Getting multiple pictures with SampleGrabber

Sample code

The following sample code shows how to use VMR9.

This sample saves three image files from a single mpeg video file. I hope this helps you find out how to get multiple frames from a video file.

#include <stdio.h>

#include <dshow.h>
#include <qedit.h> // for SampleGrabber

#define	FILENAME L"C:\\DXSDK\\Samples\\Media\\butterfly.mpg"

int
main()
{
 IGraphBuilder *pGraphBuilder;
 IMediaControl *pMediaControl;

 IBaseFilter *pSampleGrabberFilter;
 ISampleGrabber *pSampleGrabber;
 AM_MEDIA_TYPE am_media_type;

 // initialize COM
 CoInitialize(NULL);

 // create FilterGraph
 CoCreateInstance(CLSID_FilterGraph,
	NULL,
	CLSCTX_INPROC,
	IID_IGraphBuilder,
	(LPVOID *)&pGraphBuilder);

 // create SampleGrabber(Filter)
 CoCreateInstance(CLSID_SampleGrabber,
	 NULL,
	 CLSCTX_INPROC,
	 IID_IBaseFilter,
	 (LPVOID *)&pSampleGrabberFilter);

 // get ISampleGrabber interface from Filter
 pSampleGrabberFilter->QueryInterface(IID_ISampleGrabber,
	 (LPVOID *)&pSampleGrabber);

 // determine the format for connecting SampleGrabber.
 // You can configure the SampleGrabber insertion place
 // by changing the values in this structure.
 // If you use the values in this sample,
 // you can get the video frame data right before
 // it is displayed.
 ZeroMemory(&am_media_type, sizeof(am_media_type));
 am_media_type.majortype = MEDIATYPE_Video;
 am_media_type.subtype = MEDIASUBTYPE_RGB24;
 am_media_type.formattype = FORMAT_VideoInfo;
 pSampleGrabber->SetMediaType(&am_media_type);

 // add SampleGrabber Filter to the Graph
 pGraphBuilder->AddFilter(pSampleGrabberFilter,
	 L"Sample Grabber");

 // get MediaControl interface
 pGraphBuilder->QueryInterface(IID_IMediaControl,
	(LPVOID *)&pMediaControl);

 // create Graph.
 // Graph that contains SampleGrabber
 // will be created automatically.
 pMediaControl->RenderFile(FILENAME);

 // Get connection information.
 // This must be done after the Graph is created
 // by RenderFile.
 pSampleGrabber->GetConnectedMediaType(&am_media_type);
 VIDEOINFOHEADER *pVideoInfoHeader =
     (VIDEOINFOHEADER *)am_media_type.pbFormat;

 // Print the width and height of the image.
 // This is just to make the sample understandable.
 // This is not a required feature.
 printf("size = %dx%d\n",
	 pVideoInfoHeader->bmiHeader.biWidth,
	 pVideoInfoHeader->bmiHeader.biHeight);

 // Print the data size.
 // This is just for understanding too.
 printf("sample size = %d\n",
	 am_media_type.lSampleSize);

 // Configure SampleGrabber to do grabbing.
 // Buffer data can not be obtained if you
 // do not use SetBufferSamples.
 // You can use SetBufferSamples after Run() too.
 pSampleGrabber->SetBufferSamples(TRUE);

 // start playing
 pMediaControl->Run();

 int i;
 for (i = 0; i < 3; i++) {
   // block execution
   MessageBox(NULL,
	"Block Execution",
	"Block",
	MB_OK);
   // BITMAP will be saved after OK is pressed

   // prepare buffer
   long nBufferSize = am_media_type.lSampleSize;
   long *pBuffer = (long *)malloc(nBufferSize);

   // grab image data.
   pSampleGrabber->GetCurrentBuffer(&nBufferSize,
       pBuffer);

   //
   // Save image data as Bitmap.
   // This is just to make this sample easily understandable.
   //
   HANDLE fh;
   BITMAPFILEHEADER bmphdr;
   DWORD nWritten;

   memset(&bmphdr, 0, sizeof(bmphdr));

   bmphdr.bfType = ('M' << 8) | 'B';
   bmphdr.bfSize = sizeof(bmphdr) + sizeof(BITMAPINFOHEADER) + nBufferSize;
   bmphdr.bfOffBits = sizeof(bmphdr) + sizeof(BITMAPINFOHEADER);

   char filename[128];
   _snprintf(filename, sizeof(filename),
             "result%d.bmp", i);
   fh = CreateFile(filename,
                   GENERIC_WRITE, 0, NULL,
                   CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
   WriteFile(fh, &bmphdr, sizeof(bmphdr), &nWritten, NULL);
   WriteFile(fh,
       &pVideoInfoHeader->bmiHeader,
       sizeof(BITMAPINFOHEADER), &nWritten, NULL);
   WriteFile(fh, pBuffer, nBufferSize, &nWritten, NULL);
   CloseHandle(fh);

   free(pBuffer);
 } // end of for loop

 pMediaControl->Stop();

 // release
 pSampleGrabber->Release();
 pSampleGrabberFilter->Release();
 pMediaControl->Release();
 pGraphBuilder->Release();

 // finalize COM
 CoUninitialize();

 return 0;
}

This sample saves bitmap images as , result0.bmp, result1.bmp, result2.bmp. These bitmap files will be saved when you press the OK button on the MessageBox dialog. Please check the bitmap files created after executing this test application.