Audio Onset Detection based on Fusion

h1. Wiki

h2. 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.  

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.

See [[http://vamp-plugins.org/]] for more introduction about Vamp environment and the plugins.

h2. 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/]]

h2. 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/mitian/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.

<pre>

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

</pre>

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@). 

h2. Parameters and outputs of this plugin set

h3. Parameters

<pre>

    **Adjustable 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.

</pre>

h3. Outputs

# Note Onsets – The detected note onset times, returned as a single feature with timestamp.

# Smoothed Detection Function – The smoothed onset detection function.

# 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. Please check individual plugins for specific output types.

h2. Example usages of the onset detectors

To use these onset detector plugins in Sonic Visualiser and Audacity is quite straightforward. Load your audio file first, then select a feature extractor/plugin from the transform list. You will also find a set of adjustable parameters in the pop-out box associated with each transform. The extracted features, whether it is onset locations or detection functions, will be visualised in the pane on top of the waveform, synchronised with time.

For comprehensive user manuals, see

[[http://www.sonicvisualiser.org/doc/reference/2.1/en/index.html]]  

[[http://wiki.audacityteam.org/wiki/Category:Tutorial]]

<pre>

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$

</pre>

Sonic Anntator also allows for batch processing in one go. 

<pre>

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$

</pre>

h2. 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.

<pre>

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$

</pre>

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.

<pre>

mitian$

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

mitian$

</pre>

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

<pre>

        vamp:parameter [ vamp:identifier "threshold" ] ;

        vamp:value "50"^^xsd:float ;

</pre>

into 

<pre>

        vamp:parameter [ vamp:identifier "threshold" ] ;

        vamp:value "70"^^xsd:float ;

</pre>

and save it.

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

<pre>

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$

</pre>

h2. That's all guys! Let's hack with Vamp plugins :)