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* fix failure to pick up all but first plugin's outputs

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, such as measurements of particular
features of the audio or semantic output based on them.

The principal differences between Vamp and a real-time audio
processing plugin system such as VST are:

 * Vamp plugins may output complex multidimensional data with labels.
   As a consequence, they are likely to work best when the output
   data has a much lower sampling rate than the input.  (This also
   means it is usually desirable to implement them in C++ using the
   high-level base class provided rather than use the raw C API.)

 * While Vamp plugins receive data block-by-block, they are not
   required to return output immediately on receiving the input.
   A Vamp plugin may be non-causal, preferring to store up data
   based on its input until the end of a processing run and then
   return all results at once.

 * Vamp plugins have more control over their inputs than a typical
   real-time processing plugin.  For example, they can indicate to
   the host the permitted range of processing block sizes, and can
   request input data in the frequency domain instead of the time
   domain.

 * A Vamp plugin is configured once before each processing run, and
   receives no further parameter changes during use -- unlike real
   time plugin APIs in which the input parameters may change at any
   time.  This also means that fundamental properties such as the
   number of values per output or the preferred processing block
   size can depend on the input parameters.


About this SDK
==============

This Software Development Kit 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 this is the official API for Vamp, we don't recommend that
you program directly to it.  The C++ abstraction in the SDK directory
(below) is likely to be preferable for most purposes and also better
documented.

 * vamp-sdk

C++ classes for straightforwardly implementing Vamp plugins and hosts.
Plugins should subclass Vamp::Plugin (in vamp-sdk/Plugin.h) and then
use a Vamp::PluginAdapter to expose the correct C API for the plugin.
Hosts may use the Vamp::PluginHostAdapter to convert the loaded
plugin's C API back into a Vamp::Plugin object.

 * examples

Example plugins implemented using the C++ classes.  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.

 * host

The simplest possible Vamp host -- this doesn't even process anything
yet, just loads the plugins and prints out their names.


Building the SDK
================

Edit the Makefile for your platform according to the comments in it.
Type "make".


Licensing
=========

This plugin SDK is freely redistributable under the "new BSD" licence.
See the file COPYING for more details.  In short, you are permitted to
reuse the SDK and example plugins in any commercial or non-commercial,
proprietary or open-source application under almost any conditions.


See Also
========

Sonic Visualiser, an interactive open-source graphical audio
inspection, analysis and visualisation tool supporting Vamp plugins.


Chris Cannam
Centre for Digital Music
Queen Mary, University of London