Near real-time signal processing in the classroom using a sound card equipped personal computer

Many university signal-processing teaching laboratories do not have sufficient resources (both equipment and knowledgeable support personnel) to provide dedicated real-time signal-processing hardware at each student workstation position. Because of this limitation, many students must be content with using personal computers to process non-real time signals that are stored on disk and/or described by mathematical formulas. These students cannot connect a physical audio source (i.e., microphone, CD player, etc.) to a computer sound card line input, filter the source audio with a student-written software program, and play the filtered audio through the computer speakers, all in real time. This paper shows how to accomplish this task (known as full-duplex streaming) with the aid of multiple buffers that are managed by DirectSound. Using the approach outlined here, it is possible to create a PC-based, inexpensive, real-time signal-processing platform for the resource-challenged instructional signal-processing laboratory.