Salient points of Vamp document

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Vamp plugin is compiled code delivered in shared library file cannam@118:
in C or C++ cannam@118:
Needs to be recompiled for each platform cannam@118:
Requires a host to be of any use cannam@118:
advantages over e.g. matlab: applicable to any host, can be faster, doesn't require supporting framework from commercial application cannam@118:
Vamp not an acronym cannam@118:
Examples: note onset detector, chromagram, amplitude tracker cannam@118:
Plugins don't display, just compute cannam@118:
Things a plugin always has: - basic descriptive data [ identifier, name, description, maker ] - processing prefs [ input domain, step block size, channels ] - output descriptors cannam@118:
may have - parameter descriptors, programs cannam@118:
Vamp plugin inherits Vamp::Plugin which inherits Vamp::PluginBase cannam@118:
category not specified by the plugin, but through external metadata files (in a trivial text format) cannam@118:
Plugin receives non-interleaves audio data as input to process(), returns structured set of feature data representing all features that have been calculated from that audio input cannam@118:
Input to process() is quite different depending on whether plugin requests time domain or frequency domain input cannam@118:
Plugin can have more than one named output; it calculates features for all of them at once cannam@118:
Each call to process() returns zero or more features for each output cannam@118:
Each feature has a time, and zero or more values cannam@118:
Any "meaning" of the values (ranges, units etc) is defined by the Output Descriptor associated with the output on which the feature is returned -> potential for more semantics to be added via RDF later cannam@118:
Time of a feature is either explicit (timestamped in feature) or implicit (based on "time of the process call"), and this depends on the output's sample type

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Features do not have duration cannam@118:
Features can only have a single unit for all bins in the feature. So feature is an "array of values" rather than a point in a multi-dimensional space (??)

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It's not a sophisticated invention. It's just complicated by the fact that in theory the plugin should be able to return *anything* cannam@118:
There is a need to compromise between having one arbitrarily complex return structure with no "meaning", and a set of specific return structures with precisely defined meaning but no way to return anything else. -> classic data representation problem cannam@119:
A lot about the plugin design is based on existing real-time effects plugin APIs which audio programmers may be familiar with -- rather than on plugins for existing analysis systems or the like cannam@118: