Camera Control needed for Tablet

[TimStone]

A camera control to go along with the touch features added to FWH would be very helpful.

It would be nice to simply press a button to activate the tablet camera, and when the picture is taken, it can be saved to a location defined within our program.

Right now, I could leave a program, activate the camera, take the picture, and then move it to the location. However it would be nice to have a control button within my program to take the photo, and then to have it auto save to my desired location.

Thanks for considering this.

[Gale FORd]

Yes, I have been working on this also.
The twebcam class doesn't work for most tablets. It seems that some tablets only have DirectShow built in.
I tried finding twain driver for webcam but most of them are .net now.
If we could adapt twebcam class or create new one to use DirectShow that would be great.

I found a workaround using 2 different methods.

Method 1 was to use the builtin camera app. I would start the camera app (or bring to top if already running) and place "Press here when done" button on screen. They take the pictures and then press my done button. Then it collects the images and I moves them where I want.
This has been working pretty well but you lose some control over the process.
If you need it I have more information on using Windows 8/10 camera app.
Here is how I call it with Windows 10 and 8

Code: Select all  Expand view

         case ::oMain:cWinVer == '10'  // GDF Mod Windows 10 8/24/2015
            cPathInfo := 'shell:AppsFolder\Microsoft.WindowsCamera_8wekyb3d8bbwe!App'
            lMetro := .t.
         case ::oMain:cWinVer == '8'
            cPathInfo := 'shell:AppsFolder\Microsoft.MoCamera_cw5n1h2txyewy!Microsoft.Camera'
            lMetro := .t.

// Then do something like
if lMetro
   WinExec( 'C:\Windows\explorer.exe '+cPathInfo, 0 )
else
..
endif
 

Method 2 is using a little program CommandCam.exe. This app can capture images from webcam from command line. It has command line options you can use.
Users did not like this approach as much. You could put a delay before capture but still hard to sync image position before capture.

[Gale FORd]

FYI CommandCam provides source code to use Microsoft’s DirectShow API. It would have to be converted from .net
https://batchloaf.wordpress.com/commandcam/
The program is very small only 66k

[Antonio Linares]

First steps using Borland (some changes are required for MSVC)

Code: Select all  Expand view

#include "FiveWin.ch"

function Main()

   DShowCamera()

return nil

#pragma BEGINDUMP

#include <dshow.h>
#include <uuids.h>

HB_FUNC( DSHOWCAMERA )
{
   HRESULT hr;
   ICreateDevEnum *pDevEnum = NULL;
   IEnumMoniker *pEnum = NULL;
   IMoniker *pMoniker = NULL;
   IPropertyBag *pPropBag = NULL;
   IGraphBuilder *pGraph = NULL;
   ICaptureGraphBuilder2 *pBuilder = NULL;
   IBaseFilter *pCap = NULL;
   IBaseFilter *pSampleGrabberFilter = NULL;
   IBaseFilter *pNullRenderer = NULL;
   IMediaControl *pMediaControl = NULL;
   char *pBuffer = NULL;

   hr = CoInitializeEx( NULL, COINIT_MULTITHREADED );

   if( hr != S_OK )
      MessageBox( 0, "CoInitializeEx error", "ok", 0 );

   hr = CoCreateInstance( &CLSID_FilterGraph, NULL,
              CLSCTX_INPROC_SERVER, &IID_IGraphBuilder,
              ( void ** ) &pGraph );
           
   if( hr != S_OK )
      MessageBox( 0, "CoCreateInstance error", "ok", 0 );
     
   if( pGraph != NULL )
      MessageBox( 0, "pGraph seems ok", "ok", 0 );
     
    hr = CoCreateInstance( &CLSID_CaptureGraphBuilder2, NULL,
            CLSCTX_INPROC_SERVER, &IID_ICaptureGraphBuilder2,
            ( void ** ) &pBuilder );      

   if( hr != S_OK )
      MessageBox( 0, "CoCreateInstance 2 error", "ok", 0 );

   if( pBuilder != NULL )
      MessageBox( 0, "pBuilder seems ok", "ok", 0 );
}

#pragma ENDDUMP

[Antonio Linares]

Next step:

Code: Select all  Expand view

#include "FiveWin.ch"

function Main()

   DShowCamera()

return nil

#pragma BEGINDUMP

#include <dshow.h>
#include <uuids.h>

HB_FUNC( DSHOWCAMERA )
{
   HRESULT hr;
   ICreateDevEnum *pDevEnum = NULL;
   IEnumMoniker *pEnum = NULL;
   IMoniker *pMoniker = NULL;
   IPropertyBag *pPropBag = NULL;
   IGraphBuilder *pGraph = NULL;
   ICaptureGraphBuilder2 *pBuilder = NULL;
   IBaseFilter *pCap = NULL;
   IBaseFilter *pSampleGrabberFilter = NULL;
   IBaseFilter *pNullRenderer = NULL;
   IMediaControl *pMediaControl = NULL;
   char *pBuffer = NULL;

   hr = CoInitializeEx( NULL, COINIT_MULTITHREADED );

   if( hr != S_OK )
      MessageBox( 0, "CoInitializeEx error", "ok", 0 );

   hr = CoCreateInstance( &CLSID_FilterGraph, NULL,
              CLSCTX_INPROC_SERVER, &IID_IGraphBuilder,
              ( void ** ) &pGraph );
           
   if( hr != S_OK )
      MessageBox( 0, "CoCreateInstance error", "ok", 0 );
     
   if( pGraph != NULL )
      MessageBox( 0, "pGraph seems ok", "ok", 0 );
     
    hr = CoCreateInstance( &CLSID_CaptureGraphBuilder2, NULL,
            CLSCTX_INPROC_SERVER, &IID_ICaptureGraphBuilder2,
            ( void ** ) &pBuilder );      

   if( hr != S_OK )
      MessageBox( 0, "CoCreateInstance 2 error", "ok", 0 );

   if( pBuilder != NULL )
      MessageBox( 0, "pBuilder seems ok", "ok", 0 );
     
    hr = ( ( ICaptureGraphBuilder * ) pBuilder )->lpVtbl->SetFiltergraph( pBuilder, pGraph );
   
    if( hr != S_OK )
        MessageBox( 0, "Could not attach capture graph builder to graph", "ok", 0 );      
}

#pragma ENDDUMP

[TimStone]

I use xHarbour ( .com ) and MSVC, not Borland ...

[Antonio Linares]

Tim,

Yes, I know it

First we need to make it work, then we may be able to port it to MSVC

[TimStone]

OK but I haven't had Borland installed here for many years so I can't really help.

[Antonio Linares]

Tim,

This version works fine with MSVC. This is a work in progress.

You have to link MS strmiids.lib

Code: Select all  Expand view

#include "FiveWin.ch"

function Main()

   DShowCamera()

return nil

#pragma BEGINDUMP

#include <dshow.h>
#include <uuids.h>
#include <objbase.h>

HB_FUNC( DSHOWCAMERA )
{
   HRESULT hr;
   ICreateDevEnum *pDevEnum = NULL;
   IEnumMoniker *pEnum = NULL;
   IMoniker *pMoniker = NULL;
   IPropertyBag *pPropBag = NULL;
   IGraphBuilder *pGraph = NULL;
   ICaptureGraphBuilder2 *pBuilder = NULL;
   IBaseFilter *pCap = NULL;
   IBaseFilter *pSampleGrabberFilter = NULL;
   IBaseFilter *pNullRenderer = NULL;
   IMediaControl *pMediaControl = NULL;
   char *pBuffer = NULL;

   hr = CoInitializeEx( NULL, COINIT_MULTITHREADED );

   if( hr != S_OK )
      MessageBox( 0, "CoInitializeEx error", "ok", 0 );

   hr = CoCreateInstance( CLSID_FilterGraph, NULL,
              CLSCTX_INPROC_SERVER, IID_IGraphBuilder,
              ( void ** ) &pGraph );
           
   if( hr != S_OK )
      MessageBox( 0, "CoCreateInstance error", "ok", 0 );
     
   if( pGraph != NULL )
      MessageBox( 0, "pGraph seems ok", "ok", 0 );
     
    hr = CoCreateInstance( CLSID_CaptureGraphBuilder2, NULL,
            CLSCTX_INPROC_SERVER, IID_ICaptureGraphBuilder2,
            ( void ** ) &pBuilder );      

   if( hr != S_OK )
      MessageBox( 0, "CoCreateInstance 2 error", "ok", 0 );

   if( pBuilder != NULL )
      MessageBox( 0, "pBuilder seems ok", "ok", 0 );
     
    hr = ( ( ICaptureGraphBuilder * ) pBuilder )->SetFiltergraph( pGraph );
   
    if( hr != S_OK )
        MessageBox( 0, "Could not attach capture graph builder to graph", "ok", 0 );
     
    hr = CoCreateInstance( CLSID_SystemDeviceEnum, NULL,
            CLSCTX_INPROC_SERVER, IID_PPV_ARGS( &pDevEnum ) );
         
    if( hr != S_OK )
        MessageBox( 0, "Could not crerate system device enumerator", "ok", 0 );      
}

#pragma ENDDUMP

[Antonio Linares]

I appreciate if you can test it on your tablet.

It does nothing yet. We are just converting code, step by step.

[Antonio Linares]

I am going to code it for MSVC so you can help me to test it

[Antonio Linares]

This version should report the camera name:

Code: Select all  Expand view

#include "FiveWin.ch"

function Main()

   DShowCamera()

return nil

#pragma BEGINDUMP

#include <dshow.h>
#include <uuids.h>
#include <objbase.h>

HB_FUNC( DSHOWCAMERA )
{
   HRESULT hr;
   ICreateDevEnum *pDevEnum = NULL;
   IEnumMoniker *pEnum = NULL;
   IMoniker *pMoniker = NULL;
   IPropertyBag *pPropBag = NULL;
   IGraphBuilder *pGraph = NULL;
   ICaptureGraphBuilder2 *pBuilder = NULL;
   IBaseFilter *pCap = NULL;
   IBaseFilter *pSampleGrabberFilter = NULL;
   IBaseFilter *pNullRenderer = NULL;
   IMediaControl *pMediaControl = NULL;
   char *pBuffer = NULL;
   VARIANT var;
    int n = 0;
    int device_number = 0;
    char device_name[ 100 ];
   char char_buffer[100];

   strcpy( device_name, "" );

   hr = CoInitializeEx( NULL, COINIT_MULTITHREADED );

   if( hr != S_OK )
      MessageBox( 0, "CoInitializeEx error", "ok", 0 );

   hr = CoCreateInstance( CLSID_FilterGraph, NULL,
              CLSCTX_INPROC_SERVER, IID_IGraphBuilder,
              ( void ** ) &pGraph );
           
   if( hr != S_OK )
      MessageBox( 0, "CoCreateInstance error", "ok", 0 );
     
   if( pGraph != NULL )
      MessageBox( 0, "pGraph seems ok", "ok", 0 );
     
    hr = CoCreateInstance( CLSID_CaptureGraphBuilder2, NULL,
            CLSCTX_INPROC_SERVER, IID_ICaptureGraphBuilder2,
            ( void ** ) &pBuilder );      

   if( hr != S_OK )
      MessageBox( 0, "CoCreateInstance 2 error", "ok", 0 );

   if( pBuilder != NULL )
      MessageBox( 0, "pBuilder seems ok", "ok", 0 );
     
    hr = ( ( ICaptureGraphBuilder * ) pBuilder )->SetFiltergraph( pGraph );
   
    if( hr != S_OK )
        MessageBox( 0, "Could not attach capture graph builder to graph", "ok", 0 );
     
    hr = CoCreateInstance( CLSID_SystemDeviceEnum, NULL,
            CLSCTX_INPROC_SERVER, IID_PPV_ARGS( &pDevEnum ) );
         
    if( hr != S_OK )
        MessageBox( 0, "Could not crerate system device enumerator", "ok", 0 );
     
    hr = pDevEnum->CreateClassEnumerator(
                    CLSID_VideoInputDeviceCategory, &pEnum, 0 );
               
    if( hr != S_OK )
        MessageBox( 0, "No video devices found", "ok", 0 );      
     
    while(1)
    {
        // Access next device
        hr = pEnum->Next(1, &pMoniker, NULL);
        if( hr == S_OK )
            n++; // increment device count
      else  
         break;
       
        // If device was specified by name rather than number...
        if( device_number == 0 )
        {
            // Get video input device name
            hr = pMoniker->BindToStorage(0, 0, IID_PPV_ARGS(&pPropBag));
            if (hr == S_OK)
            {
                // Get current device name
                VariantInit(&var);
                hr = pPropBag->Read(L"FriendlyName", &var, 0);
               
                // Convert to a normal C string, i.e. char*
                sprintf(char_buffer, "%ls", var.bstrVal);
                VariantClear(&var);
                pPropBag->Release();
                pPropBag = NULL;
               
                // Exit loop if current device name matched devname
            MessageBox( 0, char_buffer, "device_name", 0 );
           
                if (strcmp(device_name, char_buffer) == 0) break;
            }
            else
         {
                MessageBox( 0, "Error getting device names", "ok", 0 );
            exit;
         }  
        }
        else if (n >= device_number) break;
    }      
}

#pragma ENDDUMP

[Antonio Linares]

More

You will get two warnings with verbose info that you can safely ignore

Code: Select all  Expand view

#include "FiveWin.ch"

function Main()

   DShowCamera()

return nil

#pragma BEGINDUMP

#include <dshow.h>
#include <uuids.h>
#include <objbase.h>

#import "qedit.dll" raw_interfaces_only named_guids

EXTERN_C const CLSID CLSID_NullRenderer;
EXTERN_C const CLSID CLSID_SampleGrabber;

HB_FUNC( DSHOWCAMERA )
{
   HRESULT hr;
   ICreateDevEnum *pDevEnum = NULL;
   IEnumMoniker *pEnum = NULL;
   IMoniker *pMoniker = NULL;
   IPropertyBag *pPropBag = NULL;
   IGraphBuilder *pGraph = NULL;
   ICaptureGraphBuilder2 *pBuilder = NULL;
   IBaseFilter *pCap = NULL;
   IBaseFilter *pSampleGrabberFilter = NULL;
   IBaseFilter *pNullRenderer = NULL;
   IMediaControl *pMediaControl = NULL;
   char *pBuffer = NULL;
   VARIANT var;
    int n = 0;
    int device_number = 0;
    char device_name[ 100 ];
   char char_buffer[100];
   DexterLib::ISampleGrabber *pSampleGrabber = NULL;

   strcpy( device_name, "" );

   hr = CoInitializeEx( NULL, COINIT_MULTITHREADED );

   if( hr != S_OK )
      MessageBox( 0, "CoInitializeEx error", "ok", 0 );

   hr = CoCreateInstance( CLSID_FilterGraph, NULL,
              CLSCTX_INPROC_SERVER, IID_IGraphBuilder,
              ( void ** ) &pGraph );
           
   if( hr != S_OK )
      MessageBox( 0, "CoCreateInstance error", "ok", 0 );
     
   if( pGraph != NULL )
      MessageBox( 0, "pGraph seems ok", "ok", 0 );
     
    hr = CoCreateInstance( CLSID_CaptureGraphBuilder2, NULL,
            CLSCTX_INPROC_SERVER, IID_ICaptureGraphBuilder2,
            ( void ** ) &pBuilder );      

   if( hr != S_OK )
      MessageBox( 0, "CoCreateInstance 2 error", "ok", 0 );

   if( pBuilder != NULL )
      MessageBox( 0, "pBuilder seems ok", "ok", 0 );
     
    hr = ( ( ICaptureGraphBuilder * ) pBuilder )->SetFiltergraph( pGraph );
   
    if( hr != S_OK )
        MessageBox( 0, "Could not attach capture graph builder to graph", "ok", 0 );
     
    hr = CoCreateInstance( CLSID_SystemDeviceEnum, NULL,
            CLSCTX_INPROC_SERVER, IID_PPV_ARGS( &pDevEnum ) );
         
    if( hr != S_OK )
        MessageBox( 0, "Could not crerate system device enumerator", "ok", 0 );
     
    hr = pDevEnum->CreateClassEnumerator(
                    CLSID_VideoInputDeviceCategory, &pEnum, 0 );
               
    if( hr != S_OK )
        MessageBox( 0, "No video devices found", "ok", 0 );      
     
    while(1)
    {
        // Access next device
        hr = pEnum->Next(1, &pMoniker, NULL);
        if( hr == S_OK )
            n++; // increment device count
      else  
         break;
       
        // If device was specified by name rather than number...
        if( device_number == 0 )
        {
            // Get video input device name
            hr = pMoniker->BindToStorage(0, 0, IID_PPV_ARGS(&pPropBag));
            if (hr == S_OK)
            {
                // Get current device name
                VariantInit(&var);
                hr = pPropBag->Read(L"FriendlyName", &var, 0);
               
                // Convert to a normal C string, i.e. char*
                sprintf(char_buffer, "%ls", var.bstrVal);
                VariantClear(&var);
                pPropBag->Release();
                pPropBag = NULL;
               
                // Exit loop if current device name matched devname
            MessageBox( 0, char_buffer, "device_name", 0 );
           
                if (strcmp(device_name, char_buffer) == 0) break;
            }
            else
         {
                MessageBox( 0, "Error getting device names", "ok", 0 );
            break;
         }  
        }
        else if (n >= device_number) break;
    }  
   
    // Get video input device name
    hr = pMoniker->BindToStorage(0, 0, IID_PPV_ARGS(&pPropBag));
    VariantInit(&var);
    hr = pPropBag->Read(L"FriendlyName", &var, 0);
    MessageBoxW( 0, L"Capture device", var.bstrVal, 0 );
    VariantClear(&var);  
   
    // Create capture filter and add to graph
    hr = pMoniker->BindToObject(0, 0,
                    IID_IBaseFilter, (void**)&pCap);
               
    if( hr != S_OK )
      MessageBox( 0, "Could not create capture filter", "ok", 0 );  

    // Add capture filter to graph
    hr = pGraph->AddFilter(pCap, L"Capture Filter");
   
    if( hr != S_OK )
      MessageBox( 0, "Could not add capture filter to graph", "ok", 0 );

    // Create sample grabber filter
    hr = CoCreateInstance(CLSID_SampleGrabber, NULL,
        CLSCTX_INPROC_SERVER, IID_IBaseFilter,
        (void**)&pSampleGrabberFilter);
     
    if( hr != S_OK )
        MessageBox( 0, "Could not create Sample Grabber filter", "ok", 0 );

    // Query the ISampleGrabber interface of the sample grabber filter
    hr = pSampleGrabberFilter->QueryInterface(
            DexterLib::IID_ISampleGrabber, (void**)&pSampleGrabber);
         
    if( hr != S_OK )
        MessageBox( 0, "Could not get ISampleGrabber interface to sample grabber filter", "ok", 0 );

   MessageBox( 0, "done", "ok", 0 );  
}

#pragma ENDDUMP

[TimStone]

Tried building that with MSVC and get at least 102 errors ...

[Antonio Linares]

This version shows the camara window

Code: Select all  Expand view

#include "FiveWin.ch"

function Main()

   DShowCamera()

return nil

#pragma BEGINDUMP

#include <dshow.h>
#include <uuids.h>
#include <objbase.h>

#import "qedit.dll" raw_interfaces_only named_guids

EXTERN_C const CLSID CLSID_NullRenderer;
EXTERN_C const CLSID CLSID_SampleGrabber;

HB_FUNC( DSHOWCAMERA )
{
   HRESULT hr;
   ICreateDevEnum *pDevEnum = NULL;
   IEnumMoniker *pEnum = NULL;
   IMoniker *pMoniker = NULL;
   IPropertyBag *pPropBag = NULL;
   IGraphBuilder *pGraph = NULL;
   ICaptureGraphBuilder2 *pBuilder = NULL;
   IBaseFilter *pCap = NULL;
   IBaseFilter *pSampleGrabberFilter = NULL;
   IBaseFilter *pNullRenderer = NULL;
   IMediaControl *pMediaControl = NULL;
   char *pBuffer = NULL;
   VARIANT var;
    int n = 0;
    int device_number = 0;
    char device_name[ 100 ];
   char char_buffer[100];
   DexterLib::ISampleGrabber *pSampleGrabber = NULL;

   strcpy( device_name, "" );

   hr = CoInitializeEx( NULL, COINIT_MULTITHREADED );

   if( hr != S_OK )
      MessageBox( 0, "CoInitializeEx error", "ok", 0 );

   hr = CoCreateInstance( CLSID_FilterGraph, NULL,
              CLSCTX_INPROC_SERVER, IID_IGraphBuilder,
              ( void ** ) &pGraph );
           
   if( hr != S_OK )
      MessageBox( 0, "CoCreateInstance error", "ok", 0 );
     
    hr = CoCreateInstance( CLSID_CaptureGraphBuilder2, NULL,
            CLSCTX_INPROC_SERVER, IID_ICaptureGraphBuilder2,
            ( void ** ) &pBuilder );      

   if( hr != S_OK )
      MessageBox( 0, "CoCreateInstance 2 error", "ok", 0 );

    hr = ( ( ICaptureGraphBuilder * ) pBuilder )->SetFiltergraph( pGraph );
   
    if( hr != S_OK )
        MessageBox( 0, "Could not attach capture graph builder to graph", "ok", 0 );
     
    hr = CoCreateInstance( CLSID_SystemDeviceEnum, NULL,
            CLSCTX_INPROC_SERVER, IID_PPV_ARGS( &pDevEnum ) );
         
    if( hr != S_OK )
        MessageBox( 0, "Could not crerate system device enumerator", "ok", 0 );
     
    hr = pDevEnum->CreateClassEnumerator(
                    CLSID_VideoInputDeviceCategory, &pEnum, 0 );
               
    if( hr != S_OK )
        MessageBox( 0, "No video devices found", "ok", 0 );      
     
    while(1)
    {
        // Access next device
        hr = pEnum->Next(1, &pMoniker, NULL);
        if( hr == S_OK )
            n++; // increment device count
      else  
         break;
       
        // If device was specified by name rather than number...
        if( device_number == 0 )
        {
            // Get video input device name
            hr = pMoniker->BindToStorage(0, 0, IID_PPV_ARGS(&pPropBag));
            if (hr == S_OK)
            {
                // Get current device name
                VariantInit(&var);
                hr = pPropBag->Read(L"FriendlyName", &var, 0);
               
                // Convert to a normal C string, i.e. char*
                sprintf(char_buffer, "%ls", var.bstrVal);
                VariantClear(&var);
                pPropBag->Release();
                pPropBag = NULL;
               
                // Exit loop if current device name matched devname
            // MessageBox( 0, char_buffer, "device_name", 0 );
           
                if (strcmp(device_name, char_buffer) == 0) break;
            }
            else
         {
                MessageBox( 0, "Error getting device names", "ok", 0 );
            break;
         }  
        }
        else if (n >= device_number) break;
    }  
   
    // Get video input device name
    hr = pMoniker->BindToStorage(0, 0, IID_PPV_ARGS(&pPropBag));
    VariantInit(&var);
    hr = pPropBag->Read(L"FriendlyName", &var, 0);
    // MessageBoxW( 0, L"Capture device", var.bstrVal, 0 );
    VariantClear(&var);  
   
    // Create capture filter and add to graph
    hr = pMoniker->BindToObject(0, 0,
                    IID_IBaseFilter, (void**)&pCap);
               
    if( hr != S_OK )
      MessageBox( 0, "Could not create capture filter", "ok", 0 );  

    // Add capture filter to graph
    hr = pGraph->AddFilter(pCap, L"Capture Filter");
   
    if( hr != S_OK )
      MessageBox( 0, "Could not add capture filter to graph", "ok", 0 );

    // Create sample grabber filter
    hr = CoCreateInstance(CLSID_SampleGrabber, NULL,
        CLSCTX_INPROC_SERVER, IID_IBaseFilter,
        (void**)&pSampleGrabberFilter);
     
    if( hr != S_OK )
        MessageBox( 0, "Could not create Sample Grabber filter", "ok", 0 );

    // Query the ISampleGrabber interface of the sample grabber filter
    hr = pSampleGrabberFilter->QueryInterface(
            DexterLib::IID_ISampleGrabber, (void**)&pSampleGrabber);
         
    if( hr != S_OK )
        MessageBox( 0, "Could not get ISampleGrabber interface to sample grabber filter", "ok", 0 );

    // Enable sample buffering in the sample grabber filter
    hr = pSampleGrabber->SetBufferSamples(TRUE);
   
    if( hr != S_OK )
        MessageBox( 0, "Could not enable sample buffering in the sample grabber", "ok", 0 );

    // Set media type in sample grabber filter
    AM_MEDIA_TYPE mt;
    ZeroMemory(&mt, sizeof(AM_MEDIA_TYPE));
    mt.majortype = MEDIATYPE_Video;
    mt.subtype = MEDIASUBTYPE_RGB24;
    hr = pSampleGrabber->SetMediaType((DexterLib::_AMMediaType *)&mt);
   
    if( hr != S_OK )
        MessageBox( 0, "Could not set media type in sample grabber", "ok", 0 );

    // Add sample grabber filter to filter graph
    hr = pGraph->AddFilter(pSampleGrabberFilter, L"SampleGrab");
   
    if( hr != S_OK )
        MessageBox( 0, "Could not add Sample Grabber to filter graph", "ok", 0 );

    // Create Null Renderer filter
    hr = CoCreateInstance(CLSID_NullRenderer, NULL,
        CLSCTX_INPROC_SERVER, IID_IBaseFilter,
        (void**)&pNullRenderer);

   if( hr != S_OK )
        MessageBox( 0, "Could not create Null Renderer filter", "ok", 0 );

    // Add Null Renderer filter to filter graph
    hr = pGraph->AddFilter(pNullRenderer, L"NullRender");

   if( hr != S_OK )
        MessageBox( 0, "Could not add Null Renderer to filter graph", "ok", 0 );
     
   // Connect up the filter graph's capture stream
    hr = pBuilder->RenderStream(
        &PIN_CATEGORY_CAPTURE, &MEDIATYPE_Video,
        pCap,  pSampleGrabberFilter, pNullRenderer);
     
    if( hr != S_OK )
        MessageBox( 0, "Could not render capture video stream", "ok", 0 );

    hr = pBuilder->RenderStream(
                &PIN_CATEGORY_PREVIEW, &MEDIATYPE_Video,
                pCap, NULL, NULL);
   
   if (hr != S_OK && hr != VFW_S_NOPREVIEWPIN)
            MessageBox( 0, "Could not render preview video stream", "ok", 0 );

    // Get media control interfaces to graph builder object
    hr = pGraph->QueryInterface(IID_IMediaControl,
                    (void**)&pMediaControl);

   if( hr != S_OK )
      MessageBox( 0, "Could not get media control interface", "ok", 0 );

    // Run graph
    while(1)
    {
        hr = pMediaControl->Run();
       
        // Hopefully, the return value was S_OK or S_FALSE
        if (hr == S_OK) break; // graph is now running
        if (hr == S_FALSE) continue; // graph still preparing to run
       
        // If the Run function returned something else,
        // there must be a problem
        // fprintf(stderr, "Error: %u\n", hr);
        MessageBox( 0, "Could not run filter graph", "ok", 0 );
    }
   
   MessageBox( 0, "done", "ok", 0 );  
}

#pragma ENDDUMP