madVR Scaling Algorithms Questions

[Zach_N85]

Hi guys,

I've been using madVR with PotPlayer and I have some questions I was hoping you can help me with.

My PC:
i5 2500k @ 4.5GHz
8GB DDR3-1600
GTX680

madVR settings:













With these settings my GTX680 hits about 70-80% usage when watching 1080p, but 720p causes 95% usage and artifacts, questions:

1. Can you please explain what Chroma upscaling is? I'm currently using NNEDI3 with 16 neurons for Chroma.
2. Image downscaling: Using Jinc here, can you explain when this takes place?
3. Image upscaling: Using NNEDI 3 with image doubling 64 neurons and 32 quadrupling, when I watch a 1080p movie this doesn't hit performance but when I watch a 720p movie I get mad artifacts. I assume it's only relevant to upscaling 720p to 1080p and that's why I get artifacts. I tried switching to NGU (It has the exact same performance as NNEDI3) and the artifacts were gone.
4. Can you please explain the difference between NNEDI3 and NGU? Both give the same performance exactly, but NGU doesn't stress the GPU as much as NNEDI3 and I don't get artifacts.
5. I'm currently running my PC @ 1080p resolution, if I go higher to 4K res, will that stress the GPU even more when watching 720p because it will have to upscale 720p > 4K rather than 720p >1080p?
6. PC upgrade will come soon, which GPU should I get to maximize madVR, would a GTX1070 do well, or maybe 1080?

Thanks

[sneaker]

1. Most video uses chroma subsampling. E.g. on a Blu-ray the luma plane may be 1920x1080 pixels but the colors (chroma planes) are only 960x540 pixels. So they have to be upscaled even when viewed on a 1080p display.
2. When picture is bigger than display resolution. (e.g. 4K movie on 1080p display)
4. Those are different algos. Author wants NGU to replace NNEDI to some extend because it's faster at similar quality.
5. Yes
6. The bigger the better but IMHO not worth it. Do you really see the differences in normal viewing conditions, i.e. not with the nose touching the paused and zoomed in screen?

https://forum.doom9.org/showthread.php?t=171787

[Zach_N85]

Thanks for the answers.

Can you elaborate on NGU vs NNEDI3 please? How does the quality of NGU compare to NNEDI3 which is much more stressful on the GPU?

About 5: Which GPU do I need to upscale 720p to 4K res with NGU/NNEDI 3? I assume it will take at least a GTX1070?