3 name = "Biquad Filter",
6 author = "Ardour Lua Task Force",
7 description = [[A Versatile Filter 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 = "Enable", min = 0, max = 1, default = 1, bypass = true, toggled = true },
23 { ["type"] = "input", name = "Type", min = 0, max = 4, default = 0, enum = true, scalepoints =
32 { ["type"] = "input", name = "Gain", min = -20, max = 20, default = 0, unit="dB" },
33 { ["type"] = "input", name = "Freq", min = 20, max = 20000, default = 1000, unit="Hz", logarithmic = true },
34 { ["type"] = "input", name = "Q", min = 0.1, max = 8, default = .707, logarithmic = true },
38 -- translate type parameter to DSP enum
39 -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR.DSP.Biquad.Type
42 return ARDOUR.DSP.BiquadType.LowShelf
44 return ARDOUR.DSP.BiquadType.HighShelf
46 return ARDOUR.DSP.BiquadType.LowPass
48 return ARDOUR.DSP.BiquadType.HighPass
50 return ARDOUR.DSP.BiquadType.Peaking
55 local ctrl = CtrlPorts:array ()
56 if ctrl[1] <= 0 then -- when disabled
57 ctrl[3] = 0; -- force gain to 0dB
62 -- these globals are *not* shared between DSP and UI
63 local filters = {} -- the biquad filter instances (DSP)
64 local filt -- the biquad filter instance (GUI, response)
65 local cur = {0, 0, 0, 0, 0} -- current parameters
66 local lpf = 0.03 -- parameter low-pass filter time-constant
67 local chn = 0 -- channel/filter count
69 function dsp_init (rate)
70 self:shmem ():allocate (1) -- shared mem to tell the GUI the samplerate
71 local cfg = self:shmem ():to_int (0):array ()
73 -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP:Biquad
74 filt = ARDOUR.DSP.Biquad (rate) -- initialize filter
75 lpf = 13000 / rate -- interpolation time constant
78 function dsp_configure (ins, outs)
79 assert (ins:n_audio () == outs:n_audio ())
80 local cfg = self:shmem ():to_int (0):array ()
84 filters[c] = ARDOUR.DSP.Biquad (rate) -- initialize filters
89 -- helper functions for parameter interpolation
90 function param_changed (ctrl)
91 if ctrl[2] == cur[2] and ctrl[3] == cur[3] and ctrl[4] == cur[4] and ctrl[5] == cur[5] then
97 function low_pass_filter_param (old, new, limit)
98 if math.abs (old - new) < limit then
101 return old + lpf * (new - old)
105 -- apply parameters, re-compute filter coefficients if needed
106 function apply_params (ctrl)
107 if not param_changed (ctrl) then
111 if cur[2] ~= ctrl[2] then
112 -- reset filter state when type changes
114 for k = 2,5 do cur[k] = ctrl[k] end
116 -- low-pass filter ctrl parameter values, smooth transition
117 cur[3] = low_pass_filter_param (cur[3], ctrl[3], 0.1) -- gain/dB
118 cur[4] = low_pass_filter_param (cur[4], ctrl[4], 1.0) -- freq/Hz
119 cur[5] = low_pass_filter_param (cur[5], ctrl[5], 0.01) -- quality
123 filters[c]:compute (map_type (cur[2]), cur[4], cur[5], cur[3])
128 -- the actual DSP callback
129 function dsp_run (ins, outs, n_samples)
130 local changed = false
131 local siz = n_samples
133 local ctrl = ctrl_data ()
135 -- if a parameter was changed, process at most 64 samples at a time
136 -- and interpolate parameters until the current settings match
138 if param_changed (ctrl) then
143 while n_samples > 0 do
144 if changed then apply_params (ctrl) 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 ins[c] == outs[c] then
152 filters[c]:run (ins[c]:offset (off), siz) -- in-place processing
154 -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP
155 ARDOUR.DSP.copy_vector (outs[c]:offset (off), ins[c]:offset (off), siz)
156 filters[c]:run (outs[c]:offset (off), siz)
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 < -20 then db = -20 end
191 if db > 20 then db = 20 end
192 return -.5 + 0.5 * h * (1 - db / 20)
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 = ctrl_data ()
224 for k = 2,5 do cur[k] = ctrl[k] end
225 filt:compute (map_type (cur[2]), cur[4], cur[5], cur[3])
228 -- calc height of inline display
229 local h = math.ceil (w * 10 / 16) -- use 16:10 aspect
230 h = 2 * round (h / 2) -- with an even number of vertical pixels
231 if (h > max_h) then h = max_h end -- but at most max-height
233 -- ctx is a http://cairographics.org/ context
234 -- http://manual.ardour.org/lua-scripting/class_reference/#Cairo:Context
237 ctx:rectangle (0, 0, w, h)
238 ctx:set_source_rgba (.2, .2, .2, 1.0)
241 -- set line width: 1px
242 -- Note: a cairo pixel at [1,1] spans [0.5->1.5 , 0.5->1.5]
243 -- hence the offset -0.5 in various move_to(), line_to() calls
244 ctx:set_line_width (1.0)
247 local dash3 = C.DoubleVector ()
249 ctx:set_dash (dash3, 2) -- dotted line
250 ctx:set_source_rgba (.5, .5, .5, .5)
251 grid_db (ctx, w, h, 0)
252 grid_db (ctx, w, h, 6)
253 grid_db (ctx, w, h, 12)
254 grid_db (ctx, w, h, 18)
255 grid_db (ctx, w, h, -6)
256 grid_db (ctx, w, h, -12)
257 grid_db (ctx, w, h, -18)
258 grid_freq (ctx, w, h, 100)
259 grid_freq (ctx, w, h, 1000)
260 grid_freq (ctx, w, h, 10000)
263 -- draw transfer function line
264 ctx:set_source_rgba (.8, .8, .8, 1.0)
265 ctx:move_to (-.5, db_to_y (filt:dB_at_freq (freq_at_x (0, w)), h))
267 local db = filt:dB_at_freq (freq_at_x (x, w))
268 ctx:line_to (-.5 + x, db_to_y (db, h))
270 ctx:stroke_preserve ()
272 -- fill area to zero under the curve
273 ctx:line_to (w, -.5 + h * .5)
274 ctx:line_to (0, -.5 + h * .5)
276 ctx:set_source_rgba (.5, .5, .5, .5)