[Qlab] Video Input??

[Christopher Ashworth]

On Jul 25, 2007, at 2:52 PM, Paul Gotch wrote:

> On Wed, Jul 25, 2007 at 07:37:13PM +0100, Gareth Jeanne wrote:
>> Hi Chris/Everyone
>>
>> Is there any plan to allow GLab to support video input? I have a show
>> coming up that would be great to use QLab for, but needs video input.
>
> The current way to do is makes use of the fact the video cue can  
> play Quartz
> compositions. You create a composition using Quartz Composer which  
> displays
> video input then play that with Qlab.
>
> You'll need to install the Apple developer tools (which is a free  
> download
> from Apple) to get Quartz Composer.

For a quick test, you can use the Quicktime Movie I created here:

http://figure53.com/qlab/downloads/temp/LiveVideo.mov

Be aware that while this technique has been used for Real Live Shows  
successfully (Dan Hoole at the Birmingham Rep can fill you in on his  
experience), it is a bit of a hack in its current state.

For one thing, you can only use a single "video-in" cue for the  
show.  You can't put a bunch of different video cues and start and  
stop them to bring up different live feeds.  You only get one for the  
whole show.  This is because QLab is playing the Quartz Composition  
from inside a Quicktime movie, and for whatever reason stopping the  
movie does not release the camera as it should, so QLab can't pass  
control on to other cues.

Also, in general, capturing a camera input is a bit touchy on OS X  
right now.  Only one consumer can grab the video input at any one  
time, so you must make sure other programs aren't trying to use the  
video input too.

So be careful, and be prepared for it to be a bit sensitive, but it  
can certainly be used.

> I don't know if Chris will add an interface to do this within QLab  
> at some
> point without needing the developer tools installed.

I definitely plan to add a more robust method of having video input.   
If all goes as planned, this will take the form of a Quartz Composer  
cue in which I will have more control over shutting down the camera  
when a cue no longer needs it.

Hope that helps,

Chris