[LoRd_MuldeR]

Hmm, actually my tool should be prepared for multi-channel audio and higher bit-depths. It dumps the audio data as received.

What you see below "[Audio Properties]" is exactly what the WMReader object reports for the audio stream. So it obviously does the down-mix automatically.
I don't know if there is a way to convince the WMReader object to output the "native" audio without downmixing. But I will look into this. Tomorrow...

For the moment, here is a small update that will detect and print out some Codec information.