Windows Vista features a completely re-written audio stack based on the Universal Audio Architecture. Because of the architectural changes in the redesigned audio stack,
a direct path from DirectSound to the audio drivers does not exist. DirectSound and other APIs such as MME are emulated as WASAPI Session instances.
DirectSound runs in emulation mode on the Microsoft software mixer. The emulator does not have hardware abstraction, so
there is no hardware DirectSound acceleration, meaning hardware and software relying on DirectSound acceleration may have degraded performance. It's likely a supposed performance hit might not be noticeable, depending on the application and actual system hardware.
In the case of hardware 3D audio effects played using DirectSound3D, they will not be playable.
Third-party APIs such as ASIO and OpenAL are not affected by these architectural changes in Windows Vista. A solution for applications that wish to take advantage of hardware accelerated high-quality 3D positional audio is to use OpenAL.
However, this only works if the manufacturer provides an OpenAL driver for their hardware