How to choose a video capture device?

Hello!

I'm programing with 3 webcams to build preview videos and then take 3 pictures from each one. My developing environment is visual studio c++ 2010 express/ clr/ windows forms app.

I can already successfully get three preview videos on my pc. But I'm facing with a big problem: when I connect my webcams to another computer using the same code, the capturing has an error (program breaks or showing videos in a different order).

After I tested this on several computers,
I finally found the reason. It is when the webcams are connected to another pc, the new pc may get a new order of them when the new pc counts the devices (Which means they were on my pc as usb-device 1, 2, 3; they are on the new pc as usb-device 2, 1, 3). But I need to use the webcams in the order like before. Webcam1 on pictureBox1, webcam2 on pBox2, and webcam3 on pBox3. And I would like my code to be generally useful, whatever on which pc and with any webcams.

What also means, I want to choose the webcams in an "user-wanted" order on the window(of 3 pictureBoxes). Now I'm thinking of one way to solve this, namely to put a comboBox under each pictureBox, which are used to choose the device for each pictureBox. But I don't know how to realize that. Could you please help me? Or do you have a better idea to prevent the problem???

What may also be very important: Could it be wrong with my counting devices method in the CamShow.cpp? Should I make some correctors there?

Any answers would be appreciated!

My recently code is:

Form.h:

private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
	CamShow test1;
        CamShow test2;
        CamShow test3;

	button1->Enabled=false; 
        
        hr = test1.InitComLib();
	hr = test1.CaptureVideo(1);
	System::Drawing::Rectangle rc = pictureBox1->ClientRectangle;
	hr = test1.pVW->put_Owner(OAHWND(this->pictureBox1->Handle.ToInt64()));

hr = test1.pVW->put_WindowStyle( WS_CHILD | WS_CLIPSIBLINGS | WS_CLIPCHILDREN );
hr = test1.pVW->SetWindowPosition( 0, 0, rc.Right, rc.Bottom );
hr = test1.pMC->Run();

        test1.ControlRelease();
	test1.EventRelease();
	test1.GraphBuilderRelease();
        test1.CoUnini();

        hr = test2.InitComLib();
        hr = test2.CaptureVideo(2);
	System::Drawing::Rectangle rc = pictureBox1->ClientRectangle;
	hr = test2.pVW->put_Owner(OAHWND(this->pictureBox1->Handle.ToInt64()));
        // IVideoWindow *pVW

hr = test2.pVW->put_WindowStyle( WS_CHILD | WS_CLIPSIBLINGS | WS_CLIPCHILDREN );
hr = test2.pVW->SetWindowPosition( 0, 0, rc.Right, rc.Bottom );
hr = test2.pMC->Run();

        test2.ControlRelease();
	test2.EventRelease();
	test2.GraphBuilderRelease();
        test2.CoUnini();

        hr = test3.InitComLib();
        hr= test3.CaptureVideo(3);
	System::Drawing::Rectangle rc = pictureBox1->ClientRectangle;
	hr = test3.pVW->put_Owner(OAHWND(this->pictureBox1->Handle.ToInt64()));

hr = test3.pVW->put_WindowStyle( WS_CHILD | WS_CLIPSIBLINGS | WS_CLIPCHILDREN );
hr = test3.pVW->SetWindowPosition( 0, 0, rc.Right, rc.Bottom );
hr = test3.pMC->Run();

        test3.ControlRelease();
	test3.EventRelease();
	test3.GraphBuilderRelease();
        test3.CoUnini();
}

CamShow.cpp:

I give the most relevant code-sections to my problem here. And the declarations of variables functions are in CamShow.h, which I don't need to copy here for you I think ;).

#include "stdafx.h"
#include <DShow.h>
#include <Windows.h>
#include <comdef.h>
#include "CamShow.h"

CamShow::CamShow() {...}
CamShow::~CamShow() {}

HRESULT CamShow::InitComLib()
	{
		HRESULT hr = NULL;
		hr = CoInitialize(NULL);
		return hr;
	}
HRESULT CamShow::CaptureVideo(int NO)
	{
		HRESULT hr;
		IBaseFilter *pSrcFilter=NULL;

		// Get DirectShow interfaces
		hr = GetInterfaces();
		if (FAILED(hr))
		{
			Msg(TEXT("error get interfaces: hr=0x%x"), hr);
			return hr;
		}

                // Attach the filter graph to the capture graph
		hr = pCGB2->SetFiltergraph(pGraphBuilder); //pCGB2: ICaptureGraphBuilder2 *pCGB2 = NULL;
		if (FAILED(hr))
		{
			Msg(TEXT("error Set Filtergraph: hr=0x%x"), hr);
			return hr;
		}

                // Use the system device enumerator and class enumerator to find
             // a video capture/preview device, such as a desktop USB video camera.
		hr = FindCaptureDevice(&pSrcFilter, NO); 
		if (FAILED(hr))
		{
               // Don't display a message because FindCaptureDevice will handle it
			return hr;
		}

                // Add Capture filter to our graph. 
		hr = pGraphBuilder->AddFilter(pSrcFilter, L"Capture Filter");
		if (FAILED(hr))
		{
			Msg(TEXT("Couldn't add the capture filter to the graph!  hr=0x%x\r\n\r\n") 
            TEXT("If you have a working video capture device, please make sure\r\n")
            TEXT("that it is connected and is not being used by another application.\r\n\r\n")
            TEXT("The sample will now close."), hr);
                        pSrcFilter->Release();
			return hr;
		}

		// Render the preview pin on the video capture filter
                hr = pCGB2->RenderStream (&PIN_CATEGORY_PREVIEW, &MEDIATYPE_Video,				          pSrcFilter, NULL, NULL);
		if (FAILED(hr))
		{
			Msg(TEXT("Couldn't render the video capture stream.  hr=0x%x\r\n"), hr);
			pSrcFilter->Release();
			return hr;
		}

// Now that the filter has been added to the graph and we have
// rendered its stream, we can release this reference to the filter.	
pSrcFilter->Release();
		

		// Set video window style and position		
                hr = intSetupVideoWindow();
		if (FAILED(hr))
		{
			Msg(TEXT"Couldn't initialize video window!  hr=0x%x"),hr);
			return hr;
		}

		// Start previewing video data
                hr = pMC->Run();  // IMediaControl *pMC
                if (FAILED(hr))
                {
                  Msg(TEXT("Couldn't run the graph!  hr=0x%x"), hr);
                  return hr;
                }

                // Remember current state
                psCurrent = Running;
        
                return S_OK;	
}

HRESULT CamShow::FindCaptureDevice(IBaseFilter ** ppSrcFilter, int NO)
	{
		HRESULT hr = S_OK;
		IBaseFilter * pSrc = NULL;
		IMoniker* pMoniker = NULL;
		ULONG cFetched;
		int DevNo=0;

		IEnumMoniker *pClassEnum = NULL;
		ICreateDevEnum *pDevEnum =NULL;

		if (!ppSrcFilter)  return E_POINTER; 		
		
                // Create the system device enumerator
		hr = CoCreateInstance (CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC,
					IID_ICreateDevEnum, (void **) &pDevEnum);
		if (FAILED(hr))
		{
		Msg(TEXT("Couldn't create system enumerator!  hr=0x%x"), hr);		        }
	
		 // Create an enumerator for the video capture devices
		if (SUCCEEDED(hr))
		{
              hr = pDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory, &pClassEnum, 0);
			if (FAILED(hr))
			{
		        Msg(TEXT("Couldn't create class enumerator!  hr=0x%x"), hr);			}
			pDevEnum->Release();
		}

		if (SUCCEEDED(hr))
		{
		// If there are no enumerators for the requested type, then 
		// CreateClassEnumerator will succeed, but pClassEnum will be NULL.			if (pClassEnum == NULL)
			{
				MessageBox(ghApp,TEXT("No video capture device was detected.\r\n\r\n")
				TEXT("This sample requires a video capture device, such as a USB WebCam,\r\n")
				TEXT("to be installed and working properly.  The sample will now close."),
				TEXT("No Video Capture Hardware"), MB_OK | MB_ICONINFORMATION);				
                         hr = E_FAIL;
			}
		}


// This section counts the webcam devices on the computer!! 
		while (pClassEnum->Next(1, &pMoniker, &cFetched) == S_OK)
		{	
			IPropertyBag *pBag = NULL;
                        BSTR sName;
			VARIANT var;
			VariantInit(&var);
	hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag, (void **)&pBag);

			 hr = pBag->Read(L"FriendlyName", &var, 0); 
			 sName = var.bstrVal; // Get the name, but not to be used
			 // Count the devices and give them the number in the order:1, 2, 3, ...
                         DevNo++;
			 VariantClear(&var);

			 if (SUCCEEDED(hr))
			 {
				 if (DevNo==NO) // I think this condition is problematic and kritic. What I thought is to get webcam N on pictureBox N, because I thought the devices should be counted in a same order on different PCs, that's wrong acturally.
		           { 
              // Bind Moniker to a filter object for every webcam 
	      hr = pMoniker->BindToObject(0, 0, IID_IBaseFilter, (void **)&pSrc);
	      if (FAILED(hr))
              return hr;
              
              pBag->Release();                 
	      pMoniker->Release();                 
              break; 
			   }
			 }

		}

        // Copy the found filter pointer to the output parameter.     
        if (SUCCEEDED(hr))
        {
	  *ppSrcFilter = pSrc;
	  (*ppSrcFilter)->AddRef();
	}


	return hr;
       }

......(Other functions)

I hope I've explained my problem clearly. If anything is not clear for you, just tell me and I'm going to answer you and improve my question.

Thanks for helping!

Tags: C#, C++/CLI, Windows Forms, DirectShow