Weird Large VT behavior

[terry98]

Hi Chief maybe you can help me with this, a couple of weeks ago I bought an Innocn Portable Oled monitor 1080p 60Hz, it really looks amazing, and I decided to play with the vertical totals using CRU.

I started by reducing the color to 8 bit (it does support 8bit +frc) but I prefer 8bit and thats it.. and then started increasing the vertical totals, I went as far as having 1600 total vertical lines ( blanking plus sync plus the actual 1080 lines) and the monitor would just keep showing the image with no problems everytime I reset the drivers.

But then.. using RTSS in a couple of games I noticed that I really had like 80 lines of blanking below the last visible image.. If I continued reducing the sync line using RTSS it would eventually go above the monitor and show in the first 1/10th of the image.. if I wanted to lower the sync line it would have to below 200 or 300 (ish) lines before I could see it going down.

you know why is this??

[Chief Blur Buster]

Hi Chief maybe you can help me with this, a couple of weeks ago I bought an Innocn Portable Oled monitor 1080p 60Hz, it really looks amazing, and I decided to play with the vertical totals using CRU.

I started by reducing the color to 8 bit (it does support 8bit +frc) but I prefer 8bit and thats it.. and then started increasing the vertical totals, I went as far as having 1600 total vertical lines ( blanking plus sync plus the actual 1080 lines) and the monitor would just keep showing the image with no problems everytime I reset the drivers.

But then.. using RTSS in a couple of games I noticed that I really had like 80 lines of blanking below the last visible image.. If I continued reducing the sync line using RTSS it would eventually go above the monitor and show in the first 1/10th of the image.. if I wanted to lower the sync line it would have to below 200 or 300 (ish) lines before I could see it going down.

you know why is this??

1. Doublecheck your Vertical Total is being targetted by the right screen (e.g. laptop screen versus external monitor). Use single monitor, so RTSS is not confusing VT's from multiple different displays.
2. Use negative RTSS scanline indexes.

And about the Windows behavior of tearlines almost never being visible on the first few pixel rows:

Short Answer:
It's a Windows/GPU behavior. Always try to use negative scanline indexes with RTSS Scanline Sync to move the tearline ABOVE top edge of screen! Sometimes you need larger numbers before tearlines suddenly disappear from top edge of the screen.

Long Answer:
I have noticed that drivers and Microsoft Windows compositing seems to have blocking behavior if you set scanline numbers near top edge of screen. So tearlines are always pushed down, e.g. tearlines may not ever appear in the first few pixel rows of a display because Windows/GPU is busy compositing framebuffers and doing other housekeeping behavior (e.g. scheduled GPU processing/initialization/power management)

The faster the GPU bandwidth, the shorter time this happens. Older GPUs and laptop GPUs will usually run off slower memory, which slows down DWM compositing, which expands the "never-has-tearlines" zone near top edge -- it's also a latency black hole (can affect mousefeel etc). You can reduce this problem by disabling power management and using true full screen exclusive (rather than borderless), and getting a GPU with the fastest memory bandwidth.

You need to use negative numbers. You must use scanline positions well ABOVE the top edge of the screen. The slower your performance, the bigger negative index you need to use to hide tearlines in the tearingless VSYNC OFF feature of RTSS Scanline Sync.



TL;DR: Use negative scanline indexes and keep going further into negative territory until the whole tearline-jitter band is above top edge of screen, for lowest possible QFT latency.

It is easiest to think of tearing as capable of affecting the entire Vertical Total including the offscreen region between refresh cycles. VBI is like hidden offscreen resolution padding between refresh cycles, and that's exactly how you hide tearlines via the "tearingless VSYNC OFF trick" via RTSS Scanline Sync.

What's important is that the top/bottom bounds (in number of pixels) of tearline jitter is smaller than the size of your VBI. Otherwise, you can't hide tearing. So you need to reduce tearline jitter (e.g. enable Force Flush), increase GPU performance, and/or increase the VBI (Via QFT tricks) to make it easier for RTSS Scanline Sync to hide tearlines.

Now that being said, if your monitor is unable to support QFT properly, you can reduce your vertical resolution a little bit (e.g. 1000 pixels instead of 1080). This adds letterbox bars but creates a bigger VBI to hide tearlines in. This can be useful for 60Hz monitors that doesn't allow very large vertical totals.

[terry98]

Thanks, but that's exactly I've been using it...
1 - I have been using the portable monitor as single, and yeah in CRU I make sure that I'm modifying the right one.
2- Yeah usually I have -90 as my rtss scanline sync setting because of this problem, it would set the tearline just below the last visible line.

If I continue to go down those 90 lines it wont show on screen until I get to 0 or 1 again which puts the tearline in the 1/10th of the screen.

I have noticed 2 more things... it does the same with my 4k tv (I have 165 blanking but only 90 true blanking).. if I invert vertical back and front porch, the vertical total won't take in count the value of front porch so total vertical is a lot lower number.

rtss works great on my laptop and it used to work as well on my desktop I can't say since when this is happening, I tried removing the latest amd drivers and going a couple of months back and nothing.

the actual behavior or the tearline in rtss is this, lets say we have 300 of back porch.. if the sync vlue is 0 the tearline might or not show up on screen, at 1 it shows at the 1/10th of the screen (more or less) if you start moving the tearline down you can see the sync value changing but the tearline wont move until you get to 210 (300-90), after 210 you will see the line moving down I even tried with my 4k tv with at 1080p and a vt of 2525, the last visible tealine is in -90, and at 1 the tearline shows up and wont move until the sync value at least 1400 or something like that.

[terry98]

the actual behavior or the tearline in rtss is this, lets say we have 300 of back porch.. if the sync value is 0 the tearline might or not show up on screen, at 1 it shows at the 1/10th of the screen (more or less) if you start moving the tearline down you can see the sync value changing but the tearline wont move until you get to 210 (300-90), after 210 you will see the line moving down I even tried with my 4k tv with at 1080p and a vt of 2525, the last visible tealine is in -90, and at 1 the tearline shows up and wont move until the sync value at least 1400 or something like that.

Hi Chief Blur Buster do you know why is this? it's starting to drive me crazy.