3 name = "a-High/Low Pass Filter",
6 author = "Ardour Team",
7 description = [[Example Ardour Lua DSP Plugin]]
10 function dsp_ioconfig ()
13 -- allow any number of I/O as long as port-count matches
14 { audio_in = -1, audio_out = -1},
19 function dsp_params ()
22 { ["type"] = "input", name = "Type", min = 0, max = 1, default = 0, enum = true, scalepoints =
28 { ["type"] = "input", name = "Steepness", min = 1, max = 4, default = 1, enum = true, scalepoints =
36 { ["type"] = "input", name = "Cut off frequency", min = 5, max = 20000, default = 1000, unit="Hz", logarithmic = true },
37 { ["type"] = "input", name = "Resonance", min = 0.1, max = 8, default = .707, logarithmic = true },
41 -- translate type parameter to DSP enum
42 -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR.DSP.Biquad.Type
45 return ARDOUR.DSP.BiquadType.LowPass
47 return ARDOUR.DSP.BiquadType.HighPass
51 -- these globals are *not* shared between DSP and UI
52 local filters = {} -- the biquad filter instances (DSP)
53 local filt -- the biquad filter instance (GUI, response)
54 local cur = {0, 0, 0, 0} -- current parameters
55 local lpf = 0.03 -- parameter low-pass filter time-constant
56 local chn = 0 -- channel/filter count
58 function dsp_init (rate)
59 self:shmem ():allocate (1) -- shared mem to tell the GUI the samplerate
60 local cfg = self:shmem ():to_int (0):array ()
62 lpf = 13000 / rate -- interpolation time constant
65 function dsp_configure (ins, outs)
66 assert (ins:n_audio () == outs:n_audio ())
67 local cfg = self:shmem ():to_int (0):array ()
72 -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP:Biquad
74 filters[c][k] = ARDOUR.DSP.Biquad (rate) -- initialize filters
80 -- helper functions for parameter interpolation
81 function param_changed (ctrl)
82 if math.floor(ctrl[1]) == math.floor(cur[1]) and math.floor(ctrl[2]) == math.floor(cur[2]) and ctrl[3] == cur[3] and ctrl[4] == cur[4] then
88 function low_pass_filter_param (old, new, limit)
89 if math.abs (old - new) < limit then
92 return old + lpf * (new - old)
96 -- apply parameters, re-compute filter coefficients if needed
97 function apply_params (ctrl)
98 if not param_changed (ctrl) then
102 if cur[1] ~= ctrl[1] or cur[2] ~= ctrl[2] then
103 -- reset filter state when type or order changes
106 filters[c][k]:reset ()
109 for k = 1,4 do cur[k] = ctrl[k] end
111 -- low-pass filter ctrl parameter values, smooth transition
112 cur[3] = low_pass_filter_param (cur[3], ctrl[3], 1.0) -- freq/Hz
113 cur[4] = low_pass_filter_param (cur[4], ctrl[4], 0.01) -- quality
116 if cur[2] < 1 then cur[2] = 1 end
117 if cur[2] > 4 then cur[2] = 4 end
121 filters[c][k]:compute (map_type (cur[1]), cur[3], cur[4], 0)
127 -- the actual DSP callback
128 function dsp_run (ins, outs, n_samples)
129 local changed = false
130 local siz = n_samples
133 -- if a parameter was changed, process at most 64 samples at a time
134 -- and interpolate parameters until the current settings match
136 if param_changed (CtrlPorts:array ()) then
141 local o = math.floor(cur[2])
143 while n_samples > 0 do
144 if changed then apply_params (CtrlPorts:array ()) end
145 if siz > n_samples then siz = n_samples end
147 -- process all channels
149 -- check if output and input buffers for this channel are identical
150 -- http://manual.ardour.org/lua-scripting/class_reference/#C:FloatArray
151 if not ins[c]:sameinstance (outs[c]) then
152 -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP
153 ARDOUR.DSP.copy_vector (outs[c]:offset (off), ins[c]:offset (off), siz)
156 filters[c][k]:run (outs[c]:offset (off), siz) -- in-place processing
160 n_samples = n_samples - siz
171 -------------------------------------------------------------------------------
175 return math.floor (n + .5)
178 function freq_at_x (x, w)
179 -- x-axis pixel for given freq, power-scale
180 return 20 * 1000 ^ (x / w)
183 function x_at_freq (f, w)
184 -- frequency at given x-axis pixel
185 return w * math.log (f / 20.0) / math.log (1000.0)
188 function db_to_y (db, h)
189 -- y-axis gain mapping
190 if db < -60 then db = -60 end
191 if db > 12 then db = 12 end
192 return -.5 + round (0.2 * h) - h * db / 60
195 function grid_db (ctx, w, h, db)
196 -- draw horizontal grid line
197 local y = -.5 + round (db_to_y (db, h))
203 function grid_freq (ctx, w, h, f)
204 -- draw vertical grid line
205 local x = -.5 + round (x_at_freq (f, w))
211 function render_inline (ctx, w, max_h)
213 -- the GUI is separate from the DSP, but the GUI needs to know
214 -- the sample-rate that the DSP is using.
215 local shmem = self:shmem () -- get shared memory region
216 local cfg = shmem:to_int (0):array () -- "cast" into lua-table
217 -- instantiate filter (to calculate the transfer function's response)
218 filt = ARDOUR.DSP.Biquad (cfg[1])
221 -- set filter coefficients if they have changed
222 if param_changed (CtrlPorts:array ()) then
223 local ctrl = CtrlPorts:array ()
224 for k = 1,4 do cur[k] = ctrl[k] end
225 if cur[2] < 1 then cur[2] = 1 end
226 if cur[2] > 4 then cur[2] = 4 end
227 filt:compute (map_type (cur[1]), cur[3], cur[4], 0)
230 -- calc height of inline display
231 local h = math.ceil (w * 10 / 16) -- use 16:10 aspect
232 if (h > max_h) then h = max_h end -- but at most max-height
234 -- ctx is a http://cairographics.org/ context
235 -- http://manual.ardour.org/lua-scripting/class_reference/#Cairo:Context
238 ctx:rectangle (0, 0, w, h)
239 ctx:set_source_rgba (.2, .2, .2, 1.0)
241 ctx:rectangle (0, 0, w, h)
244 -- set line width: 1px
245 -- Note: a cairo pixel at [1,1] spans [0.5->1.5 , 0.5->1.5]
246 -- hence the offset -0.5 in various move_to(), line_to() calls
247 ctx:set_line_width (1.0)
250 local dash3 = C.DoubleVector ()
251 local dash2 = C.DoubleVector ()
254 ctx:set_dash (dash2, 2) -- dotted line
255 ctx:set_source_rgba (.5, .5, .5, .8)
256 grid_db (ctx, w, h, 0)
257 ctx:set_dash (dash3, 2) -- dotted line
258 ctx:set_source_rgba (.5, .5, .5, .5)
259 grid_db (ctx, w, h, -12)
260 grid_db (ctx, w, h, -24)
261 grid_db (ctx, w, h, -36)
262 grid_freq (ctx, w, h, 100)
263 grid_freq (ctx, w, h, 1000)
264 grid_freq (ctx, w, h, 10000)
267 local o = math.floor(cur[2])
268 -- draw transfer function line
269 ctx:set_source_rgba (.8, .8, .8, 1.0)
270 ctx:move_to (-.5, db_to_y (o * filt:dB_at_freq (freq_at_x (0, w)), h))
272 local db = o * filt:dB_at_freq (freq_at_x (x, w))
273 ctx:line_to (-.5 + x, db_to_y (db, h))
275 ctx:stroke_preserve ()
277 -- fill area to zero under the curve
278 ctx:line_to (w, -.5 + round (db_to_y (0, h)))
279 ctx:line_to (0, -.5 + round (db_to_y (0, h)))
281 ctx:set_source_rgba (.5, .5, .5, .5)