The FDFilter program demonstrates how to use DirectSound to implement full duplex audio and a filter.
A microphone or other audio input is required.
Source: (SDK root)\Samples\Multimedia\DSound\Src\FDfilter
Executable: (SDK root)\Samples\Multimedia\DSound\Bin
When you start the program, it presents you with a dialog box that contains pull-down lists of the sound input and output devices attached to your computer. Select the appropriate devices. Usually the defaults are the most appropriate.
You next see lists of sampling rates for the input and output buffers. Select an output format, then an input format. You can change these formats later from the Settings menu.
The program then shows a dialog box that enables you to select the filter. The available options are None (pass-through), which just plays back the input sound as is, or Gargle, which distorts the input sound into a gargling noise. Click Enable to begin capturing and playing sound.
FDFilter is designed to be a simple example of how one might go about implementing full-duplex audio. It is designed primarily to show application developers the proper sequence of steps for dealing with the sound devices installed on the system for using full-duplex audio with waveIn as an input source and DirectSound as the output device.
For more information, see the Readme.txt file in the Fdfilter directory.