There is a nice article how to enable debugging in DirectShow here:
http://us.generation-nt.com/directshow-debug-install-instructions-help-25270602.html
The only problem with this method is that you have to mess up with Windows File Protection and system directory. There is a safer solution to use the debug version of quartz.dll. All you need is just to copy the debug version into some local folder and run regsvr32 to register all the COM objects in the dll. To return to release build just run regsvr32 on the version which is in system32 directory.
