|Microsoft DirectX 9.0|
Sources, effects, and transitions have internal pointers to other COM objects, called subobjects. The subobject performs the actual work of the object. The subobject of a source is the component that creates the video or audio data. The subobject of an effect or transition is the component that transforms the data; for example, in a video effect, it creates the visual effect in the video stream.
The type of subobject depends on the type of object:
Groups, compositions, and tracks do not have subobjects.
The application does not directly set the subobject pointer. For effects and transitions, the application calls the IAMTimelineObj::SetSubObjectGUID method to specify the GUID of the subobject. For source objects, an application typically calls the IAMTimelineSrc::SetMediaName to specify the name of a source file. However, the SetSubObjectGUID method can also be used for source objects, to specify the class identifier (CLSID) of a filter.
For more information, see Working with Sources and Working with Effects and Transitions.