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|
ardour {
["type"] = "dsp",
name = "a-High/Low Pass Filter",
category = "Filter",
license = "GPLv2",
author = "Ardour Team",
description = [[High Low Pass filter with up to 48dB / octave]]
}
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 = "High Pass Steepness", min = 0, max = 4, default = 1, enum = true, scalepoints =
{
["Off"] = 0,
["12dB/oct"] = 1,
["24dB/oct"] = 2,
["36dB/oct"] = 3,
["48dB/oct"] = 4,
}
},
{ ["type"] = "input", name = "High Pass Cut off frequency", min = 5, max = 20000, default = 100, unit="Hz", logarithmic = true },
{ ["type"] = "input", name = "High Pass Resonance", min = 0.1, max = 6, default = .707, logarithmic = true },
{ ["type"] = "input", name = "Low Pass Steepness", min = 0, max = 4, default = 1, enum = true, scalepoints =
{
["Off"] = 0,
["12dB/oct"] = 1,
["24dB/oct"] = 2,
["36dB/oct"] = 3,
["48dB/oct"] = 4,
}
},
{ ["type"] = "input", name = "Low Pass Cut off frequency", min = 20, max = 20000, default = 18000, unit="Hz", logarithmic = true },
{ ["type"] = "input", name = "Low Pass Resonance", min = 0.1, max = 6, default = .707, logarithmic = true },
}
end
-- these globals are *not* shared between DSP and UI
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} -- current parameters
local lpf = 0.03 -- parameter low-pass filter time-constant
local chn = 0 -- channel/filter count
local mem = nil -- memory x-fade buffer
function dsp_init (rate)
-- allocate some mix-buffer
mem = ARDOUR.DSP.DspShm (8192)
-- create a table of objects to share with the GUI
local tbl = {}
tbl['samplerate'] = rate
self:table ():set (tbl)
-- interpolation time constant, ~15Hz @ 64fpp
lpf = 5000 / rate
end
function dsp_configure (ins, outs)
assert (ins:n_audio () == outs:n_audio ())
local tbl = self:table ():get () -- get shared memory table
chn = ins:n_audio ()
cur = {0, 0, 0, 0, 0, 0}
hp = {}
lp = {}
collectgarbage ()
for c = 1, chn do
hp[c] = {}
lp[c] = {}
-- initialize filters
-- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP:Biquad
for k = 1,4 do
hp[c][k] = ARDOUR.DSP.Biquad (tbl['samplerate'])
lp[c][k] = ARDOUR.DSP.Biquad (tbl['samplerate'])
end
end
end
-- helper functions for parameter interpolation
function param_changed (ctrl)
for p = 1,6 do
if ctrl[p] ~= cur[p] then
return true
end
end
return false
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
-- low-pass filter ctrl parameter values, smooth transition
cur[1] = low_pass_filter_param (cur[1], ctrl[1], 0.05) -- HP order x-fade
cur[2] = low_pass_filter_param (cur[2], ctrl[2], 1.0) -- HP freq/Hz
cur[3] = low_pass_filter_param (cur[3], ctrl[3], 0.01) -- HP quality
cur[4] = low_pass_filter_param (cur[4], ctrl[4], 0.05) -- LP order x-fade
cur[5] = low_pass_filter_param (cur[5], ctrl[5], 1.0) -- LP freq/Hz
cur[6] = low_pass_filter_param (cur[6], ctrl[6], 0.01) -- LP quality
for c = 1, chn do
for k = 1,4 do
hp[c][k]:compute (ARDOUR.DSP.BiquadType.HighPass, cur[2], cur[3], 0)
lp[c][k]:compute (ARDOUR.DSP.BiquadType.LowPass, cur[5], cur[6], 0)
end
end
end
-- the actual DSP callback
function dsp_run (ins, outs, n_samples)
assert (n_samples < 8192)
assert (#ins == chn)
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
while n_samples > 0 do
if changed then apply_params (CtrlPorts:array ()) end
if siz > n_samples then siz = n_samples end
local ho = math.floor(cur[1])
local lo = math.floor(cur[4])
-- process all channels
for c = 1, #ins do
local xfade = cur[1] - ho
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
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
-- low pass
xfade = cur[4] - lo
-- copy output of high-pass into "processing memory"
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.
-- (Except if the filter is disabled (0) 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 + 1 then
ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, 1 - xfade)
end
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 + 1 then
ARDOUR.DSP.mix_buffers_with_gain (outs[c]:offset (off), mem:to_float (off), siz, xfade)
end
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)
-- frequency in Hz at given x-axis pixel
return 20 * 1000 ^ (x / w)
end
function x_at_freq (f, w)
-- x-axis pixel for given frequency, power-scale
return w * math.log (f / 20.0) / math.log (1000.0)
end
function db_to_y (db, h)
-- y-axis gain mapping
if db < -60 then db = -60 end
if db > 12 then db = 12 end
return -.5 + round (0.2 * h) - h * db / 60
end
function grid_db (ctx, w, h, db)
-- draw horizontal grid line
-- note that a cairo pixel at Y spans [Y - 0.5 to Y + 0.5]
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 response (ho, lo, f)
-- calculate transfer function response for given
-- hi/po pass order at given frequency [Hz]
local db = ho * filt['hp']:dB_at_freq (f)
return db + lo * filt['lp']:dB_at_freq (f)
end
function render_inline (ctx, w, max_h)
if not filt then
local tbl = self:table ():get () -- get shared memory table
-- instantiate filter (to calculate the transfer function's response)
filt = {}
filt['hp'] = ARDOUR.DSP.Biquad (tbl['samplerate'])
filt['lp'] = ARDOUR.DSP.Biquad (tbl['samplerate'])
end
-- set filter coefficients if they have changed
if param_changed (CtrlPorts:array ()) then
local ctrl = CtrlPorts:array ()
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)
end
-- calc height of inline display
local h = 1 | math.ceil (w * 9 / 16) -- use 16:9 aspect, odd number of y 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 ()
ctx:rectangle (0, 0, w, h)
ctx:clip ()
-- set line width: 1px
ctx:set_line_width (1.0)
-- draw grid
local dash3 = C.DoubleVector ()
local dash2 = C.DoubleVector ()
dash2:add ({1, 2})
dash3:add ({1, 3})
ctx:set_dash (dash2, 2) -- dotted line: 1 pixel 2 space
ctx:set_source_rgba (.5, .5, .5, .8)
grid_db (ctx, w, h, 0)
ctx:set_dash (dash3, 2) -- dashed line: 1 pixel 3 space
ctx:set_source_rgba (.5, .5, .5, .5)
grid_db (ctx, w, h, -12)
grid_db (ctx, w, h, -24)
grid_db (ctx, w, h, -36)
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
local ho = math.floor(cur[1])
local lo = math.floor(cur[4])
ctx:set_source_rgba (.8, .8, .8, 1.0)
ctx:move_to (-.5, db_to_y (response(ho, lo, freq_at_x (0, w)), h))
for x = 1,w do
local db = response(ho, lo, freq_at_x (x, w))
ctx:line_to (-.5 + x, db_to_y (db, h))
end
-- stoke a line, keep the path
ctx:stroke_preserve ()
-- fill area to zero under the curve
ctx:line_to (w, -.5 + round (db_to_y (0, h)))
ctx:line_to (0, -.5 + round (db_to_y (0, h)))
ctx:close_path ()
ctx:set_source_rgba (.5, .5, .5, .5)
ctx:fill ()
return {w, h}
end
|