MIDI LFO generator plugin

scripts/_midi_lfo.lua

@@ -0,0 +1,74 @@
+ardour {
+	["type"]    = "dsp",
+	name        = "MIDI LFO",
+	category    = "Example", -- Utility
+	license     = "MIT",
+	author      = "Ardour Lua Task Force",
+	description = [[MIDI CC LFO Example -- Triangle full scale CC Parameter automation]]
+}
+
+function dsp_ioconfig ()
+	return { { midi_in = 1, midi_out = 1, audio_in = 0, audio_out = 0}, }
+end
+
+function dsp_params ()
+	return
+	{
+		{ ["type"] = "input", name = "BPM", min = 40, max = 200, default = 60, unit="BPM"},
+		{ ["type"] = "input", name = "CC",  min = 0, max = 127,  default = 1, integer = true },
+	}
+end
+
+local samplerate
+local time = 0
+local step = 0
+
+function dsp_init (rate)
+	samplerate = rate
+	local bpm = 120
+	spb = rate * 60 / bpm
+end
+
+function dsp_run (_, _, n_samples)
+	assert (type(midiin) == "table")
+	assert (type(midiout) == "table")
+
+	local ctrl = CtrlPorts:array ()
+	local bpm = ctrl[1]
+	local cc  = ctrl[2]
+
+	local spb = samplerate * 60 / bpm -- samples per beat
+	local sps = spb / 254 -- samples per step (0..127..1 = 254 steps)
+
+	assert (sps > 1)
+	local i = 1
+	local m = 1
+
+	for ts = 1, n_samples do
+		time = time + 1
+
+		-- forward incoming midi
+		if i <= #midiin then
+			while midiin[i]["time"] == ts do
+				midiout[m] = midiin[i]
+				i = i + 1
+				m = m + 1
+				if i > #midiin then break end
+			end
+		end
+
+		-- inject LFO events
+		if time >= spb then
+			local val
+			if step > 127 then val = 254 - step else val = step end
+
+			midiout[m] = {}
+			midiout[m]["time"] = ts
+			midiout[m]["data"] = { 0xb0, cc, val }
+
+			m = m + 1
+			time = time - sps
+			if step == 253 then step = 0 else step = step + 1 end
+		end
+	end
+end