warning: pre-alpha subject to change

A Ruby binding for the aubio library.

What is aubio?

In their own words...

aubio is a tool designed for the extraction of annotations from audio signals. Its features include segmenting a sound file before each of its attacks, performing pitch detection, tapping the beat and producing midi streams from live audio.


brew install aubio --with-libsndfile --with-fftw --with-libsamplerate

Using ffi_gen to autogenerate bindings

brew install aubio --with-libsndfile --with-fftw --with-libsamplerate
brew install llvm --with-clang --enable-shared
# clone this repo and cd into the root folder, then run
LD_LIBRARY_PATH="/usr/local/opt/llvm35/lib/llvm-3.5/lib" ruby aubio-ffi-generator.rb


Add this line to your application's Gemfile:

gem 'aubio'

And then execute:

$ bundle

Or install it yourself as:

$ gem install aubio


Aubio just needs a path to a sound file:

my_file ="/path/to/file")

From there you can access the following:

my_file.onsets # list of extracted onsets
my_file.pitches # list of extracted pitches # where one would tap their foot
# NOT YET IMPLEMENTED # my_file.notes # list of onsets with pitches
# NOT YET IMPLEMENTED # my_file.silences # list of silent regions
# NOT YET IMPLEMENTED # my_file.mel_frequency_cepstral_coefficients # list of mfccs

All of these are Ruby Enumerators which means they'll respond to .next, and so on. If you want the whole list all at once call .to_a on it.

Avoiding memory leaks

The underlying C library allocates some memory so to clean this up you'll need to run


to free it up.

Data format

Each "event" that aubio describes is represented as a Hash like so:

my_file.onsets.first #=> {s: 0.0, ms: 0.0, start: 1, end: 0}

s and ms refer to seconds and milliseconds respectively.

start: 1 and end: 1 are special events that describe the start and the end of the audio file respectively. Whilst the start event at 0.0s is usually an onset, the end is a convenience added by the Ruby wrapper to allow for easier slicing of sound files into samples.

Still to implement

relative is the point at which the event occurs relative to the overall length of the original sound file, scaled between 0 and 1 (i.e. relative: 0.5 is exactly halfway through).

confidence is a score returned from aubio which may be useful for threshold type operations.

Optional params

The Aubio#open method can take a list of optional params like so:

# Fetch the input source, resampled at the given sampling rate. The rate should be specified in Hertz as an integer. If 0, the sampling rate of the original source will be used. Defaults to 0.
The size of the buffer to analyze, that is the length of the window used for spectral and temporal computations. Defaults to 512.

e.g."/path/to/audio/file", sample_rate: 44100)

Bugs / Still to do

  • better tests
  • use Onsets class as a basis to implement the other functions
  • improve accuracy of bpm - seems to be consistently too fast on things I've tried
  • look into streaming results for live inputs


After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to


Bug reports and pull requests are welcome on GitHub at This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.


The gem is available as open source under the terms of the MIT.