Add script to create LFO-like plugin automation

diff --git a/scripts/lfo_automation.lua b/scripts/lfo_automation.lua
new file mode 100644 (file)
index 0000000..7907ae0
--- /dev/null
+++ b/scripts/lfo_automation.lua
@@ -0,0 +1,173 @@
+ardour {
+   ["type"]    = "EditorAction",
+   name        = "Add LFO automation to region",
+   version     = "0.1.1",
+   license     = "MIT",
+   author      = "Daniel Appelt",
+   description = [[Add LFO-like plugin automation to selected region]]
+}
+
+function factory (unused_params)
+   return function ()
+      -- Retrieve the first selected region
+      -- TODO: the following statement should do just that, no!?
+      -- local region = Editor:get_selection().regions:regionlist():front()
+      local region = nil
+      for r in Editor:get_selection().regions:regionlist():iter() do
+         if region == nil then region = r end
+      end
+
+      -- Bail out if no region was selected
+      if region == nil then
+         LuaDialog.Message("Add LFO automation to region", "Please select a region first!",
+                           LuaDialog.MessageType.Info, LuaDialog.ButtonType.Close):run()
+         return
+      end
+
+      -- Identify the track the region belongs to. There really is no better way?!
+      local track = nil
+      for route in Session:get_tracks():iter() do
+         for r in route:to_track():playlist():region_list():iter() do
+            if r == region then track = route:to_track() end
+         end
+      end
+
+      -- Get a list of all available plugin parameters on the track. This looks ugly. For the original code
+      -- see https://github.com/Ardour/ardour/blob/master/scripts/midi_cc_to_automation.lua
+      local targets = {}
+      local i = 0
+      while true do -- iterate over all plugins on the route
+         if track:nth_plugin(i):isnil() then break end
+
+         local proc = track:nth_plugin(i) -- ARDOUR.LuaAPI.plugin_automation() expects a proc not a plugin
+         local plug = proc:to_insert():plugin(0)
+         local plug_label = i .. ": " .. plug:name() -- Handle ambiguity if there are multiple plugin instances
+         local n = 0 -- Count control-ports separately. ARDOUR.LuaAPI.plugin_automation() only returns those.
+         for j = 0, plug:parameter_count() - 1 do -- Iterate over all parameters
+            if plug:parameter_is_control(j) then
+               local label = plug:parameter_label(j)
+               if plug:parameter_is_input(j) and label ~= "hidden" and label:sub(1,1) ~= "#" then
+                  -- We need two return values: the plugin-instance and the parameter-id. We use a function to
+                  -- return both values in order to avoid another sub-menu level in the dropdown.
+                  local nn = n -- local scope for return value function
+                  targets[plug_label] = targets[plug_label] or {}
+                  targets[plug_label][label] = function() return {["p"] = proc, ["n"] = nn} end
+               end
+               n = n + 1
+            end
+         end
+
+         i = i + 1
+      end
+
+      -- Bail out if there are no plugin parameters
+      if next(targets) == nil then
+         LuaDialog.Message("Add LFO automation to region", "No plugin parameters found.",
+                           LuaDialog.MessageType.Info, LuaDialog.ButtonType.Close):run()
+         region, track, targets = nil, nil, nil
+         collectgarbage()
+         return
+      end
+
+      -- Display dialog to select (plugin and) plugin parameter, and LFO cycle type + min / max
+      local dialog_options = {
+         { type = "heading", title = "Add LFO automation to region", align = "left"},
+         { type = "dropdown", key = "param", title = "Plugin parameter", values = targets },
+         { type = "dropdown", key = "wave", title = "Waveform", values = {
+              ["Ramp up"] = 1, ["Ramp down"] = 2, ["Triangle"] = 3, ["Sine"] = 4,
+              ["Exp up"] = 5, ["Exp down"] = 6, ["Log up"] = 7, ["Log down"] = 8 } },
+         { type = "number", key = "cycles", title = "No. of cycles", min = 1, max = 16, step = 1, digits = 0 },
+         { type = "slider", key = "min", title = "Minimum in %", min = 0, max = 100, digits = 1 },
+         { type = "slider", key = "max", title = "Maximum in %", min = 0, max = 100, digits = 1, default = 100 }
+      }
+      local rv = LuaDialog.Dialog("Select target", dialog_options):run()
+
+      -- Return if the user cancelled
+      if not rv then
+         region, track, targets = nil, nil, nil
+         collectgarbage()
+         return
+      end
+
+      -- Parse user response
+      assert(type(rv["param"]) == "function")
+      local pp = rv["param"]() -- evaluate function, retrieve table {["p"] = proc, ["n"] = nn}
+      local al, _, pd = ARDOUR.LuaAPI.plugin_automation(pp["p"], pp["n"])
+      local wave = rv["wave"]
+      local cycles = rv["cycles"]
+      -- Compute minimum and maximum requested parameter values
+      local lower = pd.lower + rv["min"] / 100 * (pd.upper - pd.lower)
+      local upper = pd.lower + rv["max"] / 100 * (pd.upper - pd.lower)
+      track, targets, rv, pd = nil, nil, nil, nil
+      assert(not al:isnil())
+
+      -- Define lookup tables for our waves. Empty ones will be calculated in a separate step.
+      -- TODO: at this point we already know which one is needed, still we compute all.
+      local lut = {
+         { 0, 1 }, -- ramp up
+         { 1, 0 }, -- ramp down
+         { 0, 1, 0 }, -- triangle
+         {}, -- sine
+         {}, -- exp up
+         {}, -- exp down
+         {}, -- log up
+         {} -- log down
+      }
+
+      -- Calculate missing look up tables
+      local log_min = math.exp(-2 * math.pi)
+      for i = 0, 20 do
+         -- sine
+         lut[4][i+1] = 0.5 * math.sin(i * math.pi / 10) + 0.5
+         -- exp up
+         lut[5][i+1] = math.exp(-2 * math.pi + i * math.pi / 10)
+         -- log up
+         lut[7][i+1] = -math.log(1 + (i / log_min - i) / 20) / math.log(log_min)
+      end
+      -- "down" variants just need the values in reverse order
+      for i = 21, 1, -1 do
+         -- exp down
+         lut[6][22-i] = lut[5][i]
+         -- log down
+         lut[8][22-i] = lut[7][i]
+      end
+
+      -- Initialize undo
+      Session:begin_reversible_command("Add LFO automation to region")
+      local before = al:get_state() -- save previous state (for undo)
+      al:clear_list() -- clear target automation-list
+
+      local values = lut[wave]
+      local last = nil
+      for i = 0, cycles - 1 do
+         -- cycle length = region:length() / cycles
+         local cycle_start = region:position() - region:start() + i * region:length() / cycles
+         local offset = region:length() / cycles / (#values - 1)
+
+         for k, v in pairs(values) do
+            local pos = cycle_start + (k - 1) * offset
+            if k == 1 and v ~= last then
+               -- Move event one sample further. A larger offset might be needed to avoid unwanted effects.
+               pos = pos + 1
+            end
+
+            if k > 1 or v ~= last then
+               -- Create automation point re-scaled to parameter target range. Do not create a new point
+               -- at cycle start if the last cycle ended on the same value.
+               al:add(pos, lower + v * (upper - lower), false, true)
+            end
+            last = v
+         end
+      end
+
+      -- TODO: display the modified automation lane in the time line in order to make the change visible!
+
+      -- Save undo
+      -- TODO: in Ardour 5.12 this does not lead to an actual entry in the undo list?!
+      Session:add_command(al:memento_command(before, al:get_state()))
+      Session:commit_reversible_command(nil)
+
+      region, al, lut = nil, nil, nil
+      collectgarbage()
+   end
+end