Real-Time Digital Signal Processing Using pyaudio_helper and the ipywidgets

The focus of this paper is on teaching real-time digital signal processing to electrical and computer engineers using the Jupyter notebook and the code module pyaudio_helper, which is a component of the package scikit-dsp-comm. Specifically, we show how easy it is to design, prototype, and test using PC-based instrumentation, real-time DSP algorithms for processing analog signal inputs and returning analog signal outputs, all within the Jupyter notebook. A key feature is that real-time algorithm prototyping is simplified by configuring a few attributes of a DSP_io_stream object from the pyaudio_helper module, leaving the developer to focus on the real-time DSP code contained in a callback function, using a template notebook cell. Real-time control of running code is provided by ipywidgets. The PC-based instrumentation aspect allows measurement of the analog input/output (I/O) to be captured, stored in text files, and then read back into the notebook to compare with the original design expectations via matplotlib plots. In a typical application slider widgets are used to change variables in the callback. One and two channel audio applications as well as algorithms for complex signal (in-phase/quadrature) waveforms, as found in software-defined radio, can also be developed. The analog I/O devices that can be interfaced are both internal and via USB external sound interfaces. The sampling rate, and hence the bandwidth of the signal that can be processed, is limited by the operating system audio subsystem capabilities, but is at least 48 KHz and often 96 kHz.