Can't set mosaic and blend at the same time on NVS810

Using nvapi I can set a topology with overlap, however I cannot set blend.

Warping doesn’t achieve the same result as mosaic, because I can’t set the os rect.

NVidia, any help on this?

Hi, could you provide additional information on your setup:

  1. Operating system
  2. Displays being used

Ryan Park

Hi Ryan,

Thanks so much for getting back.
I’m using windows 10 home 64bit 17134, NVS 810, driver 418.81

I’m testing with 2 different displays
ancor communications inc asus vs197 (vga)
lg electronics e2360 (hdmi)

For the final system mosaic displays will of course be identical. (projectors)
Because mosaic works and warp/blend works I figured the displays weren’t the issue.

Could this be causing the incompatibility? I will test it asap and get back to you if it doesn’t solve the issue – I appreciate that your time is valuable.

Thanks, Jasper Mittelmeijer, Amsterdam

Hi Ryan,

I now have two Idek Iiyama PLX2283H displays, connected over HDMI.

The result is the same.
I’ve set up a basic mosaic in control panel.
Then using Mosaic_SetDisplayGrids to apply overlap to the grid_topo.
And GPU_setscanoutintensity to set the blend.

If overlap is zero, the blend shows up.
If an overlap x 1 applied, the blend is disabled.

Could it be that I should run an older/different driver version?
I’ve also had two crashes where I’ve had to reinstall driver 418.81

Thanks for your support on this.
Kind regards, Jasper Mittelmeijer


I just rolled back to 392.00 and that solved the issue.
I now have a single display with overlap, a correctly reduced osrect and a blend. So it looks like this should work.

If you want more details about the code and system, let me know I’ll be happy to provide them.

Jasper Mittelmeijer

Hi Jasper,

This is an interesting issue. I’ll report your solution back to the product team, maybe they have an idea what’s going on.

I’ll reach out to you further if we need the details.

Ryan Park

Hi Ryan,

By now I have all the projectors and I’ve been working towards getting everything up and running.
There appear to be quite a few limitations but it is hard to find out what they are so I’m sinking in a fair amount of time.
I would really appreciate your help.

Here’s what I’ve found:

• I can now set a 1x2 and a 2x1 grid, with overlap, and blend. Projectors are all at 1920x1200, 60hz
• This only works if I run them on different GPU’s. So slot 0,1 and slot 4,5
• I’m still on 392.00 since I’ve had to roll back to that earlier on.

• If I set the grids, and plug in my 1920x1080, 60hz monitor on slot 2 it does get picked up, and is added as a third single grid.


• If I add the monitor and try to set any topos myself I get a TOPO_NOT_ALLOWED
• If I put all projectors on gpu0 and the monitor on gpu1 I can set 3 grids but the blends fail, with NVAPI_NOT_SUPPORTED

Which suggests

• Things work when run each single topo with identical displays through a single gpu.

But clearly the card can do what I want, which is at this point just getting that additional 1920x1080 monitor to work as well.

My questions would be:

• Is the above correct?
• If I get a 1920x1200 monitor, would you expect it to work, with 1 gpu running two topos?

And a separate question,

• I’m trying to get the blend to be sticky, but I can’t find anywhere what to pass in.

Thanks so much,
Jasper Mittelmeijer


It would seem to hold true that you should only run a single multidisplay grid over a single gpu if you want to use blending as well.
I can add additional displays (using identical connectors) and set them as single grids. Which is good enough for what we’re doing.

I will say it took a lot of time to figure out, as there is no mention of these limitations. It may save others some time if you add a few high level pointers…

Which leaves me with that final question: can blend be made persistent over a reboot?

Would much appreciate your input.

All the best, Jasper