--- /dev/null
+ardour {
+ ["type"] = "dsp",
+ name = "High/Low Pass Filter",
+ category = "Filter",
+ license = "MIT",
+ author = "Robin Gareus",
+ email = "robin@gareus.org",
+ site = "http://gareus.org",
+ 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
+
+
+function dsp_params ()
+ return
+ {
+ { ["type"] = "input", name = "Type", min = 0, max = 1, default = 0, enum = true, scalepoints =
+ {
+ ["High Pass"] = 0,
+ ["Low Pass"] = 1,
+ }
+ },
+ { ["type"] = "input", name = "Steepness", min = 1, max = 4, default = 1, enum = true, scalepoints =
+ {
+ ["12dB/oct"] = 1,
+ ["24dB/oct"] = 2,
+ ["36dB/oct"] = 3,
+ ["48dB/oct"] = 4,
+ }
+ },
+ { ["type"] = "input", name = "Cut off frequency", min = 5, max = 20000, default = 1000, unit="Hz", logarithmic = true },
+ { ["type"] = "input", name = "Resonance", 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.LowPass
+ else
+ return ARDOUR.DSP.BiquadType.HighPass
+ end
+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} -- current parameters
+local lpf = 0.03 -- parameter low-pass filter time-constant
+
+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
+ for k = 1,4 do
+ filters[k] = ARDOUR.DSP.Biquad (rate) -- initialize filters
+ end
+ 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 not param_changed (ctrl) then
+ return
+ end
+
+ if cur[1] ~= ctrl[1] or cur[2] ~= ctrl[2] then
+ -- reset filter state when type or order changes
+ for k = 1,4 do
+ filters[k]:reset ()
+ end
+ for k = 1,4 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], 1.0) -- freq/Hz
+ cur[4] = low_pass_filter_param (cur[4], ctrl[4], 0.01) -- quality
+ end
+
+ if cur[2] < 1 then cur[2] = 1 end
+ if cur[2] > 4 then cur[2] = 4 end
+
+ for k = 1,4 do
+ filters[k]:compute (map_type (cur[1]), cur[3], cur[4], 0)
+ end
+end
+
+
+-- the actual DSP callback
+function dsp_run (ins, outs, n_samples)
+ 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
+
+ local o = cur[2]
+
+ 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
+ for k = 1,o do
+ filters[k]:run (ins[c]:offset (off), siz) -- in-place processing
+ end
+ else
+ -- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP
+ ARDOUR.DSP.copy_vector (outs[c]:offset (off), ins[c]:offset (off), siz)
+ for k = 1,o do
+ filters[o]:run (outs[c]:offset (off), siz)
+ 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)
+ -- 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 < -48 then db = -48 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
+ 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 = CtrlPorts:array ()
+ for k = 1,4 do cur[k] = ctrl[k] end
+ if cur[2] < 1 then cur[2] = 1 end
+ if cur[2] > 4 then cur[2] = 4 end
+ filt:compute (map_type (cur[1]), cur[3], cur[4], 0)
+ end
+
+ -- calc height of inline display
+ local h = math.ceil (w * 10 / 16) -- use 16:10 aspect
+ 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 ()
+ local dash2 = C.DoubleVector ()
+ dash2:add ({1, 2})
+ dash3:add ({1, 3})
+ ctx:set_dash (dash2, 2) -- dotted line
+ ctx:set_source_rgba (.5, .5, .5, .8)
+ grid_db (ctx, w, h, 0)
+ ctx:set_dash (dash3, 2) -- dotted line
+ 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 ()
+
+ local o = cur[2]
+ -- draw transfer function line
+ ctx:set_source_rgba (.8, .8, .8, 1.0)
+ ctx:move_to (-.5, db_to_y (o * filt:dB_at_freq (freq_at_x (0, w)), h))
+ for x = 1,w do
+ local db = o * 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 + 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
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