aubio Documentation

0.4.2~alpha

Introduction

aubio is a library to extract annotations from audio signals: it provides a set of functions that take an input audio signal, and output pitch estimates, attack times (onset), beat location estimates, and other annotation tasks.

Basics

All object structures in aubio share the same function prefixes and suffixes:

• new_aubio_foo creates the object foo
• aubio_foo_do executes the object foo
• del_aubio_foo destroys the object foo

All memory allocation and deallocation take place in the new_ and del_ functions. Optionally, more than one _do methods are available. Additional parameters can be adjusted and observed using:

• aubio_foo_get_param, getter function, gets the value of a parameter
• aubio_foo_set_param, setter function, changes the value of a parameter

Unless specified in its documentation, no memory operations take place in the getter functions. However, memory resizing can take place in setter functions.

Vectors

Two basic structures are being used in aubio: fvec_t and cvec_t. The fvec_t structures are used to store vectors of floating pointer number. cvec_t are used to store complex number, as two vectors of norm and phase elements.

Additionally, the lvec_t structure can be used to store floating point numbers in double precision. They are mostly used to store filter coefficients, to avoid instability.

Available objects

Here is a list of some of the most common objects for aubio:

  // fast Fourier transform (FFT)
  aubio_fft_t *fft = new_aubio_fft (winsize);
  // phase vocoder
  aubio_pvoc_t *pv = new_aubio_pvoc (winsize, stepsize);
  // onset detection
  aubio_onset_t *onset = new_aubio_onset (method, winsize, stepsize, samplerate);
  // pitch detection
  aubio_pitch_t *pitch = new_aubio_pitch (method, winsize, stepsize, samplerate);
  // beat tracking
  aubio_tempo_t *tempo = new_aubio_tempo (method, winsize, stepsize, samplerate);

See the list of typedefs for a complete list.

Example

Here is a simple example that creates an A-Weighting filter and applies it to a vector.

  // set window size, and sampling rate
  uint_t winsize = 1024, sr = 44100;
  // create a vector
  fvec_t *this_buffer = new_fvec (winsize);
  // create the a-weighting filter
  aubio_filter_t *this_filter = new_aubio_filter_a_weighting (sr);

  while (running) {
    // here some code to put some data in this_buffer
    // ...

    // apply the filter, in place
    aubio_filter_do (this_filter, this_buffer);

    // here some code to get some data from this_buffer
    // ...
  }

  // and free the structures
  del_aubio_filter (this_filter);
  del_fvec (this_buffer);

Several examples of C programs are available in the examples/ and tests/src directories of the source tree.

Unstable API

Several more functions are available and used within aubio, but not documented here, either because they are not considered useful to the user, or because they may need to be changed in the future. However, they can still be used by defining AUBIO_UNSTABLE to 1 before including the aubio header:

  #define AUBIO_UNSTABLE 1
  #include <aubio/aubio.h>

Future versions of aubio could break API compatibility with these functions without warning. If you choose to use functions in AUBIO_UNSTABLE, you are on your own.

Download

Latest versions, further documentation, examples, wiki, and mailing lists can be found at http://aubio.org .