From 3ee5acef0a9414eb21a596dadc3d4a8193a55bc3 Mon Sep 17 00:00:00 2001
From: lwvmobile <lwvmobile@gmail.com>
Date: Sat, 31 Jan 2026 15:40:35 -0500
Subject: [PATCH] Minor Viterbi Tweaks;

Seperate Viterbi Code into new .c file;
---
 src/dsd_misc.c        | 540 -----------------------------------------
 src/soft_viterbi_k5.c | 541 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 541 insertions(+), 540 deletions(-)
 create mode 100644 src/soft_viterbi_k5.c

diff --git a/src/dsd_misc.c b/src/dsd_misc.c
index 426604b..4a9da29 100644
--- a/src/dsd_misc.c
+++ b/src/dsd_misc.c
@@ -8,246 +8,6 @@
 
 #include "dsd.h"
 
-//Ripped from libM17
-#define K	5                       //constraint length
-#define NUM_STATES (1 << (K - 1)) //number of states
-
-static uint32_t prevMetrics[NUM_STATES];
-static uint32_t currMetrics[NUM_STATES];
-static uint32_t prevMetricsData[NUM_STATES];
-static uint32_t currMetricsData[NUM_STATES];
-static uint16_t viterbi_history[400]; //CAC needs more, expand to 400 for testing
-
-/**
-* @brief Decode unpunctured convolutionally encoded data.
-*
-* @param out Destination array where decoded data is written.
-* @param in Input data.
-* @param len Input length in bits.
-* @return Number of bit errors corrected.
-*/
-uint32_t viterbi_decode(uint8_t* out, const uint16_t* in, const uint16_t len)
-{
-	//variable in len
-	// if(len > 244*2)
-	// 	fprintf(stderr, "Input size exceeds max history\n");
-
-	viterbi_reset();
-
-	size_t pos = 0;
-	for(size_t i = 0; i < len; i += 2)
-	{
-		uint16_t s0 = in[i];
-		uint16_t s1 = in[i + 1];
-
-		viterbi_decode_bit(s0, s1, pos);
-		pos++;
-	}
-	uint32_t err = viterbi_chainback(out, pos, len/2);
-
-	//debug
-	// fprintf (stderr, "\n vcb: \n");
-	// for (size_t i = 0; i < len; i++)
-	// 	fprintf (stderr, "%02X", out[i]);
-
-	return err;
-}
-
-/**
-* @brief Decode punctured convolutionally encoded data.
-*
-* @param out Destination array where decoded data is written.
-* @param in Input data.
-* @param punct Puncturing matrix.
-* @param in_len Input data length.
-* @param p_len Puncturing matrix length (entries).
-* @return Number of bit errors corrected.
-*/
-uint32_t viterbi_decode_punctured(uint8_t* out, const uint16_t* in, const uint8_t* punct, const uint16_t in_len, const uint16_t p_len)
-{
-	//variable len now
-	// if(in_len > 244*2)
-	// 	fprintf(stderr, "Input size exceeds max history\n");
-
-	uint16_t umsg[400*2]; //unpunctured message
-	uint16_t p=0;		      //puncturer matrix entry
-	uint16_t u=0;		      //bits count - unpunctured message
-	uint16_t i=0;         //bits read from the input message
-
-	while(i<in_len)
-	{
-		if(punct[p])
-		{
-			umsg[u]=in[i];
-			i++;
-		}
-		else
-		{
-			umsg[u]=0x7FFF;
-		}
-
-		u++;
-		p++;
-		p%=p_len;
-	}
-
-	//debug
-	// fprintf (stderr, " p: %d, u: %d; p_len: %d; ", p, u, p_len); //
-
-	return viterbi_decode(out, umsg, u) - (u-in_len)*0x7FFF;
-}
-
-/**
-* @brief Decode one bit and update trellis.
-*
-* @param s0 Cost of the first symbol.
-* @param s1 Cost of the second symbol.
-* @param pos Bit position in history.
-*/
-void viterbi_decode_bit(uint16_t s0, uint16_t s1, const size_t pos)
-{
-	static const uint16_t COST_TABLE_0[] = {0, 0, 0, 0, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF};
-	static const uint16_t COST_TABLE_1[] = {0, 0xFFFF, 0xFFFF, 0, 0, 0xFFFF, 0xFFFF, 0};
-
-	for(uint8_t i = 0; i < NUM_STATES/2; i++)
-	{
-		uint32_t metric = q_abs_diff(COST_TABLE_0[i], s0)
-										+ q_abs_diff(COST_TABLE_1[i], s1);
-
-
-		uint32_t m0 = prevMetrics[i] + metric;
-		uint32_t m1 = prevMetrics[i + NUM_STATES/2] + (0x1FFFE - metric);
-
-		uint32_t m2 = prevMetrics[i] + (0x1FFFE - metric);
-		uint32_t m3 = prevMetrics[i + NUM_STATES/2] + metric;
-
-		uint8_t i0 = 2 * i;
-		uint8_t i1 = i0 + 1;
-
-		if(m0 >= m1)
-		{
-				viterbi_history[pos]|=(1<<i0);
-				currMetrics[i0] = m1;
-		}
-		else
-		{
-				viterbi_history[pos]&=~(1<<i0);
-				currMetrics[i0] = m0;
-		}
-
-		if(m2 >= m3)
-		{
-				viterbi_history[pos]|=(1<<i1);
-				currMetrics[i1] = m3;
-		}
-		else
-		{
-				viterbi_history[pos]&=~(1<<i1);
-				currMetrics[i1] = m2;
-		}
-	}
-
-	//swap
-	uint32_t tmp[NUM_STATES];
-	for(uint8_t i=0; i<NUM_STATES; i++)
-	{
-		tmp[i]=currMetrics[i];
-	}
-	for(uint8_t i=0; i<NUM_STATES; i++)
-	{
-		currMetrics[i]=prevMetrics[i];
-		prevMetrics[i]=tmp[i];
-	}
-}
-
-/**
-* @brief History chainback to obtain final byte array.
-*
-* @param out Destination byte array for decoded data.
-* @param pos Starting position for the chainback.
-* @param len Length of the output in bits.
-* @return Minimum Viterbi cost at the end of the decode sequence.
-*/
-uint32_t viterbi_chainback(uint8_t* out, size_t pos, uint16_t len)
-{
-	uint8_t state = 0;
-	size_t bitPos = len+4;
-
-	// memset(out, 0, (len-1)/8+1); //upstream bugfix, but arrays passed here are already memset / zeroed out
-
-	while(pos > 0)
-	{
-		bitPos--;
-		pos--;
-		uint16_t bit = viterbi_history[pos]&((1<<(state>>4)));
-		state >>= 1;
-		if(bit)
-		{
-			state |= 0x80;
-			out[bitPos/8]|=1<<(7-(bitPos%8));
-		}
-	}
-
-	uint32_t cost = prevMetrics[0];
-
-	for(size_t i = 0; i < NUM_STATES; i++)
-	{
-		uint32_t m = prevMetrics[i];
-		if(m < cost) cost = m;
-	}
-
-	//debug
-	// fprintf (stderr, "\n cb: \n");
-	// for (size_t i = 0; i < len; i++)
-	// 	fprintf (stderr, "%02X", out[i]);
-
-	return cost;
-}
-
-/**
- * @brief Reset the decoder state. No args.
- *
- */
-void viterbi_reset(void)
-{
-	memset((uint8_t*)viterbi_history, 0, 2*244);
-	memset((uint8_t*)currMetrics, 0, 4*NUM_STATES);
-	memset((uint8_t*)prevMetrics, 0, 4*NUM_STATES);
-	memset((uint8_t*)currMetricsData, 0, 4*NUM_STATES);
-	memset((uint8_t*)prevMetricsData, 0, 4*NUM_STATES);
-}
-
-uint16_t q_abs_diff(const uint16_t v1, const uint16_t v2)
-{
-	if(v2 > v1) return v2 - v1;
-	return v1 - v2;
-}
-
-//original sources
-//--------------------------------------------------------------------
-// M17 C library - decode/viterbi.c
-//
-// This file contains:
-// - the Viterbi decoder
-//
-// Wojciech Kaczmarski, SP5WWP
-// M17 Project, 29 December 2023
-//--------------------------------------------------------------------
-
-//--------------------------------------------------------------------
-// M17 C library - math/math.c
-//
-// This file contains:
-// - absolute difference value
-// - Euclidean norm (L2) calculation for n-dimensional vectors (float)
-// - soft-valued arrays to integer conversion (and vice-versa)
-// - fixed-valued multiplication and division
-//
-// Wojciech Kaczmarski, SP5WWP
-// M17 Project, 29 December 2023
-//--------------------------------------------------------------------
-
-
 //audio filter stuff sourced from: https://github.com/NedSimao/FilteringLibrary
 //no license / information provided in source code
 #define PI 3.141592653
@@ -261,7 +21,6 @@ uint16_t q_abs_diff(const uint16_t v1, const uint16_t v2)
 // #define HFC 50
 // #define LFC 100
 
-
 void LPFilter_Init(LPFilter *filter, float cutoffFreqHz, float sampleTimeS)
 {
 
@@ -275,7 +34,6 @@ void LPFilter_Init(LPFilter *filter, float cutoffFreqHz, float sampleTimeS)
 
 }
 
-
 float LPFilter_Update(LPFilter *filter, float v_in)
 {
 
@@ -306,7 +64,6 @@ void HPFilter_Init(HPFilter *filter, float cutoffFreqHz, float sampleTimeS)
 
 }
 
-
 float HPFilter_Update(HPFilter *filter, float v_in)
 {
 
@@ -516,300 +273,3 @@ long int raw_rms(int16_t *samples, int len, int step) //use samplespersymbol as
   if (rms < 0) rms = 150;
   return rms;
 }
-
-//same as symbol levels in m17.h (m17-fme version)
-const int8_t symbol_list[4]={-3, -1, +1, +3};
-
-/**
- * @brief Slice payload symbols into soft dibits.
- * Input (RRC filtered baseband sampled at symbol centers)
- * should be already normalized to {-3, -1, +1 +3}.
- * @param out Soft valued dibits (type-4).
- * @param inp Array of 184 floats (1 sample per symbol).
- */
-void slice_symbols(uint16_t out[2*SYM_PER_PLD], const float inp[SYM_PER_PLD])
-{
-
-    for(uint8_t i=0; i<SYM_PER_PLD; i++)
-    {
-        //bit 0
-        if(inp[i]>=symbol_list[3])
-        {
-            out[i*2+1]=0xFFFF;
-        }
-        else if(inp[i]>=symbol_list[2])
-        {
-            out[i*2+1]=-(float)0xFFFF/(symbol_list[3]-symbol_list[2])*symbol_list[2]+inp[i]*(float)0xFFFF/(symbol_list[3]-symbol_list[2]);
-        }
-        else if(inp[i]>=symbol_list[1])
-        {
-            out[i*2+1]=0x0000;
-        }
-        else if(inp[i]>=symbol_list[0])
-        {
-            out[i*2+1]=(float)0xFFFF/(symbol_list[1]-symbol_list[0])*symbol_list[1]-inp[i]*(float)0xFFFF/(symbol_list[1]-symbol_list[0]);
-        }
-        else
-        {
-            out[i*2+1]=0xFFFF;
-        }
-
-        //bit 1
-        if(inp[i]>=symbol_list[2])
-        {
-            out[i*2]=0x0000;
-        }
-        else if(inp[i]>=symbol_list[1])
-        {
-            out[i*2]=0x7FFF-inp[i]*(float)0xFFFF/(symbol_list[2]-symbol_list[1]);
-        }
-        else
-        {
-            out[i*2]=0xFFFF;
-        }
-    }
-}
-
-/**
- * @brief Slice payload symbols into soft dibits.
- * Input (RRC filtered baseband sampled at symbol centers)
- * should be already normalized to {-3, -1, +1 +3}.
- * @param out Soft valued dibits (type-4).
- * @param inp Array of len floats (1 sample per symbol).
- * @param len legnth value to run this at
- */
-void slice_symbols_to_len(uint16_t * out, const float * inp, int len)
-{
-
-	for(int i=0; i<len; i++)
-	{
-		//bit 0
-		if(inp[i]>=symbol_list[3])
-		{
-			out[i*2+1]=0xFFFF;
-		}
-		else if(inp[i]>=symbol_list[2])
-		{
-			out[i*2+1]=-(float)0xFFFF/(symbol_list[3]-symbol_list[2])*symbol_list[2]+inp[i]*(float)0xFFFF/(symbol_list[3]-symbol_list[2]);
-		}
-		else if(inp[i]>=symbol_list[1])
-		{
-			out[i*2+1]=0x0000;
-		}
-		else if(inp[i]>=symbol_list[0])
-		{
-			out[i*2+1]=(float)0xFFFF/(symbol_list[1]-symbol_list[0])*symbol_list[1]-inp[i]*(float)0xFFFF/(symbol_list[1]-symbol_list[0]);
-		}
-		else
-		{
-			out[i*2+1]=0xFFFF;
-		}
-
-		//bit 1
-		if(inp[i]>=symbol_list[2])
-		{
-			out[i*2]=0x0000;
-		}
-		else if(inp[i]>=symbol_list[1])
-		{
-			out[i*2]=0x7FFF-inp[i]*(float)0xFFFF/(symbol_list[2]-symbol_list[1]);
-		}
-		else
-		{
-			out[i*2]=0xFFFF;
-		}
-	}
-}
-
-/**
- * @brief Soft logic NOT.
- * 
- * @param a Input A.
- * @return uint16_t Output = not A.
- */
-uint16_t soft_bit_NOT(const uint16_t a)
-{
-    return 0xFFFFU-a;
-}
-
-//randomizing pattern
-const uint8_t rand_seq[46]=
-{
-    0xD6, 0xB5, 0xE2, 0x30, 0x82, 0xFF, 0x84, 0x62, 0xBA, 0x4E, 0x96, 0x90, 0xD8, 0x98, 0xDD, 0x5D, 0x0C, 0xC8, 0x52, 0x43, 0x91, 0x1D, 0xF8,
-    0x6E, 0x68, 0x2F, 0x35, 0xDA, 0x14, 0xEA, 0xCD, 0x76, 0x19, 0x8D, 0xD5, 0x80, 0xD1, 0x33, 0x87, 0x13, 0x57, 0x18, 0x2D, 0x29, 0x78, 0xC3
-};
-
-/**
- * @brief Randomize type-4 soft bits.
- * 
- * @param inp Input 368 soft type-4 bits.
- */
-void randomize_soft_bits(uint16_t inp[SYM_PER_PLD*2])
-{
-    for(uint16_t i=0; i<SYM_PER_PLD*2; i++)
-    {
-        if((rand_seq[i/8]>>(7-(i%8)))&1) //flip bit if '1'
-        {
-            inp[i]=soft_bit_NOT(inp[i]);
-        }
-    }
-}
-
-//interleaver pattern for M17
-const uint16_t intrl_seq[SYM_PER_PLD*2]=
-{
-	0, 137, 90, 227, 180, 317, 270, 39, 360, 129, 82, 219, 172, 309, 262, 31,
-	352, 121, 74, 211, 164, 301, 254, 23, 344, 113, 66, 203, 156, 293, 246, 15,
-	336, 105, 58, 195, 148, 285, 238, 7, 328, 97, 50, 187, 140, 277, 230, 367,
-	320, 89, 42, 179, 132, 269, 222, 359, 312, 81, 34, 171, 124, 261, 214, 351,
-	304, 73, 26, 163, 116, 253, 206, 343, 296, 65, 18, 155, 108, 245, 198, 335,
-	288, 57, 10, 147, 100, 237, 190, 327, 280, 49, 2, 139, 92, 229, 182, 319,
-	272, 41, 362, 131, 84, 221, 174, 311, 264, 33, 354, 123, 76, 213, 166, 303,
-	256, 25, 346, 115, 68, 205, 158, 295, 248, 17, 338, 107, 60, 197, 150, 287,
-	240, 9, 330, 99, 52, 189, 142, 279, 232, 1, 322, 91, 44, 181, 134, 271,
-	224, 361, 314, 83, 36, 173, 126, 263, 216, 353, 306, 75, 28, 165, 118, 255,
-	208, 345, 298, 67, 20, 157, 110, 247, 200, 337, 290, 59, 12, 149, 102, 239,
-	192, 329, 282, 51, 4, 141, 94, 231, 184, 321, 274, 43, 364, 133, 86, 223,
-	176, 313, 266, 35, 356, 125, 78, 215, 168, 305, 258, 27, 348, 117, 70, 207,
-	160, 297, 250, 19, 340, 109, 62, 199, 152, 289, 242, 11, 332, 101, 54, 191,
-	144, 281, 234, 3, 324, 93, 46, 183, 136, 273, 226, 363, 316, 85, 38, 175,
-	128, 265, 218, 355, 308, 77, 30, 167, 120, 257, 210, 347, 300, 69, 22, 159,
-	112, 249, 202, 339, 292, 61, 14, 151, 104, 241, 194, 331, 284, 53, 6, 143,
-	96, 233, 186, 323, 276, 45, 366, 135, 88, 225, 178, 315, 268, 37, 358, 127,
-	80, 217, 170, 307, 260, 29, 350, 119, 72, 209, 162, 299, 252, 21, 342, 111,
-	64, 201, 154, 291, 244, 13, 334, 103, 56, 193, 146, 283, 236, 5, 326, 95,
-	48, 185, 138, 275, 228, 365, 318, 87, 40, 177, 130, 267, 220, 357, 310, 79,
-	32, 169, 122, 259, 212, 349, 302, 71, 24, 161, 114, 251, 204, 341, 294, 63,
-	16, 153, 106, 243, 196, 333, 286, 55, 8, 145, 98, 235, 188, 325, 278, 47
-};
-
-/**
- * @brief Reorder (interleave) 368 soft bits.
- * 
- * @param outp Reordered soft bits.
- * @param inp Input soft bits.
- */
-void reorder_soft_bits(uint16_t outp[SYM_PER_PLD*2], const uint16_t inp[SYM_PER_PLD*2])
-{
-    for(uint16_t i=0; i<SYM_PER_PLD*2; i++)
-        outp[i]=inp[intrl_seq[i]];
-}
-
-//NXDN all-in-one function to go from dibits to valid output, return viterbi error
-uint32_t nxdn_soft_decision_viterbi(uint8_t * bits, const uint16_t * interleave, uint8_t * puncture, int d_len, int p_len, int num_bytes, int offset, uint8_t * viterbi_bits, uint8_t * viterbi_bytes)
-{
-	uint32_t error = 0;
-	uint16_t soft_bit[1000];
-	uint8_t temp_bits[500];
-	memset(temp_bits, 0, sizeof(temp_bits));
-	memset(soft_bit, 0, sizeof(soft_bit));
-
-	//deinterleaved bits
-	uint8_t deinterleaved_bits[500];
-	memset(deinterleaved_bits, 0, sizeof(deinterleaved_bits));
-
-	//deinterleaving the bits
-	for (int i = 0; i < d_len; i++)
-		deinterleaved_bits[interleave[i]] = bits[i];
-
-	//converting back to dibits
-	uint8_t dbuf[500];
-	memset(dbuf, 0, sizeof(dbuf));
-	for (int i = 0; i < d_len/2; i++)
-		dbuf[i] = (deinterleaved_bits[(i*2)+0] << 1) | deinterleaved_bits[(i*2)+1];
-
-	float sbuf[500];
-	memset(sbuf, 0.0f, sizeof(sbuf));
-
-	//convert dbuf into a symbol array
-  for (int i = 0; i < d_len/2; i++)
-  {
-    if      (dbuf[i] == 0) sbuf[i] = +1.0f;
-    else if (dbuf[i] == 1) sbuf[i] = +3.0f;
-    else if (dbuf[i] == 2) sbuf[i] = -1.0f;
-    else if (dbuf[i] == 3) sbuf[i] = -3.0f;
-    else                   sbuf[i] = +0.0f;
-  }
-
-	//slice symbols to soft dibits
-  slice_symbols_to_len(soft_bit, sbuf, d_len/2);
-
-	//viterbi
-  error = viterbi_decode_punctured(viterbi_bytes, soft_bit, puncture, d_len, p_len);
-
-	//debug
-	// fprintf (stderr, " Ve: %1.1f; ", (float)error/(float)0xFFFF);
-
-	//debug
-	// for (int i = 0; i < num_bytes+1; i++)
-	// 	fprintf(stderr, "%02X", viterbi_bytes[i]);
-
-	//load viterbi_bytes into bits
-  unpack_byte_array_into_bit_array(viterbi_bytes, temp_bits, num_bytes+1);
-
-	//rearrange bits to get correct offset
-	for (int i = 0; i < num_bytes*8; i++)
-		viterbi_bits[i] = temp_bits[i+offset];
-
-	// memset(viterbi_bytes, 0, sizeof(viterbi_bytes));
-	for (int i = 0; i < num_bytes; i++)
-		viterbi_bytes[i] = 0;
-
-	pack_bit_array_into_byte_array(viterbi_bits, viterbi_bytes, num_bytes);
-
-	return error;
-}
-
-//ysf fake puncture
-uint8_t ysf_puncture[4] = {1,1,1,1};
-
-//YSF all-in-one function to go from dibits to valid output, return viterbi error
-uint32_t ysf_soft_decision_viterbi(uint8_t * dbuf, int d_len, int num_bytes, int offset, uint8_t * viterbi_bits, uint8_t * viterbi_bytes)
-{
-	uint32_t error = 0;
-	uint16_t soft_bit[1000];
-	uint8_t temp_bits[500];
-	memset(temp_bits, 0, sizeof(temp_bits));
-	memset(soft_bit, 0, sizeof(soft_bit));
-
-	float sbuf[500];
-	memset(sbuf, 0.0f, sizeof(sbuf));
-
-	//convert dbuf into a symbol array
-  for (int i = 0; i < d_len/2; i++)
-  {
-    if      (dbuf[i] == 0) sbuf[i] = +1.0f;
-    else if (dbuf[i] == 1) sbuf[i] = +3.0f;
-    else if (dbuf[i] == 2) sbuf[i] = -1.0f;
-    else if (dbuf[i] == 3) sbuf[i] = -3.0f;
-    else                   sbuf[i] = +0.0f;
-  }
-
-	//slice symbols to soft dibits
-  slice_symbols_to_len(soft_bit, sbuf, d_len/2);
-
-	//viterbi
-  error = viterbi_decode_punctured(viterbi_bytes, soft_bit, ysf_puncture, d_len, 4);
-
-	//debug
-	// fprintf (stderr, " Ve: %1.1f; ", (float)error/(float)0xFFFF);
-
-	//debug
-	// for (int i = 0; i < num_bytes+1; i++)
-	// 	fprintf(stderr, "%02X", viterbi_bytes[i]);
-
-	//load viterbi_bytes into bits
-  unpack_byte_array_into_bit_array(viterbi_bytes, temp_bits, num_bytes+1);
-
-	//rearrange bits to get correct offset
-	for (int i = 0; i < num_bytes*8; i++)
-		viterbi_bits[i] = temp_bits[i+offset];
-
-	// memset(viterbi_bytes, 0, sizeof(viterbi_bytes));
-	for (int i = 0; i < num_bytes; i++)
-		viterbi_bytes[i] = 0;
-
-	pack_bit_array_into_byte_array(viterbi_bits, viterbi_bytes, num_bytes);
-
-	return error;
-}
diff --git a/src/soft_viterbi_k5.c b/src/soft_viterbi_k5.c
new file mode 100644
index 0000000..3b2b369
--- /dev/null
+++ b/src/soft_viterbi_k5.c
@@ -0,0 +1,541 @@
+/*-------------------------------------------------------------------------------
+ * soft_viterbi_k5.c
+ * Soft Decision Viterbi K5 Contraint for M17, NXDN, and YSF Fusion
+ *
+ * Viterbi Code from or Modified from libM17 (see bottom)
+ * Wojciech Kaczmarski, SP5WWP
+ *
+ * LWVMOBILE
+ * 2026-01 DSD-FME Florida Man Edition
+ *-----------------------------------------------------------------------------*/
+
+#include "dsd.h"
+
+//Ripped from libM17
+#define K	5                       //constraint length
+#define NUM_STATES (1 << (K - 1)) //number of states
+
+static uint32_t prevMetrics[NUM_STATES];
+static uint32_t currMetrics[NUM_STATES];
+static uint32_t prevMetricsData[NUM_STATES];
+static uint32_t currMetricsData[NUM_STATES];
+static uint16_t viterbi_history[600];
+
+/**
+* @brief Decode unpunctured convolutionally encoded data.
+*
+* @param out Destination array where decoded data is written.
+* @param in Input data.
+* @param len Input length in bits.
+* @return Number of bit errors corrected.
+*/
+uint32_t viterbi_decode(uint8_t* out, const uint16_t* in, const uint16_t len)
+{
+
+	viterbi_reset();
+
+	size_t pos = 0;
+	for(size_t i = 0; i < len; i += 2)
+	{
+		uint16_t s0 = in[i];
+		uint16_t s1 = in[i + 1];
+
+		viterbi_decode_bit(s0, s1, pos);
+		pos++;
+	}
+	uint32_t err = viterbi_chainback(out, pos, len/2);
+
+	//debug
+	// fprintf (stderr, "\n vcb: \n");
+	// for (size_t i = 0; i < len; i++)
+	// 	fprintf (stderr, "%02X", out[i]);
+
+	return err;
+}
+
+/**
+* @brief Decode punctured convolutionally encoded data.
+*
+* @param out Destination array where decoded data is written.
+* @param in Input data.
+* @param punct Puncturing matrix.
+* @param in_len Input data length.
+* @param p_len Puncturing matrix length (entries).
+* @return Number of bit errors corrected.
+*/
+uint32_t viterbi_decode_punctured(uint8_t* out, const uint16_t* in, const uint8_t* punct, const uint16_t in_len, const uint16_t p_len)
+{
+
+	uint16_t umsg[400*2]; //unpunctured message
+	uint16_t p=0;		      //puncturer matrix entry
+	uint16_t u=0;		      //bits count - unpunctured message
+	uint16_t i=0;         //bits read from the input message
+
+	while(i<in_len)
+	{
+		if(punct[p])
+		{
+			umsg[u]=in[i];
+			i++;
+		}
+		else
+		{
+			umsg[u]=0x7FFF;
+		}
+
+		u++;
+		p++;
+		p%=p_len;
+	}
+
+	//debug
+	// fprintf (stderr, " p: %d, u: %d; p_len: %d; ", p, u, p_len); //
+
+	return viterbi_decode(out, umsg, u) - (u-in_len)*0x7FFF;
+}
+
+/**
+* @brief Decode one bit and update trellis.
+*
+* @param s0 Cost of the first symbol.
+* @param s1 Cost of the second symbol.
+* @param pos Bit position in history.
+*/
+void viterbi_decode_bit(uint16_t s0, uint16_t s1, const size_t pos)
+{
+	static const uint16_t COST_TABLE_0[] = {0, 0, 0, 0, 0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF};
+	static const uint16_t COST_TABLE_1[] = {0, 0xFFFF, 0xFFFF, 0, 0, 0xFFFF, 0xFFFF, 0};
+
+	for(uint8_t i = 0; i < NUM_STATES/2; i++)
+	{
+		uint32_t metric = q_abs_diff(COST_TABLE_0[i], s0)
+										+ q_abs_diff(COST_TABLE_1[i], s1);
+
+
+		uint32_t m0 = prevMetrics[i] + metric;
+		uint32_t m1 = prevMetrics[i + NUM_STATES/2] + (0x1FFFE - metric);
+
+		uint32_t m2 = prevMetrics[i] + (0x1FFFE - metric);
+		uint32_t m3 = prevMetrics[i + NUM_STATES/2] + metric;
+
+		uint8_t i0 = 2 * i;
+		uint8_t i1 = i0 + 1;
+
+		if(m0 >= m1)
+		{
+				viterbi_history[pos]|=(1<<i0);
+				currMetrics[i0] = m1;
+		}
+		else
+		{
+				viterbi_history[pos]&=~(1<<i0);
+				currMetrics[i0] = m0;
+		}
+
+		if(m2 >= m3)
+		{
+				viterbi_history[pos]|=(1<<i1);
+				currMetrics[i1] = m3;
+		}
+		else
+		{
+				viterbi_history[pos]&=~(1<<i1);
+				currMetrics[i1] = m2;
+		}
+	}
+
+	//swap
+	uint32_t tmp[NUM_STATES];
+	for(uint8_t i=0; i<NUM_STATES; i++)
+	{
+		tmp[i]=currMetrics[i];
+	}
+	for(uint8_t i=0; i<NUM_STATES; i++)
+	{
+		currMetrics[i]=prevMetrics[i];
+		prevMetrics[i]=tmp[i];
+	}
+}
+
+/**
+* @brief History chainback to obtain final byte array.
+*
+* @param out Destination byte array for decoded data.
+* @param pos Starting position for the chainback.
+* @param len Length of the output in bits.
+* @return Minimum Viterbi cost at the end of the decode sequence.
+*/
+uint32_t viterbi_chainback(uint8_t* out, size_t pos, uint16_t len)
+{
+
+	uint8_t state = 0;
+	size_t bitPos = len+4;
+
+	while(pos > 0)
+	{
+		bitPos--;
+		pos--;
+		uint16_t bit = viterbi_history[pos]&((1<<(state>>4)));
+		state >>= 1;
+		if(bit)
+		{
+			state |= 0x80;
+			out[bitPos/8]|=1<<(7-(bitPos%8));
+		}
+	}
+
+	uint32_t cost = prevMetrics[0];
+
+	for(size_t i = 0; i < NUM_STATES; i++)
+	{
+		uint32_t m = prevMetrics[i];
+		if(m < cost) cost = m;
+	}
+
+	//debug
+	// fprintf (stderr, "\n cb: \n");
+	// for (size_t i = 0; i < len; i++)
+	// 	fprintf (stderr, "%02X", out[i]);
+
+	return cost;
+}
+
+/**
+ * @brief Reset the decoder state. No args.
+ *
+ */
+void viterbi_reset(void)
+{
+	memset(viterbi_history, 0, sizeof(viterbi_history));
+	memset(currMetrics, 0, sizeof(currMetrics));
+	memset(prevMetrics, 0, sizeof(prevMetrics));
+	memset(currMetricsData, 0, sizeof(currMetricsData));
+	memset(prevMetricsData, 0, sizeof(prevMetricsData));
+}
+
+uint16_t q_abs_diff(const uint16_t v1, const uint16_t v2)
+{
+	if(v2 > v1) return v2 - v1;
+	return v1 - v2;
+}
+
+//same as symbol levels in m17.h (m17-fme version)
+const int8_t symbol_list[4]={-3, -1, +1, +3};
+
+/**
+ * @brief Slice payload symbols into soft dibits.
+ * Input (RRC filtered baseband sampled at symbol centers)
+ * should be already normalized to {-3, -1, +1 +3}.
+ * @param out Soft valued dibits (type-4).
+ * @param inp Array of 184 floats (1 sample per symbol).
+ */
+void slice_symbols(uint16_t out[2*SYM_PER_PLD], const float inp[SYM_PER_PLD])
+{
+
+  for(uint8_t i=0; i<SYM_PER_PLD; i++)
+  {
+    //bit 0
+    if(inp[i]>=symbol_list[3])
+    {
+      out[i*2+1]=0xFFFF;
+    }
+    else if(inp[i]>=symbol_list[2])
+    {
+      out[i*2+1]=-(float)0xFFFF/(symbol_list[3]-symbol_list[2])*symbol_list[2]+inp[i]*(float)0xFFFF/(symbol_list[3]-symbol_list[2]);
+    }
+    else if(inp[i]>=symbol_list[1])
+    {
+      out[i*2+1]=0x0000;
+    }
+    else if(inp[i]>=symbol_list[0])
+    {
+      out[i*2+1]=(float)0xFFFF/(symbol_list[1]-symbol_list[0])*symbol_list[1]-inp[i]*(float)0xFFFF/(symbol_list[1]-symbol_list[0]);
+    }
+    else
+    {
+      out[i*2+1]=0xFFFF;
+    }
+
+    //bit 1
+    if(inp[i]>=symbol_list[2])
+    {
+      out[i*2]=0x0000;
+    }
+    else if(inp[i]>=symbol_list[1])
+    {
+      out[i*2]=0x7FFF-inp[i]*(float)0xFFFF/(symbol_list[2]-symbol_list[1]);
+    }
+    else
+    {
+      out[i*2]=0xFFFF;
+    }
+  }
+}
+
+/**
+ * @brief Slice payload symbols into soft dibits.
+ * Input (RRC filtered baseband sampled at symbol centers)
+ * should be already normalized to {-3, -1, +1 +3}.
+ * @param out Soft valued dibits (type-4).
+ * @param inp Array of len floats (1 sample per symbol).
+ * @param len legnth value to run this at
+ */
+void slice_symbols_to_len(uint16_t * out, const float * inp, int len)
+{
+
+	for(int i=0; i<len; i++)
+	{
+		//bit 0
+		if(inp[i]>=symbol_list[3])
+		{
+			out[i*2+1]=0xFFFF;
+		}
+		else if(inp[i]>=symbol_list[2])
+		{
+			out[i*2+1]=-(float)0xFFFF/(symbol_list[3]-symbol_list[2])*symbol_list[2]+inp[i]*(float)0xFFFF/(symbol_list[3]-symbol_list[2]);
+		}
+		else if(inp[i]>=symbol_list[1])
+		{
+			out[i*2+1]=0x0000;
+		}
+		else if(inp[i]>=symbol_list[0])
+		{
+			out[i*2+1]=(float)0xFFFF/(symbol_list[1]-symbol_list[0])*symbol_list[1]-inp[i]*(float)0xFFFF/(symbol_list[1]-symbol_list[0]);
+		}
+		else
+		{
+			out[i*2+1]=0xFFFF;
+		}
+
+		//bit 1
+		if(inp[i]>=symbol_list[2])
+		{
+			out[i*2]=0x0000;
+		}
+		else if(inp[i]>=symbol_list[1])
+		{
+			out[i*2]=0x7FFF-inp[i]*(float)0xFFFF/(symbol_list[2]-symbol_list[1]);
+		}
+		else
+		{
+			out[i*2]=0xFFFF;
+		}
+	}
+}
+
+/**
+ * @brief Soft logic NOT.
+ * 
+ * @param a Input A.
+ * @return uint16_t Output = not A.
+ */
+uint16_t soft_bit_NOT(const uint16_t a)
+{
+  return 0xFFFFU-a;
+}
+
+//randomizing pattern for M17
+const uint8_t rand_seq[46]=
+{
+  0xD6, 0xB5, 0xE2, 0x30, 0x82, 0xFF, 0x84, 0x62, 0xBA, 0x4E, 0x96, 0x90, 0xD8, 0x98, 0xDD, 0x5D, 0x0C, 0xC8, 0x52, 0x43, 0x91, 0x1D, 0xF8,
+  0x6E, 0x68, 0x2F, 0x35, 0xDA, 0x14, 0xEA, 0xCD, 0x76, 0x19, 0x8D, 0xD5, 0x80, 0xD1, 0x33, 0x87, 0x13, 0x57, 0x18, 0x2D, 0x29, 0x78, 0xC3
+};
+
+/**
+ * @brief Randomize type-4 soft bits.
+ * 
+ * @param inp Input 368 soft type-4 bits.
+ */
+void randomize_soft_bits(uint16_t inp[SYM_PER_PLD*2])
+{
+  for(uint16_t i=0; i<SYM_PER_PLD*2; i++)
+  {
+    if((rand_seq[i/8]>>(7-(i%8)))&1) //flip bit if '1'
+    {
+      inp[i]=soft_bit_NOT(inp[i]);
+    }
+  }
+}
+
+//interleaver pattern for M17
+const uint16_t intrl_seq[SYM_PER_PLD*2]=
+{
+	0, 137, 90, 227, 180, 317, 270, 39, 360, 129, 82, 219, 172, 309, 262, 31,
+	352, 121, 74, 211, 164, 301, 254, 23, 344, 113, 66, 203, 156, 293, 246, 15,
+	336, 105, 58, 195, 148, 285, 238, 7, 328, 97, 50, 187, 140, 277, 230, 367,
+	320, 89, 42, 179, 132, 269, 222, 359, 312, 81, 34, 171, 124, 261, 214, 351,
+	304, 73, 26, 163, 116, 253, 206, 343, 296, 65, 18, 155, 108, 245, 198, 335,
+	288, 57, 10, 147, 100, 237, 190, 327, 280, 49, 2, 139, 92, 229, 182, 319,
+	272, 41, 362, 131, 84, 221, 174, 311, 264, 33, 354, 123, 76, 213, 166, 303,
+	256, 25, 346, 115, 68, 205, 158, 295, 248, 17, 338, 107, 60, 197, 150, 287,
+	240, 9, 330, 99, 52, 189, 142, 279, 232, 1, 322, 91, 44, 181, 134, 271,
+	224, 361, 314, 83, 36, 173, 126, 263, 216, 353, 306, 75, 28, 165, 118, 255,
+	208, 345, 298, 67, 20, 157, 110, 247, 200, 337, 290, 59, 12, 149, 102, 239,
+	192, 329, 282, 51, 4, 141, 94, 231, 184, 321, 274, 43, 364, 133, 86, 223,
+	176, 313, 266, 35, 356, 125, 78, 215, 168, 305, 258, 27, 348, 117, 70, 207,
+	160, 297, 250, 19, 340, 109, 62, 199, 152, 289, 242, 11, 332, 101, 54, 191,
+	144, 281, 234, 3, 324, 93, 46, 183, 136, 273, 226, 363, 316, 85, 38, 175,
+	128, 265, 218, 355, 308, 77, 30, 167, 120, 257, 210, 347, 300, 69, 22, 159,
+	112, 249, 202, 339, 292, 61, 14, 151, 104, 241, 194, 331, 284, 53, 6, 143,
+	96, 233, 186, 323, 276, 45, 366, 135, 88, 225, 178, 315, 268, 37, 358, 127,
+	80, 217, 170, 307, 260, 29, 350, 119, 72, 209, 162, 299, 252, 21, 342, 111,
+	64, 201, 154, 291, 244, 13, 334, 103, 56, 193, 146, 283, 236, 5, 326, 95,
+	48, 185, 138, 275, 228, 365, 318, 87, 40, 177, 130, 267, 220, 357, 310, 79,
+	32, 169, 122, 259, 212, 349, 302, 71, 24, 161, 114, 251, 204, 341, 294, 63,
+	16, 153, 106, 243, 196, 333, 286, 55, 8, 145, 98, 235, 188, 325, 278, 47
+};
+
+/**
+ * @brief Reorder (interleave) 368 soft bits.
+ * 
+ * @param outp Reordered soft bits.
+ * @param inp Input soft bits.
+ */
+void reorder_soft_bits(uint16_t outp[SYM_PER_PLD*2], const uint16_t inp[SYM_PER_PLD*2])
+{
+  for(uint16_t i=0; i<SYM_PER_PLD*2; i++)
+    outp[i]=inp[intrl_seq[i]];
+}
+
+//NXDN all-in-one function to go from punctured bits to valid output, return viterbi error
+uint32_t nxdn_soft_decision_viterbi(uint8_t * bits, const uint16_t * interleave, uint8_t * puncture, int d_len, int p_len, int num_bytes, int offset, uint8_t * viterbi_bits, uint8_t * viterbi_bytes)
+{
+  uint32_t error = 0;
+  uint16_t soft_bit[1000];
+  uint8_t temp_bits[500];
+  memset(temp_bits, 0, sizeof(temp_bits));
+  memset(soft_bit, 0, sizeof(soft_bit));
+
+  //deinterleaved bits
+  uint8_t deinterleaved_bits[500];
+  memset(deinterleaved_bits, 0, sizeof(deinterleaved_bits));
+
+  //deinterleaving the bits
+  for (int i = 0; i < d_len; i++)
+    deinterleaved_bits[interleave[i]] = bits[i];
+
+  //converting back to dibits
+  uint8_t dbuf[500];
+  memset(dbuf, 0, sizeof(dbuf));
+  for (int i = 0; i < d_len/2; i++)
+    dbuf[i] = (deinterleaved_bits[(i*2)+0] << 1) | deinterleaved_bits[(i*2)+1];
+
+  float sbuf[500];
+  memset(sbuf, 0.0f, sizeof(sbuf));
+
+  //convert dbuf into a symbol array
+  for (int i = 0; i < d_len/2; i++)
+  {
+    if      (dbuf[i] == 0) sbuf[i] = +1.0f;
+    else if (dbuf[i] == 1) sbuf[i] = +3.0f;
+    else if (dbuf[i] == 2) sbuf[i] = -1.0f;
+    else if (dbuf[i] == 3) sbuf[i] = -3.0f;
+    else                   sbuf[i] = +0.0f;
+  }
+
+  //slice symbols to soft dibits
+  slice_symbols_to_len(soft_bit, sbuf, d_len/2);
+
+  //viterbi
+  error = viterbi_decode_punctured(viterbi_bytes, soft_bit, puncture, d_len, p_len);
+
+  //debug
+  // fprintf (stderr, " Ve: %1.1f; ", (float)error/(float)0xFFFF);
+
+  //debug
+  // for (int i = 0; i < num_bytes+1; i++)
+  // 	fprintf(stderr, "%02X", viterbi_bytes[i]);
+
+  //load viterbi_bytes into bits
+  unpack_byte_array_into_bit_array(viterbi_bytes, temp_bits, num_bytes+1);
+
+  //rearrange bits to get correct offset
+  for (int i = 0; i < num_bytes*8; i++)
+    viterbi_bits[i] = temp_bits[i+offset];
+
+  //zero out viterbi_bytes to reload packed appropriately
+  for (int i = 0; i < num_bytes; i++)
+    viterbi_bytes[i] = 0;
+
+  pack_bit_array_into_byte_array(viterbi_bits, viterbi_bytes, num_bytes);
+
+  return error;
+}
+
+//ysf fake puncture
+uint8_t ysf_puncture[4] = {1,1,1,1};
+
+//YSF all-in-one function to go from dibits to valid output, return viterbi error
+uint32_t ysf_soft_decision_viterbi(uint8_t * dbuf, int d_len, int num_bytes, int offset, uint8_t * viterbi_bits, uint8_t * viterbi_bytes)
+{
+  uint32_t error = 0;
+  uint16_t soft_bit[1000];
+  uint8_t temp_bits[500];
+  memset(temp_bits, 0, sizeof(temp_bits));
+  memset(soft_bit, 0, sizeof(soft_bit));
+
+  float sbuf[500];
+  memset(sbuf, 0.0f, sizeof(sbuf));
+
+  //convert dbuf into a symbol array
+  for (int i = 0; i < d_len/2; i++)
+  {
+    if      (dbuf[i] == 0) sbuf[i] = +1.0f;
+    else if (dbuf[i] == 1) sbuf[i] = +3.0f;
+    else if (dbuf[i] == 2) sbuf[i] = -1.0f;
+    else if (dbuf[i] == 3) sbuf[i] = -3.0f;
+    else                   sbuf[i] = +0.0f;
+  }
+
+  //slice symbols to soft dibits
+  slice_symbols_to_len(soft_bit, sbuf, d_len/2);
+
+  //viterbi
+  error = viterbi_decode_punctured(viterbi_bytes, soft_bit, ysf_puncture, d_len, 4);
+
+  //debug
+  // fprintf (stderr, " Ve: %1.1f; ", (float)error/(float)0xFFFF);
+
+  //debug
+  // for (int i = 0; i < num_bytes+1; i++)
+  // 	fprintf(stderr, "%02X", viterbi_bytes[i]);
+
+  //load viterbi_bytes into bits
+  unpack_byte_array_into_bit_array(viterbi_bytes, temp_bits, num_bytes+1);
+
+  //rearrange bits to get correct offset
+  for (int i = 0; i < num_bytes*8; i++)
+    viterbi_bits[i] = temp_bits[i+offset];
+
+  //zero out viterbi_bytes to reload packed appropriately
+  for (int i = 0; i < num_bytes; i++)
+    viterbi_bytes[i] = 0;
+
+  pack_bit_array_into_byte_array(viterbi_bits, viterbi_bytes, num_bytes);
+
+  return error;
+}
+
+//original sources for viterbi code and misc math related
+//--------------------------------------------------------------------
+// M17 C library - decode/viterbi.c
+//
+// This file contains:
+// - the Viterbi decoder
+//
+// Wojciech Kaczmarski, SP5WWP
+// M17 Project, 29 December 2023
+//--------------------------------------------------------------------
+
+//--------------------------------------------------------------------
+// M17 C library - math/math.c
+//
+// This file contains:
+// - absolute difference value
+// - Euclidean norm (L2) calculation for n-dimensional vectors (float)
+// - soft-valued arrays to integer conversion (and vice-versa)
+// - fixed-valued multiplication and division
+//
+// Wojciech Kaczmarski, SP5WWP
+// M17 Project, 29 December 2023
+//--------------------------------------------------------------------