Add some example Lua scripts

scripts/_rubberband_swing.lua

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+ardour {
+	["type"] = "EditorAction",
+	name     = "Swing It (Rubberband)",
+	license  = "MIT",
+	author   = "Ardour Team",
+description = [[
+Create a 'swing feel' in selected regions.
+
+Analyze beat-position from the selected audio regions,
+then time-stretch the audio and move 8th notes back in
+time while keeping 1/4 note beats in place.
+
+(This script also servers as example for both VAMP
+analysis as well as Rubberband region stretching.)
+
+Kudos to Chris Cannam.
+]]
+}
+
+function factory () return function ()
+
+	-- helper function --
+	-- there is currently no direct way to find the track
+	-- corresponding to a [selected] region
+	function find_track_for_region (region_id)
+		for route in Session:get_tracks ():iter () do
+			local track = route:to_track ()
+			local pl = track:playlist ()
+			if not pl:region_by_id (region_id):isnil () then
+				return track
+			end
+		end
+		assert (0) -- can't happen, region must be in a playlist
+	end
+
+	-- get Editor selection
+	-- http://manual.ardour.org/lua-scripting/class_reference/#ArdourUI:Editor
+	-- http://manual.ardour.org/lua-scripting/class_reference/#ArdourUI:Selection
+	local sel = Editor:get_selection ()
+
+	-- Instantiate the QM BarBeat Tracker
+	-- see http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:LuaAPI:Vamp
+	-- http://vamp-plugins.org/plugin-doc/qm-vamp-plugins.html#qm-barbeattracker
+	local vamp = ARDOUR.LuaAPI.Vamp ("libardourvampplugins:qm-barbeattracker", Session:nominal_sample_rate ())
+
+	-- prepare undo operation
+	Session:begin_reversible_command ("Rubberband Regions")
+	local add_undo = false -- keep track if something has changed
+
+	-- for each selected region
+	-- http://manual.ardour.org/lua-scripting/class_reference/#ArdourUI:RegionSelection
+	for r in sel.regions:regionlist ():iter () do
+		-- "r" is-a http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:Region
+
+		-- test if it's an audio region
+		local ar = r:to_audioregion ()
+		if ar:isnil () then
+			goto next
+		end
+
+		-- create Rubberband stretcher
+		local rb = ARDOUR.LuaAPI.Rubberband (ar, false)
+
+		-- the rubberband-filter also implements the readable API to read from
+		-- the master-source of the given audio-region (ignoring any prior time-stretch
+		-- or pitch-shiting).
+		-- https://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:Readable
+		local max_pos = rb:readable ():readable_length ()
+
+		-- prepare table to hold analysis results
+		-- the beat-map is a table holding audio-sample positions:
+		-- [from] = to
+		local beat_map = {}
+		local prev_beat = 0
+
+		local pdialog = LuaDialog.ProgressWindow ("Rubberband", true)
+
+		-- callback to handle Vamp-Plugin analysis results
+		function vamp_callback (_, pos)
+			return pdialog:progress (pos / max_pos, "Analyzing")
+		end
+		function rb_progress (_, pos)
+			return pdialog:progress (pos / max_pos, "Stretching")
+		end
+
+		-- run VAMP plugin, analyze the first channel of the audio-region
+		vamp:analyze (rb:readable (), 0, vamp_callback)
+		-- getRemainingFeatures returns a http://manual.ardour.org/lua-scripting/class_reference/#Vamp:Plugin:FeatureSet
+		-- get the first output. here: Beats, estimated beat locations & beat-number
+		-- "fl" is-a http://manual.ardour.org/lua-scripting/class_reference/#Vamp:Plugin:FeatureList
+		local fl = vamp:plugin ():getRemainingFeatures ():at (0)
+		local beatcount = 0
+		-- iterate over returned features
+		for f in fl:iter () do
+			-- "f" is-a  http://manual.ardour.org/lua-scripting/class_reference/#Vamp:Plugin:Feature
+			local fn = Vamp.RealTime.realTime2Frame (f.timestamp, Session:nominal_sample_rate ())
+			beat_map[fn] = fn -- keep beats (1/4 notes) unchanged
+			if prev_beat > 0 then
+				-- move the half beats (1/8th) back
+				local diff = (fn - prev_beat) / 2
+				beat_map[fn - diff] = fn - diff + diff / 3 -- moderate swing 2:1 (triplet)
+				--beat_map[fn - diff] = fn - diff + diff / 2 -- hard swing 3:1 (dotted 8th)
+				beatcount = beatcount + 1
+			end
+			prev_beat = fn
+		end
+		-- reset the plugin (prepare for next iteration)
+		vamp:reset ()
+
+		if pdialog:canceled () then goto out end
+
+		-- skip regions shorter than a bar
+		if beatcount < 8 then
+			pdialog:done ()
+			goto next
+		end
+
+		-- now stretch the region
+		rb:set_strech_and_pitch (1, 1)
+		rb:set_mapping (beat_map)
+
+		local nar = rb:process (rb_progress)
+
+		if pdialog:canceled () then goto out end
+
+		-- hide modal progress dialog and destroy it
+		pdialog:done ()
+		pdialog = nil
+
+		-- replace region
+		if not nar:isnil () then
+			print ("new audio region: ", nar:name (), nar:length ())
+			local track = find_track_for_region (r:to_stateful ():id ())
+			local playlist = track:playlist ()
+			playlist:to_stateful ():clear_changes () -- prepare undo
+			playlist:remove_region (r)
+			playlist:add_region (nar, r:position (), 1, false, 0, 0, false)
+			-- create a diff of the performed work, add it to the session's undo stack
+			-- and check if it is not empty
+			if not Session:add_stateful_diff_command (playlist:to_statefuldestructible ()):empty () then
+				add_undo = true
+			end
+		end
+
+		::next::
+	end
+
+	::out::
+
+	-- all done, commit the combined Undo Operation
+	if add_undo then
+		-- the 'nil' Command here mean to use the collected diffs added above
+		Session:commit_reversible_command (nil)
+	else
+		Session:abort_reversible_command ()
+	end
+
+	vamp = nil
+	collectgarbage ()
+end end

scripts/_tempo_map_dump.lua

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+ardour { ["type"] = "Snippet", name = "Tempo Map Dump" }
+
+function factory () return function ()
+
+	local tm = Session:tempo_map ()
+	local ts = tm:tempo_section_at_sample (0)
+
+	while true do
+		print ("TS @", ts:sample(), " | ", ts:to_tempo():note_types_per_minute (), "..", ts:to_tempo():end_note_types_per_minute (), "bpm")
+		ts = tm:next_tempo_section (ts)
+		if not ts then break end
+	end
+
+end end