Hi，
I want use one 4080 SUPER CARD with two DP outputs. One is set as 3840x2160x30fps, the other is 1920x1080x30fps. Then I turn on the G-SYNC mode. However, it seems that the two displays are not synchronized, as the videos out differ larger and larger.
If I set the two outputs with the same resolution like 1920x1080x30fps, the videos output synchronized as decades microseconds diff.
Then how can I make the videos with different resolution output synchronized?
Hi again, pls see my other posting to your similar question in a different forum. Answer there is still valid, here you are adding GSync, which is NOT a methode to sync 2 screens! (Quadro Sync, an extra HW add-in card, connected to the GPU(s), used to be called GSync, long time ago…).
GSync is a methode, to not make the screen run its fixed refresh rate, and the GPU need to send new images matching that refresh, but have the GPU send a new frame immediately when ready, and the screen refresh with the new frame immediately, so have a variable, GPU-driven refresh rate. This can only work well for a single screen, target is for lowest possible latency gaming… Running 2x screens in GSync mode the GPU will need to render 2 tasks alternativly, and refresh each screen alternating, when ready with the respective task, basically guaranteed to never refresh both screens at the same time ;-).
regards
-Frank
Hi,
Based on your response, can I understand it this way?
If I want to achieve synchronous display of multiple different resolutions on a single graphics card with several output ports, I must use a professional graphics card, like * [NVIDIA RTX™ A6000];
if I want to synchronize across multiple graphics cards, then I need use a synchronization card (like Quadro Sync) to connect them?
not really! there basically is NO sync between different resolutions EVER! ONLY if 2 screens with different res run VERY EXACTLY the same say 60.001Hz refresh rate, there is a way to sync these 2, but today that needs a LOT of HW, IIRC 2x professional GPUs 4000 class and up, AND 2x Quadro sync cards… (we might be able to run this from lesser HW sometime in the future…)
Even 2x identical screens in extended desktop mode (so NOT unified as in Mosaic mode= single desktop), running exactly same resolution and refreshrate, to be kept in sync, need a QuadroSync card! Again, can’t at all sync a say HD screen running 59,999HZ and a say 4K screen, running 60,001Hz!
No sync between individual desktops, unless using a professional RTX 4000 class GPU, so RTX 4000+, RTX A4000+ or RTX 4000ada+ and a Quadro SyncII add-on card! (plus SW must be using NVSyncAPI)
-Frank
Thanks!
Hi,
I found that the timing(pixel clock) seems to be the key to generate the actual fps. Which means, some different pixel clock can be choosed to synchronize different resolutions.
I guess, some pclk can be generated exactly as multiplier and divider supported, while some not.
Can you give me a list of pclk which can be generated precisely.
For example, 264MHz, 93.6MHz,78MHz is a group to synchronize.
Hi again,
we can drive any pixelclock (within spec limits), and any refresh rate, its all defined and requested by the sink device, via EDID. The pixelclock is determined by the overall number of pixels (including the non-pixels in the blanking region) times the refresh rate. For achieving sync between 2 outputs, we sync the vsyncs, and ‘step-lock’ the scanout, so we need both, refresh rate and pixelclock to be exactly the same.
We only very recently added a new feature, which I haven’t tested yet, to allow for 2x GPUs, with 2x Sync cards, to run 2x screens with EXACTLY the same refesh rate, but 2 different resolutions, to be in sync. So only sync the refres rate, but not lock the scanouts…
You seem to be thinking the other way, lock the pixelclock, and aim for a multiplier/dividing factor between them. We DON’T support this, I expect the control panel/API to always block/error out with screens NOT running the exact same refresh rate…
May we ask, what usecase you have, where you NEED 2 different resolutions (why can’t have identical screen devices?) - AND need sync?
thanks
-Frank
We just want NV to send out different videos with different resolutions via HDMI at the exactly same time to other device to use.
But with different screens, so firstly, bezel between the screens, and then screens of most likely different size, the human eye will not see any sync issues. Why is it important to you, to have the 2 different screens in sync?
Does your video playout SW use the sync API at all? Perfect sync has 2 parts: sync the scanout, but then on top, sync of the frames, so that all screens always show the exact same frame, the less busy outs/GPUs wait for the busiest one… otherwise 2 applications would run independent (drift over time, due to non realtime OS), just on synchronized screen scanouts…?