add an lua DSP example filter w/inline display

2 files changed, 191 insertions, 1 deletions

diff --git a/scripts/filt.lua b/scripts/filt.lua
new file mode 100644
index 0000000000..e1fa4a699a
--- /dev/null
+++ b/scripts/filt.lua
@@ -0,0 +1,190 @@
+ardour {
+	["type"]    = "dsp",
+	name        = "Biquad Filter",
+	category    = "Filter",
+	license     = "MIT",
+	author      = "Robin Gareus",
+	email       = "robin@gareus.org",
+	site        = "http://gareus.org",
+	description = [[
+	An Example DSP Plugin for processing audio, to
+	be used with Ardour's Lua scripting facility.]]
+}
+
+function dsp_ioconfig ()
+	return
+	{
+		{ audio_in = -1, audio_out = -1},
+	}
+end
+
+
+function dsp_params ()
+	return
+	{
+		{ ["type"] = "input", name = "Type", min = 0, max = 4, default = 0, enum = true, scalepoints =
+			{
+				["Peaking"]    = 0,
+				["Low Shelf"]  = 1,
+				["High Shelf"] = 2,
+				["Low Pass"]   = 3,
+				["High Pass"]  = 4,
+			}
+		},
+		{ ["type"] = "input", name = "Gain", min = -20, max = 20,    default = 0,    unit="dB" },
+		{ ["type"] = "input", name = "Freq", min =  20, max = 20000, default = 1000, unit="Hz", logarithmic = true },
+		{ ["type"] = "input", name = "Q",    min = 0.1, max = 8,     default = .707, logarithmic = true },
+	}
+end
+
+-- these globals are *not* shared between DSP and UI
+local filt -- the filter instance
+local cur = {0, 0, 0, 0} -- current settings
+
+function dsp_init (rate)
+	self:shmem ():allocate (1) -- shared mem to tell UI about samplerate
+	local cfg = self:shmem ():to_int (0):array ()
+	cfg[1] = rate
+	filt = ARDOUR.DSP.Biquad (rate) -- initialize filter
+end
+
+
+-- apply parameters, re-compute filter coefficients if needed
+function apply_params (ctrl)
+	if ctrl[1] == cur[1] and ctrl[2] == cur[2] and ctrl[3] == cur[3] and ctrl[4] == cur[4] then
+		return false
+	end
+
+	local ft
+	if     ctrl[1] == 1 then
+		ft = ARDOUR.DSP.BiQuadType.LowShelf
+	elseif ctrl[1] == 2 then
+		ft = ARDOUR.DSP.BiQuadType.HighShelf
+	elseif ctrl[1] == 3 then
+		ft = ARDOUR.DSP.BiQuadType.LowPass
+	elseif ctrl[1] == 4 then
+		ft = ARDOUR.DSP.BiQuadType.HighPass
+	else
+		ft = ARDOUR.DSP.BiQuadType.Peaking
+	end
+
+	-- TODO low-pass filter ctrl values, smooth transition
+	filt:compute (ft, ctrl[3], ctrl[4], ctrl[2])
+	cur[1] = ctrl[1]
+	cur[2] = ctrl[2]
+	cur[3] = ctrl[3]
+	cur[4] = ctrl[4]
+	return true
+end
+
+
+-- the actual DSP callback
+function dsp_run (ins, outs, n_samples)
+	if apply_params (CtrlPorts:array ()) then
+		self:queue_draw ()
+	end
+	for c = 1,#ins do
+		if ins[c]:sameinstance (outs[c]) then
+			filt:run (ins[c], n_samples) -- in-place
+		else
+			ARDOUR.DSP.copy_vector (outs[c], ins[c], n_samples)
+			filt:run (outs[c], n_samples)
+		end
+	end
+end
+
+
+-------------------------------------------------------------------------------
+--- inline display
+
+function round (n)
+	return math.floor (n + .5)
+end
+
+function freq_at_x (x, w)
+	return 20 * 1000 ^ (x / w)
+end
+
+function x_at_freq (f, w)
+	return w * math.log (f / 20.0) / math.log (1000.0)
+end
+
+function db_to_y (db, h)
+	if db < -20 then db = -20 end
+	if db >  20 then db =  20 end
+	return -.5 + 0.5 * h * (1 - db / 20)
+end
+
+function grid_db (ctx, w, h, db)
+	local y = -.5 + round (db_to_y (db, h))
+	ctx:move_to (0, y)
+	ctx:line_to (w, y)
+	ctx:stroke ()
+end
+
+function grid_freq (ctx, w, h, f)
+	local x = -.5 + round (x_at_freq (f, w))
+	ctx:move_to (x, 0)
+	ctx:line_to (x, h)
+	ctx:stroke ()
+end
+
+function render_inline (ctx, w, max_h)
+	if not filt then
+		-- instantiate filter (to calculate the transfer function)
+		local shmem = self:shmem () -- get shared memory region
+		local cfg = shmem:to_int (0):array () -- "cast" into lua-table
+		filt = ARDOUR.DSP.Biquad (cfg[1])
+	end
+
+	apply_params (CtrlPorts:array ())
+
+	-- calc height of inline display
+	local h = math.ceil (w * 10 / 16) -- 16:10 aspect
+	h = 2 * round (h / 2) -- even number of vertical px
+	if (h > max_h) then
+		h = max_h
+	end
+
+	-- clear background
+	ctx:rectangle (0, 0, w, h)
+	ctx:set_source_rgba (.2, .2, .2, 1.0)
+	ctx:fill ()
+
+	ctx:set_line_width (1.0)
+
+	-- draw grid
+	local dash3 = C.DoubleVector ()
+	dash3:add ({1, 3})
+	ctx:set_dash (dash3, 2)
+	ctx:set_source_rgba (.5, .5, .5, .5)
+	grid_db (ctx, w, h, 0)
+	grid_db (ctx, w, h, 6)
+	grid_db (ctx, w, h, 12)
+	grid_db (ctx, w, h, 18)
+	grid_db (ctx, w, h, -6)
+	grid_db (ctx, w, h, -12)
+	grid_db (ctx, w, h, -18)
+	grid_freq (ctx, w, h, 100)
+	grid_freq (ctx, w, h, 1000)
+	grid_freq (ctx, w, h, 10000)
+	ctx:unset_dash ()
+
+	-- draw transfer function
+	ctx:set_source_rgba (.8, .8, .8, 1.0)
+	ctx:move_to (-.5, db_to_y (filt:dB_at_freq (freq_at_x (0, w)), h))
+	for x = 1,w do
+		local db = filt:dB_at_freq (freq_at_x (x, w))
+		ctx:line_to (-.5 + x, db_to_y (db, h))
+	end
+	ctx:stroke_preserve ()
+
+	-- fill area to zero under the curve
+	ctx:line_to (w, -.5 + h * .5)
+	ctx:line_to (0, -.5 + h * .5)
+	ctx:close_path ()
+	ctx:set_source_rgba (.5, .5, .5, .5)
+	ctx:fill ()
+
+	return {w, h}
+end
diff --git a/scripts/scope.lua b/scripts/scope.lua
index c56512cc36..04e90592cd 100644
--- a/scripts/scope.lua
+++ b/scripts/scope.lua
@@ -20,7 +20,7 @@ function dsp_params ()
 	{
 		{ ["type"] = "input", name = "Timescale", min = .1, max = 5, default = 2, unit="sec", logarithmic = true },
 		{ ["type"] = "input", name = "Logscale", min = 0, max = 1, default = 0, toggled = true },
-		{ ["type"] = "input", name = "Height", min = 0, max = 3, default = 1, unit="dB", enum = true, scalepoints =
+		{ ["type"] = "input", name = "Height", min = 0, max = 3, default = 1, enum = true, scalepoints =
 			{
 				["Min"] = 0,
 				["16:10"] = 1,