added ntom() and mton() for converting from note names to MIDI numbers and vice versa

 * mton() can handle MIDINoteStream values just like mtof()
 * both are exposed as Stream methods as well (e.g. Stream:mton())
 * MIDIVelocityStream accepts note names now as well in addition to MIDI note numbers
 * added scoping to the cache used by mtof()

1 files changed, 53 insertions, 15 deletions

diff --git a/applause.lua b/applause.lua
index abb17f3..f43c0d3 100644
--- a/applause.lua
+++ b/applause.lua
@@ -1553,7 +1553,8 @@ end
 MIDIVelocityStream = DeriveClass(Stream)
 
 function MIDIVelocityStream:ctor(note, channel)
-	self.note = note
+	-- `note` may be a note name like "A4"
+	self.note = type(note) == "string" and ntom(note) or note
 	assert(0 <= self.note and self.note <= 127,
 	       "MIDI note out of range (0 <= x <= 127)")
 
@@ -1565,6 +1566,8 @@ end
 -- This is for calling from external code (e.g. from
 -- streams supporting MIDI natively)
 function MIDIVelocityStream.getValue(note, channel)
+	-- `note` may be a note name like "A4"
+	note = type(note) == "string" and ntom(note) or note
 	-- NOTE: The native function assert() for invalid
 	-- notes or channels to avoid segfaults
 	assert(0 <= note and note <= 127,
@@ -1652,23 +1655,58 @@ end
 
 -- MIDI primitives
 
--- There are only 128 possible MIDI notes,
--- so their frequencies can and should be cached.
--- We do this once instead of on-demand, so the lookup
--- table consists of consecutive numbers.
-local mtof_cache = table.new(128, 0)
-for note = 0, 127 do
-	-- MIDI NOTE 69 corresponds to 440 Hz
-	mtof_cache[note] = 440*math.pow(2, (note - 69)/12)
-end
+do
+	local note_names = {
+		"C", "C#", "D", "D#", "E", "F",
+		"F#", "G", "G#", "A", "A#", "B"
+	}
+
+	-- MIDI note number to name
+	-- NOTE: mton() can handle the words as generated by MIDINoteStream
+	function mton(note)
+		note = bit.band(note, 0xFF)
+		local octave = math.floor(note / 12)-1
+		return note_names[(note % 12)+1]..octave
+	end
+
+	function Stream:mton() return self:map(mton) end
 
--- Convert from MIDI note to frequency
--- NOTE: mtof() can handle the words as generated by MIDINoteStream
-function mtof(note)
-	return mtof_cache[bit.band(note, 0xFF)]
+	local ntom_offsets = {}
+	for i, name in ipairs(note_names) do
+		ntom_offsets[name] = i-1
+		-- Saving the offsets for the lower-cased note names
+		-- avoids a string.upper() call in ntom()
+		ntom_offsets[name:lower()] = i-1
+	end
+
+	-- Note name to MIDI note number
+	function ntom(name)
+		local octave = name:byte(-1) - 48 + 1
+		return octave*12 + ntom_offsets[name:sub(1, -2)]
+	end
+
+	function Stream:ntom() return self:map(ntom) end
 end
 
-function Stream:mtof() return self:map(mtof) end
+do
+	-- There are only 128 possible MIDI notes,
+	-- so their frequencies can and should be cached.
+	-- We do this once instead of on-demand, so the lookup
+	-- table consists of consecutive numbers.
+	local mtof_cache = table.new(128, 0)
+	for note = 0, 127 do
+		-- MIDI NOTE 69 corresponds to 440 Hz
+		mtof_cache[note] = 440*math.pow(2, (note - 69)/12)
+	end
+
+	-- Convert from MIDI note to frequency
+	-- NOTE: mtof() can handle the words as generated by MIDINoteStream
+	function mtof(note)
+		return mtof_cache[bit.band(note, 0xFF)]
+	end
+
+	function Stream:mtof() return self:map(mtof) end
+end
 
 -- Convert from frequency to closest MIDI note
 function ftom(freq)