IMFMediaEvent::GetValue method (mfobjects.h)

Retrieves the value associated with the event, if any. The value is retrieved as a PROPVARIANT structure. The actual data type and the meaning of the value depend on the event.

Syntax

HRESULT GetValue(
  [out] PROPVARIANT *pvValue
);

Parameters

[out] pvValue

Pointer to a PROPVARIANT structure. The method fills this structure with the data.

Return value

The method returns an HRESULT. Possible values include, but are not limited to, those in the following table.

Remarks

Before calling this method, call PropVariantInit to initialize the PROPVARIANT structure. After the method returns, call PropVariantClear to free the memory that was allocated for the PROPVARIANT data.

This interface is available on the following platforms if the Windows Media Format 11 SDK redistributable components are installed:

• Windows XP with Service Pack 2 (SP2) and later.
• Windows XP Media Center Edition 2005 with KB900325 (Windows XP Media Center Edition 2005) and KB925766 (October 2006 Update Rollup for Windows XP Media Center Edition) installed.

Examples

The following function gets the event value if the value is an IUnknown pointer. If the PROPVARIANT type is not VT_UNKOWN, the function returns MF_E_INVALIDTYPE.

//  Gets an IUnknown pointer from an IMFMediaEvent event and queries 
//  the pointer for a specified interface.
//
//  NOTE: Applies only to events that contain IUnknown pointers.
//        Otherwise, the function returns MF_E_INVALIDTYPE.

template <class Q>
HRESULT GetEventObject(IMFMediaEvent *pEvent, Q **ppObject)
{
    *ppObject = NULL;   // zero output

    PROPVARIANT var;
    HRESULT hr = pEvent->GetValue(&var);
    if (SUCCEEDED(hr))
    {
        if (var.vt == VT_UNKNOWN)
        {
            hr = var.punkVal->QueryInterface(ppObject);
        }
        else
        {
            hr = MF_E_INVALIDTYPE;
        }
        PropVariantClear(&var);
    }
    return hr;
}

Requirements

See also

IMFMediaEvent

Media Event Generators