Topology Port Driver
The Topology port driver exposes the topology of the audio adapter's mixing hardware. For example, the hardware that mixes the playback streams from the wave renderer and MIDI synthesizer in a typical adapter can be modeled as a set of control nodes (volume, mute, and sum) plus the data paths that connect the nodes. This topology is exposed as a set of controls and mixer lines by the Windows multimedia mixer API (see Kernel Streaming Topology to Audio Mixer API Translation). The adapter driver provides a corresponding Topology miniport driver that binds to the Topology port driver to form a topology filter.