DSHOW的IMediaSample接口如何使用

[icesoft2000]

想得到DSHOW的IMediaSample接口的数据，如何做？

[ouyh12345]

IMediaSample::GetPointer

[icesoft2000]

IMediaSample如何与IGraphBuilder等建立关联？

[icesoft2000]

IMediaSample如何与IGraphBuilder、IMediaControl等建立关联？

播放功能已经实现，现在想得到数据研究一下。

[vocanicy]

在ISampleGrabberCB回调接口中的SampleCB函数
HRESULT SampleCB(
double SampleTime,
IMediaSample *pSample
);

#include <windows.h>
#include <streams.h>
#include <stdio.h>
#include <atlbase.h>
#include <qedit.h>
int GrabBitmaps(TCHAR * szFile);
HRESULT GetPin(IBaseFilter * pFilter, PIN_DIRECTION dirrequired,  int iNum, IPin **ppPin);
IPin *  GetInPin ( IBaseFilter *pFilter, int Num );
IPin *  GetOutPin( IBaseFilter *pFilter, int Num );
class CSampleGrabberCB : public ISampleGrabberCB {
public:
 STDMETHODIMP_(ULONG) AddRef() { return 2; }
 STDMETHODIMP_(ULONG) Release() { return 1; }
 STDMETHODIMP QueryInterface(REFIID riid, void ** ppv) {
  CheckPointer(ppv,E_POINTER);
  if( riid == IID_ISampleGrabberCB || riid == IID_IUnknown )  {
   *ppv = (void *) static_cast<ISampleGrabberCB*> ( this );
   return NOERROR;
  }
  return E_NOINTERFACE;
 }

 STDMETHODIMP SampleCB( double SampleTime, IMediaSample * pSample ) {return 0;}
 STDMETHODIMP BufferCB( double SampleTime, BYTE * pBuffer, long BufferSize ) {
  _tprintf(TEXT("Found a sample at %f s\t[%ld]\r\n"), SampleTime , BufferSize );
  return 0;
 }
}
int _tmain(int argc, TCHAR* argv[]) {
 if( argc != 2 || !argv || !argv[1] ) {
  _tprintf( TEXT("GrabBitmaps: You must specify a media filename!\r\n") );
  _tprintf( TEXT("Usage: GrabBitmaps Filename\r\n"));
  return 0;
 }
 CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);
 // Read the filename from the command line      
 TCHAR szFile[MAX_PATH];
 _tcsncpy(szFile, argv[1], MAX_PATH-1);
 szFile[MAX_PATH-1] = 0;      // Null-terminate
 int nSuccess = GrabBitmaps(szFile);
 CoUninitialize();
 return nSuccess;
}
int GrabBitmaps(TCHAR * szFile ) {
 USES_CONVERSION;
 CComPtr< ISampleGrabber > pGrabber;
 CComPtr< IBaseFilter >    pSource;
 CComPtr< IGraphBuilder >  pGraph;
 CComPtr< IVideoWindow >   pVideoWindow;
 HRESULT hr;
 if (!szFile) return -1;
 _tprintf(TEXT("Grabbing bitmaps from %s.\r\n"), szFile);
 
 // Create the sample grabber
 pGrabber.CoCreateInstance( CLSID_SampleGrabber );
 if( !pGrabber ) {
  _tprintf( TEXT("Could not create CLSID_SampleGrabber\r\n") );
  return -1;
 }
 CComQIPtr<IBaseFilter, &IID_IBaseFilter> pGrabberBase(pGrabber);
 
 // Create the file reader
 pSource.CoCreateInstance(CLSID_AsyncReader);
 if (!pSource) {
  _tprintf( TEXT("Could not create source filter\r\n") );
  return -1;
 }
 
 // Create the graph
 pGraph.CoCreateInstance(CLSID_FilterGraph);
 if( !pGraph ) {
  _tprintf( TEXT("Could not not create the graph\r\n") );
  return -1;
 }
 
 // Put them in the graph
 hr = pGraph->AddFilter( pSource, L"Source" );
 hr = pGraph->AddFilter( pGrabberBase, L"Grabber" );
 // Load the source
 CComQIPtr<IFileSourceFilter, &IID_IFileSourceFilter> pLoad(pSource);
 hr = pLoad->Load( T2W( szFile ), NULL );
 if (FAILED(hr)) {
  _tprintf( TEXT("Could not load the media file\r\n") );
  return -1;
 }
 CMediaType GrabType;
 GrabType.SetType(&MEDIATYPE_Audio);
 GrabType.SetSubtype(&MEDIASUBTYPE_PCM);
 GrabType.SetFormatType(&FORMAT_WaveFormatEx);
 hr = pGrabber->SetMediaType(&GrabType);
 // Get the output pin and the input pin
 CComPtr< IPin > pSourcePin;
 CComPtr< IPin > pGrabPin;
 pSourcePin = GetOutPin( pSource, 0 );
 pGrabPin   = GetInPin( pGrabberBase, 0 );
 // ... and connect them
 hr = pGraph->Connect( pSourcePin, pGrabPin );
 if( FAILED( hr ) ) {
  _tprintf( TEXT("Could not connect source filter to grabber\r\n") );
  return -1;
 }
 CComPtr <IPin> pGrabOutPin = GetOutPin( pGrabberBase, 0 );
 hr = pGraph->Render( pGrabOutPin );
 if( FAILED( hr ) ) {
  _tprintf( TEXT("Could not render grabber output pin\r\n") );
  return -1;
 }
 
 // Don't buffer the samples as they pass through
 hr = pGrabber->SetBufferSamples( FALSE );
 // Only grab one at a time, stop stream after grabbing one sample
 hr = pGrabber->SetOneShot(FALSE);
 // Set the callback, so we can grab the one sample
 CSampleGrabberCB CB;
 hr = pGrabber->SetCallback(&CB, 1);
 // Keep a useless clock from being instantiated....
 CComQIPtr<IMediaFilter, &IID_IMediaFilter> pFilter(pGraph);
 hr = pFilter->SetSyncSource(NULL);
 if (FAILED(hr)) printf("SetNoClock: Failed to set sync source!  hr=0x%x\n", hr);
 CComQIPtr<IVideoWindow, &IID_IVideoWindow> pWindow(pGraph);
 if (pWindow) hr = pWindow->put_AutoShow(OAFALSE);
 // activate the threads  
 CComQIPtr< IMediaControl, &IID_IMediaControl > pControl( pGraph );
 hr = pControl->Run( );
 // wait for the graph to settle
 CComQIPtr< IMediaEvent, &IID_IMediaEvent > pEvent( pGraph );
 long EvCode = 0;
 hr = pEvent->WaitForCompletion( INFINITE, &EvCode );
 
 _tprintf(TEXT("Sample grabbing complete.\r\n"));
 return 0;
}

HRESULT GetPin( IBaseFilter * pFilter, PIN_DIRECTION dirrequired, int iNum, IPin **ppPin) {
 CComPtr< IEnumPins > pEnum;
 *ppPin = NULL;
 HRESULT hr = pFilter->EnumPins(&pEnum);
 if(FAILED(hr))  return hr;
 ULONG ulFound;
 IPin *pPin;
 hr = E_FAIL;
 while (S_OK == pEnum->Next(1, &pPin, &ulFound)) {
  PIN_DIRECTION pindir = (PIN_DIRECTION)3;
  pPin->QueryDirection(&pindir);
  if (pindir == dirrequired) {
   if (iNum == 0) {
    *ppPin = pPin;  // Return the pin's interface
    hr = S_OK;      // Found requested pin, so clear error
    break;
   }
   iNum--;
  } 
  pPin->Release();
 }
 return hr;
}
IPin * GetInPin( IBaseFilter * pFilter, int nPin ) {
 CComPtr<IPin> pComPin=0;
 GetPin(pFilter, PINDIR_INPUT, nPin, &pComPin);
 return pComPin;
}
IPin * GetOutPin( IBaseFilter * pFilter, int nPin ) {
 CComPtr<IPin> pComPin=0;
 GetPin(pFilter, PINDIR_OUTPUT, nPin, &pComPin);
 return pComPin;
}

[icesoft2000]

看来是我对IMediaSample的作用的理解有错误。

我本来的是意思是想实现音乐播放时，可以显示声音的波形。本来以为可以用IMediaSample来实现，看来是不对啦!

请问各位DX，如何实现此功能？