ardour { ["type"] = "EditorAction", name = "Swing It (Rubberband)", license = "MIT", author = "Ardour Team", description = [[ Create a 'swing feel' in selected regions. The beat position of selected audio regions is analyzed, then the audio is time-stretched, moving 8th notes back in time while keeping 1/4-note beats in place to produce a rhythmic swing style. (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. -- https://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:AudioReadable -- This allows to read from the master-source of the given audio-region. -- Any prior time-stretch or pitch-shift are ignored when reading, however -- processing retains the previous settings 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 -- construct a progress-dialog with cancle button local pdialog = LuaDialog.ProgressWindow ("Rubberband", true) -- progress dialog callbacks 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 state (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 -- configure rubberband stretch tool rb:set_strech_and_pitch (1, 1) -- no overall stretching, no pitch-shift rb:set_mapping (beat_map) -- apply beat-map from/to -- now stretch the region 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 end end function icon (params) return function (ctx, width, height, fg) local txt = Cairo.PangoLayout (ctx, "ArdourMono ".. math.ceil(width * .7) .. "px") txt:set_text ("\u{266b}\u{266a}") -- 8th note symbols local tw, th = txt:get_pixel_size () ctx:set_source_rgba (ARDOUR.LuaAPI.color_to_rgba (fg)) ctx:move_to (.5 * (width - tw), .5 * (height - th)) txt:show_in_cairo_context (ctx) end end