使用dshow如何打开指定摄像头
使用dshow如何打开指定摄像头
- 通过设备VID/PID找到指定摄像头设备
- 通过设备名打开指定摄像头设备
- 绑定设备过滤器
最近做了一个关于摄像头的项目，需要适配WindowsXP及以上系统，需要兼容XP系统就打算用dshow技术，顺便把相关技术学了一遍，这里给大家分享一下如何打开指定摄像头设备。
通过设备VID/PID找到指定摄像头设备
HRESULT GetCameraId()
{
ICreateDevEnum *pDevEnum = NULL;
IEnumMoniker *pEnum = NULL;
HRESULT hr = NULL;
CoInitialize(NULL);
int index = -1;
int iCapCount = 0;
hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC_SERVER, IID_ICreateDevEnum, reinterpret_cast<void**>(&pDevEnum));
if (SUCCEEDED(hr))
{
hr = pDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory, &pEnum, 0);
if (hr == S_OK)
{
//枚举捕获设备
IMoniker *pMoniker = NULL;
ULONG cFetched;
while (pEnum->Next(1, &pMoniker, &cFetched) == S_OK)
{
IPropertyBag* pPropBag;
hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag, reinterpret_cast<void**>(&pPropBag));
if (SUCCEEDED(hr))
{
index++;
//获取PID VID
BSTR devicePath = NULL;
hr = pMoniker->GetDisplayName(NULL, NULL, &devicePath);
if (!SUCCEEDED(hr))
{
pMoniker->Release();
continue;
}
wchar_t* lpszDevicePath = _bstr_t(devicePath);
CString strDevice;
strDevice.Format(L"%s", lpszDevicePath);
if (strDevice.Find(L"vid_0000") >= 0 && strDevice.Find(L"pid_0000") >= 0)
{
cameraID = index;
}
pPropBag->Release();
}
pMoniker->Release();
}
}
}
CoUninitialize();
return hr;
}
通过设备名打开指定摄像头设备
HRESULT GetCameraId()
{
ICreateDevEnum *pDevEnum = NULL;
IEnumMoniker *pEnum = NULL;
HRESULT hr = NULL;
CoInitialize(NULL);
int index = -1;
int iCapCount = 0;
hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC_SERVER, IID_ICreateDevEnum, reinterpret_cast<void**>(&pDevEnum));
if (SUCCEEDED(hr))
{
hr = pDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory, &pEnum, 0);
if (hr == S_OK)
{
//枚举捕获设备
IMoniker *pMoniker = NULL;
ULONG cFetched;
while (pEnum->Next(1, &pMoniker, &cFetched) == S_OK)
{
IPropertyBag* pPropBag;
hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag, reinterpret_cast<void**>(&pPropBag));
if (SUCCEEDED(hr))
{
index++;
//获取设备名称
VARIANT varName;
varName.vt = VT_BSTR;
VariantInit(&varName);
hr = pPropBag->Read(L"FriendlyName", &varName, 0);
wchar_t* lpszBSTR = L"";
if (SUCCEEDED(hr))
{
lpszBSTR = _bstr_t(varName.bstrVal);
}
int iSize;
char* pszMultiByte;
//返回接受字符串所需缓冲区的大小，已经包含字符结尾符'\0'
iSize = WideCharToMultiByte(CP_ACP, 0, lpszBSTR, -1, NULL, 0, NULL, NULL); //iSize =wcslen(pwsUnicode)+1=6
pszMultiByte = (char*)malloc(iSize * sizeof(char)); //不需要 pszMultiByte = (char*)malloc(iSize*sizeof(char)+1);
WideCharToMultiByte(CP_ACP, 0, lpszBSTR, -1, pszMultiByte, iSize, NULL, NULL);
if (0 == strcmp(szDeviceName, pszMultiByte))
{
cameraID = index;
}
free(pszMultiByte);
pPropBag->Release();
}
pMoniker->Release();
}
}
}
CoUninitialize();
return hr;
}
在WindowsXP下由于设备名都是USB Camera，此方法不适用
绑定设备过滤器
绑定设备过滤器， 我们知道了设备因为传入了id
IBaseFilter* m_pBF;
if (!BindFilter(cameraID, &m_pBF))
{
return S_FALSE;
}