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scripts/_midi_rewrite.lua

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+ardour {
+	["type"]    = "session",
+	name        = "Rewrite Midi",
+	license     = "MIT",
+	author      = "Ardour Lua Task Force",
+	description = [[An example session script preprocesses midi buffers.]]
+}
+
+function factory ()
+	-- this function is called in every process cycle, before processing
+	return function (n_samples)
+		_, t = Session:engine ():get_ports (ARDOUR.DataType.midi (), ARDOUR.PortList ())
+		for p in t[2]:iter () do
+			if not p:receives_input () then goto next end
+
+			if not p:name () == "MIDI/midi_in 1" then goto next end
+
+			midiport = p:to_midiport ()
+			assert (not midiport:isnil ())
+			mb = midiport:get_midi_buffer (n_samples);
+
+			events = mb:table() -- copy event list into lua table
+			mb:silence (n_samples, 0); -- clear existing buffer
+
+			for _,e in pairs (events) do
+				-- e is-a http://manual.ardour.org/lua-scripting/class_reference/#Evoral:MidiEvent
+				e:set_channel (2)
+				mb:push_event (e)
+			end
+
+			::next::
+		end
+	end
+end