Add Lua script to timestretch audio when tempo-map changes

share/scripts/_tempo_map.lua

@@ -0,0 +1,121 @@
+ardour {
+	["type"]    = "EditorHook",
+	name        = "Tempo Map Audio",
+	author      = "Ardour Team",
+	description = "Time Stretch Audio when Tempo Map changed",
+}
+
+-- subscribe to signals
+-- http://manual.ardour.org/lua-scripting/class_reference/#LuaSignal.LuaSignal
+function signals ()
+	s = LuaSignal.Set()
+	s:add ({[LuaSignal.TempoMapChanged] = true})
+	return s
+end
+
+-- create callback functions
+function factory ()
+	-- callback function which invoked when signal is emitted
+	return function (signal, ref, ...)
+		-- 'TempoMapChanged' passes 3 aruguments: old and current tempo-map and a boolean from_undo
+		local tmo, tmn, from_undo = ...
+
+		if from_undo or not Session:collected_undo_commands () then
+			return
+		end
+
+		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
+			return nil
+		end
+
+		local all_regions = ARDOUR.RegionFactory.regions()
+
+		-- copy region-map
+		local regions = {}
+		for _, r in all_regions:iter() do
+			local ar = r:to_audioregion ()
+			if ar:isnil () then goto next end
+			local track = find_track_for_region (r:to_stateful ():id ())
+			if not track then goto next end
+			regions[ar] = track
+			::next::
+		end
+
+		for ar, track in pairs (regions) do
+			print ("Processing Region: ", ar:name (), track:name ())
+
+			-- create Rubberband stretcher
+			local rb = ARDOUR.LuaAPI.Rubberband (ar, false)
+
+			-- the rubberband-filter also implements the readable API.
+			-- https://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:AudioReadable
+			-- This allows to read from the master-source of the given audio-region.
+			-- XXX but, it will not work for incremental tempo-map changes :(
+			local max_pos = rb:readable ():readable_length ()
+
+			-- the beat-map is a table holding audio-sample positions:
+			-- [from] = to
+			local beat_map = {}
+			beat_map[0] = 0
+
+			-- get position of region
+			local region_pos = ar:position()
+
+			local beats = tmo:quarters_at (region_pos)
+			local sample = 0
+			local beat = 0
+
+			if beats:get_ticks () > 0 then
+				beat = beats:get_beats () + 1
+			else
+				beat = beats:get_beats ()
+			end
+
+			local old_pos = tmo:sample_at_beats (beats)
+			local new_pos = tmn:sample_at_beats (beats)
+			print ("start", old_pos, new_pos)
+
+			while sample < max_pos do
+				local b = Temporal.Beats (beat, 0)
+				sample = tmo:sample_at_beats (b) - old_pos
+				local to = tmn:sample_at_beats (b) - new_pos
+				beat_map[sample] = to
+				print ("map ", sample, "to", to)
+				beat = beat + 1
+			end
+
+			local old_end_beats = tmo:quarters_at (Temporal.timepos_t (region_pos:samples () + max_pos))
+			local new_end =  tmn:sample_at_beats (old_end_beats)
+			local stretch = (new_end - new_pos) / max_pos
+			print ("stretch factor", stretch, new_pos, new_end, max_pos)
+
+			-- configure rubberband stretch tool
+			rb:set_strech_and_pitch (stretch, 1) -- no overall stretching, no pitch-shift
+			rb:set_mapping (beat_map) -- apply beat-map from/to
+
+			-- now stretch the region
+			function rb_progress (_, pos)
+			end
+
+			local nar = rb:process (rb_progress)
+
+			-- replace region
+			if not nar:isnil () then
+				print ("new audio region: ", nar:name (), nar:length ())
+				local playlist = track:playlist ()
+				playlist:to_stateful ():clear_changes () -- prepare undo
+				playlist:remove_region (ar)
+				playlist:add_region (nar, Temporal.timepos_t(new_pos), 1, false)
+				Session:add_stateful_diff_command (playlist:to_statefuldestructible ())
+			end
+		end
+
+	end
+end