Sunday, June 18th 2017

Latest 4K 144 Hz Monitors use Blurry Chroma Subsampling

Just a while ago the first 4K 144 Hz monitors became available with the ASUS PG27UQ and Acer X27. These $2,000 monitors no longer force gamers to pick between high-refresh rate or high resolution, since they support 3840x2160 and refresh rates up to 144 Hz. However, reviews of early-adopters report a noticeable degradation in image quality when these monitors are running at 144 Hz. Surprisingly refresh rates of 120 Hz and below look perfectly sharp.
The underlying reason for that is the DisplayPort 1.4 interface, which provides 26 Gbits/s of bandwidth, just enough for full 4K at 120 Hz. So monitor vendors had to get creative to achieve the magic 144 Hz that they were shooting for. The solution comes from old television technology in form of chroma subsampling (YCbCr), which, in the case of these monitors, transmits the grayscale portion of the image at full resolution (3840x2160) and the color information at half the horizontal resolution (1920x2160).

This approach is called 4:2:2 and works particularly well for the movie industry, where it is pretty much standard to ship the post-processed content to cinemas and TV using subsampling of 4:2:0 or 4:1:1. For computer generated content like text and the operating system interface, chroma subsampling has a serious effect on quality, especially text-readability, which is why it is not used here at all. In games chroma sub-sampling might be an acceptable approach, with negligible quality effects on the 3D game world, and slightly loss of sharpness for the HUD.

The images below describe how chroma subsampling works and how it affects image quality. Note how high-contrast edges look noticeably worse while low-constrast surfaces look nearly identical.

Considering that gamers have been demanding 144 Hz on their 4K monitors for quite a while, and NVIDIA has been pushing for it, too, I'm not surprised that monitor vendors simply went with this compromise. The bigger issue here is that they have been completely quiet about this and make no mention about it in their specification documents.

Technical solutions that can avoid subsampling include HDMI 2.1 and DisplayPort's DSC data compression scheme. HDMI 2.1, was just specified in December last year, so controller vendors are just figuring out how to implement it, which means it is still far away from getting used in actual monitors. DisplayPort 1.4 introduced DSC (Display Stream Compression), which is particularly optimized for this task. Even though it is not completely lossless compression, its quality is much better than chroma subsampling. The issue here seems that not a lot of display controller support exists for DSC at this time.

Given that there is not a lot of difference between 120 Hz and 144 Hz gaming, the best approach to get highest visual quality is to run these monitors at up to 120 Hz only, where they will send the full unmodified RGB image over the wire. Source: Reddit
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50 Comments on Latest 4K 144 Hz Monitors use Blurry Chroma Subsampling

#1
TheLostSwede
So you end up spending a lot of money for what in the end is an inferior product to what will be available in second generation products...
Nothing new there then, as consumers are continuing to be used as guinea pigs for new technology.
Posted on Reply
#2
nemesis.ie
Not just guinea pigs, they are also being fed misinformation or being told something is "X" because it has X's feature(s) (or some of them) but it's not actually X implemented correctly/fully.
Posted on Reply
#3
techy1
well - I am a bit disappointed, but I am happy that this product is on market finally... so it gives me a hope that after 1 years there will be monitors for 1000$ 4K with "meh" 120fps - and I will grab that and never look back (I hope 4K 100+fps capable GPU will be realistic in that time frame). but before overpiced "guinea pig" betta tests like this - it will not be possible
Posted on Reply
#4
qubit
Overclocked quantum bit
If I'd bought one of these monitors, I'd have returned it for a full refund for this. It should explicitly state the loss of quality on the product page as it's a material purchase decision. I would be running such a monitor at 144Hz on my desktop all the time, so I'd always have to put up with an inferior picture. No thanks.
Posted on Reply
#5
lynx29
Great informative read. So basically, we just need to be patient for better prices and tech standards like HDMI 2.1 to come.

I know these monitors have a fan that turns on inside as well, because they run so hot. Seems so dangerous to me, lol... really going to take a hard pass on these new monitors, and any that require a fan... can't be good for longevity.
Posted on Reply
#6
bug
At this point I'm not even sure why these were pushed to 144Hz. I highly doubt there's a noticeable difference between 120 and 144Hz and it looks like a 120Hz design would have been much simpler (thus cheaper).
For bonus points, it seems like not even DP1.4 is enough to drive HDR content (10 bits per channel) at high refresh rates :(
Posted on Reply
#7
lynx29
bug said:
At this point I'm not even sure why these were pushed to 144Hz. I highly doubt there's a noticeable difference between 120 and 144Hz and it looks like a 120Hz design would have been much simpler (thus cheaper).
For bonus points, it seems like not even DP1.4 is enough to drive HDR content (10 bits per channel) at high refresh rates :(
Seems like an oversight for sure. Logic makes more sense at 120hz anyway lol
Posted on Reply
#8
qubit
Overclocked quantum bit
bug said:
At this point I'm not even sure why these were pushed to 144Hz. I highly doubt there's a noticeable difference between 120 and 144Hz and it looks like a 120Hz design would have been much simpler (thus cheaper).
For bonus points, it seems like not even DP1.4 is enough to drive HDR content (10 bits per channel) at high refresh rates :(
My 1080p monitor does 144Hz and there's a visible difference, I can tell you. Definitely worth having the higher refresh rate.
Posted on Reply
#9
lynx29
qubit said:
My 1080p monitor does 144Hz and there's a visible difference, I can tell you. Definitely worth having the higher refresh rate.
It's all subjective. I actually hate 60hz, 75hz. but 90-100hz is what I love the most, 144 and 165hz and 240hz seem to fake to me. 100hz is my sweet spot and always will be i think. i have tried over 20+ monitors in last few years.
Posted on Reply
#10
bug
qubit said:
My 1080p monitor does 144Hz and there's a visible difference, I can tell you. Definitely worth having the higher refresh rate.
Visible difference compared to what? Because I was talking about the difference between 120 and 144Hz.
Posted on Reply
#11
Xaled
Why is nVidia behind everything like this? 120hz is just good. does they use 144hz just because it "sounds" better?

why even bother with 144hz because in LCDs you wont be able to get the smoothness and fluidity of CRTs no matter what. i remember when i was doing 165hz at my old CRT. darn wide screens!! :(
Posted on Reply
#12
GreiverBlade
lynx29 said:
It's all subjective. I actually hate 60hz, 75hz. but 90-100hz is what I love the most, 144 and 165hz and 240hz seem to fake to me. 100hz is my sweet spot and always will be i think. i have tried over 20+ monitors in last few years.
oohhh that's actually what i thought .... there is a sweet spot for each persone ...

fortunately (or unfortunately ) mine is at 60-75hz (can tolerate 30hz but not for games) and i considere 1440p to be the ideal resolution up to 32" and just as for refresh rate, up to 1620p is nice (3K) but above is gimmick (fortunately was maybe because i can find decent price around these specs :laugh: )

4k 120hz is a joke and 144hz even more ... maybe in one or two more GPU gen...

actually i rather hate the high res small size screen tendency .... 1440p/4K 24"? seriously? even at 1440/1620p 32" sitting at a adequate distance i can't see the pixels or any aliasing (never using FxAA or any AA since i swapped for that screen ) :laugh: even worse with smartphone ... i have a 1440p 5.2", previously i had a 720p 5.6", 1080p 5.5" and 1200p 8" (luckily the 1440p 5.6 was at a price lower than the other 3 ... otherwise i would never take it)
Posted on Reply
#13
IceShroom
This kind of cheap things is usually seen in cheap AMD's Freesync, not from superior G-sync.
Posted on Reply
#14
lynx29
Xaled said:
Why is nVidia behind everything like this? 120hz is just good. does they use 144hz just because it "sounds" better?

why even bother with 144hz because in LCDs you wont be able to get the smoothness and fluidity of CRTs no matter what. i remember when i was doing 165hz at my old CRT. darn wide screens!! :(
I remember playing WoW beta on my CRT with an ancient ATI gpu, it was so fluid looking I loved it, was instantly hooked. Wish I still had that setup actually, idiot me threw it all away a long time ago. I wish CRT would make a come back, I miss gaming on mine, I had some fun times with it.
Posted on Reply
#15
qubit
Overclocked quantum bit
bug said:
Visible difference compared to what? Because I was talking about the difference between 120 and 144Hz.
Yes of course, that's what I was talking about. That was in the context of your 120/144 comment.

lynx29 said:
It's all subjective. I actually hate 60hz, 75hz. but 90-100hz is what I love the most, 144 and 165hz and 240hz seem to fake to me. 100hz is my sweet spot and always will be i think. i have tried over 20+ monitors in last few years.
You're right about it being subjective. The faster the refresh the better, for me. :)

I guess it looks hyper-real when it refreshes that fast, with very little motion blur, while in everyday life, we see motion blur all the time. Anything that eliminates it, for me, is great as I can see so much more. Note that everyone else can see so much more too, which is why it feels odd to them.
Posted on Reply
#16
INSTG8R
IceShroom said:
This kind of cheap things is usually seen in cheap AMD's Freesync, not from superior G-sync.
Wow talk about drinking the green Kool Aid...:wtf:
Posted on Reply
#17
lynx29
qubit said:
Yes of course, that's what I was talking about. That was in the context of your 120/144 comment.


You're right about it being subjective. The faster the refresh the better, for me. :)

I guess it looks hyper-real when it refreshes that fast, with very little motion blur, while in everyday life, we so motion blur all the time. Anything that eliminates it, for me, is great as I can see so much more. Note that everyone else can see so much more too, which is why it feels odd to them.
100hz is pretty smooth to look at too. :) I might try 240hz 1440p 27" someday when all that comes out, I think my dream monitor is 27" 240hz 1440p micro-LED, just seems to have 0 issues with any game I throw at it, that rez and size I mean, while if I try to play older games in 4k, its just a terrible experience trying to get the text and UI to scale, and many games don't even have mod support to fix it. I probably will have two monitors in the future, one for modern games, and one for older. lol
Posted on Reply
#18
bug
Xaled said:
Why is nVidia behind everything like this? 120hz is just good. does they use 144hz just because it "sounds" better?

why even bother with 144hz because in LCDs you wont be able to get the smoothness and fluidity of CRTs no matter what. i remember when i was doing 165hz at my old CRT. darn wide screens!! :(
Huge difference between CRT and LCD though.
CRT: no image to speak of, just a dot moving at huge speeds to trick your eyes into seeing one.
LCD: image is always there, but you can't refresh it as fast.

When CRTs were everywhere, virtually everybody in their late thirties who used one at their job, had to wear glasses.
I think quantum dot could bring back that insanely fast refresh speeds while maintaining LCD's advantages. But it would take real quantum dot, not that contraption Samsung sells these days. Then again, Samsung's XL20 was also promising back in the day and the tech never took off...
Posted on Reply
#19
Caring1
lynx29 said:

I know these monitors have a fan that turns on inside as well, because they run so hot. Seems so dangerous to me, lol... really going to take a hard pass on these new monitors, and any that require a fan... can't be good for longevity.
Up until recently I had and still used an original Fluoro backlit LCD monitor, and that thing ran hot enough to warrant a fan or two, I guess it would still be alive if it had them.
Posted on Reply
#20
iO
Caring1 said:
Up until recently I had and still used an original Fluoro backlit LCD monitor, and that thing ran hot enough to warrant a fan or two, I guess it would still be alive if it had them.
Speaking of running hot, it looks like the new Gsync module needs active cooling at 144Hz so they put a whiny fan in the Acer model
Edit: Looks like Asus also has the fan...[IMG]https://www.forum-3dcenter.org/vbulletin/attachment.php?attachmentid=63553&d=1528784065[/IMG]
Posted on Reply
#21
fynxer
Haha, is this for real? i will never buy a monitor with a fan.

Acer could not take the time to make a design without fan then they are not worthy of my money.
Posted on Reply
#22
Octopuss
I don't even see the big deal about144Hz. 120 is plenty fast already.
This is what you get when you jump on trends as they surface.
...that's not an excuse for manufacturers though.
Posted on Reply
#23
bug
fynxer said:
Haha, is this for real? i will never buy a monitor with a fan.

Acer could not take the time to make a design without fan then they are not worthy of my money.
I don't know the first thing about how these are being built, but given the number of pixels they have to move each second, it may not be possible to do it without active cooling.
Octopuss said:
I don't even see the big deal about144Hz. 120 is plenty fast already.
This is what you get when you jump on trends as they surface.
...that's not an excuse for manufacturers though.
See qubit's response above. When users swear by 144Hz and your competition sells 144Hz, you either follow suit or risk being left behind.
Posted on Reply
#24
Octopuss
From marketing point of view, it makes perfect sense.
...just like abandoning 16:10 :banghead:
Posted on Reply
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