3 name = "Biquad Filter",
6 author = "Robin Gareus",
7 email = "robin@gareus.org",
8 site = "http://gareus.org",
9 description = [[Example Ardour Lua DSP Plugin]]
12 function dsp_ioconfig ()
15 -- allow any number of I/O as long as port-count matches
16 { audio_in = -1, audio_out = -1},
21 function dsp_params ()
24 { ["type"] = "input", name = "Enable", min = 0, max = 1, default = 1, bypass = true, toggled = true },
25 { ["type"] = "input", name = "Type", min = 0, max = 4, default = 0, enum = true, scalepoints =
34 { ["type"] = "input", name = "Gain", min = -20, max = 20, default = 0, unit="dB" },
35 { ["type"] = "input", name = "Freq", min = 20, max = 20000, default = 1000, unit="Hz", logarithmic = true },
36 { ["type"] = "input", name = "Q", min = 0.1, max = 8, default = .707, logarithmic = true },
40 -- translate type parameter to DSP enum
41 -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR.DSP.Biquad.Type
44 return ARDOUR.DSP.BiquadType.LowShelf
46 return ARDOUR.DSP.BiquadType.HighShelf
48 return ARDOUR.DSP.BiquadType.LowPass
50 return ARDOUR.DSP.BiquadType.HighPass
52 return ARDOUR.DSP.BiquadType.Peaking
57 local ctrl = CtrlPorts:array ()
58 if ctrl[1] <= 0 then -- when disabled
59 ctrl[3] = 0; -- force gain to 0dB
64 -- these globals are *not* shared between DSP and UI
65 local filters = {} -- the biquad filter instances (DSP)
66 local filt -- the biquad filter instance (GUI, response)
67 local cur = {0, 0, 0, 0, 0} -- current parameters
68 local lpf = 0.03 -- parameter low-pass filter time-constant
69 local chn = 0 -- channel/filter count
71 function dsp_init (rate)
72 self:shmem ():allocate (1) -- shared mem to tell the GUI the samplerate
73 local cfg = self:shmem ():to_int (0):array ()
75 -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP:Biquad
76 filt = ARDOUR.DSP.Biquad (rate) -- initialize filter
77 lpf = 13000 / rate -- interpolation time constant
80 function dsp_configure (ins, outs)
81 assert (ins:n_audio () == outs:n_audio ())
82 local cfg = self:shmem ():to_int (0):array ()
86 filters[c] = ARDOUR.DSP.Biquad (rate) -- initialize filters
91 -- helper functions for parameter interpolation
92 function param_changed (ctrl)
93 if ctrl[2] == cur[2] and ctrl[3] == cur[3] and ctrl[4] == cur[4] and ctrl[5] == cur[5] then
99 function low_pass_filter_param (old, new, limit)
100 if math.abs (old - new) < limit then
103 return old + lpf * (new - old)
107 -- apply parameters, re-compute filter coefficients if needed
108 function apply_params (ctrl)
109 if not param_changed (ctrl) then
113 if cur[2] ~= ctrl[2] then
114 -- reset filter state when type changes
116 for k = 2,5 do cur[k] = ctrl[k] end
118 -- low-pass filter ctrl parameter values, smooth transition
119 cur[3] = low_pass_filter_param (cur[3], ctrl[3], 0.1) -- gain/dB
120 cur[4] = low_pass_filter_param (cur[4], ctrl[4], 1.0) -- freq/Hz
121 cur[5] = low_pass_filter_param (cur[5], ctrl[5], 0.01) -- quality
125 filters[c]:compute (map_type (cur[2]), cur[4], cur[5], cur[3])
130 -- the actual DSP callback
131 function dsp_run (ins, outs, n_samples)
132 local changed = false
133 local siz = n_samples
135 local ctrl = ctrl_data ()
137 -- if a parameter was changed, process at most 64 samples at a time
138 -- and interpolate parameters until the current settings match
140 if param_changed (ctrl) then
145 while n_samples > 0 do
146 if changed then apply_params (ctrl) end
147 if siz > n_samples then siz = n_samples end
149 -- process all channels
151 -- check if output and input buffers for this channel are identical
152 -- http://manual.ardour.org/lua-scripting/class_reference/#C:FloatArray
153 if ins[c]:sameinstance (outs[c]) then
154 filters[c]:run (ins[c]:offset (off), siz) -- in-place processing
156 -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP
157 ARDOUR.DSP.copy_vector (outs[c]:offset (off), ins[c]:offset (off), siz)
158 filters[c]:run (outs[c]:offset (off), siz)
162 n_samples = n_samples - siz
173 -------------------------------------------------------------------------------
177 return math.floor (n + .5)
180 function freq_at_x (x, w)
181 -- x-axis pixel for given freq, power-scale
182 return 20 * 1000 ^ (x / w)
185 function x_at_freq (f, w)
186 -- frequency at given x-axis pixel
187 return w * math.log (f / 20.0) / math.log (1000.0)
190 function db_to_y (db, h)
191 -- y-axis gain mapping
192 if db < -20 then db = -20 end
193 if db > 20 then db = 20 end
194 return -.5 + 0.5 * h * (1 - db / 20)
197 function grid_db (ctx, w, h, db)
198 -- draw horizontal grid line
199 local y = -.5 + round (db_to_y (db, h))
205 function grid_freq (ctx, w, h, f)
206 -- draw vertical grid line
207 local x = -.5 + round (x_at_freq (f, w))
213 function render_inline (ctx, w, max_h)
215 -- the GUI is separate from the DSP, but the GUI needs to know
216 -- the sample-rate that the DSP is using.
217 local shmem = self:shmem () -- get shared memory region
218 local cfg = shmem:to_int (0):array () -- "cast" into lua-table
219 -- instantiate filter (to calculate the transfer function's response)
220 filt = ARDOUR.DSP.Biquad (cfg[1])
223 -- set filter coefficients if they have changed
224 if param_changed (CtrlPorts:array ()) then
225 local ctrl = ctrl_data ()
226 for k = 2,5 do cur[k] = ctrl[k] end
227 filt:compute (map_type (cur[2]), cur[4], cur[5], cur[3])
230 -- calc height of inline display
231 local h = math.ceil (w * 10 / 16) -- use 16:10 aspect
232 h = 2 * round (h / 2) -- with an even number of vertical pixels
233 if (h > max_h) then h = max_h end -- but at most max-height
235 -- ctx is a http://cairographics.org/ context
236 -- http://manual.ardour.org/lua-scripting/class_reference/#Cairo:Context
239 ctx:rectangle (0, 0, w, h)
240 ctx:set_source_rgba (.2, .2, .2, 1.0)
243 -- set line width: 1px
244 -- Note: a cairo pixel at [1,1] spans [0.5->1.5 , 0.5->1.5]
245 -- hence the offset -0.5 in various move_to(), line_to() calls
246 ctx:set_line_width (1.0)
249 local dash3 = C.DoubleVector ()
251 ctx:set_dash (dash3, 2) -- dotted line
252 ctx:set_source_rgba (.5, .5, .5, .5)
253 grid_db (ctx, w, h, 0)
254 grid_db (ctx, w, h, 6)
255 grid_db (ctx, w, h, 12)
256 grid_db (ctx, w, h, 18)
257 grid_db (ctx, w, h, -6)
258 grid_db (ctx, w, h, -12)
259 grid_db (ctx, w, h, -18)
260 grid_freq (ctx, w, h, 100)
261 grid_freq (ctx, w, h, 1000)
262 grid_freq (ctx, w, h, 10000)
265 -- draw transfer function line
266 ctx:set_source_rgba (.8, .8, .8, 1.0)
267 ctx:move_to (-.5, db_to_y (filt:dB_at_freq (freq_at_x (0, w)), h))
269 local db = filt:dB_at_freq (freq_at_x (x, w))
270 ctx:line_to (-.5 + x, db_to_y (db, h))
272 ctx:stroke_preserve ()
274 -- fill area to zero under the curve
275 ctx:line_to (w, -.5 + h * .5)
276 ctx:line_to (0, -.5 + h * .5)
278 ctx:set_source_rgba (.5, .5, .5, .5)