Sample Code

The following sample code presents a complete console application that loads and previews an XML project file, using the error logging class described in this article. The name of the project file is hard-coded into the application.

To make the code shorter, the console application uses ATL smart pointers, which removes the need to call QueryInterface and Release. If you prefer, you can modify the sample application in Loading and Previewing a Project. Simply add the code shown in the previous section.

#include <atlbase.h>
#include <dshow.h>
#include <qedit.h>
#include <stdio.h>

// Error logging class
class CErrReporter : public IAMErrorLog
{
protected:
    long    m_lRef; // Reference count.

public:
    CErrReporter() { m_lRef = 0; }

    // IUnknown
    STDMETHOD(QueryInterface(REFIID, void**));
    STDMETHOD_(ULONG, AddRef());
    STDMETHOD_(ULONG, Release());

    // IAMErrorLog
    STDMETHOD(LogError(LONG, BSTR, LONG, HRESULT, VARIANT*));
};

STDMETHODIMP CErrReporter::QueryInterface(REFIID riid, void **ppv)
{
    if (ppv == NULL)
        return E_POINTER;
    *ppv = NULL;

    if (riid == IID_IUnknown)
        *ppv = (IUnknown*)this;
    else if (riid == IID_IAMErrorLog)
        *ppv = (IAMErrorLog*)this;
        
    if (*ppv) 
    {
        AddRef();
        return S_OK;
    }
    return E_NOINTERFACE;
}

STDMETHODIMP_(ULONG) CErrReporter::AddRef()
{
    return InterlockedIncrement(&m_lRef);
}

STDMETHODIMP_(ULONG) CErrReporter::Release()
{
    if (InterlockedDecrement(&m_lRef) == 0)
    {
        delete this;
        return 0;
    }
    return m_lRef;
}

STDMETHODIMP CErrReporter::LogError(
        LONG Severity, 
        BSTR ErrorString,
        LONG ErrorCode, 
        HRESULT hresult, 
        VARIANT *pExtraInfo)
{
    char szError[256];
    WideCharToMultiByte(CP_ACP, 0, ErrorString, -1, szError, 256, 0, 0);
    printf("Error %d: %s\n", ErrorCode, szError);
    
    if( pExtraInfo )    // Report extra information, if any. 
    {                           
        printf("\tExtra info: ");
        if( pExtraInfo->vt == VT_BSTR )      // Extra info is a BSTR.
        {
            char szExtra[256];
            WideCharToMultiByte(CP_ACP, 0, pExtraInfo->bstrVal, -1, szExtra, 256, 0, 0);
            printf("%s\n", szExtra);
        } 
        else if( pExtraInfo->vt == VT_I4 )   // Extra info is an integer.
            printf("%d\n", pExtraInfo->lVal);

        else if( pExtraInfo->vt == VT_R8 )   // Extra info is floating-point.
            printf("%f\n", pExtraInfo->dblVal);
    }
    return hresult;
};

void __cdecl main(void)
{
    CoInitialize(NULL);
    {
    HRESULT hr;
    CComPtr< IAMTimeline >   pTL;
    CComPtr< IRenderEngine > pRenderEngine; 
    CComPtr< IXml2Dex >      pXML; 
    CComPtr< IGraphBuilder > pGraph;

    hr = CoCreateInstance(CLSID_AMTimeline, NULL, CLSCTX_INPROC_SERVER, 
                IID_IAMTimeline, (void**) &pTL);
    hr = CoCreateInstance(CLSID_Xml2Dex, NULL, CLSCTX_INPROC_SERVER, 
                IID_IXml2Dex, (void**) &pXML);
    hr = CoCreateInstance(CLSID_RenderEngine, NULL, CLSCTX_INPROC_SERVER,
                IID_IRenderEngine, (void**) &pRenderEngine);

    // Set the error log.
    CComQIPtr<IAMSetErrorLog, &IID_IAMSetErrorLog> pSetLog(pTL);
    if (pSetLog)
    {
        IAMErrorLog *pLog = new CErrReporter;    
        pSetLog->put_ErrorLog(pLog);
    }
   
    // Load and preview the project.
    CComBSTR bstrFile(OLESTR("C:\\example.xtl"));
    hr = pXML->ReadXMLFile(pTL, bstrFile); 
    if (SUCCEEDED(hr))
    {
        hr = pRenderEngine->SetTimelineObject(pTL);
        hr = pRenderEngine->ConnectFrontEnd( );
        hr = pRenderEngine->RenderOutputPins( );
        hr = pRenderEngine->GetFilterGraph(&pGraph);

        CComQIPtr<IMediaControl, &IID_IMediaControl> pControl(pGraph);
        CComQIPtr<IMediaEvent, &IID_IMediaEvent> pEvent(pGraph);
        pControl->Run();

        long evCode;
        hr = pEvent->WaitForCompletion(INFINITE, &evCode);
        pControl->Stop();
    }
    // Clean up.
    pRenderEngine->ScrapIt();
    }
    CoUninitialize();
}