获取Filter的三种途径 收藏

一、通过CLSID

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1. IBaseFilter *pF = 0;  
2. HRESULT hr = CoCreateInstance(clsid, 0, CLSCTX_INPROC_SERVER,  
3.         IID_IBaseFilter, reinterpret_cast<void**>(&pF));  

IBaseFilter *pF = 0;HRESULT hr = CoCreateInstance(clsid, 0, CLSCTX_INPROC_SERVER, IID_IBaseFilter, reinterpret_cast<void**>(&pF));

二、通过系统枚举器

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1. ICreateDevEnum *pSysDevEnum = NULL;  
2. hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC_SERVER,  
3.     IID_ICreateDevEnum, (void **)&pSysDevEnum);  
4. if (FAILED(hr))  
5. {  
6.     return hr;  
7. }  
8.   
9. IEnumMoniker *pEnumCat = NULL;  
10. hr = pSysDevEnum->CreateClassEnumerator(CLSID_VideoCompressorCategory, &pEnumCat, 0);  
11.   
12. if (hr == S_OK)   
13. {  
14.     IMoniker *pMoniker = NULL;  
15.     ULONG cFetched;  
16.     while(pEnumCat->Next(1, &pMoniker, &cFetched) == S_OK)  
17.     {  
18.         IPropertyBag *pPropBag;  
19.         hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag,   
20.             (void **)&pPropBag);  
21.         if (SUCCEEDED(hr))  
22.         {  
23.             VARIANT varName;  
24.             VariantInit(&varName);  
25.             hr = pPropBag->Read(L"FriendlyName", &varName, 0);  
26.   
27.             IBaseFilter *pFilter;  
28.             hr = pMoniker->BindToObject(NULL, NULL, IID_IBaseFilter,  
29.                 (void**)&pFilter);  
30.   
31.             pPropBag->Release();  
32.         }  
33.         pMoniker->Release();  
34.     }  
35.     pEnumCat->Release();  
36. }  
37. pSysDevEnum->Release();  

ICreateDevEnum *pSysDevEnum = NULL;hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC_SERVER, IID_ICreateDevEnum, (void **)&pSysDevEnum);if (FAILED(hr)){ return hr;}IEnumMoniker *pEnumCat = NULL;hr = pSysDevEnum->CreateClassEnumerator(CLSID_VideoCompressorCategory, &pEnumCat, 0);if (hr == S_OK) { IMoniker *pMoniker = NULL; ULONG cFetched; while(pEnumCat->Next(1, &pMoniker, &cFetched) == S_OK) { IPropertyBag *pPropBag; hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag, (void **)&pPropBag); if (SUCCEEDED(hr)) { VARIANT varName; VariantInit(&varName); hr = pPropBag->Read(L"FriendlyName", &varName, 0); IBaseFilter *pFilter; hr = pMoniker->BindToObject(NULL, NULL, IID_IBaseFilter, (void**)&pFilter); pPropBag->Release(); } pMoniker->Release(); } pEnumCat->Release();}pSysDevEnum->Release();

三、通过Filter Mapper

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1. IFilterMapper2 *pMapper = NULL;  
2. IEnumMoniker *pEnum = NULL;  
3.   
4. hr = CoCreateInstance(CLSID_FilterMapper2,   
5.     NULL, CLSCTX_INPROC, IID_IFilterMapper2,   
6.     (void **) &pMapper);  
7.   
8. GUID arrayInTypes[2];  
9. arrayInTypes[0] = MEDIATYPE_Video;  
10. arrayInTypes[1] = MEDIASUBTYPE_dvsd;  
11.   
12. hr = pMapper->EnumMatchingFilters(  
13.         &pEnum,  
14.         0,                  // Reserved.  
15.         TRUE,               // Use exact match?  
16.         MERIT_DO_NOT_USE+1, // Minimum merit.  
17.         TRUE,               // At least one input pin?  
18.         1,                  // Number of major type/subtype pairs for input.  
19.         arrayInTypes,       // Array of major type/subtype pairs for input.  
20.         NULL,               // Input medium.  
21.         NULL,               // Input pin category.  
22.         FALSE,              // Must be a renderer?  
23.         TRUE,               // At least one output pin?  
24.         0,                  // Number of major type/subtype pairs for output.  
25.         NULL,               // Array of major type/subtype pairs for output.  
26.         NULL,               // Output medium.  
27.         NULL);              // Output pin category.  
28.   
29. IMoniker *pMoniker;  
30. ULONG cFetched;  
31. while (pEnum->Next(1, &pMoniker, &cFetched) == S_OK)  
32. {  
33.     IPropertyBag *pPropBag = NULL;  
34.     hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag,   
35.        (void **)&pPropBag);  
36.   
37.     if (SUCCEEDED(hr))  
38.     {  
39.         VARIANT varName;  
40.         VariantInit(&varName);  
41.         hr = pPropBag->Read(L"FriendlyName", &varName, 0);  
42.         VariantClear(&varName);  
43.   
44.         IBaseFilter *pFilter;  
45.         hr = pMoniker->BindToObject(NULL, NULL, IID_IBaseFilter, (void**)&pFilter);  
46.         pPropBag->Release();  
47.     }  
48.     pMoniker->Release();  
49. }  
50.   
51. pMapper->Release();  
52. pEnum->Release();  

IFilterMapper2 *pMapper = NULL;IEnumMoniker *pEnum = NULL;hr = CoCreateInstance(CLSID_FilterMapper2, NULL, CLSCTX_INPROC, IID_IFilterMapper2, (void **) &pMapper);GUID arrayInTypes[2];arrayInTypes[0] = MEDIATYPE_Video;arrayInTypes[1] = MEDIASUBTYPE_dvsd;hr = pMapper->EnumMatchingFilters( &pEnum, 0, // Reserved. TRUE, // Use exact match? MERIT_DO_NOT_USE+1, // Minimum merit. TRUE, // At least one input pin? 1, // Number of major type/subtype pairs for input. arrayInTypes, // Array of major type/subtype pairs for input. NULL, // Input medium. NULL, // Input pin category. FALSE, // Must be a renderer? TRUE, // At least one output pin? 0, // Number of major type/subtype pairs for output. NULL, // Array of major type/subtype pairs for output. NULL, // Output medium. NULL); // Output pin category.IMoniker *pMoniker;ULONG cFetched;while (pEnum->Next(1, &pMoniker, &cFetched) == S_OK){ IPropertyBag *pPropBag = NULL; hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag, (void **)&pPropBag); if (SUCCEEDED(hr)) { VARIANT varName; VariantInit(&varName); hr = pPropBag->Read(L"FriendlyName", &varName, 0); VariantClear(&varName); IBaseFilter *pFilter; hr = pMoniker->BindToObject(NULL, NULL, IID_IBaseFilter, (void**)&pFilter); pPropBag->Release(); } pMoniker->Release();}pMapper->Release();pEnum->Release();

第一种方法是最直接的，也最简单，不过当不清楚CLSID的时候，就不得不用后面两种方法。

第二种方法和第三中方法都是使用枚举器枚举Filter，通过匹配Filter的属性来得到Filter，它们不同之处在于：第二种通过确定的种类获得枚举器，第三种通过媒体类型获得枚举器。获得枚举器以后的步骤是相同的。

这三种方法最常用的是第二种。