Sunday, April 3, 2016

Taking Back From Android

Android is an operating system developed by Google around the Linux kernel. It is not like any other Linux distribution, because not only many common subsystems have been replaced by other components, but also the user interface is radically different based on Java language running into a virtual machine called Dalvik.

An example of subsystem removed from the Linux kernel is the ALSA Sequencer, which is a key piece for MIDI input/output with routing and scheduling that makes Linux comparable in capabilities to Mac OSX for musical applications (for musicians, not whistlers) and years ahead of Microsoft Windows in terms of infrastructure. Android did not offer anything comparable until Android 6 (Marshmallow).

Another subsystem from userspace Linux not included in Android is PulseAudio. Instead, OpenSL ES that can be found on Android for digital audio output and input.

But Android also has some shining components. One of them is Sonivox EAS (originally created by Sonic Network, Inc.) released under the Apache 2 license, and the MIDI Synthesizer used by my VMPK for Android application to produce noise. Funnily enough, it provided some legal fuel to Oracle in its battle against Google, because of some Java binding sources that were included in the AOSP repositories. It is not particularly outstanding in terms of audio quality, but has the ability of providing real time wavetable GM synthesis without using external soundfont files, and consumes very little resources so it may be indicated for Linux projects on small embedded devices. Let's take it to Linux, then!

So the plan is: for the next Drumstick release, there will be a Drumstick-RT backend using Sonivox EAS. The audio output part is yet undecided, but for Linux will probably be PulseAudio. In the same spirit, for Mac OSX there will be a backend leveraging the internal Apple DLS synth. These backends will be available in addition to the current FluidSynth one, which provides very good quality, but uses expensive floating point DSP calculations and requires external soundfont files.

Meanwhile, I've published on GitHub this repository including a port of Sonivox EAS for Linux with ALSA Sequencer MIDI input and PulseAudio output. It also  depends on Qt5 and Drumstick. Enjoy!

Sonivox EAS for Linux and Qt:

Related Android project: