directshow 之 添加视频预览

HRESULT CVideoSource::AddVedioPreviewFilter(char* varDeviceName)
{
 HRESULT hr = NULL;
 IMoniker *pMoniker = NULL;
 IPropertyBag *pPropBag = NULL;
 
 BOOL bFind = false;
 VARIANT varDescriptName;
 VARIANT varFriendName;
 VariantInit(&varDescriptName);
 VariantInit(&varFriendName);

 // Create the System Device Enumerator.
 hr = CoCreateInstance( CLSID_SystemDeviceEnum,
  NULL,
  CLSCTX_INPROC_SERVER,
  IID_ICreateDevEnum,
  reinterpret_cast<void**>(&m_pDevEnum)
  );
 if (FAILED(hr))
 {
  return hr;
 }
 // Create an enumerator for the video capture category.
 hr = m_pDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory,&m_pEnumMoniker, 0);
 //if (!SUCCEEDED(hr)||pEnum)
 if (hr == S_FALSE)
 {
  //there is not video device
  return hr;
 }
 while (m_pEnumMoniker->Next(1, &pMoniker, NULL) == S_OK)
 {
  hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag, (void**)(&pPropBag));
  if (FAILED(hr))
  {
   pMoniker->Release();
   continue;  // Skip this one, maybe the next one will work.
  }
  // Find the description or friendly name.

  hr = pPropBag->Read(L"Description", &varDescriptName, 0);
  if (FAILED(hr))
  {
  }
  hr = pPropBag->Read(L"FriendlyName", &varFriendName, 0);
  
  CString str(varFriendName.bstrVal);  
  int iret = strcmp(varDeviceName,str);
  if (iret==0)
  {
   bFind = true;
   break;
  }
  VariantClear(&varDescriptName);
  VariantClear(&varFriendName);
  pPropBag->Release();
  pMoniker->Release();
 }

 if (!bFind)
 {
  ErrMsg(TEXT("没有定位到视频采集设备"));
  return NULL;
 }
 else
 {
  hr = pMoniker->BindToObject(0, 0, IID_IBaseFilter, (void**)&m_pVideoCap);
  if (SUCCEEDED(hr))
  {
   hr = m_pGrapher->AddFilter(m_pVideoCap, varFriendName.bstrVal);   
  }
  m_DeviceDescriptName = varDescriptName;
  m_DeviceFriendName = varFriendName;
  pPropBag->Release();
  pMoniker->Release();
  VariantClear(&varDescriptName);
  VariantClear(&varFriendName);

  //
  //hr = m_pBuilder->FindInterface(&PIN_CATEGORY_CAPTURE,&MEDIATYPE_Interleaved, m_pVideoCap,IID_IAMVideoCompression, (void **)&m_pAMVideoCompress);
  //if(hr != S_OK)
  //{
  // hr = m_pBuilder->FindInterface(&PIN_CATEGORY_CAPTURE,&MEDIATYPE_Video, m_pVideoCap,IID_IAMVideoCompression, (void **)&m_pAMVideoCompress);
  //}

  // !!! What if this interface isn't supported?
  // we use this interface to set the frame rate and get the capture size
  hr = m_pBuilder->FindInterface(&PIN_CATEGORY_CAPTURE,&MEDIATYPE_Interleaved,m_pVideoCap, IID_IAMStreamConfig, (void **)&m_pAMStreamConfig);

  if(hr != NOERROR)
  {
   hr = m_pBuilder->FindInterface(&PIN_CATEGORY_CAPTURE,&MEDIATYPE_Video, m_pVideoCap,IID_IAMStreamConfig, (void **)&m_pAMStreamConfig);
   if(hr != NOERROR)
   {
    // this means we can't set frame rate (non-DV only)
    ErrMsg(TEXT("Error %x: Cannot find VCapture:IAMStreamConfig"), hr);
   }
  }

 }

 //添加Smart tee到Filter graph后，连接到videocapter

 
 hr = m_pBuilder->RenderStream(&PIN_CATEGORY_CAPTURE, &MEDIATYPE_Video,m_pVideoCap, NULL,m_pSmartTee);
 //hr = m_pBuilder->RenderStream(NULL, &MEDIATYPE_Interleaved, m_pVideoCap, NULL,m_pSmartTee);
 //hr = m_pBuilder->RenderStream(NULL, NULL, m_pVideoCap, NULL,m_pSmartTee);
 return hr;
}