无法使用 Windows Media Encoder 设置默认音频设备

Question

我参考以下文档部分“用于捕获屏幕的Windows Media API”来捕获屏幕，原始代码工作正常。 当我添加附加功能时（我刚刚添加了几行以使其从默认音频设备进行录制），它在以下行处失败（我调试过，看起来它在 COM 层失败？），有任何提示吗？ 我发布了原始源代码和我修改后的源代码。

“if(FAILED(hr=pSrcGrp->put_Profile(variant_t(pProfile))))”

http ://www.geocities.com/krishnapg/screencap.html

原始源代码：

http://www.geocities.com/krishnapg/WMEncScrnCap.zip

我修改的源代码（我只修改了函数InitEncoder）

HRESULT InitEncoder(LPCTSTR szOutputFileName)
{
    HRESULT hr = E_FAIL;
    CComVariant varValue;
    IWMEncSourceGroupCollection*    pSrcGrpCollection=NULL;
    IWMEncSourceGroup*  pSrcGrp=NULL;
    IWMEncSource*   pSrc=NULL;
    IWMEncSource*   paSrc=NULL;
    IPropertyBag*   pPropertyBag=NULL;
    IWMEncVideoSource2* pSrcVid=NULL;
    IWMEncAudioSource*  pSrcAud=NULL;
    IWMEncFile* pOutFile=NULL;
    IWMEncProfile*  pProfile=NULL;

    if(FAILED(CoCreateInstance(CLSID_WMEncoder,NULL,CLSCTX_INPROC_SERVER,IID_IWMEncoder2,(void**)&g_pEncoder)))
    {
        ErrorMessage("Unable to Create Encoder Object");
        return E_FAIL;
    }
    if(FAILED(g_pEncoder->get_SourceGroupCollection(&pSrcGrpCollection)))       //Retrieve the Source Group Collection  - One Application can Have many Source Groups - We need to add as many as we want
    {
        ErrorMessage("Unable to Get Source Group Collection");
        return E_FAIL;
    }

    do
    {
        if(FAILED(hr=pSrcGrpCollection->Add(CComBSTR("SourceGroup1"),&pSrcGrp)))//Add a Source Group to the Collection - Each Source can have one video one audio source input
        {
            ErrorMessage("Unable to Add A Source Group to the Collection");
            break;
        }
        if(FAILED(hr=pSrcGrp->AddSource(WMENC_VIDEO,&pSrc)))                    //Add a Video Source to the Group
        {
            ErrorMessage("Unable to Add A Source to the Source Group");
            break;
        }
        if(FAILED(hr=pSrcGrp->AddSource(WMENC_AUDIO,&paSrc)))                   //Add an Audio Source to the Group
        {
            ErrorMessage("Unable to Add A Source to the Source Group");
            break;
        }
        if(FAILED(hr=pSrc->QueryInterface(IID_IWMEncVideoSource2,(void**)&pSrcVid)))
        {
            ErrorMessage("Unable to Query interface for Video Source");
            break;
        }
        if(FAILED(hr=paSrc->QueryInterface(IID_IWMEncAudioSource,(void**)&pSrcAud)))
        {
            ErrorMessage("Unable to Query interface for Audio Source");
            break;
        }
        if(FAILED(hr=pSrcVid->SetInput(CComBSTR("ScreenCap://ScreenCapture1"))))//The Video Input Source Device - Should be "ScreenCap" Device
        {
            ErrorMessage("Unable to Set Video Input Source");
            break;
        }
        if(FAILED(hr=pSrcAud->SetInput(CComBSTR("Device://Default_Audio_Device"))))//The Video Input Source Device - Should be "Default_Audio_Device" Device
        {
            ErrorMessage("Unable to Set Audio Input Source");
            break;
        }
        if(FAILED(hr=pSrcVid->QueryInterface(IID_IPropertyBag,(void**)&pPropertyBag)))
        {
            ErrorMessage("Unable to Query Interface for Propery bag");
            break;
        }

        varValue = CAPTURE_FULLSCREEN;
        if(FAILED(hr=pPropertyBag->Write(WMSCRNCAP_ENTIRESCREEN,&varValue)))    //Set Full Screen Property true/false
        {
            ErrorMessage("Unable to Set Capture Screen Property");
            break;
        }
        //int nLeft, nRight, nTop, nBottom;                                 //Set Capture Area - when not in full screen mode
        //                                                                  // Initialize the capture area. The size must be even.
        //  varValue = false;
        //  if ( SUCCEEDED( hr ) )
        //  {
        //      hr = pPropertyBag->Write( WMSCRNCAP_ENTIRESCREEN, &varValue );
        //  }
        //  varValue = nLeft;
        //  if ( SUCCEEDED( hr ) )
        //  {
        //      hr = pPropertyBag->Write( WMSCRNCAP_WINDOWLEFT, &varValue );
        //  }
        //  varValue = nRight;
        //  if ( SUCCEEDED( hr ) )
        //  {
        //      hr = pPropertyBag->Write( WMSCRNCAP_WINDOWRIGHT, &varValue );
        //  }
        //  varValue = nTop;
        //  if ( SUCCEEDED( hr ) )
        //  {
        //      hr = pPropertyBag->Write( WMSCRNCAP_WINDOWTOP, &varValue );
        //  }
        //  varValue = nBottom;
        //  if ( SUCCEEDED( hr ) )
        //  {
        //      hr = pPropertyBag->Write( WMSCRNCAP_WINDOWBOTTOM, &varValue );
        //  }
        //  varValue = true;
        //  if ( SUCCEEDED( hr ) )
        //  {
        //      hr = pPropertyBag->Write( WMSCRNCAP_FLASHRECT, &varValue );
        //  }

        if(FAILED(hr=SetupScreenCaptureProfile()))                                  //Setup the Custom Profile
        {
            break;
        }
        if(FAILED(hr=g_pProfile->QueryInterface(IID_IWMEncProfile,(void**)&pProfile)))
        {
            ErrorMessage("Unable to Query Interface For Profile");
            break;
        }
        if(FAILED(hr=pSrcGrp->put_Profile(variant_t(pProfile))))                    //Select the Custom Profile into the Encoder    
        {
            ErrorMessage("Unable to Set Profile For Source Group");
            break;
        }
        if(FAILED(hr=g_pEncoder->get_File(&pOutFile)))
        {
            ErrorMessage("Unable to Get Encoder Output File Object");
            break;
        }
        if(FAILED(hr=pOutFile->put_LocalFileName(CComBSTR(szOutputFileName))))      //Set the Target Output Filename
        {
            ErrorMessage("Unable to Set Output File Name");
            break;
        }
        if(FAILED(hr=g_pEncoder->PrepareToEncode(VARIANT_TRUE)))                    //Using Prepare optimizes startig latency
        {
            ErrorMessage("Unable to Prepare for Encoding");
            break;
        }
    }while(false);

    if(pProfile)
    {
        pProfile->Release();
        pProfile=NULL;
    }
    if(pOutFile)
    {
        pOutFile->Release();
        pOutFile = NULL;
    }
    if(pPropertyBag)
    {
        pPropertyBag->Release();
        pPropertyBag = NULL;
    }
    if(pSrcVid)
    {
        pSrcVid->Release();
        pSrcVid = NULL;
    }
    if(pSrc)
    {
        pSrc->Release();
        pSrc = NULL;
    }
    if(pSrcGrp)
    {
        pSrcGrp->Release();
        pSrcGrp = NULL;
    }
    if(pSrcGrpCollection)
    {
        pSrcGrpCollection->Release();
        pSrcGrpCollection = NULL;
    }
    return hr;
}

Answer 1

您可能需要重置音频：

打开控制面板 -> 打开声音

在播放中，您将看到扬声器作为默认播放。

右键单击它-> 转到属性 -> 转到高级选项卡-> 单击恢复默认值

Answer 2

您的代码可能没有任何问题。 Windows Vista 因无法以编程方式设置输出/输入而臭名昭著。