如何修复CVPixelBuffer内存泄漏

Question

使用HJImagesToVideo（来自github的源代码）将uiimages转换为mp4，但我资助它可能有内存泄漏。超过200个图像转换，会有内存警告，然后崩溃。源代码在这里：

 


 + (void)writeImageAsMovie:(NSArray )array
                   toPath:(NSString)path
                     size:(CGSize)size
                      fps:(int)fps
       animateTransitions:(BOOL)shouldAnimateTransitions
        withCallbackBlock:(SuccessBlock)callbackBlock
    {
         NSLog(@"%@", path);
         NSError *error = nil;
         AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:[NSURL fileURLWithPath:path]
                                                           fileType:AVFileTypeMPEG4
                                                              error:&error];
         if (error) 
         {
             if (callbackBlock) 
             {
                callbackBlock(NO);
             }
             return;
         }
         NSParameterAssert(videoWriter);


         NSDictionary *videoSettings = @{AVVideoCodecKey: AVVideoCodecH264,
                                AVVideoWidthKey: [NSNumber numberWithInt:size.width],
                                AVVideoHeightKey: [NSNumber numberWithInt:size.height]};

         AVAssetWriterInput* writerInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo
                                                                     outputSettings:videoSettings];

         AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:writerInput
                                                                                                                 sourcePixelBufferAttributes:nil];
    NSParameterAssert(writerInput);
    NSParameterAssert([videoWriter canAddInput:writerInput]);
        [videoWriter addInput:writerInput];

        //Start a session:
        [videoWriter startWriting];
        [videoWriter startSessionAtSourceTime:kCMTimeZero];

        CVPixelBufferRef buffer;
        CVPixelBufferPoolCreatePixelBuffer(NULL, adaptor.pixelBufferPool, &buffer);

        CMTime presentTime = CMTimeMake(0, fps);

        int i = 0;
        while (1)
        {


            if(writerInput.readyForMoreMediaData)
            {

                presentTime = CMTimeMake(i, fps);

                if (i >= [array count]) 
                {
                    buffer = NULL;
                } 
                else 
                {
                    buffer = [HJImagesToVideo pixelBufferFromCGImage:[array[i] CGImage] size:CGSizeMake(480, 320)];
                }

                if (buffer) 
                {
                //append buffer

                    BOOL appendSuccess = [HJImagesToVideo appendToAdapter:adaptor
                                                          pixelBuffer:buffer
                                                               atTime:presentTime
                                                            withInput:writerInput];
                    NSAssert(appendSuccess, @"Failed to append");

                    if (shouldAnimateTransitions && i + 1 < array.count) 
                    {

                        //Create time each fade frame is displayed
                        CMTime fadeTime = CMTimeMake(1, fps*TransitionFrameCount);

                        //Add a delay, causing the base image to have more show time before fade begins.
                        for (int b = 0; b < FramesToWaitBeforeTransition; b++) 
                        {
                            presentTime = CMTimeAdd(presentTime, fadeTime);
                        }

                        //Adjust fadeFrameCount so that the number and curve of the fade frames and their alpha stay consistant
                        NSInteger framesToFadeCount = TransitionFrameCount - FramesToWaitBeforeTransition;

                        //Apply fade frames
                        for (double j = 1; j < framesToFadeCount; j++) 
                        {

                             buffer = [HJImagesToVideo crossFadeImage:[array[i] CGImage]
                                                         toImage:[array[i + 1] CGImage]
                                                          atSize:CGSizeMake(480, 320)
                                                       withAlpha:j/framesToFadeCount];

                            BOOL appendSuccess = [HJImagesToVideo appendToAdapter:adaptor
                                                                  pixelBuffer:buffer
                                                                       atTime:presentTime
                                                                    withInput:writerInput];
                            presentTime = CMTimeAdd(presentTime, fadeTime);

                            NSAssert(appendSuccess, @"Failed to append");
                        }
                    }

                    i++;
                } 
                else 
                {

                    //Finish the session:
                    [writerInput markAsFinished];

                    [videoWriter finishWritingWithCompletionHandler:^{
                        NSLog(@"Successfully closed video writer");
                        if (videoWriter.status == AVAssetWriterStatusCompleted)                                                   {
                             if (callbackBlock) {
                                callbackBlock(YES);
                             }
                             } else {
                              if (callbackBlock) {
                              callbackBlock(NO);
                             }
                        }
                }];

                    CVPixelBufferPoolRelease(adaptor.pixelBufferPool);
                    //CVPixelBufferRelease(buffer);
                    NSLog (@"Done");
                    break;
                }
            }


         }
        }




     + (CVPixelBufferRef)pixelBufferFromCGImage:(CGImageRef)image
                                  size:(CGSize)imageSize
    {
       NSDictionary *options = @{(id)kCVPixelBufferCGImageCompatibilityKey: @YES,
                          (id)kCVPixelBufferCGBitmapContextCompatibilityKey: @YES};
       CVPixelBufferRef pxbuffer = NULL;
       CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, imageSize.width,
                                      imageSize.height, kCVPixelFormatType_32ARGB, (__bridge CFDictionaryRef) options,
                                      &pxbuffer);
       NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL);

       CVPixelBufferLockBaseAddress(pxbuffer, 0);
       void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
       NSParameterAssert(pxdata != NULL);

       CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
       CGContextRef context = CGBitmapContextCreate(pxdata, imageSize.width,
                                             imageSize.height, 8, 4*imageSize.width, rgbColorSpace,
                                             kCGImageAlphaNoneSkipFirst);
       NSParameterAssert(context);

       CGContextDrawImage(context, CGRectMake(0 + (imageSize.width-CGImageGetWidth(image))/2,
                                       (imageSize.height-CGImageGetHeight(image))/2,
                                       CGImageGetWidth(image),
                                       CGImageGetHeight(image)), image);
       CGColorSpaceRelease(rgbColorSpace);
       CGContextRelease(context);

       CVPixelBufferUnlockBaseAddress(pxbuffer, 0);

       return pxbuffer;
    }