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IUnknown::QueryInterface

  • Article
  • Note   This topic describes IUnknown in the context of the AVIFile and AVIStream interfaces. For general information about IUnknown, see the Component Object Model (COM) documentation in the Windows SDK.

The QueryInterface method determines if an interface can be used with an object. Used by the following interfaces: IAVIEditStream, IAVIFile, IAVIStream, IAVIStreaming, and IGetFrame.

HRESULT QueryInterface(
  LPUNKNOWN ps,      
  const IID & riid,  
  void **ppvObj       
);

Parameters

ps

Pointer to an IAVIEditStream, IAVIFile, IAVIStream, IAVIStreaming, or IGetFrame interface.

riid

Identifier of the interface being queried.

ppvObj

Pointer to a buffer that receives a pointer to the object whose interface is queried or NULL when an interface is not supported.

Return Values

Returns a pointer to the current interface if successful or E_NOINTERFACE otherwise.

Remarks

For handlers written in C++, QueryInterface has the following syntax:

HRESULT QueryInterface(const IID &riid, void **ppvObj);

Requirements

**  Windows NT/2000/XP:** Requires Windows NT 3.1 or later.
**  Windows 95/98/Me:** Requires Windows 95 or later.
**  Header:** Declared in unknwn.h.

See Also

Custom File and Stream Handlers, Custom File and Stream Handler Interfaces, IAVIEditStream, IAVIFile, IAVIStream, IAVIStreaming, IGetFrame