Starting with version 4.7.213, Ardour supports Lua scripts.
</p>
+
<p class="warning">
-Lua Integration is Work in Progress and far from complete.
+This Documentation is Work in Progress and far from complete. Also the documented API may be subject to change.
+</p>
+
+<h2 id="Preface">Preface</h2>
+<p>
+There are cases that Ardour cannot reasonably cater to with core functionality alone, either because they're session specific
+or user specific edge cases.
+</p><p>
+Examples for these include voice-activate (record-arm specific tracks and roll transport depending on signal levels),
+rename all regions after a specific timecode, launch an external application when a certain track is soloed, generate
+automation curves or simply provide a quick shortcut for a custom batch operation.
+</p><p>
+Cases like this call for means to extend the DAW without actually changing the DAW itself. This is where scripting comes in.
+</p><p>
+"Scripting" refers to tasks that could alternatively be executed step-by-step by a human operator.
+</p><p>
+Lua is a tiny and simple language which is easy to learn, yet allows for comprehensive solutions.
+Lua is also a glue language it allows to tie existing component in Ardour together in unprecedented ways,
+and most importantly Lua is one of the few scripting-languages which can be safely used in a real-time environment.
+</p><p>
+A good introduction to Lua is the book <a href="http://www.lua.org/pil/">Programming in Lua</a>. The first edition is
+available online, but if you have the means buy a copy of the book, it not only helps to support the Lua project, but provides
+for a much nicer reading and learning experience.
+</p>
+
+<h2 id="Overview">Overview</h2>
+<p>
+The core of Ardour is a real-time audio engine that runs and processes audio. One interfaces with an engine by sending it
+commands. Scripting can be used to interact with or modify the active Ardour session, just like a user uses the Editor/Mixer
+GUI to modify the state or parameters of the session.
+</p><p>
+Doing this programmatically requires some knowledge about the objects used internally.
+Most Ardour C++ objects and their methods are directly exposed to Lua and one can call functions or modify variables:
+</p>
+
+<div style="width:80%; margin:.5em auto;">
+ <div style="width:45%; float:left;">
+ C++<br/>
+ <code class="cxx">
+ session->set_transport_speed (1.0);
+ </code>
+ </div>
+ <div style="width:45%; float:right;">
+ Lua<br/>
+ <code class="lua">
+ Session:set_transport_speed (1.0)
+ </code>
+ </div>
+</div>
+<div style="clear:both;"></div>
+
+<p>
+You may notice that there is only a small syntactic difference in this case.
+While C++ requires recompiling the application for every change, Lua script can be loaded, written or modified while the
+application is running. Lua also abstracts away many of the C++ complexities such as object lifetime, type conversion and
+null-pointer checks.
+</p><p>
+Close ties with the underlying C++ components is where the power of scripting comes from.
+A script can orchestrate interaction of lower-level components which take the bulk of the CPU time of the final program.
+</p>
+</p><p>
+At the time of writing Ardour integrates Lua 5.3.5: <a href="http://www.lua.org/manual/5.3/manual.html">Lua 5.3 reference
+manual</a>.
+</p>
+
+<h2 id="Integration">Integration</h2>
+<p>
+Like Control surfaces and the GUI, Lua Scripts are confined to certain aspects of the program. Ardour provides the framework
+and runs Lua (not the other way around).
+</p>
+<p>
+In Ardour's case Lua is available:
+</p>
+
+<table class="dl">
+ <tr><th>Editor Action Scripts</th><td>User initiated actions (menu, shortcuts) for batch processing</td></tr>
+ <tr><th>Editor Hooks/Callbacks</th><td>Event triggered actions for the Editor/Mixer GUI</td></tr>
+ <tr><th>Session Scripts</th><td>Scripts called at the start of every audio cycle (session, real-time)</td></tr>
+ <tr><th>DSP Scripts</th><td>Audio/Midi processor - plugins with access to the Ardour session (per track/bus, real-time)</td></tr>
+ <tr><th>Script Console</th><td>Action Script commandline</td></tr>
+</table>
+
+<p>
+There are is also a special mode:
+</p>
+<table class="dl">
+ <tr><th>Commandline Tool</th><td>Replaces the complete Editor GUI, direct access to libardour (no GUI) from the
+ commandline.<br/>
+ <em>Be aware that the vast majority of complex functionality is provided by the Editor UI.</em></td></tr>
+</table>
+
+<h2 id="Managing Scripts">Managing Scripts</h2>
+
+<p>
+Ardour searches for Lua scripts in the <code>scripts</code> folder in <code>$ARDOUR_DATA_PATH</code>,
+Apart from scripts included directly with Ardour, this includes</p>
+<table>
+ <tr><th>GNU/Linux</th><td><code>$HOME/.config/ardour6/scripts</code></td></tr>
+ <tr><th>Mac OS X</th><td><code>$HOME/Library/Preferences/Ardour6/scripts</code></td></tr>
+ <tr><th>Windows</th><td><code>%localappdata%\ardour6\scripts</code></td></tr>
+</table>
+
+<p>Files must end with <code>.lua</code> file extension.</p>
+
+<p>Scripts are managed via the GUI</p>
+<table class="dl">
+ <tr><th>Editor Action Scripts</th><td>Menu → Edit → Scripted Actions → Manage</td></tr>
+ <tr><th>Editor Hooks/Callbacks</th><td>Menu → Edit → Scripted Actions → Manage</td></tr>
+ <tr><th>Session Scripts</th><td>Menu → Session → Scripting → Add/Remove Script</td></tr>
+ <tr><th>DSP Scripts</th><td>Mixer-strip → context menu (right click) → New Lua Proc</td></tr>
+ <tr><th>Script Console</th><td>Menu → Window → Scripting</td></tr>
+</table>
+
+<h2 id="Script Layout">Script Layout</h2>
+<ul>
+ <li>Every script must include an <code>ardour</code> descriptor table. Required fields are "Name" and "Type".</li>
+ <li>A script must provide a <em>Factory method</em>: A function with optional instantiation parameters which returns the
+ actual script.</li>
+ <li>[optional]: list of parameters for the "factory".</li>
+ <li>in case of DSP scripts, an optional list of automatable parameters and possible audio/midi port configurations, and a
+ <code>dsp_run</code> function, more on that later.</li>
+</ul>
+
+
+<p>A minimal example script looks like:</p>
+<div>
+<pre><code class="lua">
+ ardour {
+ ["type"] = "EditorAction",
+ name = "Rewind",
+ }
+
+ function factory (unused_params)
+ return function ()
+ Session:goto_start() -- rewind the transport
+ end
+ end
+</code></pre>
+</div>
+
+<p>
+The common part for all scripts is the "Descriptor". It's a Lua function which returns a table (key/values) with the following
+keys (the keys are case-sensitive):
+</p>
+<table class="dl">
+ <tr><th>type [required]</th><td>one of "<code>DSP</code>", "<code>Session</code>", "<code>EditorHook</code>",
+ "<code>EditorAction</code>" (the type is not case-sensitive)</td></tr>
+ <tr><th>name [required]</th><td>Name/Title of the script</td></tr>
+ <tr><th>author</th><td>Your Name</td></tr>
+ <tr><th>license</th><td>The license of the script (e.g. "GPL" or "MIT")</td></tr>
+ <tr><th>description</th><td>A longer text explaining to the user what the script does</td></tr>
+</table>
+
+<p class="note">
+Scripts that come with Ardour (currently mostly examples) can be found in the
+<a href="https://github.com/Ardour/ardour/tree/master/share/scripts">Source Tree</a>.
+</p>
+
+<h3 id="Action Scripts">Action Scripts</h3>
+<p>Action scripts are the simplest form. An anonymous Lua function is called whenever the action is triggered. A simple action
+script is shown above.</p>
+<p>There are 10 action script slots available, each of which is a standard GUI action available from the menu and hence can be
+bound to a keyboard shortcut.</p>
+
+<h3 id="Session Scripts">Session Scripts</h3>
+<p>Session scripts similar to Actions Scripts, except the anonymous function is called periodically every process cycle.
+The function receives a single parameter - the number of audio samples which are processed in the given cycle</p>
+<div>
+<pre><code class="lua">
+ardour {
+ ["type"] = "session",
+ name = "Example Session Script",
+ description = [[
+ An Example Ardour Session Script.
+ This example stops the transport after rolling for a specific time.]]
+}
+
+
+-- instantiation options, these are passed to the "factory" method below
+function sess_params ()
+ return
+ {
+ ["print"] = { title = "Debug Print (yes/no)", default = "no", optional = true },
+ ["time"] = { title = "Timeout (sec)", default = "90", optional = false },
+ }
+end
+
+function factory (params)
+ return function (n_samples)
+ local p = params["print"] or "no"
+ local timeout = params["time"] or 90
+ a = a or 0
+ if p ~= "no" then print (a, n_samples, Session:frame_rate (), Session:transport_rolling ()) end -- debug output (not rt safe)
+ if (not Session:transport_rolling()) then
+ a = 0
+ return
+ end
+ a = a + n_samples
+ if (a > timeout * Session:frame_rate()) then
+ Session:request_transport_speed (0.0, true, ARDOUR.TransportRequestSource.TRS_UI)
+ end
+ end
+end
+</code></pre>
+</div>
+
+<h3 id="Action Hooks">Action Hooks</h3>
+<p>Action hook scripts must define an additional function which returns a <em>Set</em> of Signal that which trigger the
+callback (documenting available slots and their parameters remains to be done).</p>
+<div>
+<pre><code class="lua">
+ardour {
+ ["type"] = "EditorHook",
+ name = "Hook Example",
+ description = "Rewind On Solo Change, Write a file when regions are moved.",
+}
+
+function signals ()
+ s = LuaSignal.Set()
+ s:add (
+ {
+ [LuaSignal.SoloActive] = true,
+ [LuaSignal.RegionPropertyChanged] = true
+ }
+ )
+ return s
+end
+
+function factory (params)
+ return function (signal, ref, ...)
+ -- print (signal, ref, ...)
+
+ if (signal == LuaSignal.SoloActive) then
+ Session:goto_start()
+ end
+
+ if (signal == LuaSignal.RegionPropertyChanged) then
+ obj,pch = ...
+ file = io.open ("/tmp/test" ,"a")
+ io.output (file
+ io.write (string.format ("Region: '%s' pos-changed: %s, length-changed: %s\n",
+ obj:name (),
+ tostring (pch:containsFramePos (ARDOUR.Properties.Start)),
+ tostring (pch:containsFramePos (ARDOUR.Properties.Length))
+ ))
+ io.close (file)
+ end
+ end
+end
+</code></pre>
+</div>
+
+<h3 id="DSP Scripts">DSP Scripts</h3>
+<p>See the scripts folder for examples for now.</p>
+<p>Some notes for further doc:</p>
+<ul>
+ <li>required function: <code>dsp_ioconfig ()</code>: return a list of possible audio I/O configurations - follows Audio
+ Unit conventions.</li>
+ <li>optional function: <code>dsp_dsp_midi_input ()</code>: return true if the plugin can receive midi input</li>
+ <li>optional function: <code>dsp_params ()</code>: return a table of possible parameters (automatable)</li>
+ <li>optional function: <code>dsp_init (samplerate)</code>: called when instantiation the plugin with given samplerate.</li>
+ <li>optional function: <code>dsp_configure (in, out)</code>: called after instantiation with configured plugin i/o.</li>
+ <li>required function: <code>dsp_run (ins, outs, n_samples)</code> OR <code>dsp_runmap (bufs, in_map, out_map, n_samples,
+ offset)</code>: DSP process callback. The former is a convenient abstraction that passes mapped buffers (as table). The
+ latter is a direct pass-through matching Ardour's internal <code>::connect_and_run()</code> API, which requires the caller
+ to map and offset raw buffers.</li>
+ <li>plugin parameters are handled via the global variable <code>CtrlPorts</code>.</li>
+ <li>midi data is passed via the global variable <code>mididata</code> which is valid during <code>dsp_run</code> only.
+ (dsp_runmap requires the script to pass raw data from the buffers according to in_map)</li>
+ <li>The script has access to the current session via the global variable Session, but access to the session methods are
+ limited to realtime safe functions</li>
+</ul>
+
+<h2 id="Accessing Ardour Objects">Accessing Ardour Objects</h2>
+<p>
+The top most object in Ardour is the <code>ARDOUR::Session</code>.
+Fundamentally, a Session is just a collection of other things:
+Routes (tracks, busses), Sources (Audio/Midi), Regions, Playlists, Locations, Tempo map, Undo/Redo history, Ports, Transport
+state and controls, etc.
+</p><p>
+Every Lua interpreter can access it via the global variable <code>Session</code>.
+</p><p>
+GUI context interpreters also have an additional object in the global environment: The Ardour <code>Editor</code>. The Editor
+provides access to high level functionality which is otherwise triggered via GUI interaction such as undo/redo, open/close
+windows, select objects, drag/move regions. It also holds the current UI state: snap-mode, zoom-range, etc.
+The Editor also provides complex operations such as "import audio" which under the hood, creates a new Track, adds a new
+Source Objects (for every channel) with optional resampling, creates both playlist and regions and loads the region onto the
+Track all the while displaying a progress information to the user.
+</p>
+
+<p class="note">
+Documenting the bound C++ methods and class hierarchy is somewhere on the ToDo list.
+Meanwhile <a href="https://github.com/Ardour/ardour/blob/master/libs/ardour/luabindings.cc">luabindings.cc</a> is the best we
+can offer.
+</p>
+
+<h2 id="Concepts">Concepts</h2>
+<ul>
+ <li>There are no bound constructors: Lua asks Ardour to create objects (e.g. add a new track), then receives a reference
+ to the object to modify it.</li>
+ <li>Scripts, once loaded, are saved with the Session (no reference to external files). This provides for portable
+ Sessions.</li>
+ <li>Lua Scripts are never executed directly. They provide a "factory" method which can have optional instantiation
+ parameters, which returns a Lua closure.</li>
+ <li>No external Lua modules/libraries can be used, scripts need to be self contained (portable across different systems
+ (libs written in Lua can be used, and important c-libs/functions can be included with Ardour if needed).</li>
+</ul>
+<p>
+Ardour is a highly multithreaded application and interaction between the different threads, particularly real-time threads,
+needs to to be done with care. This part has been abstracted away by providing separate Lua interpreters in different contexts
+and restricting available interaction:
</p>
+<ul>
+ <li>Editor Actions run in a single instance interpreter in the GUI thread.</li>
+ <li>Editor Hooks connect to libardour signals. Every Callback uses a dedicated Lua interpreter which is in the GUI thread
+ context.</li>
+ <li>All Session scripts run in a single instance in the main real-time thread (audio callback)</li>
+ <li>DSP scripts have a separate instance per script and run in one of the DSP threads.</li>
+</ul>
+<p>
+The available interfaces differ between contexts. For example, it is not possible to create new tracks or import audio from
+real-time context; while it is not possible to modify audio buffers from the GUI thread.
+</p>
+
+<h2 id="Current State">Current State</h2>
+Fully functional, yet still in a prototyping stage:
+
+<ul>
+ <li>The GUI to add/configure scripts is rather minimalistic.</li>
+ <li>The interfaces may change (particularly DSP, and Session script <code>run()</code>.</li>
+ <li>Further planned work includes:
+ <ul>
+ <li>Built-in Script editor (customize/modify Scripts in-place)</li>
+ <li>convenience methods (wrap more complex Ardour actions into a library). e.g set plugin parameters, write
+ automation lists from a Lua table</li>
+ <li>Add some useful scripts and more examples</li>
+ <li>Documentation (Ardour API), also usable for tab-expansion, syntax highlighting</li>
+ <li>bindings for GUI Widgets (plugin UIs, message boxes, etc)</li>
+ </ul>
+ <li>
+</ul>
+
+-<h2 id="Examples">Examples</h2>
+-<p>Please see the example <a href="https://github.com/Ardour/ardour/tree/master/share/scripts">scripts included with the source-code</a>.
+All the files that start with a leading underscore are not inlcluded with releases, but are intended as example snippets.</p>
+
+<h2 id="Commandline Session">Commandline Session</h2>
+<p>The standalone tool <code>luasession</code> allows one to access an Ardour session directly from the commandline.
+It can also be used as #! interpreter for scripted sessions.
+Interaction is limited by the fact that most actions in Ardour are provided by the Editor GUI.
+</p><p>
+<code>luasession</code> provides only two special functions <code>load_session</code> and <code>close_session</code> and
+exposes the <code>AudioEngine</code> instance as global variable.
+</p>
+
+<div>
+<pre><code class="lua">
+for i,_ in AudioEngine:available_backends():iter() do print (i.name) end
+
+backend = AudioEngine:set_backend("ALSA", "", "")
+print (AudioEngine:current_backend_name())
+
+for i,_ in backend:enumerate_devices():iter() do print (i.name) end
+
+backend:set_device_name("HDA Intel PCH")
+backend:set_buffer_size(1024)
+
+print (backend:buffer_size())
+print (AudioEngine:get_last_backend_error())
+
+s = load_session ("/home/rgareus/Documents/ArdourSessions/lua2/", "lua2")
+
+assert (s)
+
+s:request_transport_speed (1.0, true, ARDOUR.TransportRequestSource.TRS_UI)
+print (s:transport_rolling())
+
+s:goto_start()
+
+ARDOUR.LuaAPI.usleep (10 * 1000000) -- 10 seconds
+
+close_session()
-{% children %}
+</code></pre>
+</div>
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