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AMD Radeon FreeSync 2: HDR And Low Latency

AMD crammed a lot of FreeSync love into 2015, starting with a proliferation of compatible displays and ending with the introduction of low-frame rate compensation (LFC). That latter capability addressed one of G-Sync’s main advantages. Specifically, any time the frame rate of your favorite game fell below the minimum variable refresh of your FreeSync monitor, the technology stopped working, and you ended up with motion judder or tearing.

FreeSync Evolves

LFC was a much-needed addition to FreeSync, and because AMD implemented it through the Crimson driver, many monitors supported LFC right away. Others did not, though. Enabling LFC required a maximum refresh rate greater than or equal to 2.5x the minimum. So, panels with a variable refresh range between 40-60Hz, or 48-75Hz, or 55-75Hz couldn’t benefit from it.

Those early growing pains and a later lack of feature/range consistency from one monitor to the next meant many enthusiasts continued thinking of FreeSync as the more affordable, but less refined, alternative to G-Sync.

Today, AMD enjoys a sizeable lead over Nvidia when it comes to variety—the company claims that >6x as many models support FreeSync—and the latest implementations really are quite good. Improvements continue rolling in, too. FreeSync is now supported over HDMI on certain monitors, and the feature was recently made to work in full-screen borderless windowed mode.

But AMD knows it has a mindshare battle to fight against a competitor notorious for tightly controlled, proprietary IP, so it’s shedding some of those open standard ideals in a bid to attract the gamers willing to pay top dollar for an assuredly positive experience.

Enter FreeSync 2.

One Step Closer to HDR

We had a long chat with AMD about HDR back in 2015, and the company shared its vision for high-dynamic range rendering. Although it didn’t seem like much happened to further this cause on the PC in 2016, Sony’s PlayStation 4 Pro and Microsoft’s Xbox One S—both powered by AMD graphics—added support via HDR10. We also started seeing TVs capable of increased color range and brightness compared to sRGB. Even games began rolling out to validate those extra investments in marginally-faster consoles and expensive displays.

The headline feature of Radeon FreeSync 2 promises to get this same goodness onto the PC in 2017, and the result should be better than anything console gamers are getting today. FreeSync 2’s significance is summarized in a single slide:

What you’re seeing is the elimination of the tone mapping a monitor must go through to present an HDR-rendered image. FreeSync 2 enables this by feeding the game engine (all the way on the left side of the diagram) specific information about the display you’re using. In return, you get the best possible image quality that the monitor is capable of, because the game tone-maps to the screen’s native characteristics. There’s also a notable reduction in input lag, as illustrated in AMD’s slide.

Of course, you wouldn’t want to use non-managed software in the same mode. So AMD adds an automatic switch to take you into HDR and then return to however your monitor was previously configured.

The question of why not simply use the HDR10 or Dolby Vision transport spaces is already answered, then—they’d require another tone mapping step. David Glen, senior fellow architect at AMD, said that HDR10 and Dolby Vision were designed for 10 or more years of growth. Therefore, even the best HDR displays available today fall well short of what those transport spaces allow. That’s why the display normally has to tone map again, adding the extra input lag FreeSync 2 looks to squeeze out.

Sounds like a lot of work, right? Every FreeSync 2-compatible monitor needs to be characterized, to start. Then, on the software side, games and video players must be enabled through an API provided by AMD. There’s a lot of coordination that needs to happen between game developers, AMD, and display vendors, so it remains to be seen how enthusiastically AMD’s partners embrace FreeSync 2, particularly because the technology is going to be proprietary for now.

Fortunately, AMD is giving us some assurances about what FreeSync 2 is going to mean. To begin, branded displays must deliver more than 2x the perceivable brightness and color volume of sRGB. While seemingly an arbitrary benchmark to set, remember that AMD wants this technology to launch in 2017. It has to work within the bounds of what will be available, and AMD’s Glen said that satisfying a 2x requirement will already require the very best monitors you’ll see this year.

FreeSync 2 certification is also going to require low latency. Glen stopped short of giving us numbers, but he did say more than a few milliseconds of input lag would be unacceptable. Finally, low frame rate compensation is a mandatory part of FreeSync 2, suggesting that we’ll see wide VRR ranges from those displays.

AMD expects FreeSync and FreeSync 2 to coexist, so you’ll continue seeing new FreeSync-capable displays even after FreeSync 2-certified models start rolling out. Any AMD graphics card that supports FreeSync will support FreeSync 2, as well.

Chris Angelini
Chris Angelini is an Editor Emeritus at Tom's Hardware US. He edits hardware reviews and covers high-profile CPU and GPU launches.