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Add a DSP script to slowly fade in/out

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x42 committed Apr 15, 2019
1 parent eae88bc commit d6860767110c68d676982301ef2eae1e3b7e8c34
Showing with 66 additions and 0 deletions.
  1. +66 −0 scripts/a_slow_mute.lua
@@ -0,0 +1,66 @@
ardour {
["type"] = "dsp",
name = "a-Slow-Mute",
category = "Amplifier",
license = "MIT",
author = "Ardour Team",
description = [[Mute button with slow fade in/out]]
}

function dsp_ioconfig ()
-- -1, -1 = any number of channels as long as input and output count matches
return { { audio_in = -1, audio_out = -1} }
end


function dsp_params ()
return { { ["type"] = "input", name = "Mute", min = 0, max = 1, default = 0, toggled = true } }
end

local cur_gain = 1
local lpf = 0.002 -- parameter low-pass filter time-constant

function dsp_init (rate)
lpf = 100 / 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
local target_gain = ctrl[1] > 0 and 0.0 or 1.0; -- when muted, target_gain = 0.0; otherwise use 1.0
local siz = n_samples -- samples remaining to process
local off = 0 -- already processed samples
local changed = false

-- if the target gain changes, process at most 32 samples at a time,
-- and interpolate gain until the current settings match the target values
if cur_gain ~= target_gain then
changed = true
siz = 32
end

while n_samples > 0 do
if siz > n_samples then siz = n_samples end
if changed then
cur_gain = low_pass_filter_param (cur_gain, target_gain, 0.001)
end

for c = 1,#ins do -- process all channels
if ins[c] ~= outs[c] then
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, cur_gain);
end
n_samples = n_samples - siz
off = off + siz
end
end

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