NPAPI plugin not being invoked always

[adnan-kamili]

I have written NPAPI plugin using firebreath. It works fine for all the registered mime-types. The plugin is registered for video/x-flv also. Now, whenever i type a url in address bar whose response header contains video/x-flv content type, my plugin is invoked and it handles the response. But i observed, that when we play any flash video in browser, suppose in youtube, firefox sends many requests whose response contain video/x-flv as content type, but my plugin is not invoked. Why those requests remain transparent to my plugin? Same thing can be observed for vlc web plugin, which is also registered for video/x-flv content type.