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GetSample Method

Summary

Gets a delivered media sample.

Syntax

C++/CLI

public MediaSample GetSample( 
   int lTimeout 
)

public: 
MediaSample^ GetSample(  
   int lTimeout 
)

Parameters

lTimeout
A timeout value specifying the maximum time to wait for the sample, in milliseconds.

Return Value

A MediaSample object

Remarks

If the method fails, an error is raised. For more information, refer to the Error Codes.

Common errors:

VFW_E_TIMEOUT - [0x8004022E] The interval specified in 1Timeout has elapsed before a sample was ready. You can call the function again or increase the timeout value.
VFW_E_SAMPLE_REJECTED_EOS - [0x8004022C] The end of stream has been reached. There are no more samples available for this stream.

Example

using Leadtools; 
using Leadtools.Multimedia; 
using LeadtoolsMultimediaExamples.Fixtures; 
 
 
public bool _result = false; 
public CaptureCtrlForm _form = new CaptureCtrlForm(); 
 
public void CaptureFrameExample() 
{ 
   // reference the capture control 
   CaptureCtrl capturectrl = _form.CaptureCtrl; 
 
   // output file 
   string outFile = Path.Combine(LEAD_VARS.MediaDir, "CaptureCtrl_CaptureFrameExample.bmp"); 
 
   try 
   { 
      // set the video capture device, use your capture device name here 
      if (capturectrl.VideoDevices["USB"] == null) 
         throw new Exception("No USB video device available"); 
 
      capturectrl.VideoDevices["USB"].Selected = true; 
 
      // create a new sample target 
      SampleTarget st = new SampleTarget(); 
 
      // set the target media type for the video stream 
      MediaType amt = new MediaType(); 
      amt.Type = Constants.MEDIATYPE_Video; 
      amt.SubType = Constants.MEDIASUBTYPE_RGB24; 
      st.SetAcceptedMediaType(amt); 
 
      // assign the sample target to the capture control 
      capturectrl.TargetObject = st; 
      capturectrl.TargetFormat = TargetFormatType.AVI; 
 
      // prepare the manual frames capture 
      capturectrl.ReadyCapture(CaptureMode.ManualFrames); 
 
      // do something before the capture starts 
      if (capturectrl.IsModeAvailable(CaptureMode.ManualFrames)) 
      { 
      } 
 
      // set the capture mode to manual frames 
      capturectrl.StartCapture(CaptureMode.ManualFrames); 
 
      // capture a frame 
      capturectrl.CaptureFrame(); 
 
      // create a media sample using the captured sample from above  
      MediaSample ms = st.GetSample(-1); 
 
      // get the sample target's connected media type 
      MediaType mt = st.GetConnectedMediaType(); 
 
      Bitmap bmp = WriteSampleBitmap(outFile, ms, mt); 
 
      // stop the capture 
      capturectrl.StopCapture(); 
 
      // check for the capture file and set the result 
      if (File.Exists(outFile)) 
      { 
         Image test = Bitmap.FromFile(outFile); 
         _result = (test.Width == bmp.Width && test.Height == bmp.Height && test.PixelFormat == bmp.PixelFormat); 
      } 
   } 
   catch (COMException) 
   { 
      _result = false; 
   } 
   catch (Exception) 
   { 
      _result = false; 
   } 
 
   // we'll loop on the state and pump messages for this example. 
   // but you should not need to if running from a Windows Forms application. 
   while (capturectrl.State == CaptureState.Running) 
      Application.DoEvents(); 
} 
 
private Bitmap WriteSampleBitmap(string outFile, MediaSample ms, MediaType mt) 
{ 
   // get the video information  
   VideoInfoHeader vih = mt.GetVideoFormatData(); 
 
   // create a bitmap to hold the sample and copy it 
   Bitmap bmp = new Bitmap(vih.bmiHeader.biWidth, vih.bmiHeader.biHeight, FormatFromBitCount(vih.bmiHeader.biBitCount)); 
   BitmapData bmpData = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadWrite, bmp.PixelFormat); 
   int bitmapSize = GetBitmapSize(bmp, vih.bmiHeader.biBitCount); 
   if(bitmapSize <= ms.BufferSize) 
      Marshal.Copy(ms.Buffer, 0, bmpData.Scan0, bitmapSize); 
   bmp.UnlockBits(bmpData); 
 
   // flip the upside down buffer 
   bmp.RotateFlip(RotateFlipType.Rotate180FlipX); 
 
   // save the image 
   bmp.Save(outFile, ImageFormat.Bmp); 
   return bmp; 
} 
 
private PixelFormat FormatFromBitCount(int bitCount) 
{ 
   switch (bitCount) 
   { 
      case 8: 
         return PixelFormat.Format8bppIndexed; 
      case 16: 
         return PixelFormat.Format16bppRgb555; 
      case 32: 
         return PixelFormat.Format32bppRgb; 
      case 48: 
         return PixelFormat.Format48bppRgb; 
      case 24: 
         return PixelFormat.Format24bppRgb; 
   } 
   throw new Exception("Unrecognized bit count"); 
} 
 
private int GetBitmapSize(Bitmap bmp, int bitCount) 
{ 
   int pixelSize = (int)Math.Log((double)bitCount); 
   return (bmp.Width * pixelSize + pixelSize & ~3) * bmp.Height; 
} 
 
private int GetBitmapScanRowSize(int bmpSize, int stride, int width) 
{ 
   return bmpSize / (stride / width); 
} 
 
public void CaptureFrame_Helper(object sender, EventArgs e) 
{ 
   // set result 
   _result = true; 
} 
 
static class LEAD_VARS 
{ 
   public const string MediaDir = @"C:\LEADTOOLS23\Media"; 
}

Requirements

Target Platforms

Reference

SampleTarget Class

SampleTarget Members

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Help Version 23.0.2024.2.29

Leadtools.Multimedia Assembly

Introduction

Getting Started

Namespaces

Leadtools.Multimedia Namespace

Leadtools.Multimedia.Common Namespace

Assemblies