Memory leak when creating pixel buffer of image - ios

Question

I am trying to create a video with an input of images using AVAssetWriterInput for which I need to create a pixel buffer of my images.
For that I call the function below which works, but after creating a few videos the app receives a memory warning and crashes. I have debugged it using Instruments and it appears I have a memory leak here.
I have tried to put the variables pixelBufferPointer and pxData as class variables and destroy/dealloc once the video is created but that didn't appear to make any difference. Is there something that I should be doing to release this memory?
func createPixelBufferFromCGImage(image: CGImageRef) -> CVPixelBufferRef {
let options = [
"kCVPixelBufferCGImageCompatibilityKey": true,
"kCVPixelBufferCGBitmapContextCompatibilityKey": true
]
var videoWidth = 496
var videoHeight = 668
let frameSize = CGSizeMake(CGFloat(videoWidth), CGFloat(videoHeight))
var pixelBufferPointer = UnsafeMutablePointer<Unmanaged<CVPixelBuffer>?>.alloc(1)
var status:CVReturn = CVPixelBufferCreate(
kCFAllocatorDefault,
Int(frameSize.width),
Int(frameSize.height),
OSType(kCVPixelFormatType_32ARGB),
options,
pixelBufferPointer
)
var lockStatus:CVReturn = CVPixelBufferLockBaseAddress(pixelBufferPointer.memory?.takeUnretainedValue(), 0)
var pxData:UnsafeMutablePointer<(Void)> = CVPixelBufferGetBaseAddress(pixelBufferPointer.memory?.takeUnretainedValue())
let bitmapinfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.NoneSkipFirst.rawValue)
let rgbColorSpace:CGColorSpace = CGColorSpaceCreateDeviceRGB()
var context:CGContextRef = CGBitmapContextCreate(
pxData,
Int(frameSize.width),
Int(frameSize.height),
8,
//4 * CGImageGetWidth(image),
4 * Int(frameSize.width),
rgbColorSpace,
bitmapinfo
)
CGContextDrawImage(context, CGRectMake(0, 0, frameSize.width, frameSize.height), image)
CVPixelBufferUnlockBaseAddress(pixelBufferPointer.memory?.takeUnretainedValue(), 0)
UIGraphicsEndImageContext()
return pixelBufferPointer.memory!.takeUnretainedValue()
}

Answer 1

The Unmanaged<CVPixelBuffer> is leaking.
I would prefer Russell Austin's answer, but I couldn't figure out how to pass the pixelBufferPointer to CVPixelBufferCreate without syntax error (swift noob). Failing that, changing the line
return pixelBufferPointer.memory!.takeUnretainedValue()
to
return pixelBufferPointer.memory!.takeRetainedValue()
fixes the leak

Answer 2

Take a look at Memory leak on CIContext createCGImage at iOS 9?
I'm having a similar issue, the leak is due to the following code
CGImageRef processedCGImage = [_context createCGImage:ciImage
fromRect:[ciImage extent]];
Here for more contextual info: Memory Leak in CMSampleBufferGetImageBuffer

Answer 3

You don't have to use the UnsafeMutablePointer types. You were probably trying to convert from some Objective-C example. I was doing the same thing but eventually found how to do it without. Try
var pixelBufferPointer: CVPixelBuffer?
...
var status:CVReturn = CVPixelBufferCreate(
kCFAllocatorDefault,
Int(frameSize.width),
Int(frameSize.height),
OSType(kCVPixelFormatType_32ARGB),
options,
&pixelBufferPointer
)
and
var pxData = CVPixelBufferGetBaseAddress(pixelBufferPointer)
Then you don't have to do the takeUnRetainedValue, etc.
You might also try using AVAssetWriterInputPixelBufferAdaptor and a pixel buffer pool. That is supposed to be more efficient. See this example

Answer 4

When using CVPixelBufferCreate the UnsafeMutablePointer has to be destroyed after retrieving the memory of it.
When I create a CVPixelBuffer, I do it like this:
func allocPixelBuffer() -> CVPixelBuffer {
let pixelBufferAttributes : CFDictionary = [...]
let pixelBufferOut = UnsafeMutablePointer<CVPixelBuffer?>.alloc(1)
_ = CVPixelBufferCreate(kCFAllocatorDefault,
Int(Width),
Int(Height),
OSType(kCVPixelFormatType_32ARGB),
pixelBufferAttributes,
pixelBufferOut)
let pixelBuffer = pixelBufferOut.memory!
pixelBufferOut.destroy()
return pixelBuffer
}