Thread by @bgolus

I want to rant a bit about recent price & spec reveal of the Samsung Odyssey G9, and why this it is an impressive bit of tech ... and how Samsung is lying by omission.

samsung.com/us/computing/m…

Basic specs their web site (and all the press dutifully copy paste everywhere):
1000R 49” 5120x1440 HDR1000 QLED 1ms 240hz with GSync and FreeSync Premium Pro support. This has all the bells and whistles you could ever hope for. Except there’s one more spec that’s important.

DisplayPort 1.4

That one last thing means everything above is basically a lie. Here’s why.

5120x1440
240hz
HDR

It can’t do all 3 at the same time. It can’t even really do the full resolution at 240hz without some significant drawbacks!

Elsewhere on the internet people have already noticed this discrepancy, and ask Samsung to clarify if the monitor supported DSC, or Display Stream Compression. The response was yes, “that’s how 240hz even works!” And they’re right. But still leaving something out.

First, some tech talk.

DisplayPort 1.3 & 1.4’s max bandwidth is explicitly designed around 3840x2160 8bpp 120hz. This is approximately 26Gb/s. With DSC, which was added with 1.4, they can compress the display signal to get up to 4k 8bit 240hz.

And here’s the issue. 5120x1440 10bit (for HDR) is more data than 4K 8bit.

That makes me think this display requires chroma subsampling to hit the full refresh rate and resolution. That means it’s not going to be good for desktop use at full speed!

Now, it’s possible I’m wrong and w/ DSC there is actually enough bandwidth to do the full res. But there are still two remaining issues with the monitor I’m concerned with.

DSC adds some latency. How much? Hopefully not a lot. But until some pro monitor reviewers get ahold of one of these things, don’t go out and buy one if you’re looking for super low latency monitors.

The other concern I have is the refresh rate range. GSync compatibility requires the refresh rate range have a ratio of 2.4:1 to pass their testing. The G9 has a min refresh rate of 60, and a max of 240. So it has a ratio of 4:1, way better than needed.

But that kind of ratio was created around the idea that it’d be on 1080p or maybe 1440p monitors. Resolutions that top end GPUs can actually get high stable frame rates on.

This thing is 2x a normal 1440p monitor. Most games will struggle to hit 60hz with an RTX Titan.

That means there’s nothing on the planet that can drive this thing at 240hz in anything modern. And most of the time games will be running below the 60hz min. A more traditional range of 40~120, while less sexy, would actually have been useful!

So, this is a monitor designed for future GPUs that don’t yet exist, but it’s stuck with the older revision of display port.

It’s a monitor that seems to exist because Samsung spent the R&D to make it, but finished it before the GPUs that could run it exist.

Oh. One more thing. The 1ms thing is a marketing gimmick. It’s referring to the time it takes to switch from one image to another, the input latency. But even that is a lie because how that’s measured isn’t regulated.

There are a lot of monitors that have managed to get the input latency down to a little less tha 1 frame, which is excellent. The LG C9 does 6ms when at 120hz. Some Acer 240hz monitors are below 4ms... but that’s to start switching, not when the final image is displayed.

There are some LCD monitors that get close to 1ms to switch their image, but they’re uncommon, and that’s the best case scenario with the panel highly overdriven so it has serious image artifacts. 6~40ms range for LCDs is still the realistic range.

That’s a whole separate rant though. The TLDR is the same though. PC monitor marketing is bullshit.

One last thought.

DSC is described as “perceptually lossless”. Which really means it’s a lossy compression. This is fine.

But 4:2:0 has in the past been described as “perceptually lossless”, and it works great for movies. It looks like utter shit for desktop usage.

I think there are maybe 2 monitors in existence that support DSC right now, and I’ve not seen anyone do comparisons of how DSC impacts the image quality. It might be totally fine! But it might also look just as bad as 4:2:0.

It’ll end all of this with the big caveat that the monitor might actually all work as described and I could be complaining that the sky is falling too soon. Maybe some new mega GPU is getting announced soon too and asuages those issues too.

Or maybe my exteme cynism against monitor marketing will continue to be well founded.