Vamp

An API for audio analysis and feature extraction plugins.

Vamp is an API for C and C++ plugins that process sampled audio data to produce descriptive output (measurements or semantic observations).

This is version 2.10 of the Vamp plugin Software Development Kit.

Plugins and hosts built with this version of the SDK are binary compatible with those built using any other 2.x version of the SDK.
Plugins and hosts built with this version of the SDK are binary compatible with those built using version 1.0 of the SDK, with certain restrictions. See the compatibility README for more details.
See the file CHANGELOG for a list of the changes in this release.

A documentation guide to writing plugins using the Vamp SDK can be found at https://www.vamp-plugins.org/guide.pdf .

Compiling and Installing the SDK and Examples

More than one build system is currently supported:

CMake

The SDK can be compiled on most platforms using CMake, and this is what we suggest when building new plugins or vendoring the SDK into host code.

For example:

$ mkdir build && cd build
$ cmake .. -DVAMPSDK_BUILD_EXAMPLE_PLUGINS=ON
$ cmake --build .

The following custom CMake defines are supported:

`VAMPSDK_BUILD_EXAMPLE_PLUGINS`	Build the example library of Vamp plugins.
`VAMPSDK_BUILD_SIMPLE_HOST`	Build the simple host executable. This requires that libsndfile be installed in a way that CMake can detect.
`VAMPSDK_BUILD_RDFGEN`	Build the RDF template generator utility, which can help produce RDF description files for plugins.

By default all of these options are OFF and only the plugin and host SDK libraries are built.

Autoconf

An older autoconf-based build system is also provided. This is still the recommended system for building installable shared libraries on Linux, but is not really advised elsewhere.

$ ./configure && make && make install

Other build systems

Miscellaneous older build files (including Visual Studio projects) can be found in the otherbuilds directory. These are provided in case they are still useful to anyone, but nothing in here should be considered supported.

Continuous integration

Builds are tested via CI on Linux, macOS, and Windows.

Linux CI build:
macOS CI build:
Windows CI build:

What's In This SDK

This SDK contains the following:

vamp/vamp.h

The formal C language plugin API for Vamp plugins.

A Vamp plugin is a dynamic library (.so, .dll or .dylib depending on platform) exposing one C-linkage entry point (vampGetPluginDescriptor) which returns data defined in the rest of this C header.

Although the C API is the official API for Vamp, we don't recommend that you program directly to it. The C++ abstractions found in the vamp-sdk and vamp-hostsdk directories (below) are preferable for most purposes and are more thoroughly documented.

vamp-sdk

C++ classes for implementing Vamp plugins.

Plugins should subclass Vamp::Plugin and then use Vamp::PluginAdapter to expose the correct C API for the plugin. Plugin authors should read vamp-sdk/PluginBase.h and Plugin.h for code documentation.

See "examples" below for details of the example plugins in the SDK, from which you are welcome to take code and inspiration.

Plugins should link with -lvamp-sdk.

vamp-hostsdk

C++ classes for implementing Vamp hosts.

Hosts will normally use a Vamp::PluginHostAdapter to convert each plugin's exposed C API back into a useful Vamp::Plugin C++ object.

The Vamp::HostExt namespace contains several additional C++ classes to do this work for them, and make the host's life easier:

Vamp::HostExt::PluginLoader provides a very easy interface for a host to discover, load, and find out category information about the available plugins. Most Vamp hosts will probably want to use this class.
Vamp::HostExt::PluginInputDomainAdapter provides a simple means for hosts to handle plugins that want frequency-domain input, without having to convert the input themselves.
Vamp::HostExt::PluginChannelAdapter provides a simple means for hosts to use plugins that do not necessarily support the same number of audio channels as they have available, without having to apply a channel management / mixdown policy themselves.
Vamp::HostExt::PluginBufferingAdapter provides a means for hosts to avoid having to negotiate the input step and block size, instead permitting the host to use any block size they desire (and a step size equal to it). This is particularly useful for "streaming" hosts that cannot seek backwards in the input audio stream and so would otherwise need to implement an additional buffer to support step sizes smaller than the block size.
Vamp::HostExt::PluginSummarisingAdapter provides summarisation methods such as mean and median averages of output features, for use in any context where an available plugin produces individual values but the result that is actually needed is some sort of aggregate.

The PluginLoader class can also use the input domain, channel, and buffering adapters automatically to make these conversions transparent to the host if required.

Host authors should also refer to the example host code in the host directory of the SDK.

Hosts should link with -lvamp-hostsdk.

vamp-hostsdk/host-c.h

A C-linkage header wrapping the part of the C++ SDK code that handles plugin discovery and library loading. Host programs written in C or in a language with a C-linkage foreign function interface may choose to use this header to discover and load plugin libraries, together with the vamp/vamp.h formal API to interact with plugins themselves. See the header for more documentation.

examples

Example plugins implemented using the C++ classes.

These plugins are intended to be useful examples you can draw code from in order to provide the basic shape and structure of a Vamp plugin. They are also intended to be correct and useful, if simple.

ZeroCrossing calculates the positions and density of zero-crossing points in an audio waveform.
SpectralCentroid calculates the centre of gravity of the frequency domain representation of each block of audio.
PowerSpectrum calculates a power spectrum from the input audio. Actually, it doesn't do any work except calculating power from a cartesian complex FFT output. The work of calculating this frequency domain output is done for it by the host or host SDK; the plugin just needs to declare that it wants frequency domain input. This is the simplest of the example plugins.
AmplitudeFollower is a simple implementation of SuperCollider's amplitude-follower algorithm.
PercussionOnsetDetector estimates the locations of percussive onsets using a simple method described in "Drum Source Separation using Percussive Feature Detection and Spectral Modulation" by Dan Barry, Derry Fitzgerald, Eugene Coyle and Bob Lawlor, ISSC 2005.
FixedTempoEstimator calculates a single beats-per-minute value which is an estimate of the tempo of a piece of music that is assumed to be of fixed tempo, using autocorrelation of a frequency domain energy rise metric. It has several outputs that return intermediate results used in the calculation, and may be a useful example of a plugin having several outputs with varying feature structures.

skeleton

Skeleton code that could be used as a template for your new plugin implementation.

host

A simple command-line Vamp host, capable of loading a plugin and using it to process a complete audio file, with its default parameters.

This host also contains a number of options for listing the installed plugins and their properties in various formats. For that reason, it isn't really as simple as one might hope. The core of the code is still reasonably straightforward, however.

Plugin Lookup and Categorisation

The Vamp API does not officially specify how to load plugin libraries or where to find them. However, the SDK does include a function (Vamp::PluginHostAdapter::getPluginPath()) that returns a recommended directory search path that hosts may use for plugin libraries, and a class (Vamp::HostExt::PluginLoader) that implements a sensible cross-platform lookup policy using this path. We recommend using this class in your host unless you have a good reason not to want to. This implementation also permits the user to set the environment variable VAMP_PATH to override the default path if desired.

The policy used by Vamp::HostExt::PluginLoader -- and our recommendation for any host -- is to search each directory in the path returned by getPluginPath for .DLL (on Windows), .so (on Linux, Solaris, BSD etc) or .dylib (on OS/X) files, then to load each one and perform a dynamic name lookup on the vampGetPluginDescriptor function to enumerate the plugins in the library. This operation will necessarily be system-dependent.

Vamp also has an informal convention for sorting plugins into functional categories. In addition to the library file itself, a plugin library may install a category file with the same name as the library but .cat extension. The existence and format of this file are not specified by the Vamp API, but by convention the file may contain lines of the format

vamp:pluginlibrary:pluginname::General Category > Specific Category

which a host may read and use to assign plugins a location within a category tree for display to the user. The expectation is that advanced users may also choose to set up their own preferred category trees, which is why this information is not queried as part of the Vamp plugin's API itself. The Vamp::HostExt::PluginLoader class also provides support for plugin category lookup using this scheme.

Licensing

This plugin SDK is freely redistributable under a "new-style BSD" licence. See the file COPYING for more details. In short, you may modify and redistribute the SDK and example plugins within any commercial or non-commercial, proprietary or open-source plugin or application under almost any conditions, with no obligation to provide source code, provided you retain the original copyright note.

Authors

Vamp and the Vamp SDK were designed and made at the Centre for Digital Music at Queen Mary, University of London.

The CMake support was provided by Lukas Berbuer.

Mark Sandler and Christian Landone provided ideas and direction, and Mark Levy, Dan Stowell, Martin Gasser and Craig Sapp provided testing and other input for the 1.0 API and SDK. The API also uses some ideas from prior plugin systems, notably DSSI (http://dssi.sourceforge.net) and FEAPI (http://feapi.sourceforge.net).

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