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I am trying to make a Rust program that emulates a webcam. This question and this answer suggest that the best way to do this is by creating a DirectShow source filter. Based on the PushSource sample in the Windows SDK and some C# implementations on CodeProject, it seems like the canonical way to do this is to extend the DirectShow BaseClasses provided in the Windows SDK. However, this is where my understanding breaks down.

  • I found the cxx crate and was able to get the classes from BaseClasses into my program, but how do I inherit from them or instantiate them? This crate does not seem to be designed for use with COM, and it is not clear how to call the constructors of classes.
  • Once I have done that first part, how do I expose my new classes as COM components? I found the com crate, but it seems to expect me to import the base classes using their GUIDs. However, I have no idea how to figure out what their GUIDs might be.
laptou
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    Well, I recommend thinking about it in a different way. You cannot "inherit" another COM class in this way. It's probably even wrong to think at all of what language the DirectShow base classes are written in. Instead, you want to implement your new object that supports the interfaces. You can reuse objects already made through COM containment or aggregation. See this answer for other ways to think about the problem: https://stackoverflow.com/questions/1644273/what-is-the-difference-between-aggregation-composition-and-dependency – Joseph Willcoxson Aug 28 '20 at 13:43

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