diff options
| -rw-r--r-- | src/core/ao_viterbi.c | 94 |
1 files changed, 47 insertions, 47 deletions
diff --git a/src/core/ao_viterbi.c b/src/core/ao_viterbi.c index 2d441f4b..916c4d7c 100644 --- a/src/core/ao_viterbi.c +++ b/src/core/ao_viterbi.c @@ -23,22 +23,22 @@ * 'len' is output byte length */ -static const uint8_t ao_fec_encode_table[16] = { -/* next 0 1 state */ - 0, 3, /* 000 */ - 1, 2, /* 001 */ - 3, 0, /* 010 */ - 2, 1, /* 011 */ - 3, 0, /* 100 */ - 2, 1, /* 101 */ - 0, 3, /* 110 */ - 1, 2 /* 111 */ -}; - struct ao_soft_sym { uint8_t a, b; }; +static const struct ao_soft_sym ao_fec_decode_table[16] = { +/* next 0 1 state */ + { 0x00, 0x00 }, { 0xff, 0xff }, /* 000 */ + { 0x00, 0xff }, { 0xff, 0x00 }, /* 001 */ + { 0xff, 0xff }, { 0x00, 0x00 }, /* 010 */ + { 0xff, 0x00 }, { 0x00, 0xff }, /* 011 */ + { 0xff, 0xff }, { 0x00, 0x00 }, /* 100 */ + { 0xff, 0x00 }, { 0x00, 0xff }, /* 101 */ + { 0x00, 0x00 }, { 0xff, 0xff }, /* 110 */ + { 0x00, 0xff }, { 0xff, 0x00 } /* 111 */ +}; + struct ao_soft_sym ao_soft_sym(uint8_t bits) { @@ -57,71 +57,71 @@ ao_next_state(uint8_t state, uint8_t bit) static inline abs(int x) { return x < 0 ? -x : x; } -int +static inline uint16_t ao_cost(struct ao_soft_sym a, struct ao_soft_sym b) { return abs(a.a - b.a) + abs(a.b - b.b); } +#define NUM_STATE 8 + uint8_t ao_fec_decode(uint8_t *in, int len, uint8_t *out) { - int cost[len/2 + 1][8]; - uint8_t prev[len/2 + 1][8]; - int c; - int i, b; - uint8_t state = 0, min_state; - uint8_t bits[len/2]; - - for (c = 0; c < 8; c++) - cost[0][c] = 10000; + uint16_t cost[2][NUM_STATE]; + uint8_t prev[len/2 + 1][NUM_STATE]; + int c; + int i, b; + uint8_t p, n; + uint8_t state = 0, min_state; + uint8_t bits[len/2]; + + p = 0; + for (c = 0; c < NUM_STATE; c++) + cost[0][c] = 0xffff; cost[0][0] = 0; for (i = 0; i < len; i += 2) { b = i/2; + n = p ^ 1; struct ao_soft_sym s = { .a = in[i], .b = in[i+1] }; - for (state = 0; state < 8; state++) - cost[b+1][state] = 10000; + for (state = 0; state < NUM_STATE; state++) + cost[n][state] = 0xffff; + + for (state = 0; state < NUM_STATE; state++) { + int zero_cost = ao_cost(s, ao_fec_decode_table[state * 2 + 0]); + int one_cost = ao_cost(s, ao_fec_decode_table[state * 2 + 1]); - for (state = 0; state < 8; state++) { - struct ao_soft_sym zero = ao_soft_sym(ao_fec_encode_table[state * 2 + 0]); - struct ao_soft_sym one = ao_soft_sym(ao_fec_encode_table[state * 2 + 1]); uint8_t zero_state = ao_next_state(state, 0); uint8_t one_state = ao_next_state(state, 1); - int zero_cost = ao_cost(s, zero); - int one_cost = ao_cost(s, one); - -#if 0 - printf ("saw %02x %02x expected %02x %02x (%d) or %02x %02x (%d)\n", - s.a, s.b, zero.a, zero.b, zero_cost, one.a, one.b, one_cost); -#endif - zero_cost += cost[b][state]; - one_cost += cost[b][state]; - if (zero_cost < cost[b+1][zero_state]) { + + zero_cost += cost[p][state]; + one_cost += cost[p][state]; + if (zero_cost < cost[n][zero_state]) { prev[b+1][zero_state] = state; - cost[b+1][zero_state] = zero_cost; + cost[n][zero_state] = zero_cost; } - if (one_cost < cost[b+1][one_state]) { + if (one_cost < cost[n][one_state]) { prev[b+1][one_state] = state; - cost[b+1][one_state] = one_cost; + cost[n][one_state] = one_cost; } } printf ("bit %3d symbol %2x %2x:", i/2, s.a, s.b); - for (state = 0; state < 8; state++) { - printf (" %5d", cost[b+1][state]); + for (state = 0; state < NUM_STATE; state++) { + printf (" %5d", cost[n][state]); } printf ("\n"); + p = n; } - b = len / 2; - c = cost[b][0]; + c = cost[p][0]; min_state = 0; - for (state = 1; state < 8; state++) { - if (cost[b][state] < c) { - c = cost[b][state]; + for (state = 1; state < NUM_STATE; state++) { + if (cost[p][state] < c) { + c = cost[p][state]; min_state = state; } } |