From e23cfe2942f48f89236fdf7bcc7d2c192b191319 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Thu, 6 Jul 2023 00:27:30 +0200
Subject: [PATCH] Add ACE Stereo Routing

---
 share/scripts/a_stereo_routing.lua | 107 +++++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100644 share/scripts/a_stereo_routing.lua

diff --git a/share/scripts/a_stereo_routing.lua b/share/scripts/a_stereo_routing.lua
new file mode 100644
index 00000000000..b8c2e70ff0e
--- /dev/null
+++ b/share/scripts/a_stereo_routing.lua
@@ -0,0 +1,107 @@
+ardour {
+	["type"]    = "dsp",
+	name        = "ACE Stereo Routing",
+	category    = "Utility",
+	license     = "MIT",
+	author      = "Ardour Community",
+	description = [[Stereo Signal Routing, re-assign or mix channels. This is a drop-in replacement for https://x42-plugins.com/x42/x42-stereoroute]]
+}
+
+function dsp_ioconfig ()
+	return { { audio_in = 2, audio_out = 2} }
+end
+
+function dsp_params ()
+	return {
+		{ ["type"] = "input", name = "Mode", min = 0, max = 8, default = 0, enum = true, scalepoints =
+			{
+				["No-OP: L->L, R->R (Straight Bypass)"]    = 0,
+				["Downmix to Mono -3dB (Equal Power)"]     = 1,
+				["Downmix to Mono -6dB (Equal Amplitude)"] = 2,
+				["Downmix to Mono -0dB (Sum Channels)"]    = 3,
+				["Route Left Only: L->L, L->R"]            = 4,
+				["Route Right Only: R->R, R->L"]           = 5,
+				["Swap Channels: L->R, R->L"]              = 6,
+				["M/S: (L+R)/2, (L-R)/2 (to Mid/Side)"]    = 7,
+				["M/S: (L+R), (L-R) (from Mid/Side)"]      = 8,
+			}
+		}
+	}
+end
+
+function dsp_init (rate)
+	cmem = ARDOUR.DSP.DspShm (8192)
+end
+
+function copy_no_inplace (ins, outs, n_samples)
+	assert (#ins == #outs)
+	for c = 1, #outs do
+		if ins[c] ~= outs[c] then
+			ARDOUR.DSP.copy_vector (outs[c], ins[c], n_samples) -- ..copy data from input to output.
+		end
+	end
+end
+
+function dsp_run (ins, outs, n_samples)
+	assert (n_samples <= 8192)
+	local ctrl = CtrlPorts:array()
+	local m = ctrl[1]
+	if (m < 1) then
+		-- NO-OP
+		copy_no_inplace (ins, outs, n_samples)
+	elseif (m < 2) then
+		-- Sum to Mono -3dB
+		copy_no_inplace (ins, outs, n_samples)
+		ARDOUR.DSP.mix_buffers_no_gain (outs[1], outs[2], n_samples)
+		ARDOUR.DSP.apply_gain_to_buffer (outs[1], n_samples, 0.707945784);
+		ARDOUR.DSP.copy_vector (outs[2], outs[1], n_samples)
+	elseif (m < 3) then
+		-- Sum to Mono -6dB
+		copy_no_inplace (ins, outs, n_samples)
+		ARDOUR.DSP.mix_buffers_no_gain (outs[1], outs[2], n_samples)
+		ARDOUR.DSP.apply_gain_to_buffer (outs[1], n_samples, 0.5);
+		ARDOUR.DSP.copy_vector (outs[2], outs[1], n_samples)
+	elseif (m < 4) then
+		-- Sum to Mono
+		copy_no_inplace (ins, outs, n_samples)
+		ARDOUR.DSP.mix_buffers_no_gain (outs[1], outs[2], n_samples)
+		ARDOUR.DSP.copy_vector (outs[2], outs[1], n_samples)
+	elseif (m < 5) then
+		-- Left only
+		if ins[1] ~= outs[1] then
+			ARDOUR.DSP.copy_vector (outs[1], ins[1], n_samples)
+		end
+		ARDOUR.DSP.copy_vector (outs[2], outs[1], n_samples)
+	elseif (m < 6) then
+		-- Right only
+		if ins[2] ~= outs[2] then
+			ARDOUR.DSP.copy_vector (outs[2], ins[2], n_samples)
+		end
+		ARDOUR.DSP.copy_vector (outs[1], outs[2], n_samples)
+	elseif (m < 7) then
+		-- Swap channels
+		ARDOUR.DSP.copy_vector (cmem:to_float(0), ins[1], n_samples)
+		ARDOUR.DSP.copy_vector (outs[1], ins[2], n_samples)
+		ARDOUR.DSP.copy_vector (outs[2], cmem:to_float(0), n_samples)
+	elseif (m < 8) then
+		-- to Mid/Side
+		ARDOUR.DSP.copy_vector (cmem:to_float(0), ins[1], n_samples)
+		ARDOUR.DSP.mix_buffers_with_gain (cmem:to_float(0), ins[2], n_samples, -1) -- (L - R)
+		if ins[1] ~= outs[1] then
+			ARDOUR.DSP.copy_vector (outs[1], ins[1], n_samples)
+		end
+		ARDOUR.DSP.mix_buffers_no_gain (outs[1], ins[2], n_samples) -- (L + R)
+		ARDOUR.DSP.copy_vector (outs[2], cmem:to_float(0), n_samples)
+		ARDOUR.DSP.apply_gain_to_buffer (outs[1], n_samples, 0.5);
+		ARDOUR.DSP.apply_gain_to_buffer (outs[2], n_samples, 0.5);
+	else
+		-- from Mid/Side
+		ARDOUR.DSP.copy_vector (cmem:to_float(0), ins[1], n_samples)
+		ARDOUR.DSP.mix_buffers_with_gain (cmem:to_float(0), ins[2], n_samples, -1) -- (L - R)
+		if ins[1] ~= outs[1] then
+			ARDOUR.DSP.copy_vector (outs[1], ins[1], n_samples)
+		end
+		ARDOUR.DSP.mix_buffers_no_gain (outs[1], ins[2], n_samples) -- (L + R)
+		ARDOUR.DSP.copy_vector (outs[2], cmem:to_float(0), n_samples)
+	end
+end