iOS 上的双 AVCaptureSession 输出

Question

我正在尝试同时从 iOS 设备上的两个摄像头拍照。我还想在屏幕上实时预览两个摄像头。我使用此代码：

- (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];
    }

}

但当应用启动前置摄像头会话时，后置摄像头会话停止并留下静止图像。

有没有办法实时显示两个摄像头的输出？

谢谢

Answer 1

不，不是。使用 AVCaptureSession 时，一次只能使用一个相机源。

不允许同时使用多个 AVCaptureInput。因此，一旦一个会话开始，另一个会话就会停止。

最好的办法是创建两个会话，启动第一个，一旦报告帧，停止它并启动第二个。然后停止第二个并开始第一个，继续这样做。这会起作用，但您收到的输入会有明显的延迟。