使用DirectShow預覽攝像頭

Question

我在調用RenderStream（）時總是收到「E_INVALIDARG」。

我的程序輸出是：

SUCCESS - Initialized COM library. 
SUCCESS - Created the Filter Graph Manager. 
SUCCESS - Created the Media Control and Media Event Interfaces. 
SUCCESS - Enumerated devices. 
--------------DEVICE INFORMATION-------------- 
Integrated Webcam 
------------END DEVICE INFORMATION------------ 
SUCCESS - Bound to moniker. 

下面是代碼：

#include "stdafx.h" 

#include <dshow.h>  //direct show 
#include <windows.h> //windows 

#pragma comment(lib,"Strmiids.lib") //used for direct show 

HRESULT InitCaptureGraphBuilder(
    IGraphBuilder **ppGraph, // Receives the pointer. 
    ICaptureGraphBuilder2 **ppBuild // Receives the pointer. 
    ) 
{ 
    if (!ppGraph || !ppBuild) 
    { 
     return E_POINTER; 
    } 
    IGraphBuilder *pGraph = NULL; 
    ICaptureGraphBuilder2 *pBuild = NULL; 

    // Create the Capture Graph Builder. 
    HRESULT hr = CoCreateInstance(CLSID_CaptureGraphBuilder2, NULL, 
     CLSCTX_INPROC_SERVER, IID_ICaptureGraphBuilder2, (void**)&pBuild); 
    if (SUCCEEDED(hr)) 
    { 
     // Create the Filter Graph Manager. 
     hr = CoCreateInstance(CLSID_FilterGraph, 0, CLSCTX_INPROC_SERVER, 
      IID_IGraphBuilder, (void**)&pGraph); 
     if (SUCCEEDED(hr)) 
     { 
      // Initialize the Capture Graph Builder. 
      pBuild->SetFiltergraph(pGraph); 

      // Return both interface pointers to the caller. 
      *ppBuild = pBuild; 
      *ppGraph = pGraph; // The caller must release both interfaces. 
      return S_OK; 
     } 
     else 
     { 
      pBuild->Release(); 
     } 
    } 
    return hr; // Failed 
} 
HRESULT EnumerateDevices(REFGUID category, IEnumMoniker **ppEnum) 
{ 
    // Create the System Device Enumerator. 
    ICreateDevEnum *pDevEnum; 
    HRESULT hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, 
     CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&pDevEnum)); 

    if (SUCCEEDED(hr)) 
    { 
     // Create an enumerator for the category. 
     hr = pDevEnum->CreateClassEnumerator(category, ppEnum, 0); 
     if (hr == S_FALSE) 
     { 
      hr = VFW_E_NOT_FOUND; // The category is empty. Treat as an error. 
     } 
     pDevEnum->Release(); 
    } 
    return hr; 
} 
void DisplayDeviceInformation(IEnumMoniker *pEnum, IMoniker** pMoniker) 
{ 
    while (pEnum->Next(1, pMoniker, NULL) == S_OK) 
    { 
     IPropertyBag *pPropBag; 
     HRESULT hr = (*pMoniker)->BindToStorage(0, 0, IID_PPV_ARGS(&pPropBag)); 
     if (FAILED(hr)) 
     { 
      (*pMoniker)->Release(); 
      continue; 
     } 

     VARIANT var; 
     VariantInit(&var); 

     // Get description or friendly name. 
     hr = pPropBag->Read(L"Description", &var, 0); 
     if (FAILED(hr)) 
     { 
      hr = pPropBag->Read(L"FriendlyName", &var, 0); 
     } 
     if (SUCCEEDED(hr)) 
     { 
      printf("%S\n", var.bstrVal); 
      if(0 == wcscmp(var.bstrVal, L"Integrated Webcam")) 
      { 
       VariantClear(&var); 
       pPropBag->Release(); 
       return; 
      } 
      VariantClear(&var); 
     } 

     hr = pPropBag->Write(L"FriendlyName", &var); 

     pPropBag->Release(); 
    } 
} 

void main() 
{ 
    HRESULT hr = CoInitializeEx(NULL, COINIT_MULTITHREADED); 

    IGraphBuilder *pGraph = NULL; 
    ICaptureGraphBuilder2 *pBuild = NULL; 
    IMediaControl *pControl = NULL; 
    IMediaEvent *pEvent = NULL; 

    if (FAILED(hr)) 
    { 
     printf("ERROR - Could not initialize COM library\n"); 
     return; 
    } 

    printf("SUCCESS - Initialized COM library.\n"); 

    hr = InitCaptureGraphBuilder(&pGraph, &pBuild); 

    if (FAILED(hr)) 
    { 
     printf("ERROR - Could not create the Filter Graph Manager.\n"); 
     return; 
    } 

    printf("SUCCESS - Created the Filter Graph Manager.\n"); 

    hr = pGraph->QueryInterface(IID_IMediaControl, (void **)&pControl); 
    hr = pGraph->QueryInterface(IID_IMediaEvent, (void **)&pEvent); 

    if (FAILED(hr)) 
    { 
     printf("ERROR - Could not create the Media Control or Media Event Interfaces.\n"); 
     return; 
    } 

    printf("SUCCESS - Created the Media Control and Media Event Interfaces.\n"); 

    IEnumMoniker *pEnum; 

    hr = EnumerateDevices(CLSID_VideoInputDeviceCategory, &pEnum); 

    if(FAILED(hr)) 
    { 
     printf("ERROR - Failed to enumerate devices.\n"); 
     return; 
    } 

    printf("SUCCESS - Enumerated devices.\n"); 
    IMoniker* pMoniker = NULL; 

    printf("--------------DEVICE INFORMATION--------------\n"); 
    DisplayDeviceInformation(pEnum, &pMoniker); 
    printf("------------END DEVICE INFORMATION------------\n"); 

    IBaseFilter *pCap = NULL; 
    hr = pMoniker->BindToObject(0, 0, IID_IBaseFilter, (void**)&pCap); 

    if(FAILED(hr)) 
    { 
     printf("ERROR - Failed to bind to moniker.\n"); 
     return; 
    } 

    printf("SUCCESS - Bound to moniker.\n"); 

    hr = pBuild->RenderStream(&PIN_CATEGORY_PREVIEW, &MEDIATYPE_Video, pCap, NULL, NULL); 

    if(FAILED(hr)) 
    { 
     printf("ERROR - RenderStream() failed.\n"); 
     return; 
    } 

    printf("SUCCESS - RenderStream() succeeded.\n"); 

    hr = pControl->Run(); 

    if(FAILED(hr)) 
    { 
     printf("ERROR - Run() failed.\n"); 
     return; 
    } 

    printf("SUCCESS - Running.\n"); 

    long evCode; 
    hr = pEvent->WaitForCompletion(INFINITE, &evCode); 

    if(FAILED(hr)) 
    { 
     printf("ERROR - WaitForCompletion() failed.\n"); 
     return; 
    } 

    hr = pControl->Stop(); 

    if(FAILED(hr)) 
    { 
     printf("ERROR - Stop() failed.\n"); 
     return; 
    } 

    printf("SUCCESS - Stopping.\n"); 

    pControl->Release(); 
    pEvent->Release(); 
    pGraph->Release(); 
    pMoniker->Release(); 
    pEnum->Release(); 

    CoUninitialize(); 
} 

Answer 1

使用RenderStream您需要將相機過濾IGraphBuilder::AddFilter到圖形之前。