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
}
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
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)
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)
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)
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
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