Question

我让我的AVCaptureSession工作，它几乎完美地复制了Camera.app用户界面，然而，几秒钟后应用程序将崩溃，我只是找不到我做错了什么。我真的希望有人知道如何优化这个！

我 AM 使用ARC;而且，整个会话运行良好，但稍微崩溃了。 AVCaptureSession委托方法被调用似乎每秒钟。如果只有当用户按下“拍照”按钮时才有办法调用该方法，那么如何在保持“实时”预览图层的同时执行此操作？

提前致谢！

设置会话

NSError *error = nil;
session = [[AVCaptureSession alloc] init];
session.sessionPreset = AVCaptureSessionPresetMedium;
device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
[session addInput:input];

output = [[AVCaptureVideoDataOutput alloc] init];
[session addOutput:output];

dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);
[output setSampleBufferDelegate:self queue:queue];
dispatch_release(queue);

output.videoSettings = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
if(version >= 4.0 && version < 5.0) {
    output.minFrameDuration = CMTimeMake(1, 15);
}
output.alwaysDiscardsLateVideoFrames = YES;

previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session];
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
[self.view.layer addSublayer:previewLayer];
[self.view addSubview:camera_overlay];
[session startRunning];

AVCaptureSession正在调用的代理：

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    UIImage *capture_image = [self imageFromSampleBuffer:sampleBuffer];
    return capture_image;
}

从样本缓冲区获取UIImage的方法

- (UIImage *)imageFromSampleBuffer:(CMSampleBufferRef)sampleBuffer {

    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); 
    CVPixelBufferLockBaseAddress(imageBuffer, 0); 
    void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer); 
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer); 
    size_t width = CVPixelBufferGetWidth(imageBuffer); 
    size_t height = CVPixelBufferGetHeight(imageBuffer); 
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst); 
    CGImageRef quartzImage = CGBitmapContextCreateImage(context); 
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);
    CGContextRelease(context); 
    CGColorSpaceRelease(colorSpace);
    UIImage *image = [UIImage imageWithCGImage:quartzImage];
    CGImageRelease(quartzImage);

    return image;

}

Answer 1

请查看Apple的AVCam Demo应用程序以获取完整示例。

方法

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

每次相机帧准备好时都会调用

，在您的情况下，每秒调用15次，或者至少应调用15次，因为您将帧速率指定为output.minFrameDuration = CMTimeMake(1, 15);

从您提供的代码中，我能想到的唯一原因是您没有发布UIImage *capture_image

您可以使用XCode Instruments分析您的应用程序并查看其发生的原因：Instruments Guide

Leaks工具是你的第一站，网上有很多教程，这里有一个：Tracking iPhone Memory Leaks写了一个SO用户OwenGross，如果我没弄错的话{{ 3}}

Answer 2

帖子看起来很旧但是如果有人看到这个：

您是谁在委托方法中将图片返回（

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    UIImage *capture_image = [self imageFromSampleBuffer:sampleBuffer];
    return capture_image;
}

）？

您可以使用一个引发标志的按钮，在委托方法中检查是否引发了标志，然后才创建图像。图像应该是一个实例变量，否则它在任何情况下都会丢失。

还有委托方法来捕获图像 captureStillImageAsynchronouslyFromConnection

正确的方法来优化我的AVCaptureSession？

2 个答案: