DSC compression artifact(?)

[AnonymousGuy]

I've seen smaller versions of artifacts that come with DSC (4K 144Hz, DP 1.4) but never this big.  I thought it was youtube messing up but if I put some other stuff on screen or change to 120Hz it cleans up.  So is it "lossless" as I see quoted everywhere?  Doesn't seem so.

 

Real life:
 

 

Actual (screenshot):

 

[porina]

It's called perceptually lossless, so not actually lossless but you're not supposed to notice the difference normally. Not sure what I'm supposed to be seeing in the top pic since the pixels of the display and camera interacting can also make really funky effects.

[AnonymousGuy]

7 minutes ago, porina said:

It's called perceptually lossless, so not actually lossless but you're not supposed to notice the difference normally. Not sure what I'm supposed to be seeing in the top pic since the pixels of the display and camera interacting can also make really funky effects.

Everything that is purple is what I see IRL.  The screendoor effect is the camera but that's it.

[porina]

1 minute ago, AnonymousGuy said:

Everything that is purple is what I see IRL.

I was wondering as that looked way out of place. Might not directly be a fault of DSC but something to do with the implementation on one end or other. Either way I guess it doesn't help you.

 

This seems to be the video you used, any particular time stamp? Maybe around 4:15 or so? I don't have any systems with DSC but maybe others can try to replicate this in case it is a problem elsewhere.

 

[Glenwing]

I ran your provided screenshot through the DSC reference encoder and I don't see the same artifacts. So I don't think it's caused by DSC, or at least if it is, it's some kind of implementation mistake, not a problem with the algorithm itself.

[Andrewtst]

DSC is not as good as it announced. My Samsung Odyssey Neo G8 will have scan line issue in certain color icon and also little banding in certain scenes when 4K HDR video playback when I set to 240hz. As for my another Samsung Odyssey Neo G9 don't have scan line issue but you can notice less sharpen and also little banding as well when I set to 240hz. 

 

Due to this, now I am using it under 120hz and all issues gone. I truly hope Samsung make it possible 240hz for the HDMI 2.1 output as I believe it will be better as the compress ratio is lower since HDMI 2.1 had bigger bandwidth than DP 1.4, but too bad until now both monitor HDMI 2.1 also not support 240hz.

[Stahlmann]

4 hours ago, Andrewtst said:

DSC is not as good as it announced. My Samsung Odyssey Neo G8 will have scan line issue in certain color icon and also little banding in certain scenes when 4K HDR video playback when I set to 240hz. As for my another Samsung Odyssey Neo G9 don't have scan line issue but you can notice less sharpen and also little banding as well when I set to 240hz. 

That doesn't have to do with DSC. It's a problem pretty much all 240Hz Samsung monitors have. It's easy to find out because they have the same issues when used with HDMI 2.1 where no DSC is used. It's just the usual Samsung BS.

[Andrewtst]

20 minutes ago, Stahlmann said:

That doesn't have to do with DSC. It's a problem pretty much all 240Hz Samsung monitors have. It's easy to find out because they have the same issues when used with HDMI 2.1 where no DSC is used. It's just the usual Samsung BS.

Samsung did not support 240hz in HDMI 2.1, no way to find out as 120hz in HDMI 2.1 and DP 1.4 totally no issue. 

 

120hz also required DSC in 4K or my another 5120x1440 resolution when use in DP 1.4.

 

They is obvious in high compression DSC got issue as I don't have scan line issue using 240hz in 5120x1440 but got scan line issue in 3840x2160.

[Glenwing]

5 hours ago, Andrewtst said:

Samsung did not support 240hz in HDMI 2.1, no way to find out as 120hz in HDMI 2.1 and DP 1.4 totally no issue. 

 

120hz also required DSC in 4K or my another 5120x1440 resolution when use in DP 1.4.

 

They is obvious in high compression DSC got issue as I don't have scan line issue using 240hz in 5120x1440 but got scan line issue in 3840x2160.

Samsung monitors have had scanline issues since all the way back with the CHG70, which is a 1440p 144 Hz monitor and did not use DSC. It's just a Samsung issue.

 

 

[Andrewtst]

2 hours ago, Glenwing said:

Samsung monitors have had scanline issues since all the way back with the CHG70, which is a 1440p 144 Hz monitor and did not use DSC. It's just a Samsung issue.

 

 

This is not the scanline issue I mean, I did not face this issue.

Also the scan line at icon or cetain specific color will gone when you switch from 240hz to 120hz.

 

I mean icon appear scan line issue, it is only appear at icon or any specific color and not appear the entire screen or horizontally.

These two issues you mentioned is always there nor-matter what hz you use. It is difference thing.

 

From internet source, below image demonstrate the scan line issue I mentioned.

 

Left image at 120hz (no issue), right image at 240hz (scan line)

 

[Glenwing]

11 hours ago, Andrewtst said:

This is not the scanline issue I mean, I did not face this issue.

Also the scan line at icon or cetain specific color will gone when you switch from 240hz to 120hz.

 

I mean icon appear scan line issue, it is only appear at icon or any specific color and not appear the entire screen or horizontally.

These two issues you mentioned is always there nor-matter what hz you use. It is difference thing.

 

From internet source, below image demonstrate the scan line issue I mentioned.

 

Left image at 120hz (no issue), right image at 240hz (scan line)

 

I see. People also have this issue on the G7 and many other Samsung monitors. Including people who lowered the refresh rate to 144 Hz (DSC not used):

 

Or 60 Hz:

 

And people using 10-series graphics cards that don't even support DSC:

 

[e22big]

12 hours ago, Andrewtst said:

This is not the scanline issue I mean, I did not face this issue.

Also the scan line at icon or cetain specific color will gone when you switch from 240hz to 120hz.

 

I mean icon appear scan line issue, it is only appear at icon or any specific color and not appear the entire screen or horizontally.

These two issues you mentioned is always there nor-matter what hz you use. It is difference thing.

 

From internet source, below image demonstrate the scan line issue I mentioned.

 

Left image at 120hz (no issue), right image at 240hz (scan line)

 

I think it's more likely to be the bandwitch limitation issue rather than DSC. 4k 240hz 10 bit is a massive amount of data, probably reaching 80 Gbph uncompressed at the maximum. That was at the very edge of DP 1.4 DSC if we assumed 1/3 bandwidth reduction with DSC (which is around 75 Gbph uncompressed.)

 

I think it's probably not that illogical to expect some artefacts when you bandwidth-starved. Like, Samsung probably believe they can compress 80 Gbph worth of streaming data to the usable chunk otherwise they wouldn't be including it in the first place, but when you're running at the absolute edge, every little of errors will probably count - and Samsung wasn't know for their QC procedure.

[Andrewtst]

2 hours ago, e22big said:

I think it's more likely to be the bandwitch limitation issue rather than DSC. 4k 240hz 10 bit is a massive amount of data, probably reaching 80 Gbph uncompressed at the maximum. That was at the very edge of DP 1.4 DSC if we assumed 1/3 bandwidth reduction with DSC (which is around 75 Gbph uncompressed.)

 

I think it's probably not that illogical to expect some artefacts when you bandwidth-starved. Like, Samsung probably believe they can compress 80 Gbph worth of streaming data to the usable chunk otherwise they wouldn't be including it in the first place, but when you're running at the absolute edge, every little of errors will probably count - and Samsung wasn't know for their QC procedure.

I agreed and it is the reason I said DSC in too high compression is not a workable solution and Samsung should enable 240hz at HDMI 2.1 which will reduce the compress ratio and may prevent the scan line issue in certain color. 

[AnonymousGuy]

On 3/28/2023 at 8:24 PM, Glenwing said:

I ran your provided screenshot through the DSC reference encoder and I don't see the same artifacts. So I don't think it's caused by DSC, or at least if it is, it's some kind of implementation mistake, not a problem with the algorithm itself.

I'll send you a PM shortly with the full resolution whole-screen screenshot.  It seems like the thing goes freaky depending on the entire screen contents.

 

Edit: sent.  I can't completely avoid something in the chain compressing the screenshots but I tried.

 

I'm not public posting the whole thing cause it has tabs open and whatnot but the only difference between "glitchy" with the purple haze and "not glitchy" is this one little bit of the screen changing: