From d6aa79bca5452409b7bd6e20ba306d75e31d08de Mon Sep 17 00:00:00 2001 From: Robin Gareus Date: Sat, 21 May 2016 16:24:15 +0200 Subject: complete lua DSP filter with parameter interpolation & comments --- scripts/filt.lua | 151 +++++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 109 insertions(+), 42 deletions(-) (limited to 'scripts') diff --git a/scripts/filt.lua b/scripts/filt.lua index e1fa4a699a..5f22a48953 100644 --- a/scripts/filt.lua +++ b/scripts/filt.lua @@ -6,14 +6,13 @@ ardour { 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.]] + description = [[Example Ardour Lua DSP Plugin]] } function dsp_ioconfig () return { + -- allow any number of I/O as long as port-count matches { audio_in = -1, audio_out = -1}, } end @@ -37,59 +36,111 @@ function dsp_params () } 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 + -- these globals are *not* shared between DSP and UI -local filt -- the filter instance -local cur = {0, 0, 0, 0} -- current settings +local filt -- the biquad filter instance +local cur = {0, 0, 0, 0} -- current parameters +local lpf = 0.03 -- parameter low-pass filter time-constant function dsp_init (rate) - self:shmem ():allocate (1) -- shared mem to tell UI about samplerate + 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 + +-- helper functions for parameter interpolation +function param_changed (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 + 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 ctrl[1] == cur[1] and ctrl[2] == cur[2] and ctrl[3] == cur[3] and ctrl[4] == cur[4] then - return false + if not param_changed (ctrl) then + return 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 + if cur[1] ~= ctrl[1] then + -- reset filter state when type changes + filt:reset () + for k = 1,4 do cur[k] = ctrl[k] end else - ft = ARDOUR.DSP.BiQuadType.Peaking + -- low-pass filter ctrl parameter values, smooth transition + cur[2] = low_pass_filter_param (cur[2], ctrl[2], 0.1) -- gain/dB + cur[3] = low_pass_filter_param (cur[3], ctrl[3], 1.0) -- freq/Hz + cur[4] = low_pass_filter_param (cur[4], ctrl[4], 0.01) -- quality 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 + filt:compute (map_type (cur[1]), cur[3], cur[4], cur[2]) end -- the actual DSP callback function dsp_run (ins, outs, n_samples) - if apply_params (CtrlPorts:array ()) then - self:queue_draw () + local changed = false + local siz = n_samples + local off = 0 + + -- 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 (CtrlPorts:array ()) then + changed = true + siz = 64 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) + + while n_samples > 0 do + if changed then apply_params (CtrlPorts:array ()) 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 + filt: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) + filt: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 @@ -102,20 +153,24 @@ function round (n) 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) @@ -123,6 +178,7 @@ function grid_db (ctx, w, h, db) 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) @@ -131,32 +187,43 @@ end function render_inline (ctx, w, max_h) if not filt then - -- instantiate filter (to calculate the transfer function) + -- 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 - apply_params (CtrlPorts:array ()) + -- set filter coefficients if they have changed + if param_changed (CtrlPorts:array ()) then + local ctrl = CtrlPorts:array () + for k = 1,4 do cur[k] = ctrl[k] end + filt:compute (map_type (cur[1]), cur[3], cur[4], cur[2]) + end -- 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 + 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) + 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) @@ -170,7 +237,7 @@ function render_inline (ctx, w, max_h) grid_freq (ctx, w, h, 10000) ctx:unset_dash () - -- draw transfer function + -- 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 -- cgit v1.2.3