diff --git a/decode.cc b/decode.cc
index 93a0fc6..86e0e8c 100644
--- a/decode.cc
+++ b/decode.cc
@@ -57,13 +57,14 @@ struct Decoder
 	static const int cols_max = 273 + 16;
 	static const int rows_max = 32;
 	static const int cons_max = cols_max * rows_max;
-	static const int mls0_len = 127;
-	static const int mls0_off = - mls0_len + 1;
-	static const int mls0_poly = 0b10001001;
+	static const int mls0_len = 320;
+	static const int mls0_poly = 0b1100110001;
+	static const int mls0_seed = 214;
+	static const int mls0_off = - mls0_len / 2;
 	static const int mls1_len = 255;
 	static const int mls1_off = - mls1_len / 2;
 	static const int mls1_poly = 0b100101011;
-	static const int buffer_len = 4 * extended_len;
+	static const int buffer_len = 5 * extended_len;
 	static const int search_pos = extended_len;
 	DSP::ReadPCM<value> *pcm;
 	DSP::FastFourierTransform<symbol_len, cmplx, -1> fwd;
@@ -71,7 +72,7 @@ struct Decoder
 	DSP::Hilbert<cmplx, filter_len> hilbert;
 	DSP::BipBuffer<cmplx, buffer_len> input_hist;
 	DSP::TheilSenEstimator<value, cols_max> tse;
-	SchmidlCox<value, cmplx, search_pos, symbol_len/2, guard_len> correlator;
+	SchmidlCox<value, cmplx, search_pos, symbol_len, guard_len> correlator;
 	CODE::CRC<uint16_t> crc0;
 	CODE::CRC<uint32_t> crc1;
 	CODE::OrderedStatisticsDecoder<255, 71, 4> osddec;
@@ -110,11 +111,12 @@ struct Decoder
 	}
 	const cmplx *mls0_seq()
 	{
-		CODE::MLS seq0(mls0_poly);
-		for (int i = 0; i < symbol_len/2; ++i)
+		CODE::MLS seq0(mls0_poly, mls0_seed);
+		for (int i = 0; i < symbol_len; ++i)
 			fdom[i] = 0;
-		for (int i = 0; i < mls0_len; ++i)
-			fdom[(i+mls0_off/2+symbol_len/2)%(symbol_len/2)] = nrz(seq0());
+		value cur = 0, prv = 0;
+		for (int i = 0; i < mls0_len; ++i, prv = cur)
+			fdom[bin(i+mls0_off)] = prv * (cur = nrz(seq0()));
 		return fdom;
 	}
 	cmplx mod_map(code_type *b)
@@ -222,7 +224,7 @@ struct Decoder
 
 			osc.omega(-cfo_rad);
 			for (int i = 0; i < symbol_len; ++i)
-				tdom[i] = buf[i+symbol_pos+extended_len] * osc();
+				tdom[i] = buf[i+symbol_pos+symbol_len+extended_len] * osc();
 			fwd(fdom, tdom);
 			CODE::MLS seq1(mls1_poly);
 			for (int i = 0; i < mls1_len; ++i)
@@ -352,7 +354,7 @@ struct Decoder
 			int comb_off = comb_cols ? comb_dist / 2 : 1;
 			int code_off = - cons_cols / 2;
 
-			for (int i = 0; i < symbol_pos+extended_len; ++i)
+			for (int i = 0; i < symbol_pos+symbol_len+extended_len; ++i)
 				correlator(buf = next_sample());
 			for (int i = 0; i < symbol_len; ++i)
 				tdom[i] = buf[i] * osc();
diff --git a/encode.cc b/encode.cc
index 7b6f4fd..df2d4e8 100644
--- a/encode.cc
+++ b/encode.cc
@@ -32,8 +32,9 @@ struct Encoder
 	static const int bits_max = 65536;
 	static const int data_max = 1024;
 	static const int cols_max = 273 + 16;
-	static const int mls0_len = 127;
-	static const int mls0_poly = 0b10001001;
+	static const int mls0_len = 320;
+	static const int mls0_poly = 0b1100110001;
+	static const int mls0_seed = 214;
 	static const int mls1_len = 255;
 	static const int mls1_poly = 0b100101011;
 	static const int mls2_poly = 0b100101010001;
@@ -108,7 +109,7 @@ struct Encoder
 				tdom[i] -= orig * kern[(symbol_len-peak+i)%symbol_len];
 		}
 	}
-	void symbol(bool papr_reduction = true)
+	void symbol(bool papr_reduction = true, bool guard_interval = true)
 	{
 		bwd(tdom, fdom);
 		value scale = 2;
@@ -139,7 +140,8 @@ struct Encoder
 			papr_min = std::min(papr_min, papr);
 			papr_max = std::max(papr_max, papr);
 		}
-		pcm->write(reinterpret_cast<value *>(guard), guard_len, 2);
+		if (guard_interval)
+			pcm->write(reinterpret_cast<value *>(guard), guard_len, 2);
 		pcm->write(reinterpret_cast<value *>(tdom), symbol_len, 2);
 		for (int i = 0; i < guard_len; ++i)
 			guard[i] = tdom[i];
@@ -156,16 +158,14 @@ struct Encoder
 	}
 	void schmidl_cox()
 	{
-		CODE::MLS seq0(mls0_poly);
-		value mls0_fac = std::sqrt(value(2 * symbol_len) / value(mls0_len));
+		CODE::MLS seq0(mls0_poly, mls0_seed);
+		value mls0_fac = std::sqrt(value(symbol_len) / value(mls0_len));
 		for (int i = 0; i < symbol_len; ++i)
 			fdom[i] = 0;
-		fdom[bin(mls0_off-2)] = mls0_fac;
 		for (int i = 0; i < mls0_len; ++i)
-			fdom[bin(2*i+mls0_off)] = nrz(seq0());
-		for (int i = 0; i < mls0_len; ++i)
-			fdom[bin(2*i+mls0_off)] *= fdom[bin(2*(i-1)+mls0_off)];
+			fdom[bin(i+mls0_off)] = mls0_fac * nrz(seq0());
 		symbol(false);
+		symbol(false, false);
 	}
 	void meta_data(uint64_t md)
 	{
@@ -363,7 +363,7 @@ struct Encoder
 		}
 		int data_bytes = data_bits / 8;
 		int offset = (freq_off * symbol_len) / rate;
-		mls0_off = offset - mls0_len + 1;
+		mls0_off = offset - mls0_len / 2;
 		mls1_off = offset - mls1_len / 2;
 		cons_cols = code_cols + comb_cols;
 		code_off = offset - cons_cols / 2;