Windows Driver Kit: Audio Devices
Windows Vista Default sAPOs
With Windows Vista the audio driver does not provide digital audio system effects. All digital signal processing for creating system effects is provided by real-time in-process COM objects called system effects audio processing objects (sAPOs).
provides an Enhancements tab with the Sound applet on the Control Panel for configuring these system effects. The sAPOs provided by default with Windows Vista are shown in the following list.