用DirectShow实现视频采集(二)
2010-09-21 15:55:37| 分类:
DirectShow
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3.具体实现
首先我们需要创建几个接口全局变量。
IGraphBuilder *pGraph; //过滤器图表管理器
ICaptureGraphBuilder2 *pBuild; //视频采集过滤器图表
IBaseFilter *pCap; //Video Capture Filter
IBaseFilter *pSmartTee; //Smart Tee Filter
IBaseFilter *pRender; //Video Renderer Filter
IMediaControl *pControl; //用户命令接口,用来控制过滤器图表
IMediaEvent *pEvent; //过滤器图表事件接口
1) 采集设备枚举
在构造Video Capture Filter前,我们必须列举出系统的所有采集设备,然后才能根据列举的设备名称创建Video Capture Filter。列举设备的函数实现如下
bool ListCaptureDevices()
{
ICreateDevEnum *pDevEnum = NULL; //设备枚举器Interface
IEnumMoniker *pEnum = NULL; //名称枚举Interface
// Create the System Device Enumerator.
HRESULT hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL,
CLSCTX_INPROC_SERVER, IID_ICreateDevEnum,
reinterpret_cast(&pDevEnum)); //创建设备枚举COM对象
if (SUCCEEDED(hr))
{
// Create an enumerator for the video capture category.
hr = pDevEnum->CreateClassEnumerator(
CLSID_VideoInputDeviceCategory,
&pEnum, 0); //创建视频采集设备枚举COM对象
}
////////////////////////////////////////////////////////////
IMoniker *pMoniker = NULL;
if(pEnum == NULL)
{
return false; //如果没有设备,返回
}
while (pEnum->Next(1, &pMoniker, NULL) == S_OK) //依次枚举,直至为空
{
IPropertyBag *pPropBag;
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.
VARIANT varName;
VariantInit(&varName);
hr = pPropBag->Read(L"Description", &varName, 0);
if (FAILED(hr))
{
hr = pPropBag->Read(L"FriendlyName", &varName, 0); //设备友好名称
}
if (SUCCEEDED(hr))
{
// Add it to the application‘s list box.
char displayName[1024];
WideCharToMultiByte(CP_ACP,0,varName.bstrVal,-1,displayName,1024,"",NULL);
m_nList.AddString(displayName); //字符转换,枚举名称均为UNICODE码
VariantClear(&varName);
}
pPropBag->Release();
pMoniker->Release();
}
return true;
}
2)创建Video Capture Filter
根据枚举出来的设备友好名称(FriendlyName)创建Video Capture Filter。
bool CTest_capDlg::CreateHardwareFilter(const char * friendlyName)
{ //将friendlyName与所有的设备名称依次对比,如果相同,则创建Filter
ICreateDevEnum * enumHardware = NULL;
HRESULT hr = CoCreateInstance(CLSID_SystemDeviceEnum,NULL,CLSCTX_ALL
,IID_ICreateDevEnum,(void **)&enumHardware);
if( FAILED(hr) )
{
return false;
}
IEnumMoniker * enumMoniker = NULL;
hr = enumHardware->CreateClassEnumerator(CLSID_VideoInputDeviceCategory,&enumMoniker,0);
if(enumMoniker)
{
enumMoniker->Reset();
ULONG fetched = 0;
IMoniker * moniker = NULL;
char friendlyName[256];
while(!pCap && SUCCEEDED(enumMoniker->Next(1,&moniker,&fetched)) && fetched)
{
if(moniker)
{
IPropertyBag * propertyBag = NULL;
VARIANT name;
friendlyName[0]=0;
hr=moniker->BindToStorage(0,0,IID_IPropertyBag,(void **)&propertyBag);
if(SUCCEEDED(hr))
{
name.vt=VT_BSTR;
hr = propertyBag->Read(L"FriendlyName",&name,NULL);
}
else
return false;
if(SUCCEEDED(hr))
{
WideCharToMultiByte(CP_ACP,0,name.bstrVal,-1,friendlyName,256,NULL,NULL);
moniker->BindToObject(0,0,IID_IBaseFilter,(void **)&pCap);
}
else
return false;
if(propertyBag)
{
propertyBag->Release();
propertyBag=NULL;
}
moniker->Release();
}
}
enumMoniker->Release();
}
enumHardware->Release();
return true;
}
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