Editing DirectSound (section)

===Windows 9x===
In Windows 95, 98 and Me, the DirectSound mixer component and the sound card drivers were both implemented as a [[kernel-mode]] [[VxD]] driver (Dsound.vxd), allowing direct access to the primary buffer used by the audio hardware and thus, providing the lowest possible latency between the user-mode API and the underlying hardware, but in some cases causing instability and [[Blue Screen of Death|blue screen]] errors.

Windows 98 introduced WDM Audio and the ''Kernel Audio Mixer'' driver ([[KMixer]]), which enabled digital mixing, routing and processing of simultaneous audio streams with a higher quality sample rate conversion as well as kernel streaming. Under WDM, DirectSound sends data to the software-based KMixer. Windows 98 Second Edition improved WDM audio support by adding DirectSound hardware buffering, DirectSound3D hardware abstraction, KMixer sample-rate conversion (SRC) for capture streams, multichannel audio support and introduction of [[DirectMusic]]. If the audio hardware supports [[hardware mixing]] (also known as hardware buffering or DirectSound hardware acceleration), DirectSound buffers directly to the rendering device.<ref>[http://msdn.microsoft.com/en-us/library/windows/desktop/ee416769(v=vs.85).aspx DirectSound Driver Models]</ref> If DirectSound streams use hardware mixing, KMixer and its latency delay are bypassed.<ref>[http://msdn.microsoft.com/en-us/library/windows/hardware/ff537603(v=vs.85).aspx Overview of DirectSound Hardware Acceleration]</ref> On Windows 98 and Windows Me, WDM audio drivers were preferred but compatibility with VxD driver model was preserved.

Although [[Windows Driver Model]] (WDM) was available starting with Windows 98, few audio card manufacturers used it. Due to internal buffering, KMixer introduced significant processing latency (30 ms on then-current systems). Windows 98 also includes a WDM streaming class driver (Stream.sys) to address these real time multimedia data stream processing requirements. When the sound card uses a custom driver for use with the system supplied port class driver ''PortCls.sys'' or implements a mini-driver for use with the streaming class driver, applications can bypass the KMixer completely and use the kernel streaming interfaces instead to reduce latency.