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https://github.com/brmlab/osmo-tetra.git
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lower_mac/viterbi: Use the viterbi code provided in libosmocore
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
This commit is contained in:
Sylvain Munaut
Harald Welte
parent
24177bce48
commit
2d9b3e2560
2 changed files with 47 additions and 225 deletions
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@ -20,24 +20,26 @@
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#include <stdint.h>
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#include <string.h>
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#include <osmocom/core/conv.h>
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#include <lower_mac/viterbi_cch.h>
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#define CONV_CCH_N 4
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#define CONV_CCH_K 5
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#define CONV_CCH_N_STATES (1<<(CONV_CCH_K-1))
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/*
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* G1 = 1 + D + D4
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* G2 = 1 + D2 + D3 + D4
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* G3 = 1 + D + D2 + D4
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* G4 = 1 + D + D3 + D4
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*/
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#define MAX_AE 0x00ffffff
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static const uint8_t conv_cch_next_output[CONV_CCH_N_STATES][2] = {
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static const uint8_t conv_cch_next_output[][2] = {
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{ 0, 15 }, { 11, 4 }, { 6, 9 }, { 13, 2 },
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{ 5, 10 }, { 14, 1 }, { 3, 12 }, { 8, 7 },
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{ 15, 0 }, { 4, 11 }, { 9, 6 }, { 2, 13 },
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{ 10, 5 }, { 1, 14 }, { 12, 3 }, { 7, 8 },
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};
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static const uint8_t conv_cch_next_state[CONV_CCH_N_STATES][2] = {
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static const uint8_t conv_cch_next_state[][2] = {
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{ 0, 1 }, { 2, 3 }, { 4, 5 }, { 6, 7 },
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{ 8, 9 }, { 10, 11 }, { 12, 13 }, { 14, 15 },
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{ 0, 1 }, { 2, 3 }, { 4, 5 }, { 6, 7 },
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@ -45,119 +47,27 @@ static const uint8_t conv_cch_next_state[CONV_CCH_N_STATES][2] = {
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};
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int conv_cch_encode(uint8_t *input, uint8_t *output, int n)
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{
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uint8_t state;
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int i;
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static const struct osmo_conv_code conv_cch = {
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.N = 4,
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.K = 5,
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.next_output = conv_cch_next_output,
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.next_state = conv_cch_next_state,
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};
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state = 0;
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for (i=0; i<n; i++) {
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int bit = input[i];
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uint8_t out = conv_cch_next_output[state][bit];
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state = conv_cch_next_state[state][bit];
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output[(i<<2) ] = (out >> 3) & 1;
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output[(i<<2)+1] = (out >> 2) & 1;
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output[(i<<2)+2] = (out >> 1) & 1;
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output[(i<<2)+3] = out & 1;
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}
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return 0;
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}
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int conv_cch_decode(int8_t *input, uint8_t *output, int n)
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{
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int i, s, b;
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unsigned int ae[CONV_CCH_N_STATES];
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unsigned int ae_next[CONV_CCH_N_STATES];
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int8_t in_sym[CONV_CCH_N];
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int8_t ev_sym[CONV_CCH_N];
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int state_history[CONV_CCH_N_STATES][n];
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int min_ae;
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int min_state;
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int cur_state;
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struct osmo_conv_decoder decoder;
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int rv, l;
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/* Initial error (only state 0 is valid) */
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ae[0] = 0;
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for (i=1; i<CONV_CCH_N_STATES; i++) {
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ae[i] = MAX_AE;
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}
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osmo_conv_decode_init(&decoder, &conv_cch, n);
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/* Scan the treillis */
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for (i=0; i<n; i++) {
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/* Reset next accumulated error */
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for (s=0; s<CONV_CCH_N_STATES; s++) {
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ae_next[s] = MAX_AE;
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}
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l = osmo_conv_decode_scan(&decoder, input, n);
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l = osmo_conv_decode_finish(&decoder, &input[l]);
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/* Get input */
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in_sym[0] = input[(i<<2) ];
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in_sym[1] = input[(i<<2)+1];
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in_sym[2] = input[(i<<2)+2];
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in_sym[3] = input[(i<<2)+3];
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rv = osmo_conv_decode_get_output(&decoder, output, 1);
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/* Scan all states */
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for (s=0; s<CONV_CCH_N_STATES; s++)
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{
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/* Scan possible input bits */
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for (b=0; b<2; b++)
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{
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int nae;
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osmo_conv_decode_deinit(&decoder);
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/* Next output and state */
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uint8_t out = conv_cch_next_output[s][b];
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uint8_t state = conv_cch_next_state[s][b];
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/* Expand */
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ev_sym[0] = (out >> 3) & 1 ? -127 : 127;
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ev_sym[1] = (out >> 2) & 1 ? -127 : 127;
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ev_sym[2] = (out >> 1) & 1 ? -127 : 127;
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ev_sym[3] = out & 1 ? -127 : 127;
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/* New error for this path */
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#define DIFF(x,y) (((x-y)*(x-y)) >> 9)
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nae = ae[s] + \
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DIFF(ev_sym[0], in_sym[0]) + \
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DIFF(ev_sym[1], in_sym[1]) + \
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DIFF(ev_sym[2], in_sym[2]) + \
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DIFF(ev_sym[3], in_sym[3]);
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/* Is it survivor */
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if (ae_next[state] > nae) {
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ae_next[state] = nae;
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state_history[state][i+1] = s;
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}
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}
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}
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/* Copy accumulated error */
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memcpy(ae, ae_next, sizeof(int) * CONV_CCH_N_STATES);
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}
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/* Find state with least error */
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min_ae = MAX_AE;
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min_state = -1;
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for (s=0; s<CONV_CCH_N_STATES; s++)
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{
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if (ae[s] < min_ae) {
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min_ae = ae[s];
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min_state = s;
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}
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}
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/* Traceback */
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cur_state = min_state;
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for (i=n-1; i >= 0; i--)
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{
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min_state = cur_state;
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cur_state = state_history[cur_state][i+1];
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if (conv_cch_next_state[cur_state][0] == min_state)
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output[i] = 0;
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else
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output[i] = 1;
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}
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return 0;
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return rv;
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}
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@ -20,140 +20,52 @@
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#include <stdint.h>
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#include <string.h>
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#include <osmocom/core/conv.h>
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#include <lower_mac/viterbi_tch.h>
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#define CONV_TCH_N 3
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#define CONV_TCH_K 5
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#define CONV_TCH_N_STATES (1<<(CONV_TCH_K-1))
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/*
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* G1 = 1 + D + D2 + D3 + D4
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* G2 = 1 + D + D3 + D4
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* G3 = 1 + D2 + D4
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*/
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#define MAX_AE 0x00ffffff
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static const uint8_t conv_tch_next_output[CONV_TCH_N_STATES][2] = {
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static const uint8_t conv_tch_next_output[][2] = {
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{ 0, 7 }, { 6, 1 }, { 5, 2 }, { 3, 4 },
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{ 6, 1 }, { 0, 7 }, { 3, 4 }, { 5, 2 },
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{ 7, 0 }, { 1, 6 }, { 2, 5 }, { 4, 3 },
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{ 1, 6 }, { 7, 0 }, { 4, 3 }, { 2, 5 },
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};
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static const uint8_t conv_tch_next_state[CONV_TCH_N_STATES][2] = {
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static const uint8_t conv_tch_next_state[][2] = {
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{ 0, 1 }, { 2, 3 }, { 4, 5 }, { 6, 7 },
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{ 8, 9 }, { 10, 11 }, { 12, 13 }, { 14, 15 },
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{ 0, 1 }, { 2, 3 }, { 4, 5 }, { 6, 7 },
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{ 8, 9 }, { 10, 11 }, { 12, 13 }, { 14, 15 },
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};
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static const struct osmo_conv_code conv_tch = {
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.N = 4,
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.K = 5,
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.next_output = conv_tch_next_output,
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.next_state = conv_tch_next_state,
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};
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int conv_tch_encode(uint8_t *input, uint8_t *output, int n)
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{
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uint8_t state;
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int i;
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state = 0;
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for (i=0; i<n; i++) {
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int bit = input[i];
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uint8_t out = conv_tch_next_output[state][bit];
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state = conv_tch_next_state[state][bit];
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output[(i<<2) ] = (out >> 2) & 1;
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output[(i<<2)+1] = (out >> 1) & 1;
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output[(i<<2)+2] = out & 1;
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}
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return 0;
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}
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int conv_tch_decode(int8_t *input, uint8_t *output, int n)
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{
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int i, s, b;
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unsigned int ae[CONV_TCH_N_STATES];
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unsigned int ae_next[CONV_TCH_N_STATES];
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int8_t in_sym[CONV_TCH_N];
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int8_t ev_sym[CONV_TCH_N];
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int state_history[CONV_TCH_N_STATES][n];
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int min_ae;
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int min_state;
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int cur_state;
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struct osmo_conv_decoder decoder;
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int rv, l;
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/* Initial error (only state 0 is valid) */
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ae[0] = 0;
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for (i=1; i<CONV_TCH_N_STATES; i++) {
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ae[i] = MAX_AE;
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}
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osmo_conv_decode_init(&decoder, &conv_tch, n);
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/* Scan the treillis */
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for (i=0; i<n; i++) {
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/* Reset next accumulated error */
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for (s=0; s<CONV_TCH_N_STATES; s++) {
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ae_next[s] = MAX_AE;
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}
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l = osmo_conv_decode_scan(&decoder, input, n);
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l = osmo_conv_decode_finish(&decoder, &input[l]);
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/* Get input */
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in_sym[0] = input[(i<<2) ];
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in_sym[1] = input[(i<<2)+1];
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in_sym[2] = input[(i<<2)+2];
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rv = osmo_conv_decode_get_output(&decoder, output, 1);
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/* Scan all states */
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for (s=0; s<CONV_TCH_N_STATES; s++)
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{
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/* Scan possible input bits */
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for (b=0; b<2; b++)
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{
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int nae;
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osmo_conv_decode_deinit(&decoder);
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/* Next output and state */
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uint8_t out = conv_tch_next_output[s][b];
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uint8_t state = conv_tch_next_state[s][b];
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/* Expand */
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ev_sym[0] = (out >> 2) & 1 ? -127 : 127;
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ev_sym[1] = (out >> 1) & 1 ? -127 : 127;
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ev_sym[2] = out & 1 ? -127 : 127;
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/* New error for this path */
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#define DIFF(x,y) (((x-y)*(x-y)) >> 9)
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nae = ae[s] + \
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DIFF(ev_sym[0], in_sym[0]) + \
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DIFF(ev_sym[1], in_sym[1]) + \
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DIFF(ev_sym[2], in_sym[2]);
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/* Is it survivor */
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if (ae_next[state] > nae) {
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ae_next[state] = nae;
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state_history[state][i+1] = s;
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}
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}
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}
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/* Copy accumulated error */
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memcpy(ae, ae_next, sizeof(int) * CONV_TCH_N_STATES);
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}
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/* Find state with least error */
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min_ae = MAX_AE;
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min_state = -1;
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for (s=0; s<CONV_TCH_N_STATES; s++)
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{
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if (ae[s] < min_ae) {
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min_ae = ae[s];
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min_state = s;
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}
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}
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/* Traceback */
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cur_state = min_state;
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for (i=n-1; i >= 0; i--)
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{
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min_state = cur_state;
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cur_state = state_history[cur_state][i+1];
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if (conv_tch_next_state[cur_state][0] == min_state)
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output[i] = 0;
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else
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output[i] = 1;
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}
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return 0;
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return rv;
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}
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