iOS CVPixelBuffer在swift 2中创建泄漏内存答案

【问题标题】：iOS CVPixelBufferCreate leaking memory in swift 2iOS CVPixelBuffer在swift 2中创建泄漏内存
【发布时间】：2016-02-18 05:06:26
【问题描述】：

我正在尝试将图像转换为视频，正确的方法似乎是使用 AVAssetWriter 和 AVAssetWriterInputPixelBufferAdaptor，并且效果很好，但是会泄漏内存。

当我将 CGImage 转换为 CVPixelBuffer 时，我调用 CVPixelBufferCreate，它永远不会释放它的内存。

func CGImageToPixelBuffer(image: CGImageRef, frameSize: CGSize) -> CVPixelBuffer {

    // stupid CFDictionary stuff
    let keys: [CFStringRef] = [kCVPixelBufferCGImageCompatibilityKey, kCVPixelBufferCGBitmapContextCompatibilityKey]
    let values: [CFTypeRef] = [kCFBooleanTrue, kCFBooleanTrue]
    let keysPointer = UnsafeMutablePointer<UnsafePointer<Void>>.alloc(1)
    let valuesPointer =  UnsafeMutablePointer<UnsafePointer<Void>>.alloc(1)
    keysPointer.initialize(keys)
    valuesPointer.initialize(values)
    let options = CFDictionaryCreate(kCFAllocatorDefault, keysPointer, valuesPointer, keys.count,
        UnsafePointer<CFDictionaryKeyCallBacks>(), UnsafePointer<CFDictionaryValueCallBacks>())

    let buffer = UnsafeMutablePointer<CVPixelBuffer?>.alloc(1)

    // here's the leak >:[
    let status = CVPixelBufferCreate(kCFAllocatorDefault, Int(frameSize.width), Int(frameSize.height),
        kCVPixelFormatType_32ARGB, options, buffer)

    CVPixelBufferLockBaseAddress(pixelBuffer.memory!, 0);
    let bufferData = CVPixelBufferGetBaseAddress(buffer.memory!);

    let rgbColorSpace = CGColorSpaceCreateDeviceRGB();
    let context = CGBitmapContextCreate(bufferData, Int(frameSize.width),
        Int(frameSize.height), 8, 4*Int(frameSize.width), rgbColorSpace,
        CGImageAlphaInfo.NoneSkipFirst.rawValue);

    CGContextDrawImage(context, CGRectMake(0, 0,
        CGFloat(CGImageGetWidth(image)),
        CGFloat(CGImageGetHeight(image))), image);

    CVPixelBufferUnlockBaseAddress(pixelBuffer.memory!, 0);
    return buffer.memory!
}

这是调用 CGImageToPixelBuffer 的代码

func saveImageAsVideoFile(path: NSURL, image: UIImage, duration: Double) {
    let writer = try! AVAssetWriter(URL: path, fileType: AVFileTypeQuickTimeMovie)

    let videoSettings: NSDictionary = [
        AVVideoCodecKey : AVVideoCodecH264,
        AVVideoWidthKey : NSNumber(integer: Int(image.size.width)),
        AVVideoHeightKey : NSNumber(integer: Int(image.size.height))
    ]
    let input = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: videoSettings as? [String : AnyObject])
    let inputAdaptor = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: input, sourcePixelBufferAttributes: nil)
    input.expectsMediaDataInRealTime = false
    writer.addInput(input)
    writer.startWriting()
    writer.startSessionAtSourceTime(kCMTimeZero)

    // leak starts here
    let buffer = CGImageToPixelBuffer(image.CGImage!, frameSize: image.size)

    // append 30 frames to AVAssetWriter thing
    for i in 0..<30
        if input.readyForMoreMediaData {
            inputAdaptor.appendPixelBuffer(buffer, withPresentationTime: CMTimeMake(i, 30))
        }
    }

    //CVPixelBufferRelease(buffer) ??

    input.markAsFinished()
    writer.finishWritingWithCompletionHandler({ () -> Void in
        print("yay")
    })
}

CVPixelBufferRelease 在 swift 2 中不可用

CVPixelBufferCreate 在 swift 2 中没有返回非托管指针，所以我不能使用这个 guys code

我尝试在 unsafepointer 上手动调用 destroy 和 dealloc，但无济于事。

每次调用它都会增加内存使用量，如果调用足够多，会导致设备崩溃

任何帮助或建议将不胜感激。

【问题讨论】：

标签： swift2 avfoundation avassetwriter cvpixelbuffer

【解决方案1】：

您的let buffer = UnsafeMutablePointer<CVPixelBuffer?>.alloc(1) 没有被dealloc 平衡，但是添加这似乎并不能解决泄漏问题。只需使用 CVPixelBuffer? 即可，而且看起来更简单：

var buffer: CVPixelBuffer?

// TODO: handle status != noErr
let status = CVPixelBufferCreate(kCFAllocatorDefault, Int(frameSize.width), Int(frameSize.height),
    kCVPixelFormatType_32ARGB, options, &buffer)

CVPixelBufferLockBaseAddress(buffer!, 0);
let bufferData = CVPixelBufferGetBaseAddress(buffer!);

let rgbColorSpace = CGColorSpaceCreateDeviceRGB();
let context = CGBitmapContextCreate(bufferData, Int(frameSize.width),
    Int(frameSize.height), 8, 4*Int(frameSize.width), rgbColorSpace,
    CGImageAlphaInfo.NoneSkipFirst.rawValue);

CGContextDrawImage(context, CGRectMake(0, 0,
    CGFloat(CGImageGetWidth(image)),
    CGFloat(CGImageGetHeight(image))), image);

CVPixelBufferUnlockBaseAddress(buffer!, 0);

您还应该处理status != noErr 并尽快打开可选缓冲区，以避免所有这些buffer!s。

【讨论】：

【解决方案2】：

我也有类似的泄漏。我不确定，但我认为可以使用以下内容：

let bufferPointer = UnsafeMutablePointer<CVPixelBuffer?>.alloc(1)
...
let pixelBuffer = bufferPointer.memory!
bufferPointer.destroy()
return pixelBuffer

【讨论】：