iOS上的Double AVCaptureSession输出

Question

我试图在iOS设备上同时拍摄两张照片。我也想在屏幕上预览两台相机。我用这个代码：

- (void)prepareCameraView:(UIView *)window 
{ 
    NSArray *captureDevices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo]; 

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

     CALayer *viewLayer = window.layer; 
     NSLog(@"viewLayer = %@", viewLayer); 

     AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session]; 
     captureVideoPreviewLayer.frame = CGRectMake(0.0f, 0.0f, window.bounds.size.width/2.0f, window.bounds.size.height); 
     [window.layer addSublayer:captureVideoPreviewLayer]; 

     NSError *error = nil; 
     AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:[captureDevices objectAtIndex:0] error:&error]; 
     if (!input) 
     { 
      NSLog(@"ERROR : trying to open camera : %@", error); 
     } 

     [session addInput:input]; 

     [session startRunning]; 
    } 

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

     CALayer *viewLayer = window.layer; 
     NSLog(@"viewLayer = %@", viewLayer); 

     AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session]; 
     captureVideoPreviewLayer.frame = CGRectMake(window.bounds.size.width/2.0f, 0.0f, window.bounds.size.width/2.0f, window.bounds.size.height); 
     [window.layer addSublayer:captureVideoPreviewLayer]; 

     NSError *error = nil; 
     AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:[captureDevices objectAtIndex:1] error:&error]; 
     if (!input) 
     { 
      NSLog(@"ERROR : trying to open camera : %@", error); 
     } 

     [session addInput:input]; 

     [session startRunning]; 
    } 

} 

但是，当应用程序启动的前置摄像头的会议上，背部摄像头的会话停止，留下了静止图像。

有没有办法显示两台摄像机的输出？

谢谢

Answer 1

没有它没有。在使用AVCaptureSession时，一次只能使用一个摄像头。

不允许同时使用多个AVCaptureInput。所以只要一个会话开始，另一个会停止。

最好的办法是创建两个会话，首先开始第一个会话，一旦它报告一个帧，停止它并开始第二个会话。然后停下来，开始第一个，继续做下去。这将起作用，但您收到的输入中会有明显的延迟。