AVCaptureVideoPreviewLayer 运行速度随时间变慢

Question

我有一个 UIViewController，我在 init 方法上设置了一个 AVCaptureVideoPreviewLayer 来拍照。拍摄照片时，我关闭 UIViewController。

每次我打开这个 UIViewController 时，Ipad 的运行速度都会变慢，直到崩溃。我收到内存警告，所以我认为它不是免费的，另一方面，我使用的是 ARC，所以我认为每次关闭 UIViewController 时它都会释放内存。

下面是 UIViewController 的 init 方法的代码：

    session = [[AVCaptureSession alloc] init];
    session.sessionPreset = AVCaptureSessionPresetMedium;

    AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
    captureVideoPreviewLayer.affineTransform = CGAffineTransformMakeRotation(M_PI+M_PI_2);
    captureVideoPreviewLayer.frame = CGRectMake(45, 55, 512, 387);
    [self.cameraPlace.layer addSublayer:captureVideoPreviewLayer];


    NSArray *cameras=[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    AVCaptureDevice *device = [cameras objectAtIndex:1];

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

    stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
    NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
    [stillImageOutput setOutputSettings:outputSettings];

    [session addOutput:stillImageOutput];

    [session startRunning];

我有什么问题吗？或者你有什么线索吗？

Answer 1

我遇到了同样的问题，因为我正在添加一个已添加会话的图层。

self.captureVideoPreviewLayer = [AVCaptureVideoPreviewLayer 
                layerWithSession:self.session];

请在上面的行设置一个断点，你会发现它需要 3-4 秒才能继续。有时它会产生内存警告，有时则不会。 所以只需添加检查它是否已经添加，如下所示。

NSError *error;
[self.deviceCamera lockForConfiguration:&error];

if (self.session == nil)
{
    self.session = [[AVCaptureSession alloc] init];  
    self.captureVideoPreviewLayer = [AVCaptureVideoPreviewLayer 
    layerWithSession:self.session];
    CGRect screenBounds = [[UIScreen mainScreen]bounds];
    self.captureVideoPreviewLayer.frame = screenBounds;
    self.captureVideoPreviewLayer.videoGravity = 
    AVLayerVideoGravityResizeAspectFill; //  to fill the camera fullscreen view
    self.userInteractionEnabled = YES;

    if ([self.session canAddInput:_input]) {
        [self.session addInput:_input];
     }
}
  
[self.session startRunning];
      
[self.layer addSublayer:self.captureVideoPreviewLayer];
        
if (self.stillImageOutput ==  nil)
{
    self.stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
    NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
    [self.stillImageOutput setOutputSettings:outputSettings];
    NSString* preset = 0;
    if (!preset) {
        preset = AVCaptureSessionPresetPhoto;
    }
    
    if ([self.session canSetSessionPreset:preset]) {
        
        self.session.sessionPreset = preset;
    }
    
    
    if ([self.session canAddOutput:self.stillImageOutput]) {
        [self.session addOutput:self.stillImageOutput];
    }
}

objective-ciosavcapturesession