[QLab] sluggish performance

[Christopher Ashworth]

Hi Vinnie,

Thanks for the detailed descriptions.  Some thoughts below:

On Nov 13, 2007, at 1:25 AM, Vincent Olivieri wrote:

> Hi all,
>
> I'm having some dreadfully sluggish performance issues with QLab,  
> and I was
> wondering if anyone on the list might have some points of advice.
>
> I'm running QLab 1.3.1, Enhanced Audio/Pro Control/Pro Midi/Pro  
> Video.  The
> computer is a MacBook running OS 10.4.10, 2.16GHz processor, 1GB  
> memory.
> I'm using a Digidesign mBox Pro as my interface, but am only running  
> two
> outputs.  All of my sounds are aiff, 16-bit, 44.1KHz, two-channel.
>
> The show is in one master cuelist, and involves about 230 sound and  
> slide
> cues.  Altogether, there's about 500 lines in the session.  About  
> 200 of
> those are video cues, but they are all jpeg images.  No movies or  
> such.
>
> My problems start when I open the session.  Before I loaded all of  
> the video
> cues (when the session was just audio), the session loaded very  
> quickly
> (less than 5 seconds).  Now that I've added the video cues, the  
> session
> takes about 5 minutes to load.  If I change preferences at all  
> (assigning a
> different key to 'go' for example), when I close the preferences  
> window, the
> computer hangs for about 3 minutes.

These both reflect the cost of initializing a QuickTime movie.  There  
are a couple of optimizations that need to happen here, one of which  
is an easy one (making the Video Cue a bit more intelligent about what  
it needs to reload when preferences are saved), and one of which is  
less easy (creating a threaded loading model so that cue information  
can be loaded progressively and the GUI will remain responsive and  
show a progress indicator while it happens).

I agree that the sluggishness of load time with a lot of cues  
(especially video cues) is an issue that really needs addressing, and  
plan to rework the architecture to support this.

> In tech and performance, I'm finding very sluggish performance.   
> Sound and
> video cues are executing with a variable lag of between 0 and 700 ms,
> despite pre-cueing the elements.

This could possibly be due to the subsequent sequence loading up when  
you hit go.  Try putting a dummy cue between sequences to prevent the  
next sequence from loading and see if that helps.

> If I hit escape during the running of
> cues, I get a lag of between 500 ms and 45 s.


Pressing escape is essentially running down the list of cues and  
sending every one a message to stop.  This implementation does start  
to get slower as the the workspace gets bigger, which is not really  
acceptable and something I plan to work on.

> In tonight's run, I noticed slow-down of the sounds. whenever there  
> were
> more than 4 sound files running at once.

What do you mean by slow-down here?

>
> Last night when I quit QLab, the Finder decided to relaunch.

Hard to say if that's related to QLab or not.

> Just now I apple-tabbed to the finder. When I apple-tabbed back to  
> QLab, the
> computer began a hang.  It hung for 10 minutes before I force-quit.

Yikes...that's gotta be incredibly frustrating.  And in this case I'm  
not actually sure what would be causing that.  Would it be possible to  
get a copy of the workspace off list to play with?

> I'm grateful for any advice anyone can offer, and I have a couple of
> questions to kick off the advice-giving.
>
> 1.  When I load the session, does QLab load all of the video into  
> buffers?
> Is that what's taking so long?  Can I turn that feature off?

It's not buffers but things like reading all the video/image files to  
find their length, native size, etc.

> 2.  My video programming is shown in this example:
>
>   Q 1 VIDEO A.JPG
>   Q 2 VIDEO B.JPG
>   Q 3 VIDEO C.JPG
>   Q 4 VIDEO FADE C.JPG
>
>   Do I save processing power if I program according to this model:
>
>   Q 1 VIDEO A.JPG
>   Q 2 VIDEO B.JPG (cont)
>       VIDEO FADE A.JPG
>   Q 3 VIDEO C.JPG (cont)
>       VIDEO FADE B.JPG
>   Q 4 VIDEO FADE C.JPG

I'm not sure I see how these map to each other (are the fades up or  
down?), and another factor would be how many of the cues need to be  
simultaneously visible.  But in general stopping earlier video cues  
when you're done with them will always help.

Best,
Christopher