The functionality can be implemented in software or in hardware. Data buffering is typically required to smooth out momentary mismatches in the rates at which an output pin produces data and an input pin consumes it.Ī KS filter is implemented as a kernel-mode driver object that encapsulates some number of related stream-processing functions. The data stream from the output pin must have a data format that the input pin can accept.

The output pin of the upstream filter is connected to the input pin of the downstream filter. In some contexts, the terms pin and stream can be used interchangeably. A client instantiates an input or output pin on a filter when the client needs to route a data stream into or out of that filter.

A pin on an audio filter can be thought of as an audio jack. KS filters are connected together through their pins. The operating system connects the filters to other filters to form filter graphs that process audio streams on behalf of application programs. The adapter driver can wrap each of these audio devices in a KS filter that it exposes to the operating system. More complex functions can be constructed in a modular way by cascading several filters together to form a filter graph.Ī typical audio adapter card might contain audio devices for playing a wave stream through a set of speakers, converting the audio signal from a microphone to a wave stream, and synthesizing sound from a MIDI stream. A set of related nodes is grouped together to form a KS filter, which represents a more-or-less independent block of stream-processing functionality. Conceptually, a stream undergoes processing as it flows along a data path containing some number of processing nodes. Kernel streaming (KS) services support kernel-mode processing of data streams for audio and for other types of continuous media.

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