X-Git-Url: https://git.carlh.net/gitweb/?a=blobdiff_plain;f=scripts%2FHiAndLowPass.lua;h=75704d97016577d5d3ece380903f2db726bf7005;hb=d5d297c4071240d8a462fa22d53dba03cbdc211d;hp=dae22a00836284ebe307d12ae2a84910a1ba3f76;hpb=3458844878baeff66246a6611b6ba227e8a4f77c;p=ardour.git diff --git a/scripts/HiAndLowPass.lua b/scripts/HiAndLowPass.lua index dae22a0083..75704d9701 100644 --- a/scripts/HiAndLowPass.lua +++ b/scripts/HiAndLowPass.lua @@ -4,7 +4,7 @@ ardour { category = "Filter", license = "GPLv2", author = "Ardour Team", - description = [[Example Ardour Lua DSP Plugin]] + description = [[High and Low Pass Filter with de-zipped controls, written in Ardour-Lua]] } function dsp_ioconfig () @@ -49,9 +49,11 @@ end local hp = {} -- the biquad high-pass filter instances (DSP) local lp = {} -- the biquad high-pass filter instances (DSP) local filt = nil -- the biquad filter instance (GUI, response) -local cur = {0, 0, 0, 0, 0, 0, 0} -- current parameters +local cur = {0, 0, 0, 0, 0, 0} -- current parameters local lpf = 0.03 -- parameter low-pass filter time-constant local chn = 0 -- channel/filter count +local lpf_chunk = 0 -- chunk size for audio processing when interpolating parameters +local max_freq = 20000 local mem = nil -- memory x-fade buffer @@ -59,13 +61,32 @@ function dsp_init (rate) -- allocate some mix-buffer mem = ARDOUR.DSP.DspShm (8192) + -- max allowed cut-off frequency + max_freq = .499 * rate + -- create a table of objects to share with the GUI local tbl = {} tbl['samplerate'] = rate + tbl['max_freq'] = max_freq self:table ():set (tbl) - -- interpolation time constant, 64fpp - lpf = 5000 / rate + + -- Parameter smoothing: we want to filter out parameter changes that are + -- faster than 15Hz, and interpolate between parameter values. + -- For performance reasons, we want to ensure that two consecutive values + -- of the interpolated "steepness" are less that 1 apart. By choosing the + -- interpolation chunk size to be 64 in most cases, but 32 if the rate is + -- strictly less than 22kHz (there's only 8kHz in standard rates), we can + -- ensure that steepness interpolation will never change the parameter by + -- more than ~0.86. + lpf_chunk = 64 + if rate < 22000 then lpf_chunk = 32 end + -- We apply a discrete version of the standard RC low-pass, with a cutoff + -- frequency of 15Hz. For more information about the underlying math, see + -- https://en.wikipedia.org/wiki/Low-pass_filter#Discrete-time_realization + -- (here Δt is lpf_chunk / rate) + local R = 2 * math.pi * lpf_chunk * 15 -- Hz + lpf = R / (R + rate) end function dsp_configure (ins, outs) @@ -85,6 +106,12 @@ function dsp_configure (ins, outs) lp[c] = {} -- initialize filters -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP:Biquad + + -- A different Biquad is needed for each pass and channel because they + -- remember the last two samples seen during the last call of Biquad:run(). + -- For continuity these have to come from the previous audio chunk of the + -- same channel and pass and would be clobbered if the same Biquad was + -- called several times by cycle. for k = 1,4 do hp[c][k] = ARDOUR.DSP.Biquad (tbl['samplerate']) lp[c][k] = ARDOUR.DSP.Biquad (tbl['samplerate']) @@ -92,6 +119,21 @@ function dsp_configure (ins, outs) end end +function santize_params (ctrl) + -- don't allow manual cross-fades. enforce enums + ctrl[1] = math.floor(ctrl[1] + .5) + ctrl[4] = math.floor(ctrl[4] + .5) + + -- high pass, clamp range + ctrl[2] = math.min (max_freq, math.max (5, ctrl[2])) + ctrl[3] = math.min (6, math.max (0.1, ctrl[3])) + + -- low pass, clamp range + ctrl[5] = math.min (max_freq, math.max (20, ctrl[5])) + ctrl[6] = math.min (6, math.max (0.1, ctrl[6])) + return ctrl +end + -- helper functions for parameter interpolation function param_changed (ctrl) for p = 1,6 do @@ -135,23 +177,24 @@ end -- the actual DSP callback function dsp_run (ins, outs, n_samples) - assert (n_samples < 8192) + assert (n_samples <= 8192) assert (#ins == chn) + local ctrl = santize_params (CtrlPorts:array ()) 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 + -- if a parameter was changed, process at most lpf_chunk samples + -- at a time and interpolate parameters until the current settings + -- match the target values + if param_changed (ctrl) then changed = true - siz = 64 + siz = lpf_chunk end while n_samples > 0 do - if changed then apply_params (CtrlPorts:array ()) end + if changed then apply_params (ctrl) end if siz > n_samples then siz = n_samples end local ho = math.floor(cur[1]) @@ -160,61 +203,59 @@ function dsp_run (ins, outs, n_samples) -- process all channels for c = 1, #ins do + -- High Pass local xfade = cur[1] - ho - assert (xfade >= 0 and xfade < 1) + -- prepare scratch memory ARDOUR.DSP.copy_vector (mem:to_float (off), ins[c]:offset (off), siz) - -- initialize output - if cur[1] == 0 then - -- high pass is disabled, just copy data. - ARDOUR.DSP.copy_vector (outs[c]:offset (off), mem:to_float (off), siz) - else - -- clear output, The filter mixes into the output buffer - ARDOUR.DSP.memset (outs[c]:offset (off), 0, siz) - end - - -- high pass - -- allways run all filters so that we can interplate as needed. - for k = 1,4 do - if xfade > 0 and k == ho + 1 then - ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, 1 - xfade) - end - + -- run at least |ho| biquads... + for k = 1,ho do hp[c][k]:run (mem:to_float (off), siz) - - if k == ho and xfade == 0 then - ARDOUR.DSP.copy_vector (outs[c]:offset (off), mem:to_float (off), siz) - elseif k == ho + 1 then - ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, xfade) - end + end + ARDOUR.DSP.copy_vector (outs[c]:offset (off), mem:to_float (off), siz) + + -- mix the output of |ho| biquads (with weight |1-xfade|) + -- with the output of |ho+1| biquads (with weight |xfade|) + if xfade > 0 then + ARDOUR.DSP.apply_gain_to_buffer (outs[c]:offset (off), siz, 1 - xfade) + hp[c][ho+1]:run (mem:to_float (off), siz) + ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, xfade) + -- also run the next biquad because it needs to have the correct state + -- in case it start affecting the next chunck of output. Higher order + -- ones are guaranteed not to be needed for the next run because the + -- interpolated order won't increase more than 0.86 in one step thanks + -- to the choice of the value of |lpf|. + if ho + 2 <= 4 then hp[c][ho+2]:run (mem:to_float (off), siz) end + elseif ho + 1 <= 4 then + -- run the next biquad in case it is used next chunk + hp[c][ho+1]:run (mem:to_float (off), siz) end - -- low pass + -- Low Pass xfade = cur[4] - lo - assert (xfade >= 0 and xfade < 1) - -- copy output of high-pass into "processing memory" + -- prepare scratch memory (from high pass output) ARDOUR.DSP.copy_vector (mem:to_float (off), outs[c]:offset (off), siz) - if cur[4] > 0 then - -- clear output, Low-pass mixes interpolated data into output, - -- in which case we just keep the output - ARDOUR.DSP.memset (outs[c]:offset (off), 0, siz) - end - - for k = 1,4 do - if xfade > 0 and k > lo and k <= lo + 1 then - ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, 1 - xfade) - end - + -- run at least |lo| biquads... + for k = 1,lo do lp[c][k]:run (mem:to_float (off), siz) - - if k == lo and xfade == 0 then - ARDOUR.DSP.copy_vector (outs[c]:offset (off), mem:to_float (off), siz) - elseif k > lo and k <= lo + 1 then - ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, xfade) - end + end + ARDOUR.DSP.copy_vector (outs[c]:offset (off), mem:to_float (off), siz) + + -- mix the output of |lo| biquads (with weight |1-xfade|) + -- with the output of |lo+1| biquads (with weight |xfade|) + if xfade > 0 then + ARDOUR.DSP.apply_gain_to_buffer (outs[c]:offset (off), siz, 1 - xfade) + lp[c][lo+1]:run (mem:to_float (off), siz) + ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, xfade) + -- also run the next biquad in case it start affecting the next + -- chunck of output. + if lo + 2 <= 4 then lp[c][lo+2]:run (mem:to_float (off), siz) end + elseif lo + 1 <= 4 then + -- run the next biquad in case it is used next chunk + lp[c][lo+1]:run (mem:to_float (off), siz) end end @@ -285,11 +326,12 @@ function render_inline (ctx, w, max_h) filt = {} filt['hp'] = ARDOUR.DSP.Biquad (tbl['samplerate']) filt['lp'] = ARDOUR.DSP.Biquad (tbl['samplerate']) + max_freq = tbl['max_freq'] end + local ctrl = santize_params (CtrlPorts:array ()) -- set filter coefficients if they have changed - if param_changed (CtrlPorts:array ()) then - local ctrl = CtrlPorts:array () + if param_changed (ctrl) then for k = 1,6 do cur[k] = ctrl[k] end filt['hp']:compute (ARDOUR.DSP.BiquadType.HighPass, cur[2], cur[3], 0) filt['lp']:compute (ARDOUR.DSP.BiquadType.LowPass, cur[5], cur[6], 0)