Making Musical Apps

Chapter 4. Embedding Pure Data with libpd

Pure Data was originally designed to be an interactive tool for computer music and multimedia, tightly integrating a dataflow programming language and signal processing with a graphical user interface and support for various audio and MIDI interfaces. In this capacity, Pd runs as the top-level application, managing most aspects of its operation and only intermittently delegating control to the audio subsystem of the operating system. The usual way to port Pd to a new platform is by extending Pd, adding support for a new audio API and possibly new objects, known as externals, that make special capabilities of the new platform available to Pd.

When I started thinking about porting Pd to Android, I quickly realized that the usual approach wouldn’t work. At the time, it was possible for Android apps to have native components written in C, but the main body of an app still had to be written in Java. This restriction has since been lifted, but at the time it was impossible to run an extension of Pd as an Android app. Rather, I had to turn the usual model on its head; instead of extending Pd for a new purpose, I had to find a way to embed Pd into Android apps.

Introducing libpd

After much refactoring, the first prototype of an Android port of Pd fell into five main pieces: Pd itself; a thin wrapper on top of Pd that turns it into an embeddable audio library; Java bindings for this library; some platform-specific glue that ties the Java bindings into ...