From e5801a698e6b775a66c13ac34f97c5adbae57593 Mon Sep 17 00:00:00 2001
From: Ahmet Inan <xdsopl@gmail.com>
Date: Thu, 10 Jul 2025 19:06:02 +0200
Subject: [PATCH] try to improve papr of first symbol

---
 decode.cc | 2 +-
 encode.cc | 7 ++++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/decode.cc b/decode.cc
index 6d2fec1..1636f6e 100644
--- a/decode.cc
+++ b/decode.cc
@@ -234,7 +234,7 @@ struct Decoder : Common
 			auto clamp = [](int v){ return v < -127 ? -127 : v > 127 ? 127 : v; };
 			for (int i = 0; i < pilot_tones; ++i)
 				meta[i] = clamp(std::nearbyint(127 * demod_or_erase(fdom[bin(i*block_length+first_pilot+tone_off)], chan[i*block_length+first_pilot]).real() * nrz(seq1())));
-			int mode = hadamard_decoder(meta);
+			int mode = hadamard_decoder(meta) & 31;
 			if (mode < 0 || mode > 27) {
 				std::cerr << "operation mode " << mode << " unsupported." << std::endl;
 				continue;
diff --git a/encode.cc b/encode.cc
index 24ee3d1..1fab8c1 100644
--- a/encode.cc
+++ b/encode.cc
@@ -73,11 +73,12 @@ struct Encoder : public Common
 	{
 		for (int i = 0; differential && symbol_number > 0 && i < tone_count; ++i)
 			tone[i] *= temp[i];
-		for (int trial = 63; trial >= 0; --trial) {
+		int trials = symbol_number ? 128 : 4;
+		for (int trial = trials - 1; trial >= 0; --trial) {
 			for (int i = 0; i < tone_count; ++i)
 				temp[i] = tone[i];
 			if (symbol_number >= 0) {
-				int meta_data = symbol_number ? trial : oper_mode;
+				int meta_data = symbol_number ? trial : (oper_mode | (trial << 5));
 				hadamard_encoder(meta, meta_data);
 				CODE::MLS seq(0x163, meta_data);
 				for (int i = 0, m = 0; i < tone_count; ++i)
@@ -110,7 +111,7 @@ struct Encoder : public Common
 			}
 			mean /= symbol_len;
 			value papr(peak / mean);
-			if (symbol_number == 0 || papr < 5 || trial == 0) {
+			if (papr < 5 || trial == 0) {
 				std::cerr << " " << DSP::decibel(papr);
 				break;
 			}