ardour { ["type"] = "dsp", name = "Biquad Filter", category = "Filter", license = "MIT", author = "Ardour Team", description = [[A Versatile Filter Plugin]] } function dsp_ioconfig () return { -- allow any number of I/O as long as port-count matches { audio_in = -1, audio_out = -1}, } end function dsp_params () return { { ["type"] = "input", name = "Enable", min = 0, max = 1, default = 1, bypass = true, toggled = true }, { ["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 -- translate type parameter to DSP enum -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR.DSP.Biquad.Type function map_type (t) if t == 1 then return ARDOUR.DSP.BiquadType.LowShelf elseif t == 2 then return ARDOUR.DSP.BiquadType.HighShelf elseif t == 3 then return ARDOUR.DSP.BiquadType.LowPass elseif t == 4 then return ARDOUR.DSP.BiquadType.HighPass else return ARDOUR.DSP.BiquadType.Peaking end end function ctrl_data () local ctrl = CtrlPorts:array () if ctrl[1] <= 0 then -- when disabled ctrl[3] = 0; -- force gain to 0dB end return ctrl end -- these globals are *not* shared between DSP and UI local filters = {} -- the biquad filter instances (DSP) local filt -- the biquad filter instance (GUI, response) local cur = {0, 0, 0, 0, 0} -- current parameters local lpf = 0.03 -- parameter low-pass filter time-constant local chn = 0 -- channel/filter count function dsp_init (rate) self:shmem ():allocate (1) -- shared mem to tell the GUI the samplerate local cfg = self:shmem ():to_int (0):array () cfg[1] = rate -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP:Biquad filt = ARDOUR.DSP.Biquad (rate) -- initialize filter lpf = 13000 / rate -- interpolation time constant end function dsp_configure (ins, outs) assert (ins:n_audio () == outs:n_audio ()) local cfg = self:shmem ():to_int (0):array () local rate = cfg[1] chn = ins:n_audio () for c = 1, chn do filters[c] = ARDOUR.DSP.Biquad (rate) -- initialize filters end cur = {0, 0, 0, 0, 0} end -- helper functions for parameter interpolation function param_changed (ctrl) if ctrl[2] == cur[2] and ctrl[3] == cur[3] and ctrl[4] == cur[4] and ctrl[5] == cur[5] then return false end return true end function low_pass_filter_param (old, new, limit) if math.abs (old - new) < limit then return new else return old + lpf * (new - old) end end -- apply parameters, re-compute filter coefficients if needed function apply_params (ctrl) if not param_changed (ctrl) then return end if cur[2] ~= ctrl[2] then -- reset filter state when type changes filt:reset () for k = 2,5 do cur[k] = ctrl[k] end else -- low-pass filter ctrl parameter values, smooth transition cur[3] = low_pass_filter_param (cur[3], ctrl[3], 0.1) -- gain/dB cur[4] = low_pass_filter_param (cur[4], ctrl[4], 1.0) -- freq/Hz cur[5] = low_pass_filter_param (cur[5], ctrl[5], 0.01) -- quality end for c = 1, chn do filters[c]:compute (map_type (cur[2]), cur[4], cur[5], cur[3]) end end -- the actual DSP callback function dsp_run (ins, outs, n_samples) local changed = false local siz = n_samples local off = 0 local ctrl = ctrl_data () -- if a parameter was changed, process at most 64 samples at a time -- and interpolate parameters until the current settings match -- the target values if param_changed (ctrl) then changed = true siz = 64 end while n_samples > 0 do if changed then apply_params (ctrl) end if siz > n_samples then siz = n_samples end -- process all channels for c = 1,#ins do -- check if output and input buffers for this channel are identical -- http://manual.ardour.org/lua-scripting/class_reference/#C:FloatArray if ins[c]:sameinstance (outs[c]) then filters[c]:run (ins[c]:offset (off), siz) -- in-place processing else -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP ARDOUR.DSP.copy_vector (outs[c]:offset (off), ins[c]:offset (off), siz) filters[c]:run (outs[c]:offset (off), siz) end end n_samples = n_samples - siz off = off + siz end if changed then -- notify display self:queue_draw () end end ------------------------------------------------------------------------------- --- inline display function round (n) return math.floor (n + .5) end function freq_at_x (x, w) -- x-axis pixel for given freq, power-scale return 20 * 1000 ^ (x / w) end function x_at_freq (f, w) -- frequency at given x-axis pixel return w * math.log (f / 20.0) / math.log (1000.0) end function db_to_y (db, h) -- y-axis gain mapping 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) -- draw horizontal grid line 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) -- draw vertical grid line 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 -- the GUI is separate from the DSP, but the GUI needs to know -- the sample-rate that the DSP is using. local shmem = self:shmem () -- get shared memory region local cfg = shmem:to_int (0):array () -- "cast" into lua-table -- instantiate filter (to calculate the transfer function's response) filt = ARDOUR.DSP.Biquad (cfg[1]) end -- set filter coefficients if they have changed if param_changed (CtrlPorts:array ()) then local ctrl = ctrl_data () for k = 2,5 do cur[k] = ctrl[k] end filt:compute (map_type (cur[2]), cur[4], cur[5], cur[3]) end -- calc height of inline display local h = math.ceil (w * 10 / 16) -- use 16:10 aspect h = 2 * round (h / 2) -- with an even number of vertical pixels if (h > max_h) then h = max_h end -- but at most max-height -- ctx is a http://cairographics.org/ context -- http://manual.ardour.org/lua-scripting/class_reference/#Cairo:Context -- clear background ctx:rectangle (0, 0, w, h) ctx:set_source_rgba (.2, .2, .2, 1.0) ctx:fill () -- set line width: 1px -- Note: a cairo pixel at [1,1] spans [0.5->1.5 , 0.5->1.5] -- hence the offset -0.5 in various move_to(), line_to() calls ctx:set_line_width (1.0) -- draw grid local dash3 = C.DoubleVector () dash3:add ({1, 3}) ctx:set_dash (dash3, 2) -- dotted line 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 line 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