IAMWMBufferPass interface

The IAMWMBufferPass interface is implemented on the output pins of the WM ASF Reader and the input pins of the WM ASF Writer. Applications can use this interface to get or set properties on individual samples in an ASF stream. Applications can also use it to get or set data unit extensions. To use this interface, implement the IAMWMBufferPassCallback interface in your application. Then call IAMWMBufferPass::SetNotify on the filter's pin with a pointer to the callback interface.

One common use for this interface is to force key-frame insertion in a variable bit rate video stream during file writing. To do this, you must set the WM_SampleExtensionGUID_OutputCleanPoint property using the INSSBuffer3 interface on the sample. For more information about sample extensions, see the Windows Media Format SDK documentation.


The IAMWMBufferPass interface inherits from the IUnknown interface. IAMWMBufferPass also has these types of members:


The IAMWMBufferPass interface has these methods.


Sets an application-defined callback on the filter.



Minimum supported client

Windows XP with SP2 [desktop apps only]

Minimum supported server

Windows Server 2003 R2 [desktop apps only]


Windows Media Format 9 Series or later



See also

Using Windows Media in DirectShow