我有代码在Objective-C中创建，配置和启动视频捕获会话而没有任何问题。我将示例移植到C＃和MonoTouch 4.0.3并遇到一些问题，这里是代码：
void Initialize ()
{
// Create notifier delegate class
captureVideoDelegate = new CaptureVideoDelegate(this);
// Create capture session
captureSession = new AVCaptureSession();
captureSession.SessionPreset = AVCaptureSession.Preset640x480;
// Create capture device
captureDevice = AVCaptureDevice.DefaultDeviceWithMediaType(AVMediaType.Video);
// Create capture device input
NSError error;
captureDeviceInput = new AVCaptureDeviceInput(captureDevice, out error);
captureSession.AddInput(captureDeviceInput);
// Create capture device output
captureVideoOutput = new AVCaptureVideoDataOutput();
captureSession.AddOutput(captureVideoOutput);
captureVideoOutput.VideoSettings.PixelFormat = CVPixelFormatType.CV32BGRA;
captureVideoOutput.MinFrameDuration = new CMTime(1, 30);
//
// ISSUE 1
// In the original Objective-C code I was creating a dispatch_queue_t object, passing it to
// setSampleBufferDelegate:queue message and worked, here I could not find an equivalent to
// the queue mechanism. Also not sure if the delegate should be used like this).
//
captureVideoOutput.SetSampleBufferDelegatequeue(captureVideoDelegate, ???????);
// Create preview layer
previewLayer = AVCaptureVideoPreviewLayer.FromSession(captureSession);
previewLayer.Orientation = AVCaptureVideoOrientation.LandscapeRight;
//
// ISSUE 2:
// Didn't find any VideoGravity related enumeration in MonoTouch (not sure if string will work)
//
previewLayer.VideoGravity = "AVLayerVideoGravityResizeAspectFill";
previewLayer.Frame = new RectangleF(0, 0, 1024, 768);
this.View.Layer.AddSublayer(previewLayer);
// Start capture session
captureSession.StartRunning();
}
#endregion
public class CaptureVideoDelegate : AVCaptureVideoDataOutputSampleBufferDelegate
{
private VirtualDeckViewController mainViewController;
public CaptureVideoDelegate(VirtualDeckViewController viewController)
{
mainViewController = viewController;
}
public override void DidOutputSampleBuffer (AVCaptureOutput captureOutput, CMSampleBuffer sampleBuffer, AVCaptureConnection connection)
{
// TODO: Implement - see: http://go-mono.com/docs/index.aspx?link=T%3aMonoTouch.Foundation.ModelAttribute
}
}
问题1： 不确定如何正确使用SetSampleBufferDelegatequeue方法中的委托。也找不到与dispatch_queue_t对象相同的机制，它在Objective-C中正常工作以传入第二个参数。
问题2： 我没有在MonoTouch库中找到任何VideoGravity枚举，不确定传递具有常量值的字符串是否有效。
我已经找到了解决这个问题的任何线索，但没有明确的样本。任何有关如何在MonoTouch中执行此操作的样本或信息都将受到高度赞赏。
非常感谢。
答案 0 :(得分：1)
这是我的代码。好好利用它。我只是删除了重要的东西，所有的初始化都在那里，以及读取样本输出缓冲区。
然后我有代码处理CVImageBuffer形式一个链接的自定义ObjC库，如果你需要在Monotouch中处理它，那么你需要加倍努力并将其转换为CGImage或UIImage。在Monotouch（AFAIK）中没有这个功能，所以你需要自己绑定它，从普通的ObjC。 ObjC中的示例如下：how to convert a CVImageBufferRef to UIImage
public void InitCapture ()
{
try
{
// Setup the input
NSError error = new NSError ();
captureInput = new AVCaptureDeviceInput (AVCaptureDevice.DefaultDeviceWithMediaType (AVMediaType.Video), out error);
// Setup the output
captureOutput = new AVCaptureVideoDataOutput ();
captureOutput.AlwaysDiscardsLateVideoFrames = true;
captureOutput.SetSampleBufferDelegateAndQueue (avBufferDelegate, dispatchQueue);
captureOutput.MinFrameDuration = new CMTime (1, 10);
// Set the video output to store frame in BGRA (compatible across devices)
captureOutput.VideoSettings = new AVVideoSettings (CVPixelFormatType.CV32BGRA);
// Create a capture session
captureSession = new AVCaptureSession ();
captureSession.SessionPreset = AVCaptureSession.PresetMedium;
captureSession.AddInput (captureInput);
captureSession.AddOutput (captureOutput);
// Setup the preview layer
prevLayer = new AVCaptureVideoPreviewLayer (captureSession);
prevLayer.Frame = liveView.Bounds;
prevLayer.VideoGravity = "AVLayerVideoGravityResize"; // image may be slightly distorted, but red bar position will be accurate
liveView.Layer.AddSublayer (prevLayer);
StartLiveDecoding ();
}
catch (Exception ex)
{
Console.WriteLine (ex.ToString ());
}
}
public void DidOutputSampleBuffer (AVCaptureOutput captureOutput, MonoTouch.CoreMedia.CMSampleBuffer sampleBuffer, AVCaptureConnection connection)
{
Console.WriteLine ("DidOutputSampleBuffer: enter");
if (isScanning)
{
CVImageBuffer imageBuffer = sampleBuffer.GetImageBuffer ();
Console.WriteLine ("DidOutputSampleBuffer: calling decode");
// NSLog(@"got image w=%d h=%d bpr=%d",CVPixelBufferGetWidth(imageBuffer), CVPixelBufferGetHeight(imageBuffer), CVPixelBufferGetBytesPerRow(imageBuffer));
// call the decoder
DecodeImage (imageBuffer);
}
else
{
Console.WriteLine ("DidOutputSampleBuffer: not scanning");
}
Console.WriteLine ("DidOutputSampleBuffer: quit");
}
答案 1 :(得分：1)
所有问题都解决了，最后工作正常，冻结正在发生，因为在我的测试中我还没有在方法DidOutputSampleBuffer中处理sampleBuffer。我的观点的最终代码在这里：
更新1 ：更改了VideoSettings CVPixelFormat的分配，这是错误的，会导致sampleBuffer中出现错误的BytesPerPixel。
public partial class VirtualDeckViewController : UIViewController
{
public CaptureVideoDelegate captureVideoDelegate;
public AVCaptureVideoPreviewLayer previewLayer;
public AVCaptureSession captureSession;
public AVCaptureDevice captureDevice;
public AVCaptureDeviceInput captureDeviceInput;
public AVCaptureVideoDataOutput captureVideoOutput;
...
public override void ViewDidLoad ()
{
base.ViewDidLoad ();
SetupVideoCaptureSession();
}
public void SetupVideoCaptureSession()
{
// Create notifier delegate class
captureVideoDelegate = new CaptureVideoDelegate();
// Create capture session
captureSession = new AVCaptureSession();
captureSession.BeginConfiguration();
captureSession.SessionPreset = AVCaptureSession.Preset640x480;
// Create capture device
captureDevice = AVCaptureDevice.DefaultDeviceWithMediaType(AVMediaType.Video);
// Create capture device input
NSError error;
captureDeviceInput = new AVCaptureDeviceInput(captureDevice, out error);
captureSession.AddInput(captureDeviceInput);
// Create capture device output
captureVideoOutput = new AVCaptureVideoDataOutput();
captureVideoOutput.AlwaysDiscardsLateVideoFrames = true;
// UPDATE: Wrong videosettings assignment
//captureVideoOutput.VideoSettings.PixelFormat = CVPixelFormatType.CV32BGRA;
// UPDATE Correct videosettings assignment
captureVideoOutput.VideoSettings = new AVVideoSettings(CVPixelFormatType.CV32BGRA);
captureVideoOutput.MinFrameDuration = new CMTime(1, 30);
DispatchQueue dispatchQueue = new DispatchQueue("VideoCaptureQueue");
captureVideoOutput.SetSampleBufferDelegateAndQueue(captureVideoDelegate, dispatchQueue);
captureSession.AddOutput(captureVideoOutput);
// Create preview layer
previewLayer = AVCaptureVideoPreviewLayer.FromSession(captureSession);
previewLayer.Orientation = AVCaptureVideoOrientation.LandscapeLeft;
previewLayer.VideoGravity = "AVLayerVideoGravityResizeAspectFill";
previewLayer.Frame = new RectangleF(0, 0, 1024, 768);
this.View.Layer.AddSublayer(previewLayer);
// Start capture session
captureSession.CommitConfiguration();
captureSession.StartRunning();
}
public class CaptureVideoDelegate : AVCaptureVideoDataOutputSampleBufferDelegate
{
public CaptureVideoDelegate() : base()
{
}
public override void DidOutputSampleBuffer (AVCaptureOutput captureOutput, CMSampleBuffer sampleBuffer, AVCaptureConnection connection)
{
// TODO: Implement buffer processing
// Very important (buffer needs to be disposed or it will freeze)
sampleBuffer.Dispose();
}
}
我最终在这里找到的Miguel de Icaza样本回答了最后一块拼图：link
感谢Miguel和Pavel