dual video output with TB for Qlab

[ra byn (robin)]

Just as I get ready to order some mac minis for a dual Qlab rig that will
do video as well as audio, I'm told the director wants two projectors for
the next show in the theater.

The native HDMI output from the mac minis will be serving KVM duties so
they aren't available.

Is there a break out box to do (2) different video streams from (1) TB port?
TB to dual VGA that is known to work with Qlab?

If so, recommendations for such a device?

If not, what is the preferred 2 output option that can be added to a
current mac mini for Qlab purposes?

I'm starting to wonder if I shouldn't be moving toward 27" Imacs with TB x 2
instead of the mac minis... & skip the whole KVM concept.

Thoughts?

Thanks,

ra byn

[Paul Gotch]

On Tue, Jul 17, 2012 at 06:32:12PM -0500, ra byn (robin) wrote:
> Is there a break out box to do (2) different video streams from (1)
> TB port? TB to dual VGA that is known to work with Qlab?

There is no such box in existence. The thunderbolt adpators/docks
currently in existence only have one output even though it is
theoretically possible for them to have two.

You can use a Matrox DualHead2Go Digital ME. Which will present a
maximum of a single 3840x1200 desktop stretched across two
MiniDisplayPort outputs at 1920x1080.

You would then need two active converstion boxes to turn the DVI-D
output of the DualHead2Go into analogue VGA.

For example two of these

http://www.kramerelectronics.com/products/model.asp?pid=1409

Howwever that's still going to mean faffing with two different video
streams in QLab being sent to the same display from the Mac's point of
view.

-p
--
Paul Gotch
--------------------------------------------------------------------

[Dave "luckydave" Memory]

You could also use the DisplayPort edition of the DualHead. I haven't tried it, but Thunderbolt has DisplayPort baked in. You'd need a Mini DisplayPort adapter to go into it, and two vga adapters to come out, but it should work.

luckydave

--

luckydave@figure 53.com

[Mike P]

I don't know that getting the iMacs would do anything for you in performance (other than a generally faster computer). Does anyone know how the graphic cards deal with Thunderbolt on a iMac? Does each port have a separate card, or is it a simple parallel connection? I'm betting it's a single GPU forked to the two TB ports (or whatever processing gets you there...)

An alternate to Paul Gotch's option is a DualHead2Go Analogue version. That way you're only converting the Thunderbolt to VGA on the input sideinstead of converting 2 DVI-Ds to VGA. Unless you can stay in DVI-D to the projector in while case forget VGA.

Mike Post
(601) 307-8657
mdp...@mac.com
http://mdpostdesign.com

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[Mike P]

> You could also use the DisplayPort edition of the DualHead. I haven't tried it, but Thunderbolt has DisplayPort baked in. You'd need a Mini DisplayPort adapter to go into it, and two vga adapters to come out, but it should work.

I can vouch that a single MiniDisplay to VGA works on Thunderbolt. Is there a dual option?

[Dave "luckydave" Memory]

http://www.matrox.com/graphics/en/products/gxm/dh2go/displayport/

--

luckydave@figure 53.com

[Mike P]

Always a new toy... :-)

Mike Post
(601) 307-8657
mdp...@mac.com
http://mdpostdesign.com

On Jul 17, 2012, at 8:06 PM, Dave luckydave Memory wrote:

> http://www.matrox.com/graphics/en/products/gxm/dh2go/displayport/
>
> --
>
> luckydave@figure 53.com

[Paul Gotch]

On Tue, Jul 17, 2012 at 08:02:18PM -0400, Mike P wrote:
> I don't know that getting the iMacs would do anything for you in
> performance (other than a generally faster computer). Does anyone
> know how the graphic cards deal with Thunderbolt on a iMac?

There is a single GPU managing multiple frame buffers. See

http://support.apple.com/kb/HT5219?viewlocale=en_US#dispnum

For the number of external displays supported by ecach Mac.

> An alternate to Paul Gotch's option is a DualHead2Go Analogue
> version. That way you're only converting the Thunderbolt to VGA on
> the input sideinstead of converting 2 DVI-Ds to VGA. Unless you can
> stay in DVI-D to the projector in while case forget VGA.

This won't give you enough resolution. The MiniDisplayPort to VGA
adaptor does 1920x1080 at a maximum.

http://support.apple.com/kb/HT3382#16

While the analogue DualHead2Go needs an input resolution of 2560x1024
in order to provide 2x 1280x1024 on the outputs.

[Thomas Vecchione]

On Tue, Jul 17, 2012 at 8:29 PM, Paul Gotch <paulg...@chiark.greenend.org.uk> wrote:

http://support.apple.com/kb/HT5219?viewlocale=en_US#dispnum

For the number of external displays supported by ecach Mac.

That is only Apple Thunderbolt displays for the record.  People have already tested the Retina MBP with Three external displays on it as well and succeeded apparently(Using the HDMI port).  Don't know if anyone has tried daisychaining two thunderbolt displays on either port of the MBP though.

             Thomas Vecchione

[Gareth Evans]

What about hardware such as this?

http://www.sapphiretech.com/images/product/datasheet/Vid-2X_Datasheet.pdf

[Paul Gotch]

On Tue, Jul 17, 2012 at 11:43:26PM -0700, Gareth Evans wrote:
> What about hardware such as this?
>
> http://www.sapphiretech.com/images/product/datasheet/Vid-2X_Datasheet.pdf

As far as I can tell that does the same as the Matrox box that is to
say it looks like a single 3840x1200 display and appears as such to
QLab. However I couldn't be sure without getting once and testing it.

[Douglas Heriot]

Sounds like you need a retina MacBook Pro. I’ve got one, and have connected it to 3 external displays, all running at 1080p, without using TripleHead2Go’s or anything. I haven’t actually used that in a show or anything – just while playing around to show off. ;)

The 2 thunderbolt ports on the left can have a Mini DisplayPort to VGA, DVI or HDMI adaptors, and there’s also the HDMI port on the right side of the Mac too. If you had a rMBP, you’d just need 2 regular cheap Mini DisplayPort adaptors and you’re all set.

I think I’ve heard the HDMI port is limited to 1080p resolution (but haven’t verified that – I only have 1080p screens around anyway), but the thunderbolt ports should support whatever your adaptors do.

When I was at WWDC, I had a brief chat to one of the Apple engineers about all this. The limit is the graphics card itself only supports up to 4 screens. These can be attached via any of the ports. Theoretically, you could daisy chain 4 thunderbolt displays (with the internal screen off), however the bandwidth of thunderbolt itself would stop you. (But you could have 2 chains of 2 displays off each port)

I haven’t tried it, but I’d bet if you wanted you could run 2x Mini DIsplayPort TripleHead2Go via the Thunderbolt ports, 1080p HDMI, and the internal retina screen, for a total of 8 screens! (that looks as 4 to the OS)

To answer the original question, no I haven’t yet seen any device that can split a thunderbolt port into 2 more, or multiple DVI/VGA outputs either.

Matrox’s thunderbolt dock has a DVI output, but only 1 thunderbolt port (in), while Belkin’s thunderbolt dock has 2 thunderbolt ports (in & out) but no DVI/VGA.

http://www.anandtech.com/show/5933/thunderbolt-docks-are-here-belkin-thunderbolt-express-dock-matrox-ds1

I also haven’t seen any Thunderbolt hubs (like a USB hub). The guy I chatted to at Apple said it would be possible, but all the manufacturers seem to be busy enough getting the first generation of devices that have a slightly wider appeal on the market first. (Belkin/Matrox releases aren’t till September still)

[Doug Rankin]

We just purchased the new Mac Pro. I haven't installed QLab yet but have started to try out video. We have a simple need: a high res monitor and a QLab VGA out to an older video projector. I was able to plug a DVI monitor (using an adapter)  into a thunderbolt port at 1200x800 I think, but when I plugged in a VGA monitor using a mini display to VGA adapter, it worked for a second and then blanked out the other screen.  Does this have something to do with not choosing different busses? For QLab out, should I use HDMI and convert to VGA for the projector? Can the MacPro output to different resolutions?