[QLab] projecting video across 2 projectors

[Michael Sider]

Hello,

I'm looking to spread a wide (16:9) video image across two 4:3
projectors in QLab and then project them beside each other onto the
same wide screen, hopefully creating a wider seamless image.
Does anyone have experience with this?
When QLab is outputting one video image to two screens, does it give a
bit of overlap so the images can display seamlessly beside each other
on the same screen? Is there a way to accomplish this?

Thanks,

Michael
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[Jeremy Lee]

Why not use one of the Matrox Dual Head adapters? Then it's one
monitor to the computer, but 2 outputs to your projectors. Then ya
don't gotta think about it.

On Jul 17, 2009, at 2:06 PM, Michael Sider wrote:

> Hello,
>
> I'm looking to spread a wide (16:9) video image across two 4:3
> projectors in QLab and then project them beside each other onto the
> same wide screen, hopefully creating a wider seamless image.
> Does anyone have experience with this?
> When QLab is outputting one video image to two screens, does it give a
> bit of overlap so the images can display seamlessly beside each other
> on the same screen? Is there a way to accomplish this?
>
> Thanks,
>
> Michael

--
Jeremy Lee
Sound Designer, NYC - USA 829
http://www.jjlee.com

[Dan Scully]

The only snag on that is you often want to feather the edge of each
projector and overlap them to make it more seamless. If I were you I
would bribe Lucky Dave into making some clever Quartz Composition to
do the feathering....

ds

[Juniper Shuey]

OOOHHHH yeah,

Lets bribe lucky dave.

I need a feather crossover. I am sure it is not as simple as a bribe
but that would be an amazing addition to the dual head to go.

Juniper Shuey
Zoe|Juniper
Co-Artistic Director

2003 Boylston Ave East #1
Seattle, WA 98102
USA
206.200.7230
junipe...@gmail.com
AIM: joonbug206

[luckydave]

> The only snag on that is you often
> want to feather the edge of each projector and overlap them
> to make it more seamless.  If I were you I would bribe

> luckydave into making some clever Quartz Composition to do
> the feathering....

Oh, the temptation, and the flattery, and the complications. I've given this tons of thought over the past many many months, and I just don't see a solution until QLab handles its displays differently. I suppose something could be done, but it ain't gonna be how I would do it, and so it won't be how I'd recommend it.

Thing is, if you're overlapping multiple projections, your best bet is to overlap about 30% of each screen, so two 9' wide projections overlap by 3' each, and the total becomes 12' instead of 18'. Of course, that's only a rough estimate, and each installation comes with its own requirements, so the feather mask has to be flexible.

Then, there's the important note that edge blending requires more than just a feather mask. There is also a gamma curve that needs to be calculated along the blend fade, in order to make it all look like one image. Again, that needs to be flexible, and calculated according to equations I haven't even come close to comprehending yet.

While all of this can probably be done in Quartz Composer, the flexibility is a huge challenge in the context of QLab until those derned published ports become revealed. Then, of course, there's the fact that the screens' layout in QLab is determined by how those screens are laid out in the System Preferences, so they don't overlap as far as the program is concerned.

Unfortunately, if you need to overlap projections to create one image, I hate to do it, but I have to recommend that you use a different piece of software. All of the ways to do it are expensive, and really, overlapping is the biggest thing that keeps QLab from knocking 3 other strong solutions right out of the running, as far as I'm concerned.

If you do the thinking and start the math for me, I can probably give some pointers, but each situation has its own solution, and that consultation would have to come with a fee - the aforementioned bribe, I suppose. But there really is no blanket solution at this juncture.

IMHO,
luckydave

[Gareth Jeanne]

The only way I have found to do this with Qlab is to use a bit of
trickery and Panasonic projectors. Newer Panasonic projectors have an
in built edge blending function with it's own line up grid and full
adjutment of black levels and colour matching. It's actually pretty
impressive how seamless you can get the blend on them. What I have
done in the past is to setup the projectors and blend them using the
internal grid. Then output from qlab one video signal that is much
higher res than the native projector res and is the correct aspect
ratio for the double width but with it's aspect forced 4x3 or 16x9
(preferred) by qlab. Then I send this video signal to both projectors.
Then within the projectors themselves I use the digital zoom and shift
controls to move the image on each projector until it is the correct
size for the percentage of blend being used, you can knock up a still
for this bit quickly in illustrator to make it easier. And voilà a
beautiful and seamless blend from qlab using only one output.

Hope that's of some help

Gareth

[Mackay Rippey]

We were able to use use Dual Head to go and instead of an overlap,
left a slight 1/2" gap between projected images. In almost all images
the gap was not noticeable and avoided the annoying bright line
created by the overlap.

We also found QLab uneven on controlling video, I was assuming because
we were underpowered using MacBooks.

We ended up using a two projector Dual Head to Go set up for the cyc
running a Keynote presentation with imbeded quicktime and a iPod Touch
wifi remote all running off a MacBook.

In the sound booth, we had another MacBook running QLab for sound
effects and another projector.

Not Broadway standard, but then again I didn't have a broadway budget.

[Michael Sider]

Perfect. This sounds like exactly what I'm after.

Thanks so much!

Michael

On Jul 18, 2:54 am, Gareth Jeanne