Python Vamp plugin host

This module allows Python code to load and use native-code Vamp plugins (http://vamp-plugins.org) for audio feature analysis.

The module consists of a native-code extension ("vampyhost") that provides a low-level wrapper for the Vamp plugin SDK, along with a Python wrapper ("vamp") that provides a higher-level abstraction.

No code for loading audio files is included; you'll need to use some other module for that. This code expects to receive decoded audio data of one or more channels, either as a series of frames or as a single whole buffer.

Written by Chris Cannam and George Fazekas at the Centre for Digital Music, Queen Mary University of London. Copyright 2008-2015 Queen Mary, University of London. Refer to COPYING.rst for licence details.

See home page at https://code.soundsoftware.ac.uk/projects/vampy-host for more details.

A simple example

Using librosa (http://bmcfee.github.io/librosa/) to read an audio file, and the NNLS Chroma Vamp plugin (https://code.soundsoftware.ac.uk/projects/nnls-chroma/) for analysis:

>>> import vamp
>>> import librosa
>>> data, rate = librosa.load("example.wav")
>>> chroma = vamp.collect(data, rate, "nnls-chroma:nnls-chroma")
>>> chroma
{'matrix': ( 0.092879819, array([[  61.0532608 ,   60.27478409,   59.3938446 , ...,  182.13394165,
          42.40084457,  116.55457306],
       [  68.8901825 ,   63.98115921,   60.77633667, ...,  245.88218689,
          68.51251984,  164.70120239],
       [  58.59794617,   50.3429184 ,   45.44804764, ...,  258.02362061,
          83.95749664,  179.91200256],
       ...,
       [   0.        ,    0.        ,    0.        , ...,    0.        ,
           0.        ,    0.        ],
       [   0.        ,    0.        ,    0.        , ...,    0.        ,
           0.        ,    0.        ],
       [   0.        ,    0.        ,    0.        , ...,    0.        ,
           0.        ,    0.        ]], dtype=float32))}
>>> stepsize, chromadata = chroma["matrix"]
>>> import matplotlib.pyplot as plt
>>> plt.imshow(chromadata)
<matplotlib.image.AxesImage object at 0x7fe9e0043fd0>
>>> plt.show()

And a pitch-chroma plot appears.

High-level interface (vamp)

This module contains three sorts of function:

1. Basic info and lookup functions

• vamp.list_plugins
• vamp.get_outputs_of
• vamp.get_category_of

These retrieve the installed plugin keys and get basic information about each plugin. (For more detailed information, load a plugin and inspect it using the low-level interface described below.)

2. Process functions

• vamp.process_audio
• vamp.process_frames
• vamp.process_audio_multiple_outputs
• vamp.process_frames_multiple_outputs

These accept audio input, and produce output in the form of a list of feature sets structured similarly to those in the C++ Vamp plugin SDK. The plugin to be used is specified by its key (the identifier as returned by vamp.list_plugins). A dictionary of plugin parameter settings may optionally be supplied.

The _audio versions take a single (presumably long) array of audio samples as input, and chop it into frames according to the plugin's preferred step and block sizes. The _frames versions instead accept an enumerable sequence of audio frame arrays.

3. The process-and-collect function

• vamp.collect

This accepts a single array of audio samples as input, and returns an output structure that reflects the underlying structure of the feature output (depending on whether it is a curve, grid, etc). The plugin to be used is specified by its key. A dictionary of plugin parameter settings may optionally be supplied.

The collect function processes the whole input before returning anything; if you need to supply a streamed input, or retrieve results as they are calculated, then you must use one of the process functions (above) or else the low-level interface (below).

Low-level interface (vampyhost)

This extension contains facilities that operate on Vamp plugins in a way analogous to the existing C++ Vamp Host SDK: list_plugins, get_plugin_path, get_category_of, get_library_for, get_outputs_of, load_plugin, and a utility function frame_to_realtime.

Calling load_plugin gets you a vampyhost.Plugin object, which then exposes all of the methods found in the Vamp SDK Plugin class.

(Note that methods wrapped directly from the Vamp SDK are named using camelCase, so as to match the names found in the C++ SDK. Elsewhere this module follows Python PEP8 naming.)

See the individual module and function documentation for further details.