Wiki¶

Vamp environment for feature extraction¶

Vamp is an audio processing plugin system for plugins that extract descriptive information from audio data — typically referred to as audio analysis plugins or audio feature extraction plugins. The vamp plugins are distributed in shared library files with extension .dll, .so, or .dylib depending on the platform.
See [[http://vamp-plugins.org/]] for more details about Vamp plugins.

Several common audio file formats are supported, including MP3, Ogg, and a number of PCM formats such as WAV and AIFF. AAC is supported on OS/X only, and only if not DRM protected. WMA is not supported.

Host applications¶

A vamp plugin cannot be used on its own, but only with a conforming host application which loads the plugin from its shared library and calls functions within the plugin code to configure it, supply it with data, and run it.

• Sonic Visualiser -- An interactive audio analysis and visualisation tool using Vamp plugins
  [[http://www.sonicvisualiser.org/]]
• Sonic Annotator -- A command line tool facilitating facilitating feature extraction, parameter configuration and output manipulation for a large bunch of audio files.
  [[https://code.soundsoftware.ac.uk/projects/sonic-annotator]]
• Audacity -- An audio editor which enables recording, labelling and editing the audio.
  [[http://audacityteam.org/]]

Plugin installation¶

The vamp plugins need to be put in a directory where the host can locate, i.e., the VAMP_PATH. See [[http://vamp-plugins.org/download.html#install]] for installation instructions.

Alternatively, you can set your own VAMP_PATH environment variable to list the locations a host should look in for Vamp plugins. For example, the following command will set /homes/mtian/hg/onset-fusion as an alternative VAMP_PATH. Plugins placed in this directory will also be locatable for the hosts besides those under the system specified vamp directories.

mitian$ export VAMP_PATH=$VAMP_PATH:/homes/mtian/hg/onset-fusion

Once the plugins are installed in the Vamp path, they will show themselves under the Transform tab in Sonic Visualiser, or the Analyze tab in Audacity, or in the terminal when you list them using Sonic Annotator ( sonic-annotator -l).

Parameters and outputs of this plugin set¶

Parameters

    Fusion Type                        Fusion type [0: early fusion, 1: linear fusion, 2: decision fusion]
    Detection Sensitivity           Sensitivity level for peak detection in the onset likelihood function.
                                       The higher the sensitivity, the more onsets will (rightly or wrongly) be detected.
    Delta Threshold                 Constant offset used for adaptive theresholding using the median of the detection function.
    Backtracking Threshold             Backtracking threshold used determine the stopping condition for backtracking the detected onset location
                                    to an earlier 'perceived' location.
    Tolerance window                   Tolerance window to combine events from different detection functions for decision fusion.
    Linear combination coefficient     Combination coefficient for linear fusion.
    Median filter window               Median filter window size.
    Cutoff frequency                   Cutoff frequency for the low pass filter.

    **bool parameters**                [0: off, 1: on]
    Polynomial fitting                 Use polynomial fitting to evaluate detection function peaks.
    Median filtering                   Use median filter based adaptive thresholding.
    Low-pass filtering                 Use low pass filtering to smooth onset detection functions.
    Adaptive whitening                 Use adaptive whitening. It evens out the temporal and frequency variation in the signal.

Outputs¶

1. Note Onsets – The detected note onset times, returned as a single feature with timestamp.
2. Smoothed Detection Function – The smoothed onset detection function.
3. Note Onsets – The detected note onset times, returned as a single feature with timestamp.

NOTE: The last two outputs are not available in fusion based onset detectors.

Example usages of the onset detectors¶

mitian$ sonic-annotator -l | grep vampy-onsets
vamp:vampy:vampy-onsets-bersf:vampy-onsets-bersf-onsets
vamp:vampy:vampy-onsets-cdsf:vampy-onsets-cdsf-onsets
vamp:vampy:vampy-onsets-ber:vampy-onsets-ber-df
vamp:vampy:vampy-onsets-ber:vampy-onsets-ber-onsets
vamp:vampy:vampy-onsets-ber:vampy-onsets-ber-sdf
vamp:vampy:vampy-onsets-cd:vampy-onsets-cd-df
vamp:vampy:vampy-onsets-cd:vampy-onsets-cd-onsets
vamp:vampy:vampy-onsets-cd:vampy-onsets-cd-sdf
vamp:vampy:vampy-onsets-hfc:vampy-onsets-hfc-df
vamp:vampy:vampy-onsets-hfc:vampy-onsets-hfc-onsets
vamp:vampy:vampy-onsets-hfc:vampy-onsets-hfc-sdf
vamp:vampy:vampy-onsets-pd:vampy-onsets-pd-df
vamp:vampy:vampy-onsets-pd:vampy-onsets-pd-onsets
vamp:vampy:vampy-onsets-pd:vampy-onsets-pd-sdf
vamp:vampy:vampy-onsets-sd:vampy-onsets-sd-df
vamp:vampy:vampy-onsets-sd:vampy-onsets-sd-onsets
vamp:vampy:vampy-onsets-sd:vampy-onsets-sd-sdf
vamp:vampy:vampy-onsets-sf:vampy-onsets-sf-df
vamp:vampy:vampy-onsets-sf:vampy-onsets-sf-onsets
vamp:vampy:vampy-onsets-sf:vampy-onsets-sf-sdf
mitian$
mitian$ sonic-annotator -d vamp:vampy:vampy-onsets-cdsf:vampy-onsets-cdsf-onsets -w csv test.wav --csv-basedir /homes/mitian/hg/workspace/onsetdetection
Extracting and writing features... Done

Vampy::~PyExtensionManager: Extension module cleaned.
mitian$
mitian$

Sonic Anntator also allows for batch processing in one go.

mitian$
mitian$ sonic-annotator -d vamp:vampy:vampy-onsets-cdsf:vampy-onsets-cdsf-onsets -w csv /homes/mitian/documents/audio/*.wav --csv-basedir /homes/mitian/hg/workspace/onsetdetection
Extracting and writing features... Done

Vampy::~PyExtensionManager: Extension module cleaned.
mitian$
mitian$

Play around with your vamp plugin feature extractors¶

We may want use parameter settings other the default. With Sonic Visualiser or Audacity, you can easily access the GUI to modify them. Whiles with Sonic Annotator, you would need to interact with

Firstly, we can check the current parameter configurations in the skeleton transform description using Sonic Annotator's -s command.

mitian$
mitian$ sonic-annotator -s vamp:vampy:vampy-onsets-cdsf:vampy-onsets-cdsf-onsets
@prefix xsd:      <http://www.w3.org/2001/XMLSchema> .
  @prefix vamp:     <http://purl.org/ontology/vamp/> .
  @prefix :         <#> .

:transform_plugin a vamp:Plugin ;
    vamp:identifier "vampy-onsets-cdsf" .

:transform_library a vamp:PluginLibrary ;
    vamp:identifier "vampy" ;
    vamp:available_plugin :transform_plugin .

:transform a vamp:Transform ;
    vamp:plugin :transform_plugin ;
    vamp:step_size "512"^^xsd:int ;
    vamp:block_size "1024"^^xsd:int ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "bt-threshold" ] ;
        vamp:value "0.9"^^xsd:float ;
    ] ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "cut-off" ] ;
        vamp:value "0.34"^^xsd:float ;
    ] ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "dthreshold" ] ;
        vamp:value "0"^^xsd:float ;
    ] ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "filtfilt" ] ;
        vamp:value "1"^^xsd:float ;
    ] ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "fusion-type" ] ;
        vamp:value "2"^^xsd:float ;
    ] ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "lin-threshold" ] ;
        vamp:value "0.5"^^xsd:float ;
    ] ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "med-threshold" ] ;
        vamp:value "7"^^xsd:float ;
    ] ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "medfilt" ] ;
        vamp:value "1"^^xsd:float ;
    ] ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "polyfit" ] ;
        vamp:value "1"^^xsd:float ;
    ] ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "threshold" ] ;
        vamp:value "50"^^xsd:float ;
    ] ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "tol-threshold" ] ;
        vamp:value "0.03"^^xsd:float ;
    ] ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "whitening" ] ;
        vamp:value "0"^^xsd:float ;
    ] ;
    vamp:output [ vamp:identifier "vampy-onsets-cdsf-onsets" ] .
mitian$

Transforms are usually described in RDF, following the transform part of the Vamp plugin ontology. Now, how can be change the parameter settings in the transform specification file?

The solution is to save this RDF file and modify any content in it as we wish, then to run this transform by specifying the saved file with -t options. Let's see an example.

mitian$
mitian$ sonic-annotator -s vamp:vampy:vampy-onsets-cdsf:vampy-onsets-cdsf-onsets >param_config.n3
mitian$

Now the transform file has been saved to the .n3 (RDF) file. Say, we want to use a higher threshold and change it from 50 to 70. Open an text editor, simple modify the corresponding line

        vamp:parameter [ vamp:identifier "threshold" ] ;
        vamp:value "50"^^xsd:float ;

into

        vamp:parameter [ vamp:identifier "threshold" ] ;
        vamp:value "70"^^xsd:float ;

and save it.

Now we can run the same plugin using the modified parameter settings.

mitian$
mitian$ sonic-annotator -t param_config.n3 -w csv test.wav --csv-basedir /homes/mitian/hg/workspace/onsetdetection
Extracting and writing features... Done

Vampy::~PyExtensionManager: Extension module cleaned.
mitian$
mitian$

That's all guys! Let's hack with Vamp plugins :)¶