IPreFetchOffset interface (portcls.h)

The IPreFetchOffset interface controls the prefetch offset, which is the number of bytes separating the play and write cursors in a DirectSound output stream. A WavePci miniport driver can use this interface to prevent the prefetch offset from growing too large when the driver allocates a large number of mappings. This interface is supported only in Windows XP and later. To determine whether the WavePci port driver supports the IPreFetchOffset interface, a miniport driver calls the port stream (IPortWavePciStream) object's QueryInterface method with REFIID IID_IPreFetchOffset.

For more information about the IPreFetchOffset interface, see Prefetch Offsets.

Inheritance

The IPreFetchOffset interface inherits from the IUnknown interface. IPreFetchOffset also has these types of members:

Methods

The IPreFetchOffset interface has these methods.

IPreFetchOffset::SetPreFetchOffset The SetPreFetchOffset method sets the prefetch offset, which is the number of bytes of data separating the write cursor from the play cursor in a DirectSound output stream.

Requirements

Requirement	Value
Target Platform	Windows
Header	portcls.h