Implementing Directshow IFileSourceFilter interface in a CSource based Filter

I implement simple Directshow Filter which derived from CSource filter. It work fine. What i want is to add the filter IFileSourceFilter. So what i do for this is:

I implement FileSourceFilter interface with two methods:

HRESULT Load(LPCOLESTR lpwszFileName, const AM_MEDIA_TYPE *pmt)
HRESULT GetCurFile(LPOLESTR * ppszFileName, AM_MEDIA_TYPE *pmt)

For now [ Just for test purposses] They do nothing

// Required by  IFileSourceFilter 

STDMETHODIMP Load(LPCOLESTR lpwszFileName, const AM_MEDIA_TYPE *pmt)
{
         // do nothing for now...Just for test
         return S_OK;
}
STDMETHODIMP GetCurFile(LPOLESTR * ppszFileName, AM_MEDIA_TYPE *pmt)
{
         // do nothing for now...Just for test
          return S_OK;
}

And also add the IFileSourceFilter interface to NonDelegatingQueryInterface method of my source filter.

 STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void **ppv)
{
     if (riid == IID_IFileSourceFilter) 
     {
           return GetInterface((IFileSourceFilter *)this, ppv);
     }
     else
     {
     return CSource::NonDelegatingQueryInterface(riid, ppv);
     }
}

When i insert my SourceFilter into the grapgEdit it nicely ask me file location...I give a random file[ for test porposes IFileSourceFilter interfcae DO开发者_如何学JAVA nothing for now)...

AndThen my SourceFilter Crash at the grah edit tool suddenly... .

Whay may be wrong?Do i missing something while implementing IFileSourceFilter interface? Any suggestion ideas for which may cause this?

Best Wishes

My SourceFilter Structure:

 class MySourceFilter : public CSource,public IFileSourceFilter 
{
public:

....
DECLARE_IUNKNOWN;

STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void **ppv)
{
     if (riid == IID_IFileSourceFilter) 
     {
           return GetInterface((IFileSourceFilter *)this, ppv);
     }
     else
     {
     return CSource::NonDelegatingQueryInterface(riid, ppv);
     }
}

// Required by  IFileSourceFilter 

STDMETHODIMP Load(LPCOLESTR lpwszFileName, const AM_MEDIA_TYPE *pmt)
{
         // do nothing for now...Just for test
         return S_OK;
}
STDMETHODIMP GetCurFile(LPOLESTR * ppszFileName, AM_MEDIA_TYPE *pmt)
{
         // do nothing for now...Just for test
          return S_OK;
}

}

I think you should return E_FAIL for now in the getCurFile function. Graphedit will ask the filter which file is loaded, and expects to receive the filename when GetCurFile returns S_OK. But ppszFileName will point to random memory, if you don't initialize it.

It would be better to actually return a value in getCurFile. Allocate memory using CoTaskMemAlloc for both the filename and mediatype. Then set a dummy filename, and memset the mediatype to 0. (but check if the pointers are not null).