[QLab] live video - can i add delay

[mick ritchie]

Hi

Ive been experimenting for a show with live video projection via qlab
- is there any easy was to add delay to the video ie 10 minutes - i
assume buffering is the problem as the data would be large - if not
possible maybe i need one mac to record the video and then sync it
with qlab for playback but then i am allocating cues on the fly

thanks

mick
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[Christopher Ashworth]

Hi Mick,

There is not a way built-in to QLab to add a delay to the video feed.
I suppose there might be some way with Quartz Composer, although as
you note a 10 minute delay is going to be quite a large buffer.

It's an interesting challenge. I'm not quite sure how it could best
be approached.

-Chris

On Jan 27, 2010, at 5:09 AM, mick ritchie wrote:

> Hi
>
> Ive been experimenting for a show with live video projection via
> qlab - is there any easy was to add delay to the video ie 10
> minutes - i assume buffering is the problem as the data would be
> large - if not possible maybe i need one mac to record the video
> and then sync it with qlab for playback but then i am allocating
> cues on the fly

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[Steven Devino]

Just curious mick but is there a reason you can't just use a 10 minute pre-wait on your video cue to accomplish this?

Steve

[Christopher Ashworth]

On Jan 27, 2010, at 8:08 AM, Steven Devino wrote:

> Just curious mick but is there a reason you can't just use a 10
> minute pre-wait on your video cue to accomplish this?

I think he's talking about displaying a camera cue 10 minutes after
the moment it actually happened. So a delay on the feed, not on the
start of a cue.

-C

[Steven Devino]

Oh yeah I see that now.

Steve

[luckydave]

Seems like writing 5-minute files with incrementing file names might be a good way. Just record to disk, have naming handled by your capturing software, however you're doing that, or have a folder action or something that monitors a "watch" folder for new files - when a new 5-minute file shows up, it moves and renames it so it's ready for QLab. Maybe it moves the files into another watched folder with its own folder action - every time a new file shows up, it copies the file name, and passes it to an AppleScript. The script writes a new cue in that list in QLab, and it's ready for the GO when it happens. Lots of trouble, lots of coding, lots of testing. And lots of testing. But I think it could be done.

For Quartz to do it, you'd have to hold onto 10 minutes of video in RAM, and that's only once you start playing. As you're playing, it's capturing, so there's a huge bottleneck there, and frames to add to the queue and frames to leave behind, all with a composition that you can't interact with because it's called per frame, rather than something running in the background. Seems like this is a job for file juggling and scripting.

Do the things that please you, and do them well.

--- On Wed, 1/27/10, mick ritchie <mi...@superorg.com> wrote:

[Sander Loonen]

dave is right, the writing to file is the way to go I think
I tried to have the que patch in quartz to hold 10 secs and it already becomes unresponsive.
also timing might become an issue in quartz.
however I do think that quartz composer is the way to go for you.
but like dave says, write to file.
then have quartz replay that file (or write a script if you are more comfortable)
quartz responds very well to MIDI so that is an other way to get your video and sound in sync.
something like,
midi q tell quartz to start recording to file
midi q tell quartz to stop recording
midi q tell quartz to play file ....

this way it might be easier to do it on separate computers as well.

let me know if it helps

sander

[mick ritchie]

Thanks all

its great not to have to reinvent the wheel everytimr threr is a
challenge. The show is just in workshop form
at the moment with a few video repeats wanted for memories so no
exact timings needed or quality as it will be distressed anyway

I can see a 2nd mac for recording small sections & autonaming is the
best way and then synced with qlab for playback manually when
required. Ive had a look at quartz composer So when i have time i'll
get my head around it

As a quick backup my domestic dvb recorder will allow me to record
from camera and then allow restart playback while still recording -
not cueable but can i get qlab to control the projector ?

thanks again

mick

[vengb]

A thought.. even when you get some version of the live-record/PB
thing workable, shooting a generic version of the moment/s and having
it cued and on-deck as a fallback when the live rig gets the willies
might be a Good Thing.

J.V

J. Vengrouskie
Soundscenes DC
Everybody does better when everybody does better.