Robin Gareus
8edc94edea
This fixes an issue with a-Amp interpolating the parameter in dB, resulting in a double-exponential fade when the parameter changes. Now fade is linear in dB, also using Ardour' Amp processor is more efficient, since interpolation happens in C++.
80 lines
2.3 KiB
Lua
80 lines
2.3 KiB
Lua
ardour {
|
|
["type"] = "dsp",
|
|
name = "Simple Amp IV",
|
|
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
|
|
-- XXX this interpolates dB, resulting in a double-exponential fade XXX
|
|
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
|
|
end
|