Requirements for a GFX Filter Factory

In order for the operating system to be able to treat an AVStream filter factory as a factory for GFX filters, the factory should do the following:

• It should register its device interface in both the KSCATEGORY_AUDIO and KSCATEGORY_DATATRANSFORM device classes.
• It should have one input and one output pin.
• It should add a Gfx subkey to the filter's KSCATEGORY_AUDIO device-interface registry key. The filter factory’s INF file typically uses AddReg directives to add the Gfx subkey to the registry path during driver installation.