diff --git a/common.hh b/common.hh
index 0f90071..549bec8 100644
--- a/common.hh
+++ b/common.hh
@@ -29,6 +29,9 @@ struct Common
 	static const int block_skew = 3;
 	static const int first_meta = 4;
 	static const int first_seed = 9;
+	static constexpr int slm_poly[16] = {
+			0x11d, 0x12b, 0x12d, 0x14d, 0x15f, 0x163, 0x165, 0x169,
+			0x171, 0x187, 0x18d, 0x1a9, 0x1c3, 0x1cf, 0x1e7, 0x1f5 };
 	CODE::CRC<uint32_t> crc0;
 	CODE::HadamardEncoder<6> hadamard_encoder;
 	int8_t meta[32];
diff --git a/decode.cc b/decode.cc
index 01ce723..306c9b8 100644
--- a/decode.cc
+++ b/decode.cc
@@ -278,6 +278,10 @@ struct Decoder : Common
 				for (int i = 0; i < meta_tones; ++i)
 					meta[i] = clamp(std::nearbyint(127 * demod[i*block_length+meta_off].real()));
 				int meta_data = hadamard_decoder(meta);
+				if (meta_data < 0) {
+					std::cerr << "meta data damaged" << std::endl;
+					meta_data = 0;
+				}
 				hadamard_encoder(meta, meta_data);
 				for (int i = 0; i < meta_tones; ++i) {
 					tone[block_length*i+meta_off] *= meta[i];
@@ -290,6 +294,10 @@ struct Decoder : Common
 				for (int i = 0; i < seed_tones; ++i)
 					seed[i] = clamp(std::nearbyint(127 * demod[i*block_length+seed_off].real()));
 				int seed_data = hadamard_decoder(seed);
+				if (seed_data < 0) {
+					std::cerr << "seed data damaged" << std::endl;
+					seed_data = 0;
+				}
 				hadamard_encoder(seed, seed_data);
 				for (int i = 0; i < seed_tones; ++i) {
 					tone[block_length*i+seed_off] *= seed[i];
@@ -315,10 +323,15 @@ struct Decoder : Common
 					for (int i = seed_off; i < tone_count; i += block_length)
 						chan[i] = DSP::lerp(chan[i], tone[i], value(0.5));
 				}
-				CODE::MLS seq2(mls2_poly, seed_data);
+				int poly_index = j ? meta_data : 0;
+				if (poly_index < 0 || poly_index > 15) {
+					std::cerr << "poly index damaged" << std::endl;
+					meta_data = 0;
+				}
+				CODE::MLS seq(slm_poly[poly_index], seed_data+1);
 				for (int i = 0; i < tone_count; ++i)
 					if (i % block_length != meta_off && i % block_length != seed_off)
-						demod[i] *= nrz(seq2());
+						demod[i] *= nrz(seq());
 				value sp = 0, np = 0;
 				for (int i = 0, l = k; i < tone_count; ++i) {
 					cmplx hard(1, 0);
diff --git a/encode.cc b/encode.cc
index 442a6f9..aa7510c 100644
--- a/encode.cc
+++ b/encode.cc
@@ -79,23 +79,25 @@ struct Encoder : public Common
 		value scale = value(0.5) / std::sqrt(value(tone_count));
 		for (int i = 0; differential && symbol_number > 0 && i < tone_count; ++i)
 			tone[i] *= prev[i];
-		if (symbol_number >= 0) {
-			hadamard_encoder(meta, symbol_number ? symbol_number : oper_mode);
-			for (int i = 0; i < meta_tones; ++i)
-				tone[block_length*i+meta_off] *= meta[i];
-		}
 		value best_papr = 1000;
-		for (int trial = 0; trial < 64; ++trial) {
+		int trials = symbol_number ? 16 * 64 : 64;
+		for (int trial = 0; trial < trials; ++trial) {
 			for (int i = 0; i < tone_count; ++i)
 				temp[i] = tone[i];
 			if (symbol_number >= 0) {
-				hadamard_encoder(seed, trial);
-				CODE::MLS seq2(mls2_poly, trial);
-				for (int i = 0, s = 0; i < tone_count; ++i)
-					if (i % block_length == seed_off)
+				int poly_index = trial >> 6;
+				int meta_data = symbol_number ? poly_index : oper_mode;
+				hadamard_encoder(meta, meta_data);
+				int seed_data = trial & 63;
+				hadamard_encoder(seed, seed_data);
+				CODE::MLS seq(slm_poly[poly_index], seed_data + 1);
+				for (int i = 0, m = 0, s = 0; i < tone_count; ++i)
+					if (i % block_length == meta_off)
+						temp[i] *= meta[m++];
+					else if (i % block_length == seed_off)
 						temp[i] *= seed[s++];
-					else if (i % block_length != meta_off)
-						temp[i] *= nrz(seq2());
+					else
+						temp[i] *= nrz(seq());
 			}
 			for (int i = 0; i < symbol_len; ++i)
 				fdom[i] = 0;