Learn about CLAP

CLAP stands for CLever Audio Plugin. It is an interface that provides a stable ABI to define a standard for Digital Audio Workstations and audio plugins (synthesizers, audio effects, ...) to work together.

The ABI, or Application Binary Interface, serves as a means of communication between a host and a plugin. It provides backwards compatibility, that is, a plugin binary compiled with CLAP 1.x can be loaded by any other CLAP 1.y.

To work with CLAP, include clap/clap.h. To also include the draft extensions, include clap/all.h.

The two most important objects are clap_host and clap_plugin.

src/plugin-template.c is a very minimal example which demonstrates how to wire a CLAP plugin.

Entry point

The entry point is declared in entry.h.

Extensions

Most features come from extensions, which are in fact C interfaces.

// host extension
const clap_host_log *log = host->extension(host, CLAP_EXT_LOG);
if (log)
   log->log(host, CLAP_LOG_INFO, "Hello World! ;^)");

// plugin extension
const clap_plugin_params *params = plugin->extension(plugin, CLAP_EXT_PARAMS);
if (params)
{
   uint32_t paramsCount = params->count(plugin);
   // ...
}

The extensions are defined in the ext folder.

Some extensions are still in the progress of being designed and they are in the draft folder.

An extension comes with:

a header #include <clap/ext/xxx.h>
an extension identifier: #define CLAP_EXT_XXX "clap/XXX"
host interfaces are named like: struct clap_host_xxx
plugin interfaces are named like: struct clap_plugin_xxx
each method must have a clear thread specification

You can create your own extensions and share them. Make sure that the extension identifier:

includes versioning in case the ABI breaks
is a unique identifier

All strings are valid UTF-8.

Fundamental extensions

This is a list of the extensions that you most likely want to implement and use to get a basic plugin experience:

state, save and load the plugin state
- state-context, same as state but with additional context info (preset, duplicate, project)
- resource-directory, host provided folder for the plugin to save extra resource like multi-samples, ... (draft)
params, parameters management
note-ports, define the note ports
audio-ports, define the audio ports
- surround, inspect surround channel mapping
- ambisonic, inspect ambisonic channel mapping
- configurable-audio-ports, request the plugin to apply a given configuration
- audio-ports-config, simple list of pre-defined audio ports configurations, meant to be exposed to the user
- audio-ports-activation, activate and deactivate a given audio port
- extensible-audio-ports, let the host add audio ports to the plugin, this is useful for dynamic number of audio inputs (draft)
render, renders realtime or offline
latency, report the plugin latency
tail, processing tail length
gui, generic gui controller
voice-info, let the host know how many voices the plugin has, this is important for polyphonic modulations
track-info, give some info to the plugin about the track it belongs to
tuning, host provided microtuning (draft)
triggers, plugin's triggers, similar to parameters but stateless

Support extensions

thread-check, check which thread you are currently on, useful for correctness validation
thread-pool, use the host thread pool
log, lets the host aggregate plugin logs
timer-support, lets the plugin register timer handlers
posix-fd-support, lets the plugin register I/O handlers

Deeper Host integration

remote-controls, bank of controls that can be mapped on a controlles with 8 knobs
preset-discovery, let the host index the plugin's preset in their native file format
preset-load, let the host ask the plugin to load a preset
param-indication, let the plugin know when a physical control is mapped to a parameter and if there is automation data
note-name, give a name to notes, useful for drum machines
transport-control, let the plugin control the host's transport (draft)
context-menu, exchange context menu entries between host and plugin, let the plugin ask the host to popup its own context menu

Third-party extensions

cockos.reaper_extension, access the REAPER API

Adapters

clap-wrapper, wrappers for using CLAP in other plugin environments

Resources

clap-validator, a validator and automatic test suite for CLAP plugins.
clapdb, a list of plugins and DAWs which supports CLAP

Examples

clap-host, very simple host
clap-plugins, very simple plugins

Community related projects

clap-juce-extension, juce add-on
MIP2, host and plugins
Avendish, a reflection-based API for media plug-ins in C++ which supports Clap
NIH-plug, an API-agnostic, Rust-based plugin framework aiming to reduce boilerplate without getting in your way

Programming Language Bindings

clap-sys, rust binding
CLAP-for-Delphi, Delphi binding

Artwork

CLAP Logo Pack.zip

sjoerdvankreel/clap