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livetrax/scripts/synth1.lua

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ardour {
["type"] = "dsp",
name = "Simple Synth",
license = "MIT",
author = "Robin Gareus",
email = "robin@gareus.org",
site = "http://gareus.org",
description = [[An Example Synth for prototyping.]]
}
function dsp_ioconfig ()
return
{
-- { audio_in = 0, audio_out = -1}, -- any number of channels
-- { audio_in = 0, audio_out = 1}, -- values > 0, precisely N channels
{ audio_in = 0, audio_out = 2}, -- values > 0, precisely N channels
{ audio_in = 0, audio_out = 4}, -- values > 0, precisely N channels
{ audio_in = 0, audio_out = 8}, -- values > 0, precisely N channels
-- { audio_in = 0, audio_out = -6}, -- values < -2, up to -N channels, here 1,..,6
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}
end
function dsp_midi_input ()
return true
end
local note_table = {}
local active_notes = {}
local phases = {}
local env = .01;
function dsp_init (rate)
for n = 1,128 do
note_table [n] = (440 / 32) * 2^((n - 10.0) / 12.0) / rate
end
env = 100 / rate
end
function dsp_run (ins, outs, n_samples)
-- initialize output buffer
local a = {}
for s = 1, n_samples do a[s] = 0 end
-- very basic synth, simple sine, basic envelope
local function synth (s_start, s_end)
for n,v in pairs (active_notes) do
local vel = v["vel"] or 0
local tgt = v["tvel"];
for s = s_start,s_end do
local phase = phases[n] or 0
vel = vel + env * (tgt - vel)
a[s] = a[s] + math.sin(6.283185307 * phase) * vel / 167
phase = phase + note_table[n]
if (phase > 1.0) then
phases[n] = phase - 2.0
else
phases[n] = phase
end
end
if vel < 1 and tgt == 0 then
active_notes[n] = nil
else
active_notes[n]["vel"] = vel;
end
end
end
local tme = 1
-- parse midi messages
assert (type(mididata) == "table") -- global table of midi events (for now)
for _,b in pairs (mididata) do
local t = b["time"] -- t = [ 1 .. n_samples ]
-- synth sound until event
synth(tme, t)
tme = t + 1
local d = b["data"] -- get midi-event
-- we ignore the midi channel
if (#d == 3 and bit32.band (d[1], 240) == 144) then -- note on
local n = 1 + d[2];
active_notes[n] = active_notes[n] or {}
active_notes[n]["tvel"] = d[3]
end
if (#d == 3 and bit32.band (d[1], 240) == 128) then -- note off
local n = 1 + d[2];
active_notes[n] = active_notes[n] or {}
active_notes[n]["tvel"] = 0
end
if (#d == 3 and bit32.band (d[1], 240) == 176) then -- CC
if (d[2] == 120 or d[2] == 123) then -- panic
active_notes = {}
end
end
end
-- synth rest of cycle
synth(tme, n_samples)
-- copy
for c = 1,#outs do
outs[c]:set_table(a, n_samples)
end
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end