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Coding control components

core:custom is the base type for components that work with control signals within any graph type. You have access to a range of useful functions - see the CORE Javadocs included with the IDE to see a full, up-to-date list. The API is similar to the non-graphical Processing APIs, but does not include functions not suitable for real-time operation.

Key method hooks

The key method hooks you can override inside a core:custom component are -

  • init() : called each time the pipeline is started and any time the code is updated. Because this method is called on code updates, it needs to be suitable for real-time usage.
  • update() : called every update cycle (audio buffer, video frame, etc.). If your component reacts solely to input and doesn't need to be called every cycle, remove this method for efficiency.
  • starting() : called after init whenever the pipeline is started (not called on code updates).


Use the @In annotation on a method to provide a port with which to receive control values -

@In(1) void in(double input) {
  // do something with input

The method will be automatically be called at the correct time with the input value. Supported types are double, int, String and Value subclasses.

You can also receive input using the @T annotation on a method, or using the @OnChange annotation to define a method to call when a property changes value.


Use the @Out annotation on a field of type Output to provide control signal output ports on your component.

The Output object supports methods for sending double, String and Value subclasses, as well as an empty signal.

@Out(1) Output out;

@In(1) void in(double input) {