Note that the waveOut API always uses the best SRC quality regardless of the setting of the DirectSound SRC slider. These settings affect only DirectSound applications. This behavior improves stability and prevents software from placing the audio system in a state from which it cannot be removed without rebooting.
No API is available for changing the hardware-acceleration or SRC setting from an application program. The hardware-acceleration and SRC settings can be changed only by direct end-user action.
Changes made to the hardware-acceleration and SRC sliders are persistent across boot-ups. The sliders control the level of hardware acceleration and quality of sample-rate conversion (SRC) that are made available to DirectSound applications. Windows provides global slider controls for altering DirectSound performance on a system-wide basis. DirectSound Hardware-Acceleration and SRC Sliders