What computer will allow Qlab to use the most HD video outputs?

[Jacques M]

Hello,

I am most wondering if and when QLab will support external GPUs via TB3 or TB2?

The desire is to enable FIVE (5) discreet outputs from a single computer. 

1) Control Screen

2) Projector No 1 (1920x1200)

3) Projector No 2 (1920x1200)

4) Projector No 3 (1920x1200)

5) Projector No 4 (1920x1200)

Is this possible now using only a single computer or when might we look forward to having the ability - for example - to take a new iMac and hook that up to an external GPU like those made by Sonnet? and output four channels of HD video?

[Patrick Andrews]

Apple only supports eGPUs with Thunderbolt 3. If it’s supported by the system then it’s supported in QLab. I recently upgraded a 2009 Mac Pro and put a Saphire RX580 in it. I’m getting 7 discrete displays, 5 on the new card and 2 on stock one. The trick is finding a card that’s compatible with your Mac. If you only have TB2 then your SOL.

[Stephen Harrison]

Depending on what you are doing within QLab, you can do this without an eGPU.

I have successfully run 4 projectors out of a 2016 MBP 15, using HDMI adapters (in my case 1 Sonnet TB3->Dual HDMI and 2 USB-C->HDMI) without any problems. I was running them at 1080p but these computers will support up to 4 4K external monitors.

Whether you can then maintain an acceptable frame rate depends on the processing load of your show (surface warping, video effects, multiple layers, alpha blend, codecs, etc). Only testing will tell you that for sure.

[Rusty Wandall]

You can get 6 displays out of a Mac Pro. This requires the use of active DVI adapters that aren’t cheap. I’m actually working on a project that has 8 outputs achieved through a TripleHead2Go and the active DVI adapters. It does get tricky, but can be done.

This document is your friend for the Mac Pro.
https://support.apple.com/en-us/HT202801

And of course your friendly Figure53 support team who are ROCKSTARS will give you amazing support if you ask.

Rusty

[Bryan Wilson]

Rusty,

I will second this, but it isn't for the faint of heart for long-term repeatable setups.  I would actively campaign against it. 

I was once able to do 9 total video devices = 8 projectors and 1 control monitor.  I used it in this configuration as a video backdrop for a stage production and annual dance recitals.  The final image was 40' wide by 15' or 16' tall.

I had 8 separate short-throw projectors in a 2-high by 4-wide array, setup as a single Qlab surface.  12-15% overlay/edge-blending between projectors.  I then had the 9th display as my Qlab control window.  These were all connected to a 'stock' 2013 Mac Pro with the Dual D500 ATI video cards.  No external GPU.  I utilized a Matrox TripleHead2Go connected to an active Dual-Link DVI adapter, a DualHead2Go connected via Thunderbolt 2/VGA adapter, and the rest of the projectors connected via Thunderbolt 2/VGA adapters.  I connected the final, 9th display using the HDMI port on the Mac Pro.  All projectors are native 1280x800 resolution, connected via VGA with the final display being run at 1680x1050.

This took a TON of work to pull off.  Matrox absolutely does not support 2 simultaneous TH2G or DH2G adapters connected to the same Mac. Matrox software will only connect to and program one at a time.  Officially connecting and using 2 of them simultaneously is a Windows Only thing.  I was able to get around the limitation with lots of patience, a separate USB power adapter on the DH2G (once it was programmed successfully I removed it from the Mac Pro quickly and it held it's programming) and a VGA EDID clone box (which didn't like my DH2G resolution for around the first 2 hours of fiddling).  I made sure absolutely every projector, adapter, monitor, usb hub, etc. was connected to battery backups before starting because my setup had to run for a little over a week and if power failed in ANY way on ANY adapter, it would reset the video map in MacOS and would never come back up correctly. (Ask me how I know this.)

The 2013 Mac Pro doesn't let you use all 7 available outputs at the same time.  Look at Rusty's link above again.  You have 3 Thunderbolt Buses available and the HDMI port is part of one of them.  Apple officially supports connecting 6 Dual-Link DVI adapters simultaneously, but the HDMI connection cannot be used then.  Under mixed-adapter use, or use with the HDMI port, the active Dual-Link DVI adapters can connect to one of the TB2 connections, but that completely 'fills up' the capability for 1 of the 3 Thunderbolt Busses.  That removes the ability to connect something to the 2nd port on that Thunderbolt Bus.  So when I connected one active DVI-D adapter to the TripleHead2Go, I really only gained 1 extra projector (2 TB2 connections 'used' for 3 projectors on 1 TB bus).  I hope that all makes sense.  I revised it about 8 times for clarity.

I now have well over 100 hours of Mac/Matrox video connection fiddling experience and climbing.  You think aligning a few projectors and edge-blending them in Qlab wouldn't be that bad until you have to do it.  I'm a bit of a perfectionist and it about killed me the first time I set it up.  Not only were my upper projectors suspended above the stage on some truss, but they would sway JUST SO SLIGHTLY when the AC kicked on in the venue, ruining my alignment by an inch or so.  I was projecting onto an 20'x40' CYC curtain.  It wasn't perfectly flat, and had the same problem of movement with ANY wind or air pressure change.  I got into the habit of corner-pinning the center of the whole thing slightly overlapping because when the main curtain/grand drape opened, the heat from the audience would fill the stage and put a bit of positive air pressure against the CYC for the rest of the show.  I'm pretty good at guessing how far it will move now.

Another problem I ran into was jittery video playback.  Like Stephen said above, any time you use multiple video connections to make a single video surface in Qlab, it puts a lot more stress on your CPU/GPU.  It adds a measurable load each time you corner-pin a bit of the Qlab surface, add video effects, use multiple layers, alpha blend, etc.  I really started to notice this when I tried to display a 1080p video file across all 8 projectors with video-effects enabled.  I needed to do some color correction effects then layer another video file and text above the 1080p video.  If I triggered cues natively on the Mac Pro, they would playback at maybe 10fps.  In attempting some trial-and-error, I tried to connect to the MacBook Pro using Apple Desktop Sharing (which is just Apple's fancy version of VNC).  It connected and I was able to see the Qlab editor window.  If I triggered cues from here, the video was smooth and there were no jitters.  I eventually setup network cue triggering from a Qlab instance running on this MacBook Pro.  As long as cues were triggered from somewhere over the network, the video played flawlessly.  Native bad, Network good.

Sorry for the long-winded explanations, but I think you folks will understand what I mean.

Again - something like this is not for the faint of heart or casual Mac users.  It was what I had to work with, so I made it work.  Learn from my stubborn stupidity: DO NOT DO THIS.