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Step 5. Store a Pointer to the Filter

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[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

Override the CBasePropertyPage::OnConnect method to store a pointer to the filter. The following example queries the pUnk parameter for the filter's custom ISaturation interface:

HRESULT CGrayProp::OnConnect(IUnknown *pUnk)
{
    if (pUnk == NULL)
    {
        return E_POINTER;
    }
    ASSERT(m_pGray == NULL);
    return pUnk->QueryInterface(IID_ISaturation, 
        reinterpret_cast<void**>(&m_pGray));
}

Next: Step 6. Initialize the Dialog.

Creating a Filter Property Page