Well it only shows IPC as playing if the driver is engaged. So I think something must be engaging the WDM driver.
Thank you for reiterating that. It led me to figure out the issue. A small app (now) called AVR Guard:
http://forums.guru3d.com/showthread.php?t=339273The version I had was called AVR Audio Switch Fix, before it was finalised as AVR Guard.
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A lot of people have the Silent Stream Bug with their HDMI outputs from nVidia cards to their AVRs. When audio is played, starting from silence the AVR would switch modes and since that took up to 2 seconds or so, the beginning of the audio was missed; short sounds were lost altogether.
AVR Guard was a solution for this, by playing 'silence' through the HDMI all the time. However, it never worked for me, or many others. Over time I forgot I had it installed, or resolved to play with the settings, upgrade to new versions etc. I never did.
My 'WDM problem' was due to this app working in the background. When I pause or deactivate the app, all is well in the MC world.
I will eliminate AVR Audio Switch Fix / AVR Guard from my system.
The GREAT news is that the WDM properly fixes the Silent Stream Bug for me. I will confirm that it does so independently of AVR Audio Switch Fix / AVR Guard once I have removed the latter totally.