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