Long Delay for Lua Protoplug

longdelay.lua

--[[
name: Delay Line
description: Simple delay line effect with DC removal
author: osar.fr (adapted by Phil Jones )

See  : https://www.youtube.com/watch?v=PEUZZCpzkWo
--]]

require "include/protoplug"

local length, feedback

stereoFx.init()

DELAY_BUFFER_SIZE = 1400000

-- everything is per stereo channel
function stereoFx.Channel:init()
	self.delay_buffer = ffi.new("double[1400000]")
	self.current_time_idx = 0 	-- iterator
	self.dc1, self.dc2 = 0,0
end

function stereoFx.Channel:goBack()
	local past_idx = self.current_time_idx-length
	if past_idx<0 then past_idx = past_idx+DELAY_BUFFER_SIZE end
	local v = self.delay_buffer[past_idx]
	past_idx = past_idx-1
	if past_idx<0 then past_idx = past_idx+DELAY_BUFFER_SIZE end
	v = v+self.delay_buffer[past_idx]
	v = v*0.4992*feedback
	return v
end

function stereoFx.Channel:dcRemove(s)  -- don't worry about this
	self.dc1 = self.dc1 + (s - self.dc2) * 0.000002
	self.dc2 = self.dc2 + self.dc1
	self.dc1 = self.dc1 * 0.96
	return s-self.dc2
end

function stereoFx.Channel:processBlock(audio_buffer, smax)
	for i = 0,smax do
		audio_buffer[i] = audio_buffer[i]+self:dcRemove(audio_buffer[i]+self:goBack())
		self.delay_buffer[self.current_time_idx] = audio_buffer[i]
		self.current_time_idx = self.current_time_idx+1
		if self.current_time_idx>=DELAY_BUFFER_SIZE then self.current_time_idx=0 end
	end
end

params = plugin.manageParams {
	{
		name = "Length";
		type = "int";
		max = DELAY_BUFFER_SIZE;
		changed = function(val) length = val end;
	};
	{
		name = "Feedback";
		max = 1;
		changed = function(val) feedback = val end;
	};
}