Multiple SDI Outputs

luemas · October 20, 2015, 3:53pm

Hi There,

We are looking to send multiple outputs in a studio via SDI-outputs… I have only ever used touch with pc monitors, we have 5 outputs in total but only 3 of those have to go to SDI for the studios gallery.

Is there a Max on the SDIs touch can output or is it only our hardware that limits this?

Cheers,
Sam

elburz · October 20, 2015, 5:24pm

Only hardware. You can put multiple Blackmagic Quads into a machine and output more and more SDI signals.

luemas · October 21, 2015, 10:00am

Thanks elburz, is the card you speak of this… blackmagicdesign.com/uk/pro … s/W-DLK-30

Does touch handle all 8 sdi playbacks on the v2 or just the 4?

Cheers,
Sam

flowb · October 21, 2015, 11:46am

AFAIK The Quad v2 isn’t out yet.

luemas · October 21, 2015, 2:00pm

Ahhh… shame, the idea of having 8 SDI outputs on one card would be perfect!

elburz · October 21, 2015, 3:10pm

Nice, looking forward to that coming out. In the mean time, the current Quad has 4 i/o channels.

flowb · October 22, 2015, 1:03pm

@elburz
Hi, have you profiled the latency for outputting to SDI in Touch w/ Blackmagic cards? It seems like there should be a penalty for copying framebuffers off the GPU and back onto the PCI bus.

elburz · October 22, 2015, 2:36pm

I have not, its always been fine for our needs.

You can private message @piwolf, he’s the guru of SDI i/o.

luemas · October 23, 2015, 2:28pm

Hi there,

that sounds great, would a blackmagic quad use a videodeviceout TOP or a SDI-out TOP.

When using the videodeviceout TOP with a blackmagic quad can you output more then one SDI Feed? There only seems to be one possible input.

Cheers,
Sam

elburz · October 23, 2015, 3:21pm

SDI In and Out TOPs are specifically for the nvidia cards, everything else uses the Video Device In and Out.

Each Video Device Out TOP is 1 texture. So if you want to send it to all the outs, make as many Video Device Out TOPs as you need, then set each out individually.

luemas · October 23, 2015, 3:55pm

So each SDI out on the card appears as an individual device in the TOPs ‘Device’ list?

malcolm · October 23, 2015, 4:06pm

Yes, that’s correct.

luemas · October 26, 2015, 10:44am

Awesome! Thanks Malcolm,

Just a quick note to say that we have been testing Blackmagic mini monitors with touch and they work beautifully with our bootcamped mac pro. So have managed to get an SDI feed out per Thunderbolt port using that. Note though, the SDI conversion lag is slightly increased when using 2 Mini Monitors on the same thunderbolt bus (the mac pro has 6 thunderbolts ports over 3 buses) so anyone looking to do something similar be wary of this

Thanks so much for everyones help!
Sam

elburz · October 26, 2015, 2:33pm

Ya those thunderbolt buses are a PITA.

ben · November 2, 2015, 6:29pm

In a recent project using Blackmagic 4K Extreme card we observed 1-2 frames latency running on a 30fps setup.

flowb · November 2, 2015, 8:16pm

@ben

Thanks! That seems pretty consistent with Live Capture as well.

I know there are several api’s from Nvidia and I’m guessing Blackmagic, to optimize copying buffers to and from the GPU more quickly.

Does this figure reflect any of those or is this just in a vanilla setup with normal drivers and OS level integration? Are there any crafty driver or API tricks that would speed this up?

Thanks again!

malcolm · November 2, 2015, 9:54pm

I tried using the Nvidia GPUDirect example in the BlackMagic sample programs but I did not need any latency decrease using it vs. regular transfers in the same sample.
I think the benefit there is just reducing memory/bus bandwidth usage.