From d1a2ec19f0f3e519f3d759a4c76b5f25e88322b7 Mon Sep 17 00:00:00 2001
From: Ahmet Inan <xdsopl@gmail.com>
Date: Fri, 15 Dec 2023 17:54:54 +0100
Subject: [PATCH] added three new, non-differential modes

---
 decode.cc | 28 ++++++++++++++--------------
 encode.cc | 16 +++++++++-------
 2 files changed, 23 insertions(+), 21 deletions(-)

diff --git a/decode.cc b/decode.cc
index 600ec1a..9a1b8a1 100644
--- a/decode.cc
+++ b/decode.cc
@@ -189,6 +189,7 @@ struct Decoder
 	static const int mls1_len = 255;
 	static const int mls1_off = - mls1_len / 2;
 	static const int mls1_poly = 0b100101011;
+	static const int mls2_poly = 0b100101010001;
 	static const int buffer_len = 4 * extended_len;
 	static const int search_pos = extended_len;
 	DSP::ReadPCM<value> *pcm;
@@ -206,7 +207,7 @@ struct Decoder
 	int8_t genmat[255*71];
 	mesg_type mesg[max_bits], mess[code_len];
 	code_type code[code_len];
-	cmplx cons[cons_total], prev[cons_cols];
+	cmplx cons[cons_total], chan[cons_cols];
 	cmplx fdom[symbol_len], tdom[symbol_len];
 	value index[cons_cols], phase[cons_cols];
 	value cfo_rad, sfo_rad;
@@ -219,15 +220,15 @@ struct Decoder
 	{
 		return (carrier + symbol_len) % symbol_len;
 	}
-	static int nrz(bool bit)
+	static value nrz(bool bit)
 	{
 		return 1 - 2 * bit;
 	}
-	static cmplx demod_or_erase(cmplx curr, cmplx prev)
+	static cmplx demod_or_erase(cmplx curr, cmplx chan)
 	{
-		if (!(norm(prev) > 0))
+		if (!(norm(chan) > 0))
 			return 0;
-		cmplx cons = curr / prev;
+		cmplx cons = curr / chan;
 		if (!(norm(cons) <= 4))
 			return 0;
 		return cons;
@@ -328,7 +329,7 @@ struct Decoder
 				continue;
 			}
 			oper_mode = md & 255;
-			if (oper_mode && (oper_mode < 14 || oper_mode > 16)) {
+			if (oper_mode && (oper_mode < 17 || oper_mode > 19)) {
 				std::cerr << "operation mode " << oper_mode << " unsupported." << std::endl;
 				continue;
 			}
@@ -348,15 +349,16 @@ struct Decoder
 		if (!okay || !oper_mode)
 			return;
 
-		for (int i = 0; i < symbol_pos+extended_len; ++i)
+		for (int i = 0; i < symbol_pos+2*extended_len; ++i)
 			buf = next_sample();
 		for (int i = 0; i < symbol_len; ++i)
 			tdom[i] = buf[i] * osc();
 		for (int i = 0; i < guard_len; ++i)
 			osc();
 		fwd(fdom, tdom);
+		CODE::MLS seq2(mls2_poly);
 		for (int i = 0; i < cons_cols; ++i)
-			prev[i] = fdom[bin(i+code_off)];
+			chan[i] = nrz(seq2()) * fdom[bin(i+code_off)];
 		std::cerr << "demod ";
 		for (int j = 0; j < cons_rows; ++j) {
 			for (int i = 0; i < extended_len; ++i)
@@ -367,9 +369,7 @@ struct Decoder
 				osc();
 			fwd(fdom, tdom);
 			for (int i = 0; i < cons_cols; ++i)
-				cons[cons_cols*j+i] = demod_or_erase(fdom[bin(i+code_off)], prev[i]);
-			for (int i = 0; i < cons_cols; ++i)
-				prev[i] = fdom[bin(i+code_off)];
+				cons[cons_cols*j+i] = demod_or_erase(fdom[bin(i+code_off)], chan[i]);
 			std::cerr << ".";
 		}
 		std::cerr << " done" << std::endl;
@@ -425,15 +425,15 @@ struct Decoder
 		}
 		int data_bits = 0;
 		switch (oper_mode) {
-		case 14:
+		case 17:
 			data_bits = 1360;
 			frozen_bits = frozen_2048_1392;
 			break;
-		case 15:
+		case 18:
 			data_bits = 1024;
 			frozen_bits = frozen_2048_1056;
 			break;
-		case 16:
+		case 19:
 			data_bits = 680;
 			frozen_bits = frozen_2048_712;
 			break;
diff --git a/encode.cc b/encode.cc
index 4fbd728..6277b58 100644
--- a/encode.cc
+++ b/encode.cc
@@ -216,15 +216,15 @@ struct Encoder
 			const uint32_t *frozen_bits = nullptr;
 			int data_bits = 0;
 			switch (oper_mode) {
-			case 14:
+			case 17:
 				data_bits = 1360;
 				frozen_bits = frozen_2048_1392;
 				break;
-			case 15:
+			case 18:
 				data_bits = 1024;
 				frozen_bits = frozen_2048_1056;
 				break;
-			case 16:
+			case 19:
 				data_bits = 680;
 				frozen_bits = frozen_2048_712;
 				break;
@@ -239,9 +239,11 @@ struct Encoder
 			for (int i = 0; i < 32; ++i)
 				mesg[i+data_bits] = nrz((crc1()>>i)&1);
 			polarenc(code, mesg, frozen_bits, code_order);
+			pilot_block();
+			value code_fac = std::sqrt(value(symbol_len) / value(cons_cols));
 			for (int j = 0; j < cons_rows; ++j) {
 				for (int i = 0; i < cons_cols; ++i)
-					fdom[bin(i+code_off)] *=
+					fdom[bin(i+code_off)] = code_fac *
 						mod_map(code+mod_bits*(cons_cols*j+i));
 				symbol();
 			}
@@ -328,13 +330,13 @@ int main(int argc, char **argv)
 	int oper_mode = 0;
 	for (int i = 128; i < 170; ++i)
 		if (!oper_mode && input_data[i])
-			oper_mode = 14;
+			oper_mode = 17;
 	for (int i = 85; i < 128; ++i)
 		if (!oper_mode && input_data[i])
-			oper_mode = 15;
+			oper_mode = 18;
 	for (int i = 0; i < 85; ++i)
 		if (!oper_mode && input_data[i])
-			oper_mode = 16;
+			oper_mode = 19;
 	CODE::Xorshift32 scrambler;
 	for (int i = 0; i < data_len; ++i)
 		input_data[i] ^= scrambler();