@Roman Ryltsov, Four years have past since I raised this question. Now I found the problem was in my EnumPins handling. I declared CComPtr<IPin> outside of the loop, but forgot to release it before next iteration, quite primitive mistake.

Now, my own media player can play audio as well as video at least on my setup, upnp connections and CD ripping too. I know VLC or others are already available, but I wanted to build my own, haha