Editing Lua audio add-on API (section)

== Declaration ==
<syntaxhighlight lang="lua">
simtx.addon {
  name = "Limiter",
  description = "Limits audio peaks.",
  controls = {
    simtx.controls.slider("peak", {
      label = "Peak", min = 0.1, max = 1, step = 0.01, default = 0.9,
    }),
  },
  start = function(ctx)
    -- Optional per-session initialization.
  end,
  process = function(audio, ctx)
    audio:limit(ctx:control("peak"))
  end,
  stop = function(ctx)
    -- Optional per-session cleanup.
  end,
}
</syntaxhighlight>

<code>simtx.processor</code> is an alias of <code>simtx.addon</code>. The <code>name</code> and <code>process</code> fields are required. <code>description</code>, <code>controls</code>, <code>start</code>, and <code>stop</code> are optional. Controls use the declarations in [[Lua extension API]].

Each transmission receives isolated callback state. Add-ons may be used with mono audio sources and with Lua modulation modes that produce audio. They do not apply to direct GNU Radio IQ, PipeWire Stereo, white noise, or an IQ-producing Lua mode.