G-Sync and Cloned Displays

[Boildown]

I have a question for G-Sync users:

Can a G-Synced Displayport be cloned with one of the DVI or HDMI ports on my GTX 680?

Background:

I like to stream PC games to Twitch.com. To create my stream, I clone my main screen (Dual-Link DVI, 120Hz) to my HDMI port (at whatever Hz I pick using CRU), which goes to a video capture card in a second PC, which runs Open Broadcaster Software.

I'd like to know if its even possible to clone a display when G-Sync is active on one display (the DisplayPort, although I heard G-Sync will eventually work on any port), and of course not active on the other "display" (which is really a video capture card, but is indistinguishable from any other non-G-Sync display).

Secondly, does anyone have a video capture card to verify that the video capture function isn't freaked out by G-Sync being active? I used to use an Avermedia Live Gamer HD, but last year I upgraded to a Datapath VisionRGB-E1S. The Datapath card is outstanding at adjusting to any resolution and framerate I throw at it, but adjusting on the fly 100 times per second... that seems dubious. But if display cloning is disabled, and I need to use a splitter, it might be the only way.

Anyone have any insight into this, or at least the first part: display cloning?

Thanks!

Edit: Someone altered the title. Its not just for Twitch streaming, although that's my primary objective at this time, but I've used cloned screens for a variety of things, including displaying on multiple monitors or big screen TVs simultaneously, for ease of spectating.

[Chief Blur Buster]

Wow, that's quite an interesting question! I'd imagine that it might not yet be possible, but then again, I seem to recall that NVIDIA's ShadowPlay feature also can record during GSYNC. And NVIDIA ShadowPlay is beginning to get twitch support (soon, if not already). Have you considered that approach?

EDIT: ShadowPlay gained support for live twitch streaming in GeForce Experience 1.8.1 just last month in December 2013. Maybe give this a try?

[Boildown]

Wow, that's quite an interesting question! I'd imagine that it might not yet be possible, but then again, I seem to recall that NVIDIA's ShadowPlay feature also can record during GSYNC. And NVIDIA ShadowPlay is beginning to get twitch support (soon, if not already). Have you considered that approach?

EDIT: ShadowPlay gained support for live twitch streaming in GeForce Experience 1.8.1 just last month in December 2013. Maybe give this a try?

Considered and rejected. The quality per bitrate of the NVEnc encoder used by Shadowplay is really bad, so its not an option. I'd sooner run OBS in software mode or the Intel Quicksync mode. And I don't do those because I can completely eliminate (instead of mostly eliminate) all game-impact of streaming by using a second PC, and simultaneously use a really nice encoding preset that blows away any hardware encoder. I'm doing this now, but if G-Sync doesn't work with cloned displays, then I have to decide which is more important to me.

Basically, what I'd like to find is someone with a G-Sync monitor and another monitor, try to clone their displays and run a G-Sync game, and make sure it all works right on both monitors.

[Chief Blur Buster]

Aha, that makes sense.
This is an advanced question that might require an answer directly from NVIDIA. Next time I contact them, I'll throw this question in.

[nimbulan]

The quality per bitrate of the NVEnc encoder used by Shadowplay is really bad, so its not an option. I'd sooner run OBS in software mode or the Intel Quicksync mode. And I don't do those because I can completely eliminate (instead of mostly eliminate) all game-impact of streaming by using a second PC, and simultaneously use a really nice encoding preset that blows away any hardware encoder. I'm doing this now, but if G-Sync doesn't work with cloned displays, then I have to decide which is more important to me.

I got that impression when ShadowPlay was released and discovered the high quality setting was 50 Mbit. Any reasonable quality encoder should not need anywhere near that high of a bitrate. I only did brief tests but it seems like nVidia's hardware encoder is around the same quality as the very fast setting in OBS: bad. But without a second PC to stream with, it's not a bad choice.

[shadman]

I just checked and yes, it does go to 50Mbps max. thoguh, the Twitch feature might differ, because that is still a new-ish feature just added. I haven't tested it out myself yet, but I believe its something they could possibly fix later, from the sound of it. We will see.

Also Boildown, are you asking this question because you haven't gotten the G-sync monitor yet?

I've spent the last 10 minutes sitting here and pondering this whole thing myself, but I have absolutely no idea how it will respond. Honestly, I think it will just record at the rate you set it at (60fps?) and behave like it does now, as the refresh rate/fps communication is only going through the DisplayPort port. As for it actually working though, when you have it cloned. I think it should as well. Either way, its quite a specific arrangement, and I wish you luck on finding out!

[nimbulan]

I just checked and yes, it does go to 50Mbps max. thoguh, the Twitch feature might differ, because that is still a new-ish feature just added. I haven't tested it out myself yet, but I believe its something they could possibly fix later, from the sound of it. We will see.

I believe Twitch will not allow streams above 3.5 Mbit (which is what high quality ShadowPlay Twitch streaming uses) so with such a low quality encoder, the quality is not good, especially at 1080p.

[joncppl]

I can confirm that G-SYNC DOES NOT work with cloned/duplicated monitors, at least in my setup.

I have 3 VG248QEs,
one with G-SYNC.

Normally when I play G-SYNC games I turn the side two off and just play on the middle one, and G-SYNC works fine.
If I want to use NVIDIA Surround, I have to turn G-SYNC off. (I'm waiting for a patch that will allow just the middle monitor of a surround set up to be G-SYNC)

However if I set it up so that one or two other displays are clones of the G-SYNC display, G-SYNC fails to work, despite getting no warning from the software, which acts as if G-SYNC is still enabled.

I am using two GTX 770s. Same situation with SLI enabled or not.
Both are connected via DVI, and I have tried plugging the other monitors into the other cards as well.

Again this is something that could probably be patched in the driver.

Thankfully it's not an issue for me because I don't use fancy game streaming set ups (no affordable internet service in Canada that I know of actually provides adequate upload speed to stream anything more than 480p at decent quality), and having the same image on all three monitors is ridiculous.

For your sake though, I hope there is so way it can be made to work.

[shadman]

I just checked and yes, it does go to 50Mbps max. thoguh, the Twitch feature might differ, because that is still a new-ish feature just added. I haven't tested it out myself yet, but I believe its something they could possibly fix later, from the sound of it. We will see.

I believe Twitch will not allow streams above 3.5 Mbit (which is what high quality ShadowPlay Twitch streaming uses) so with such a low quality encoder, the quality is not good, especially at 1080p.

Ah I see. I thought it was because of the Twitch limitation, but I forgot that different encoders can have different quality at the same bitrate. I remember reading about how GPU acceleration in encoding (mainly CUDA when that started it) did not look as good, but I see that reigns on for the Shadowplay as well. Easy to cover with a high bitrate of 50 though (when recording locally).

@joncppl, thanks for the heads up.

[Boildown]

I can confirm that G-SYNC DOES NOT work with cloned/duplicated monitors, at least in my setup.

I have 3 VG248QEs,
one with G-SYNC.

Normally when I play G-SYNC games I turn the side two off and just play on the middle one, and G-SYNC works fine.
If I want to use NVIDIA Surround, I have to turn G-SYNC off. (I'm waiting for a patch that will allow just the middle monitor of a surround set up to be G-SYNC)

However if I set it up so that one or two other displays are clones of the G-SYNC display, G-SYNC fails to work, despite getting no warning from the software, which acts as if G-SYNC is still enabled.

I am using two GTX 770s. Same situation with SLI enabled or not.
Both are connected via DVI, and I have tried plugging the other monitors into the other cards as well.

Jon, thanks for that test! Disappointing for sure, but its early yet. So reading the sticky post at the top, I guess this question now goes to @ManuelG_NVIDIA, is this something that can be added in a future driver version, or is this an unavoidable G-Sync limitation?

Also Boildown, are you asking this question because you haven't gotten the G-sync monitor yet?

Yes, that's correct. I have a GTX680, but if cloning a G-Synced display isn't made to work, then I probably won't get one, unless reviews of the tech are so incredible that I'd rather give up streaming and recording.

Which brings me to another point, I also record to my streaming computer's hard drive a high quality version without a downscale, in addition to the stream. Even on Super Fast x264 preset, its transparent at a CRF of 24, which averages to around a 15Mb/s bitrate. Needing 50Mb/s to achieve the same using Shadowplay is really bad, and SuperFast is itself a really bad preset. If I used Shadowplay and recorded until my hard drive was full, I'd have less than 1/3rd the footage recorded than with my current system.

This is an advanced question that might require an answer directly from NVIDIA. Next time I contact them, I'll throw this question in.

I'd appreciate that, thanks!