摄像头视频在下次打开该对话框时捕获不到视频了？

我做的小程序在A对话框中单击按钮显示B对话框，在B对话框中显示了摄像头视频，但在不退出主程序的情况下关闭B对话框后再显示B对话框，此时捕获不到视频了，显示错误，发现程序出错在hr = m_pCapture->RenderStream(&PIN_CATEGORY_PREVIEW, &MEDIATYPE_Video,m_pBF,pGrabBase,NULL);处。我也看了能Release的都Release了。同样的类在A对话框中显示视频，然后A对话框退出(A为主对话框，所以就退出该进程了)，此时再打开该进程视频是可以显示出来的。所以我怀疑还有什么没释放掉，请大家帮我看看。我使用的是一个网上的类：// CaptureVideo.cpp : implementation file
//#include "stdafx.h"
#include "CaptureVideo.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif/////////////////////////////////////////////////////////////////////////////
// CCaptureVideo
BOOL bOneShot;
CSampleGrabberCB mCB;
CCaptureVideo::CCaptureVideo()
{
//COM Library Intialization
if(FAILED(CoInitialize(NULL))) /*, COINIT_APARTMENTTHREADED)))*/
{
AfxMessageBox("CoInitialize Failed!\r\n"); 
return;
}
m_hWndDummy = NULL;
m_pVW = NULL;
m_pMC = NULL;
m_pGB = NULL;
m_pCapture = NULL; 
m_pBF = NULL;
}CCaptureVideo::~CCaptureVideo()
{
// Stop media playback
if(m_pMC)m_pMC->Stop();
if(m_pVW){
m_pVW->put_Visible(OAFALSE);
m_pVW->put_Owner(NULL);
} SAFE_RELEASE(m_pCapture);
SAFE_RELEASE(m_pMC);
SAFE_RELEASE(m_pGB);
SAFE_RELEASE(m_pBF);
CoUninitialize( );
}void CCaptureVideo::GrabOneFrame(BOOL bGrab)
{
bOneShot = bGrab;
}HRESULT CCaptureVideo::Init(int iDeviceID, HWND hWnd)
{
HRESULT hr;
hr = InitCaptureGraphBuilder();
if (FAILED(hr)){
AfxMessageBox("Failed to get video interfaces!");
return hr;
}
// Bind Device Filter. We know the device because the id was passed in
if(!BindFilter(iDeviceID, &m_pBF))return S_FALSE;
hr = m_pGB->AddFilter(m_pBF, L"Capture Filter");
// hr = m_pCapture->RenderStream(&PIN_CATEGORY_PREVIEW, &MEDIATYPE_Video, 
// m_pBF, NULL, NULL);
// create a sample grabber
hr = m_pGrabber.CoCreateInstance( CLSID_SampleGrabber );
if( !m_pGrabber ){
AfxMessageBox("Fail to create SampleGrabber, maybe qedit.dll is not registered?");
return hr;
}
CComQIPtr< IBaseFilter, &IID_IBaseFilter > pGrabBase( m_pGrabber );
//设置视频格式
AM_MEDIA_TYPE mt; 
ZeroMemory(&mt, sizeof(AM_MEDIA_TYPE));
mt.majortype = MEDIATYPE_Video;
mt.subtype = MEDIASUBTYPE_RGB24;
hr = m_pGrabber->SetMediaType(&mt);
if( FAILED( hr ) ){
AfxMessageBox("Fail to set media type!");
return hr;
}
hr = m_pGB->AddFilter( pGrabBase, L"Grabber" );
if( FAILED( hr ) ){
AfxMessageBox("Fail to put sample grabber in graph");
return hr;
}
// try to render preview/capture pin
ASSERT(m_pBF != NULL);
ASSERT(pGrabBase != NULL);          hr = m_pCapture->RenderStream(&PIN_CATEGORY_PREVIEW, &MEDIATYPE_Video,m_pBF,pGrabBase,NULL); // 此处在第二次时就出错了
if( FAILED( hr ) )
{
           hr = m_pCapture->RenderStream(&PIN_CATEGORY_CAPTURE, &MEDIATYPE_Video,m_pBF,pGrabBase,NULL);
}


if( FAILED( hr ) )
{
strFormat.Format("hr2 = %x", hr);
AfxMessageBox(strFormat); AfxMessageBox("Can’t build the graph");
return hr;
}

hr = m_pGrabber->GetConnectedMediaType( &mt );
if ( FAILED( hr) ){
AfxMessageBox("Failt to read the connected media type");
return hr;
}

VIDEOINFOHEADER * vih = (VIDEOINFOHEADER*) mt.pbFormat;
mCB.lWidth = vih->bmiHeader.biWidth;
mCB.lHeight = vih->bmiHeader.biHeight;
FreeMediaType(mt);
hr = m_pGrabber->SetBufferSamples( FALSE );
hr = m_pGrabber->SetOneShot( FALSE );
hr = m_pGrabber->SetCallback( &mCB, 1 );

//设置视频捕捉窗口
m_hWndDummy = hWnd ; 
SetupVideoWindow();
hr = m_pMC->Run();//开始视频捕捉
if(FAILED(hr)){AfxMessageBox("Couldn’t run the graph!");return hr;}
return S_OK;
}int CCaptureVideo::EnumDevices(HWND hList)
{
if (!hList)
return -1;
int id = 0;
//枚举视频扑捉设备
ICreateDevEnum *pCreateDevEnum;
HRESULT hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC_SERVER,IID_ICreateDevEnum, (void**)&pCreateDevEnum);
if (hr != NOERROR)return -1;
CComPtr<IEnumMoniker> pEm;
hr = pCreateDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory,&pEm, 0);
if (hr != NOERROR)return -1;
pEm->Reset();
ULONG cFetched;
IMoniker *pM;
while(hr = pEm->Next(1, &pM, &cFetched), hr==S_OK)
{
IPropertyBag *pBag;
hr = pM->BindToStorage(0, 0, IID_IPropertyBag, (void **)&pBag);
if(SUCCEEDED(hr)) 
{
VARIANT var;
var.vt = VT_BSTR;
hr = pBag->Read(L"FriendlyName", &var, NULL);
if (hr == NOERROR) 
{
TCHAR str[2048]; 
id++;
WideCharToMultiByte(CP_ACP,0,var.bstrVal, -1, str, 2048, NULL, NULL);
::SendMessage(hList, LB_ADDSTRING, 0,(LPARAM)str);
SysFreeString(var.bstrVal);
}
pBag->Release();
}
pM->Release();
}
return id;
}void CCaptureVideo::FreeMediaType(AM_MEDIA_TYPE &mt)
{
if (mt.cbFormat != 0) {
CoTaskMemFree((PVOID)mt.pbFormat);
// Strictly unnecessary but tidier
mt.cbFormat = 0;
mt.pbFormat = NULL;
}
if (mt.pUnk != NULL) {
mt.pUnk->Release();
mt.pUnk = NULL;
}
}bool CCaptureVideo::BindFilter(int deviceId, IBaseFilter **pFilter)
{
if (deviceId < 0)
return false;
// enumerate all video capture devices
CComPtr<ICreateDevEnum> pCreateDevEnum;
HRESULT hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC_SERVER,
IID_ICreateDevEnum, (void**)&pCreateDevEnum);
if (hr != NOERROR)
{
return false;
}
CComPtr<IEnumMoniker> pEm;
hr = pCreateDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory,&pEm, 0);
if (hr != NOERROR) 
{
return false;
}
pEm->Reset();
ULONG cFetched;
IMoniker *pM;
int index = 0;
while(hr = pEm->Next(1, &pM, &cFetched), hr==S_OK, index <= deviceId)
{
IPropertyBag *pBag;
hr = pM->BindToStorage(0, 0, IID_IPropertyBag, (void **)&pBag);
if(SUCCEEDED(hr)) 
{
VARIANT var;
var.vt = VT_BSTR;
hr = pBag->Read(L"FriendlyName", &var, NULL);
if (hr == NOERROR) 
{
if (index == deviceId)
{
pM->BindToObject(0, 0, IID_IBaseFilter, (void**)pFilter);
}
SysFreeString(var.bstrVal);
}
pBag->Release();
}
pM->Release();
index++;
}
return true;
}void CCaptureVideo::ResizeVideoWindow()
{
if (m_pVW){
//让图像充满整个窗口
CRect rc;
::GetClientRect(m_hWndDummy,&rc);
m_pVW->SetWindowPosition(0, 0, rc.right, rc.bottom);
}
}HRESULT CCaptureVideo::SetupVideoWindow()
{
HRESULT hr;
hr = m_pVW->put_Owner((OAHWND)m_hWndDummy);
if (FAILED(hr))return hr;
hr = m_pVW->put_WindowStyle(WS_CHILD | WS_CLIPCHILDREN);
if (FAILED(hr))return hr;
ResizeVideoWindow();
hr = m_pVW->put_Visible(OATRUE);
return hr;
}HRESULT CCaptureVideo::InitCaptureGraphBuilder()
{
HRESULT hr;
// 创建IGraphBuilder接口
hr=CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, IID_IGraphBuilder, (void **)&m_pGB);
// 创建ICaptureGraphBuilder2接口
hr = CoCreateInstance (CLSID_CaptureGraphBuilder2 , NULL, CLSCTX_INPROC,
IID_ICaptureGraphBuilder2, (void **) &m_pCapture);
if (FAILED(hr))return hr;
m_pCapture->SetFiltergraph(m_pGB);
hr = m_pGB->QueryInterface(IID_IMediaControl, (void **)&m_pMC);
if (FAILED(hr))return hr;
hr = m_pGB->QueryInterface(IID_IVideoWindow, (LPVOID *) &m_pVW);
if (FAILED(hr))return hr;
return hr;
}void CCaptureVideo::SetCaptureFileName(const CString& strCaptureFileName)
{
mCB.setPhotoName(strCaptureFileName);
}