I guess you forget to register you components in manifest. (Needs to open by text editor directly.)
Here are the steps:
Step 1: Register the dll in the extensions section of the package.appxmanifest file
<Extensions>
<Extension Category="windows.activatableClass.inProcessServer">
<InProcessServer>
<Path>SSMFPluginM.dll</Path>
<ActivatableClass ActivatableClassId="Microsoft.IIS.SSMFByteStreamHandler" ThreadingModel="both" />
</InProcessServer>
</Extension>
</Extensions>
Step 2: In your app, register the BSH for a certain extension/mime-type
var plugins = new Windows.Media.MediaExtensionManager();
try {
// Register custom ByteStreamHandler
plugins.registerByteStreamHandler("Microsoft.IIS.SSMFByteStreamHandler", ".ism", "text/xml");
}
catch (e) {
log(e.message);
}
You can check the Media Plugins Sample for more detail.
http://code.msdn.microsoft.com/windowsapps/Media-Plugins-Sample-8913a7e9
Eric