Shimmering at 1440p

[muteki]

Hi,
I'm runnning MiSTer on a 1440p monitor (Gigabyte G27Q) with video_mode=12, vsync_adjust=1 and integer scaling (set at V-integer in core), all cores are butter smooth.

Lately I started noticing shimmering and blur in games that have heavy horizontal scrolling (SMB1 & 3, Mega Man, Contra, etc). So I launched the 240p Test Suite and in the Hill zone scroll test everything is smooth but the mountain in the background is shimmering AND stuttering. In the scroll test you can adjust speed and what I've noticed is that the shimmering appears only on every second speed step, the stuttering is there all the time. The foreground is perfectly smooth, whatever the scrolling speed.

I managed to get rid of the shimmering by setting the scaling filter to Comp_Blend_H_025, even though there is still some kind of stuttering.

I don't have a CRT nearby to compare and at this point it has become an OCD, so I don't know if it's supposed to be like that on the original NES or not.
All other cores are perfectly smooth.

Am I missing something in the settings to get rid of the shimmering, stutter and blur?
Thank you in advance.

[bootsector]

Do you get shimmering with No Interpolation filter and horizontal integer scale enabled?

[muteki]

Thanks for taking the time to answer.
No, I don't. I still think the background is stuttering. It's quite visible on games like Metal Storm that have lots of scrolling and backgrounds that have many patterns. Is that normal behaviour for the NES core or can it be related to the monitor I'm using?

[FoxbatStargazer]

Horizontal shimmering is normal when you aren't using horizontal integer scaling, pixels will be uneven because getting the correct aspect ratio is instead prioritized. In that case one of the many scaling filters can blur that out for you. Even sharp interpolation is usually sufficient.

As for the backgrounds, some stutter might be normal. NES has no hardware support for parallax scrolling, so devs had to come up with quite a few tricks to pull it off. Sometimes the results are a little flaky when the CPU is being pushed to the limit to accomplish these tasks and still run the rest of the game. Here's a fairly technical video that goes into depth on how these were achieved.

[muteki]

Thanks a lot for the explanation.
I have now Wider HV integer scaling activated for NES and it seems better to me. AR is not correct anymore, but the skew is acceptable.

Also I think, my memory is playing tricks on me and I was definitely not playing NES with such sharp pixels at the time.

Thanks all for your help.