Re: My First Plug-In

1) You can't specify what input you want, you'll get what's optimal for QC / GPU / etc...

2) Keep directly the input images in your plug-in and use:

- (BOOL) didValueForInputKeyChange:(NSString*)key;

3/4) If you want the best performances for data that you must generate on the fly (it's not already around in a buffer), use a QCPlugInOutputImageProvider, not the -[QCPlugInContext outputImageProviderFromBufferWithPixelFormat]

On Oct 28, 2007, at 9:41 PM, Sam Kass wrote:

I wrote a couple plug-ins for QC 3.0 (detailed on my QC blog: http://www.samkass.com/blog). They're not very efficient, and I was wondering if anyone had started hacking around with the official plug-in interface yet. I included the source to my plug-ins for reference.

Performance Issues:
1. The KLT feature tracking library I have assumes a black and white, 8-bits-per-pixel input image with rowBytes = pixelsWide. Is there any way to, instead of copying bytes around to ensure the correct input, simply specify that that's what I need and use the input buffer directly?
2. Is it less expensive, if I need two subsequent "frames" from the input stream, to use an accumulator latch in patches, or to snag-and-buffer two shots within the plug-in? Probably the latter-- if so, how do I know the input image has changed?
3. In my other plug-in, I try to plot the output from the first plug-in. I basically turn the image into bytes, malloc a new image of the same size, copy the old image over, change a few pixels, then output the new image. This is probably extremely sub-optimal. Ideas?
4. Related to 3, Is valloc better even when I'm changing the data?

--Sam

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Pierre-Olivier Latour - email@hidden

Technologist - Apple, Inc.

References:
	>My First Plug-In (From: Sam Kass <email@hidden>)