Screens randomly cutting out w/ white snow

[talkingtobrian]

This may not be a Qlab issue, but I figure some of you may have been running a similar setup and might have seen this happen.

We just bought a MacPro (El Capitan, 3.7 Ghz processor, AMD D300 graphics card, 16 GB of RAM) for a new show we are putting up. Here is the setup:

One monitor for Qlab, connected via Apple's Dual Link DVI

Four Panasonic D6000 projectors, connected via Apple's Dual Link DVI to an Extron DVI Extender and back to DVI into the projector.

All Dual Link DVI adapters are getting their USB power via a 7 port USB3 hub, which is in turn plugged into the wall and the MacPro USB.

All 5 screens are at 720p (we tried 1080 when we did the initial hang with only three projectors, and we got a lot of flickering that suggested we were past the number of pixels that the MacPro could spit out, all together).

Randomly, one screen will drop out to white snow. Only way to bring it back is to unplug the screen's video signal, or all of the screens via the USB power. 

We are in tech, and you can imagine how much of a problem this can be. It has happened to every single video feed, including the monitor. So we have ruled out display hardware, and almost all of the DVI adapters are brand new, if not all of them. It's not the Extron DVI extenders since it is also prone to happen to the monitor. It shouldn't be the USB hub, since we swapped it out from another system and still got the problem (same model, some Chinese brand called Pluggable). We even swapped to our sound engineer's MacPro, which has Yosemite, and we got snow there, too.  

We updated to the latest version of Qlab (we were running the prior release during load in - so we've tried two different builds and had snow for each one). It's an intermittent problem - we get it, and then it goes away, we run rehearsal and then try swapping something, and it still comes back on another screen. 

We are showing still images and videos - it has not related to any of the content. (We were almost all still images at the start of tech, slowly they are converting everything to videos.)

Has anyone had anything like this? I've contacted Apple and escalated it to another level of support. We sent them some logs, but don't know if they will find anything, and while all signs point to it being an OSX/computer issue, we're really open to any suggestions.

-Brian

[Gareth Risdale]

Am guessing Figure53 have been in touch directly on this, but Ineould be curious to know if this is an El Capitan issue with the Mac Pro? Downgrading to Yosemite might be worth a go if Apple haven't offered you anything better.

Hope you got it sorted!

Gareth

[talkingtobrian]

I may have forgotten to note this, but we tried swapping with Audio's identical MacPro (has a little more RAM but that's it). It went and did the snowing on the main monitor immediately.

We are thinking the hub isn't providing enough/stable USB power. Upgrading today, will report back.

[Andy Lang]

On Tue, Feb 16, 2016 at 2:01 AM Gareth Risdale gar...@compositelight.com wrote:

Am guessing Figure53 have been in touch directly on this, but Ineould be curious to know if this is an El Capitan issue with the Mac Pro? Downgrading to Yosemite might be worth a go if Apple haven't offered you anything better.

This almost certainly sounds like a hardware problem, not a software or OS problem, so I would not advise this as any of the first few steps of troubleshooting.

I think you’re on the right track looking at the power, to start, and then further investigating the signal chain from computer to projectors, Brian. Keep us updated with how you fare taking a systematic approach to troubleshooting one part of that chain at a time.

Thanks!

-Andy

—
Andy Lang
@SoundGuyAndy
sup...@figure53.com

​

[talkingtobrian]

Yeah, we are trying to eliminate all of the common links. I figured such a supportive group who clearly has a lot of collective knowledge might have run into this, and, if not, I'll update you with the resolution in case some one else has this problem.

[Carey Dodge]

was this with Qlab3?

I have had similar issues with Qlab2 but not with Qlab3.

Cheers,

[Carey Dodge]

upon reading more carefully, the issue is almost certainly your adapters being powered from a hub and/or a faulty adaptor/cable.

if you have time, I would replace cable and/or adaptors.  If you are staying in DVI land that why do you need to power the adaptors?

Cheers,

[talkingtobrian]

"If you are staying in DVI land that why do you need to power the adaptors?"

Dual Link DVI requires USB bus power, as opposed to the single link. They support a higher resolution. We swapped the USB cable back to the desktop from the hub, which was a bit unneeded, and the problem seemed to go away. But regardless, we switched to iPad 10w adapters, to give them strong, steady power. So far we have been clear of the snow!

[Greg Leeper]

Are you familiar with what HDCP failure looks like?  It's white snow covering the whole screen... I would make sure your extenders and everything else in the chain are HDCP compliant.  You can use Gefen DVI Detective+'s to tell the mac not to enable HDCP otherwise it will be on all the time.  Some switchers can do this to, or a DVI Parrot.

I've been having trouble with our 2013 not supporting more than 2 displays - they either don't show up at all, or show up in display prefs but the displays say they have no signal.  After Genius bar, and lots of head banging we are finding that our active output adaptors (we've tried both monoprice (yeah I know.. risky) and Accell thunderbolt to HDMI - well they don't work consistently between various displays - and some are picky about the cable we use between them too.  In the end the monoprice surprised us and have been more stable and compatible.

All the genius bar did was re-install my OS.  We also swapped mac pro's and got similar results.  In some cases when misbehaving a restart with all connections made would fix it.. but then you can't hot plug any outputs reliably.... 

On Monday, February 15, 2016 at 6:10:41 AM UTC+7, talkingtobrian wrote:

This may not be a Qlab issue, but I figure some of you may have been running a similar setup and might have seen this happen.

We just bought a MacPro (El Capitan, 3.7 Ghz processor, AMD D300 graphics card, 16 GB of RAM) for a new show we are putting up. Here is the setup:

[Andy Lang]

On Thu, Feb 18, 2016 at 2:38 AM Greg Leeper gr...@opticusvideo.com wrote:

After Genius bar, and lots of head banging we are finding that our active output adaptors (we've tried both monoprice (yeah I know.. risky) and Accell thunderbolt to HDMI - well they don't work consistently between various displays - and some are picky about the cable we use between them too.  In the end the monoprice surprised us and have been more stable and compatible.

I think I’ve posted this before, but either way, this is a good opportunity to share it as a reminder… I’ve found, the hard way, that display adapters are a really awful place to save a few bucks, and not just with active adapters. Even with the “simple” MiniDisplayPort to single link DVI adapters, the corners that other manufacturers cut to save you $10 or so over the Apple one can cause problems, especially if you’re in a situation that requires using a DVI Detective or other EDID/DDC emulator.

I recently spent a long and frustrating morning at a Broadway show trying to sort out some display issues, swapping out multiple brands of EDID emulator when none of them seemed to be working properly. Eventually, we discovered that four different brands of MDP to DVI adapters didn’t properly work with the emulators; only the Apple one did. Because of some missing pin, or resistor, or…something…every other adapter we tried would properly read the emulated data when a monitor was connected to the output side of the emulator, but as soon as the monitor was disconnected by the video switch—the one thing the emulator was intended to help with—the emulator would effectively disappear. It would still show power, but the computer couldn’t read it.

So don’t save yourself the money on something so key; name brand adapters are less likely to cut corners and cause you huge headaches.