iPhone：AVCaptureSession捕获输出崩溃（AVCaptureVideoDataOutput）

Question

我捕获视频并将其转换为CGImage以对其进行处理。它会工作约10秒钟，获得内存警告，然后崩溃（通常它说数据格式化器暂时不可用）。有人可以帮我解决问题吗？

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

// CONVERT CMSAMPLEBUFFER INTO A CGIMAGE 
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); 

CVPixelBufferLockBaseAddress(imageBuffer,0); 


uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer); 
size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer); 
size_t width = CVPixelBufferGetWidth(imageBuffer); 
size_t height = CVPixelBufferGetHeight(imageBuffer); 


CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 
CGContextRef newContext = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst); 
CGImageRef cgimage = CGBitmapContextCreateImage(newContext); 
UIImage *sourceImage= [UIImage imageWithCGImage:cgimage scale:1.0f orientation:UIImageOrientationLeftMirrored]; 
CGImageRelease(cgimage); 
CGContextRelease(newContext); 
CGColorSpaceRelease(colorSpace); 

CVPixelBufferUnlockBaseAddress(imageBuffer,0); 


// *** 
// Adding code after this point to do image transformation usually causes it to crash 
UIImage *rot = [self scaleAndRotateImage:sourceImage]; 
self.detectImage = rot; 



} 

代码转换图像....

- (UIImage*)scaleAndRotateImage:(UIImage *)image{ 
    int kMaxResolution = 320; // Or whatever 

    CGImageRef imgRef = image.CGImage; 

    CGFloat width = CGImageGetWidth(imgRef); 
    CGFloat height = CGImageGetHeight(imgRef); 

    CGAffineTransform transform = CGAffineTransformIdentity; 
    CGRect bounds = CGRectMake(0, 0, width, height); 
    if (width > kMaxResolution || height > kMaxResolution) { 
     CGFloat ratio = width/height; 
     if (ratio > 1) { 
      bounds.size.width = kMaxResolution; 
      bounds.size.height = bounds.size.width/ratio; 
     } 
     else { 
      bounds.size.height = kMaxResolution; 
      bounds.size.width = bounds.size.height * ratio; 
     } 
    } 

    CGFloat scaleRatio = bounds.size.width/width; 
    CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef)); 
    CGFloat boundHeight; 
    UIImageOrientation orient = image.imageOrientation; 
    switch(orient) { 

     case UIImageOrientationUp: //EXIF = 1 
      transform = CGAffineTransformIdentity; 
      break; 

     case UIImageOrientationUpMirrored: //EXIF = 2 
      transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0); 
      transform = CGAffineTransformScale(transform, -1.0, 1.0); 
      break; 

     case UIImageOrientationDown: //EXIF = 3 
      transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height); 
      transform = CGAffineTransformRotate(transform, M_PI); 
      break; 

     case UIImageOrientationDownMirrored: //EXIF = 4 
      transform = CGAffineTransformMakeTranslation(0.0, imageSize.height); 
      transform = CGAffineTransformScale(transform, 1.0, -1.0); 
      break; 

     case UIImageOrientationLeftMirrored: //EXIF = 5 
      boundHeight = bounds.size.height; 
      bounds.size.height = bounds.size.width; 
      bounds.size.width = boundHeight; 
      transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.height); 
      transform = CGAffineTransformScale(transform, -1.0, 1.0); 
      transform = CGAffineTransformRotate(transform, 3.0 * M_PI/2.0); 
      break; 

     case UIImageOrientationLeft: //EXIF = 6 
      boundHeight = bounds.size.height; 
      bounds.size.height = bounds.size.width; 
      bounds.size.width = boundHeight; 
      transform = CGAffineTransformMakeTranslation(0.0, imageSize.width); 
      transform = CGAffineTransformRotate(transform, 3.0 * M_PI/2.0); 
      break; 

     case UIImageOrientationRightMirrored: //EXIF = 7 
      boundHeight = bounds.size.height; 
      bounds.size.height = bounds.size.width; 
      bounds.size.width = boundHeight; 
      transform = CGAffineTransformMakeScale(-1.0, 1.0); 
      transform = CGAffineTransformRotate(transform, M_PI/2.0); 
      break; 

     case UIImageOrientationRight: //EXIF = 8 
      boundHeight = bounds.size.height; 
      bounds.size.height = bounds.size.width; 
      bounds.size.width = boundHeight; 
      transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0); 
      transform = CGAffineTransformRotate(transform, M_PI/2.0); 
      break; 

     default: 
      [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"]; 

    } 

    UIGraphicsBeginImageContext(bounds.size); 

    CGContextRef context = UIGraphicsGetCurrentContext(); 

    if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) { 
     CGContextScaleCTM(context, -scaleRatio, scaleRatio); 
     CGContextTranslateCTM(context, -height, 0); 
    } 
    else { 
     CGContextScaleCTM(context, scaleRatio, -scaleRatio); 
     CGContextTranslateCTM(context, 0, -height); 
    } 

    CGContextConcatCTM(context, transform); 

    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef); 
    UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 

    //[self setRotatedImage:imageCopy]; 
    return imageCopy; 
} 

此功能只是背景，看我的设置视频输出......

AVCaptureVideoDataOutput *videoOut = [[AVCaptureVideoDataOutput alloc] init]; 
[videoOut setAlwaysDiscardsLateVideoFrames:YES]; 
[videoOut setVideoSettings:[NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey]]; // BGRA is necessary for manual preview 
dispatch_queue_t my_queue = dispatch_queue_create("com.example.subsystem.taskXYZ", NULL); 
[videoOut setSampleBufferDelegate:self queue:my_queue]; 
if ([self.captureSession canAddOutput:videoOut]) [self.captureSession addOutput:videoOut]; 
else NSLog(@"Couldn't add video output"); 
[videoOut release]; 

Answer 1

在如何建立视频输出，新创建的调度队列不被释放。你可以释放它

dispatch_release(queue); 

但我不相信这个函数被调用得太频繁，所以泄漏可能源自其他地方。多次浏览您的代码，找不到任何其他的罪魁祸首......

您是否尝试过使用泄漏仪器工具搜索泄漏？

Answer 2

我有类似的问题。最终发生的情况是队列中充满了未处理的帧，因为我在委托对象中处理速度不够快。

我的解决办法是（每处理的帧一次）执行：

proctr++; 
if ((proctr % 20) == 0) { 
    deferImageProcessing = true; 
    dispatch_sync(queue, ^{ 
    [self queueFlushed]; 
    }); 
} 

- (void)queueFlushed { 
    deferImageProcessing = false; 
} 

然后，在实际的图像处理代码

- (void)captureOutput:(AVCaptureOutput *)captureOutput 
    didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer 
    fromConnection:(AVCaptureConnection *)connection 
{ 
    if (deferImageProcessing) 
    return; 
    // do whatever else I'm doing... 
} 

本质上，我们偶尔暂停图像处理，直到队列清空。
我希望这是有用的。