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In Windows 98 and Windows 2000, the WDM audio framework did not allow Windows clients to use the standard audio APIs (waveOut, DirectSound, and DirectShow) to play non-PCM audio data through the PortCls system driver.
This limitation has been removed in Windows Me, and Microsoft® Windows® XP and later, which can play audio data encoded in a non-PCM format such as AC3. In addition, a QFE (quick-fix engineering) package is available for Windows 98 SE that contains all fixes necessary to play non-PCM data through waveOut and DirectSound. Service Pack 2 for Windows 2000 also contains these fixes.
This section describes limitations in earlier versions of Windows that prevented clients from playing non-PCM audio, and presents a set of guidelines for adapting a WDM audio driver to support non-PCM data formats on more recent versions of Windows.