For more information about AVStream, see AVStream Overview. For more information about PortCls, see Introduction to Port Class. PortCls is the correct choice for most audio adapters. Both PortCls and AVStream are part of the Windows operating system. However, if a vendor-supplied custom audio driver is necessary, the vendor must choose whether the driver should be designed to work in conjunction with the PortCls system driver (Portcls.sys) or the AVStream class system driver (Ks.sys). The vendor does not need to provide a custom driver for a UAA-compatible audio device. Windows contains operating-system support for PCI, USB, and IEEE 1394 devices that conform to the Microsoft Universal Audio Architecture (UAA) guidelines.

The first decision is whether to design an audio device that requires a vendor-supplied custom driver. Hardware vendors should make several design decisions before beginning development of a Windows-based audio hardware device. Windows Driver Model (WDM) audio drivers make use of the kernel streaming (KS) components, which operate in kernel mode and are part of the operating system.

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