ABout RegisterByteStreamHandler

Question

I need to develop a source reader for system unsupport format, like, mkv.

So i call RegisterByteStreamHandler in the client app, like this:

_extensionManager->RegisterByteStreamHandler("MKVSource.MKVByteStreamHandler", ".mkv", "video/mkv");

define IDL:

namespace MKVSource
{
	[version(NTDDI_WIN8)]
    runtimeclass MKVByteStreamHandler
    {
		[default] interface Windows.Media.IMediaExtension;
    }
}

But when i call SetSource of mediaelement, MF didn't instance the MKVByteStreamHandler, why?

---

haha