[MacRuby-devel] Memory & Performance Issue with QTCaptureView & CIFilter

[Adam Elliot]

Hello,

I've been playing around with QTCaptureView to grab input from my  
iSight and I want to then run some Core Image filters over the image  
it's receiving. I first attempted this with Hotcoca and I got  
everything working, except when I ran everything the performance was  
significantly slower than the same application written in Objective-C.

I went and rewrote things right in MacRuby to check if there were any  
overhead with the Hotcocoa libraries that could account for the  
slowness. Unfortunately the problem still existed. After analysis I'm  
noticing the application is eating memory rather quickly and then all  
at once releasing much of it and the cycle begins again.

	EG Starts at 40megs, grows quickly to 300megs, then drops to 40megs  
again.

The same application in Objective-C runs steadily.

Here's the basic code:

   def awakeFromNib
     session = QTCaptureSession.alloc.init
     device =  
QTCaptureDevice.defaultInputDeviceWithMediaType(QTMediaTypeVideo)
     device.open(nil)
     input = QTCaptureDeviceInput.alloc.initWithDevice(device)
     success = session.addInput(input, error:nil)

     @filter = CIFilter.filterWithName("CICrystallize")
     @filter.setDefaults
     @filter.setValue(5, forKey:"inputRadius")

     captureView.setCaptureSession(session)
     captureView.setDelegate(self)

     session.startRunning

   end

   def view(v, willDisplayImage:image)
     @filter.setValue(image, forKey:"inputImage")
     @filter.valueForKey "outputImage"
   end

If you remove the setDelegate call things run just fine, but then you  
don't get the filtering. Also if you remove all the code from the  
delegate method the memory growth still occurs, but the video runs  
just as smoothly as the straight Objective C version. I'm not sure if  
the slowness is related to the memory growth or if they are separate  
issues. I've also had the memory grow quite uncontrollably to up to a  
gig before my system started thrashing and about a minute later it  
recovered.

I'd love to try and fix this problem, but I'm out of ideas on where to  
look. If anyone has any suggestions on where I could dig around I'm  
all ears.

Thanks,
Adam Elliot

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