CMSampleBufferGetImageBuffer 中的内存泄漏

我得到了一个UIImage from a CMSampleBufferRef每 N 个视频帧进行视频缓冲，例如：

- (void)imageFromVideoBuffer:(void(^)(UIImage* image))completion {
    CMSampleBufferRef sampleBuffer = _myLastSampleBuffer;
    if (sampleBuffer != nil) {
        CFRetain(sampleBuffer);
        CIImage *ciImage = [CIImage imageWithCVPixelBuffer:CMSampleBufferGetImageBuffer(sampleBuffer)];
        _lastAppendedVideoBuffer.sampleBuffer = nil;
        if (_context == nil) {
            _context = [CIContext contextWithOptions:nil];
        }
        CVPixelBufferRef buffer = CMSampleBufferGetImageBuffer(sampleBuffer);
        CGImageRef cgImage = [_context createCGImage:ciImage fromRect:
                              CGRectMake(0, 0, CVPixelBufferGetWidth(buffer), CVPixelBufferGetHeight(buffer))];
        __block UIImage *image = [UIImage imageWithCGImage:cgImage];

        CGImageRelease(cgImage);
        CFRelease(sampleBuffer);

        if(completion) completion(image);

        return;
    }
    if(completion) completion(nil);
}

XCode 和 Instruments 检测到内存泄漏，但我无法消除它。 我像往常一样发布 CGImageRef 和 CMSampleBufferRef：

CGImageRelease(cgImage);
CFRelease(sampleBuffer);

[UPDATE]我把AVCapture输出回调以获取sampleBuffer.

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    if (captureOutput == _videoOutput) {
        _lastVideoBuffer.sampleBuffer = sampleBuffer;
        id<CIImageRenderer> imageRenderer = _CIImageRenderer;

        dispatch_async(dispatch_get_main_queue(), ^{
            @autoreleasepool {
                CIImage *ciImage = nil;
                ciImage = [CIImage imageWithCVPixelBuffer:CMSampleBufferGetImageBuffer(sampleBuffer)];
                if(_context==nil) {
                    _context = [CIContext contextWithOptions:nil];
                }
                CGImageRef processedCGImage = [_context createCGImage:ciImage
                                                             fromRect:[ciImage extent]];
                //UIImage *image=[UIImage imageWithCGImage:processedCGImage];
                CGImageRelease(processedCGImage);
                NSLog(@"Captured image %@", ciImage);
            }
        });

泄漏的代码是createCGImage:ciImage:

CGImageRef processedCGImage = [_context createCGImage:ciImage
                                                             fromRect:[ciImage extent]];

甚至有一个autoreleasepool, the CGImageRelease of the CGImage参考和一个CIContext作为实例属性。

这似乎是这里解决的同一问题：无法在 iOS 上将 CIImage 保存到文件而不发生内存泄漏

[更新] 泄漏似乎是由于错误造成的。该问题在中得到了很好的描述iOS 9 上 CIContext createCGImage 内存泄漏？

示例项目展示了如何重现此泄漏：http://www.osamu.co.jp/DataArea/VideoCameraTest.zip

最后的评论保证

看起来他们在 9.1b3 中修复了这个问题。如果有人需要解决方法 在 iOS 9.0.x 上工作，我能够让它工作：

在测试代​​码中（在本例中为 Swift）：

[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error)  
    {  
        if (error) return;  

        __block NSString *filePath = [NSTemporaryDirectory() stringByAppendingPathComponent:[NSString stringWithFormat:@"ipdf_pic_%i.jpeg",(int)[NSDate date].timeIntervalSince1970]];  

        NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];  
        dispatch_async(dispatch_get_main_queue(), ^  
        {  

            @autoreleasepool  
            {  
                CIImage *enhancedImage = [CIImage imageWithData:imageData];  

                if (!enhancedImage) return;  

                static CIContext *ctx = nil; if (!ctx) ctx = [CIContext contextWithOptions:nil];  

                CGImageRef imageRef = [ctx createCGImage:enhancedImage fromRect:enhancedImage.extent format:kCIFormatBGRA8 colorSpace:nil];  

                UIImage *image = [UIImage imageWithCGImage:imageRef scale:1.0 orientation:UIImageOrientationRight];  

                [[NSFileManager defaultManager] createFileAtPath:filePath contents:UIImageJPEGRepresentation(image, 0.8) attributes:nil];  

                CGImageRelease(imageRef);  
            }  
        });  
    }]; 

iOS9.0 的解决方法应该是

extension CIContext {  
    func createCGImage_(image:CIImage, fromRect:CGRect) -> CGImage {  
        let width = Int(fromRect.width)  
        let height = Int(fromRect.height)  

        let rawData =  UnsafeMutablePointer<UInt8>.alloc(width * height * 4)  
        render(image, toBitmap: rawData, rowBytes: width * 4, bounds: fromRect, format: kCIFormatRGBA8, colorSpace: CGColorSpaceCreateDeviceRGB())  
        let dataProvider = CGDataProviderCreateWithData(nil, rawData, height * width * 4) {info, data, size in UnsafeMutablePointer<UInt8>(data).dealloc(size)}  
        return CGImageCreate(width, height, 8, 32, width * 4, CGColorSpaceCreateDeviceRGB(), CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedLast.rawValue), dataProvider, nil, false, .RenderingIntentDefault)!  
    }  
}  

我们在创建的应用程序中遇到了类似的问题，我们使用 OpenCV 处理每个帧的特征关键点，并每隔几秒发送一帧。运行一段时间后，我们最终会收到相当多的内存压力消息。

我们设法通过在它自己的自动释放池中运行我们的处理代码来纠正这个问题，如下所示（jpegDataFromSampleBufferAndCrop 执行与您正在执行的操作类似的操作，但添加了裁剪）：

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
        @autoreleasepool {

            if ([self.lastFrameSentAt timeIntervalSinceNow] < -kContinuousRateInSeconds) {

                NSData *imageData = [self jpegDataFromSampleBufferAndCrop:sampleBuffer];

                if (imageData) {
                    [self processImageData:imageData];
                }

                self.lastFrameSentAt = [NSDate date];

                imageData = nil;
            }
        }
    }
}