even though, in practice, what it means is you’re mostly sharing SDR video.

Or, in practice, what it means is most people aren’t using phones with HDR/HLG displays. Apple isn’t afraid of pushing to market a new tech that is grossly incompatible with everyone else, because they know everyone else will eventually catch up.

This is a great explainer of what Dolby Vision on the iPhone is and how it will work with existing screens, all tucked inside a great review of the new iPhone 12 Pro.

This might also be the first iPhone review from Patel not to lament the loss of the headphone jack.