在iOS上使用AVCaptureSession加载相机的速度很慢 - 如何加快速度？

Question

现在我试图允许用户在我的应用程序中拍照而不使用UIImagePickerController.我正在使用AVCaptureSession和所有相关的类来加载相机提要作为我在其中一个视图控制器上的全屏视图的子图层.代码可以工作,但遗憾的是相机加载速度很慢.通常需要2-3秒.这是我的代码:

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

if ([session canSetSessionPreset:AVCaptureSessionPresetHigh])
    //Check size based configs are supported before setting them
    [session setSessionPreset:AVCaptureSessionPresetHigh];

[session setSessionPreset:AVCaptureSessionPreset1280x720];

CALayer *viewLayer = self.liveCameraFeed.layer;
//NSLog(@"viewLayer = %@", viewLayer);

AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];

captureVideoPreviewLayer.frame = viewLayer.bounds;
[viewLayer addSublayer:captureVideoPreviewLayer];

AVCaptureDevice *device;

if(isFront)
{
    device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
}
else
{
    device = [self frontCamera];
}

AVCaptureDevice *audioDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
AVCaptureDeviceInput * audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioDevice error:nil];
[session addInput:audioInput];

NSError *error = nil;
input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
if (!input) {
    // Handle the error appropriately.
    //NSLog(@"ERROR: trying to open camera: %@", error);
}

[session addInput:input];
[session startRunning];

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

有没有办法加快速度？我已经尝试使用Grand Central Dispatch和NSThread在另一个线程上加载它,虽然这使得应用程序冻结它使得相机的加载时间更长.任何帮助表示赞赏.

Answer 1

在我的情况下,我需要等待session开始运行

dispatch_async(queue) {
  self.session.startRunning()

  dispatch_async(dispatch_get_main_queue()) {
    self.delegate?.cameraManDidStart(self)

    let layer = AVCaptureVideoPreviewLayer(session: self.session)
  }
}

Answer 2

等待AVCaptureSession的startRunning功能也是我的解决方案。您可以startRunning在全局异步中运行，然后在主线程中添加您的AVCaptureVideoPreviewLayer。

斯威夫特 4示例

DispatchQueue.global().async {
    self.captureSession.startRunning()
    DispatchQueue.main.async {
        let videoPreviewLayer = AVCaptureVideoPreviewLayer(session: self.captureSession)
    }
}

Answer 3

对于任何感兴趣的人，我想出的解决方案是在不同的线程上预加载相机并保持其打开状态。