Efficient Cocoa Animation w/raw bitmap data

Question

I have a raw bitmap image of RGBA malloc-ed data; rows are obviously a multiple of 4 bytes. This data actually originates from an AVI (24-bit BGR format), but I convert it to 32-bit ARGB. There's about 8mb of 32-bit data (1920x1080) per frame.

For each frame:

• I convert that frame's data into a NSData object via NSData:initWithBytes:length.
• I then convert that into a CIImage object via CIImage:imageWithBitmapData:bytesPerRow:size:format:colorSpace.
• From that CIImage, I draw it into my final NSOpenGLView context using NSOpenGLView:drawImage:inRect:fromRect. Due to the "mosaic" nature of the target images, there are approximately 15-20 calls made on this with various source/destination Rects.

Using a 30hz NSTimer that calls [self setNeedsDisplay:YES] on the NSOpenGLView, I can attain about 20-25fps on a 2012 MacMini/2.6ghz/i7 -- it's not rock solid at 30hz. This to be expected with an NSTimer instead of a CVDisplayLink.

But... ignoring the NSTimer issue for now, are there any suggestions/pointers on making this frame-by-frame rendering a little more efficient?

Thanks!

NB: I would like to stick with CIImage objects as I'll want to access transition effects at some point.

Answer 1

Every frame, the call to NSData's initWithBytes:length: causes an 8MB memory allocation & an 8MB copy.

You can get rid of this per-frame allocation/copy by replacing theNSData object with a persistent NSMutableData object (set up once at the beginning), and using its mutableBytes as the destination buffer for the frame's 24- to 32-bit conversion.

(Alternatively, if you prefer to manage the destination-buffer memory yourself, leave the object as NSData class, but initialize it with initWithBytesNoCopy:length:freeWhenDone: & pass NO as the last parameter.)