创建AVCaptureVideoDataOutput会话后不会产生任何帧。没有丢帧，检查了设备日志，但里面没有任何内容，设备也没有产生错误。
这已经过测试，可以在 iPod 上运行，但不能在 iPad Pro 上运行。
我正在使用的当前代码实现是：
namespace Bluewire.MobileGlass.Application
{
public enum IPDFCameraViewType
{
BlackAndWhite,
Normal
}
[Register("IPDFCameraViewController")]
public class IPDFCameraViewController : UIView
{
private static readonly CIDetector HighAccuracyRectangleDetector = CIDetector.CreateRectangleDetector(null, new CIDetectorOptions { Accuracy = FaceDetectorAccuracy.High });
private AVCaptureSession captureSession;
private AVCaptureDevice captureDevice;
private EAGLContext context;
private AVCaptureStillImageOutput stillImageOutput;
private bool forceStop;
private CGSize _intrinsicContentSize;
private static CIContext ctx = null;
private static readonly CIDetector QRCodeDetector = CIDetector.CreateQRDetector(null, new CIDetectorOptions { Accuracy = FaceDetectorAccuracy.High });
private CIContext _coreImageContext;
private uint _renderBuffer;
private GLKView _glkView;
private bool _isStopped;
private nfloat _imageDetectionConfidence;
private NSTimer _borderDetectTimeKeeper;
private bool _borderDetectFrame;
private CGRectangle _borderDetectLastRectangleFeature;
private bool _isCapturing;
private DispatchQueue _captureQueue;
private IPDFCameraViewType _cameraViewType;
private bool _enableTorch;
private IDisposable willResignActiveToken;
private IDisposable didBecomeActiveToken;
public IPDFCameraViewController(System.IntPtr handle)
: base(handle)
{ }
public void SetupCameraView()
{
CreateGLKView();
var possibleDevices = AVCaptureDevice.DevicesWithMediaType(AVMediaType.Video);
var device = possibleDevices.FirstOrDefault();
if (device == null) return;
_imageDetectionConfidence = 0.0f;
var session = new AVCaptureSession();
captureSession = session;
session.BeginConfiguration();
captureDevice = device;
var input = CheckForError((out NSError err) => AVCaptureDeviceInput.FromDevice(captureDevice, out err));
session.SessionPreset = AVCaptureSession.PresetPhoto;
session.AddInput(input);
var dataOutput = new AVCaptureVideoDataOutput();
dataOutput.AlwaysDiscardsLateVideoFrames = true;
dataOutput.WeakVideoSettings = VideoSettings;
dataOutput.SetSampleBufferDelegateQueue(new IPDFVideoDataDelegateImpl(this), _captureQueue);
session.AddOutput(dataOutput);
var connection = dataOutput.Connections.First();
connection.VideoOrientation = AVCaptureVideoOrientation.Portrait;
stillImageOutput = new AVCaptureStillImageOutput();
session.AddOutput(stillImageOutput);
if (device.FlashAvailable)
{
CheckForError((out NSError err) => device.LockForConfiguration(out err));
device.FlashMode = AVCaptureFlashMode.Off;
device.UnlockForConfiguration();
if (device.IsFocusModeSupported(AVCaptureFocusMode.ContinuousAutoFocus))
{
CheckForError((out NSError err) => device.LockForConfiguration(out err));
device.FocusMode = AVCaptureFocusMode.ContinuousAutoFocus;
device.UnlockForConfiguration();
}
}
session.CommitConfiguration();
}
private NSDictionary VideoSettings = new NSDictionary<NSString, NSObject>(CoreVideo.CVPixelBuffer.PixelFormatTypeKey, new NSNumber((int)CoreVideo.CVPixelFormatType.CV32BGRA));
private delegate void ErrorFunc(out NSError error);
private delegate T ErrorFunc<T>(out NSError error);
private void CheckForError(ErrorFunc e)
{
NSError error;
e(out error);
if (error != null)
{
throw new NSErrorException(error);
}
}
private T CheckForError<T>(ErrorFunc<T> e)
{
NSError error;
var result = e(out error);
if (error != null)
{
throw new NSErrorException(error);
}
return result;
}
public void Start()
{
_isStopped = false;
captureSession.StartRunning();
_borderDetectTimeKeeper = NSTimer.CreateRepeatingScheduledTimer(TimeSpan.FromSeconds(0.5), (timer) =>
{
_borderDetectFrame = true;
});
HideGLKView(false);
}
public bool EnableBorderDetection { get; set; }
public bool EnableTorch {
get
{
return _enableTorch;
}
set
{
_enableTorch = value;
var device = captureDevice;
if (device.HasTorch && device.HasFlash)
{
CheckForError((out NSError err) => device.LockForConfiguration(out err));
if (_enableTorch)
{
device.TorchMode = AVCaptureTorchMode.On;
}
else
{
device.TorchMode = AVCaptureTorchMode.Off;
}
device.UnlockForConfiguration();
}
}
}
private void HideGLKView(bool hidden)
{
Animate(0.1, () =>
{
_glkView.Alpha = (hidden) ? 0.0f : 1.0f;
}, () => { });
}
public IPDFCameraViewType CameraViewType
{
get
{
return _cameraViewType;
}
set
{
var effect = UIBlurEffect.FromStyle(UIBlurEffectStyle.Dark);
var viewWithBlurredBackground = new UIVisualEffectView(effect);
viewWithBlurredBackground.Frame = Bounds;
InsertSubviewAbove(viewWithBlurredBackground, _glkView);
_cameraViewType = value;
DispatchQueue.MainQueue.DispatchAfter(new DispatchTime(DispatchTime.Now, TimeSpan.FromSeconds(0.3)), () =>
{
viewWithBlurredBackground.RemoveFromSuperview();
});
}
}
public override void AwakeFromNib()
{
base.AwakeFromNib();
willResignActiveToken = UIApplication.Notifications.ObserveWillResignActive((sender, args) =>
{
forceStop = true;
});
didBecomeActiveToken = UIApplication.Notifications.ObserveDidBecomeActive((sender, args) =>
{
forceStop = false;
});
_captureQueue = new DispatchQueue("com.instapdf.AVCameraCaptureQueue");
}
~IPDFCameraViewController()
{
willResignActiveToken.Dispose();
didBecomeActiveToken.Dispose();
}
private class IPDFVideoDataDelegateImpl : AVCaptureVideoDataOutputSampleBufferDelegate
{
private readonly IPDFCameraViewController mainController;
public IPDFVideoDataDelegateImpl(IPDFCameraViewController mainController)
{
this.mainController = mainController;
}
public override void DidDropSampleBuffer(AVCaptureOutput captureOutput, CMSampleBuffer sampleBuffer, AVCaptureConnection connection)
{
Console.WriteLine("Dropped frame");
}
public override void DidOutputSampleBuffer(AVCaptureOutput captureOutput, CMSampleBuffer sampleBuffer, AVCaptureConnection connection)
{
Console.WriteLine("Captured Image");
}
}
private void CreateGLKView()
{
if (context != null) return;
context = new EAGLContext(EAGLRenderingAPI.OpenGLES2);
var view = new GLKView(Bounds);
view.AutoresizingMask = UIViewAutoresizing.FlexibleWidth | UIViewAutoresizing.FlexibleHeight;
view.TranslatesAutoresizingMaskIntoConstraints = true;
view.Context = context;
view.ContentScaleFactor = 1.0f;
view.DrawableDepthFormat = GLKViewDrawableDepthFormat.Format24;
InsertSubview(view, 0);
_glkView = view;
_coreImageContext = CIContext.FromContext(context, new CIContextOptions() { WorkingColorSpace = null, UseSoftwareRenderer = false });
}
public override CGSize IntrinsicContentSize
{
get
{
if (_intrinsicContentSize.Width == 0|| _intrinsicContentSize.Height == 0)
{
return new CGSize(1.0, 1.0);
}
return _intrinsicContentSize;
}
}
}
}