1ardour {
2	["type"]    = "dsp",
3	name        = "Midi Filter",
4	category    = "Example", -- "Utility"
5	license     = "MIT",
6	author      = "Ardour Team",
7	description = [[An Example Midi Filter for prototyping.]]
8}
9
10function dsp_ioconfig ()
11	return { { midi_in = 1, midi_out = 1, audio_in = 0, audio_out = 0}, }
12end
13
14function dsp_run (_, _, n_samples)
15	assert (type(midiin) == "table")
16	assert (type(midiout) == "table")
17	local cnt = 1;
18
19	function tx_midi (time, data)
20		midiout[cnt] = {}
21		midiout[cnt]["time"] = time;
22		midiout[cnt]["data"] = data;
23		cnt = cnt + 1;
24	end
25
26	-- for each incoming midi event
27	for _,b in pairs (midiin) do
28		local t = b["time"] -- t = [ 1 .. n_samples ]
29		local d = b["data"] -- get midi-event
30		local event_type
31		if #d == 0 then event_type = -1 else event_type = d[1] >> 4 end
32
33		if (#d == 3 and event_type == 9) then -- note on
34			tx_midi (t, d)
35		elseif (#d == 3 and event_type == 8) then -- note off
36			tx_midi (t, d)
37		end
38	end
39end
40