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ardour {
["type"] = "dsp",
name = "a-Amplifier",
category = "Amplifier",
license = "MIT",
author = "Ardour Team",
description = [[Versatile +/- 20dB multichannel amplifier]]
}
function dsp_ioconfig ()
return
{
-- -1, -1 = any number of channels as long as input and output count matches
{ audio_in = -1, audio_out = -1},
}
end
function dsp_params ()
return
{
{ ["type"] = "input", name = "Gain", min = -20, max = 20, default = 0, unit="dB"},
}
end
local lpf = 0.02 -- parameter low-pass filter time-constant
local cur_gain = 0 -- current smoothed gain (dB)
-- called once when plugin is instantiated
function dsp_init (rate)
lpf = 780 / rate -- interpolation time constant
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
-- the DSP callback function
-- "ins" and "outs" are http://manual.ardour.org/lua-scripting/class_reference/#C:FloatArray
function dsp_run (ins, outs, n_samples)
local ctrl = CtrlPorts:array() -- get control port array (read/write)
local siz = n_samples -- samples remaining to process
local off = 0 -- already processed samples
local changed = false
-- if the gain parameter was changed, process at most 32 samples at a time
-- and interpolate gain until the current settings match the target values
if cur_gain ~= ctrl[1] then
changed = true
siz = 32
end
while n_samples > 0 do
if siz > n_samples then siz = n_samples end -- process at most "remaining samples"
if changed then
-- smooth gain changes above 0.02 dB difference
cur_gain = low_pass_filter_param (cur_gain, ctrl[1], 0.02)
end
local gain = ARDOUR.DSP.dB_to_coefficient (cur_gain) -- 10 ^ (0.05 * cur_gain)
for c = 1,#ins do -- process all channels
-- check if output and input buffers for this channel are identical
-- http://manual.ardour.org/lua-scripting/class_reference/#C:FloatArray
if ins[c] ~= outs[c] then
-- http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:DSP
ARDOUR.DSP.copy_vector (outs[c]:offset (off), ins[c]:offset (off), siz)
end
ARDOUR.DSP.apply_gain_to_buffer (outs[c]:offset (off), siz, gain); -- apply-gain, process in-place
end
n_samples = n_samples - siz
off = off + siz
end
--[[
if changed then
self:queue_draw () -- notify display
end
--]]
end
-------------------------------------------------------------------------------
--- inline display + text example
--[[
local txt = nil -- cache pango context globally
function render_inline (ctx, w, max_h)
local ctrl = CtrlPorts:array () -- get control ports
if not txt then
-- allocate PangoLayout and set font
--http://manual.ardour.org/lua-scripting/class_reference/#Cairo:PangoLayout
txt = Cairo.PangoLayout (ctx, "Mono 8px")
end
txt:set_text (string.format ("%+.2f dB", ctrl[1]));
tw, th = txt:get_pixel_size ()
local h = th + 4 -- use text-height with 4px padding
if (h > max_h) then h = max_h end -- but at most max-height
-- clear background
ctx:rectangle (0, 0, w, h)
ctx:set_source_rgba (.2, .2, .2, 1.0)
ctx:fill ()
-- center text
ctx:set_source_rgba (.8, .8, .8, 1.0)
ctx:move_to (.5 * (w - tw), .5 * (h - th))
txt:show_in_cairo_context (ctx)
return {w, h}
end
--]]
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