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fec/trellis: logic error
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@tehmaze
tehmaze committed Feb 12, 2016
1 parent 9b89470 commit e014d96
Showing 1 changed file with 100 additions and 100 deletions.
200 changes: 100 additions & 100 deletions src/dmr/fec/trellis.c
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/* Table B.7: Trellis encoder state transition table */
static uint8_t state_transition_table[] = {
0, 8, 4, 12, 2, 10, 6, 14,
4, 12, 2, 10, 6, 14, 0, 8,
1, 9, 5, 13, 3, 11, 7, 15,
5, 13, 3, 11, 7, 15, 1, 9,
3, 11, 7, 15, 1, 9, 5, 13,
7, 15, 1, 9, 5, 13, 3, 11,
2, 10, 6, 14, 0, 8, 4, 12,
6, 14, 0, 8, 4, 12, 2, 10
0, 8, 4, 12, 2, 10, 6, 14,
4, 12, 2, 10, 6, 14, 0, 8,
1, 9, 5, 13, 3, 11, 7, 15,
5, 13, 3, 11, 7, 15, 1, 9,
3, 11, 7, 15, 1, 9, 5, 13,
7, 15, 1, 9, 5, 13, 3, 11,
2, 10, 6, 14, 0, 8, 4, 12,
6, 14, 0, 8, 4, 12, 2, 10
};

/* Table B.8: Constellation to dibit pair mapping */
static int8_t constellation_point_mapping[16][2] = {
{+1, -1}, {-1, -1}, {+3, -3}, {-3, -3},
{-3, -1}, {+3, -1}, {-1, -3}, {+1, -3},
{-3, +3}, {+3, +3}, {-1, +1}, {+1, +1},
{+1, +3}, {-1, +3}, {+3, +1}, {-3, +1}
{+1, -1}, {-1, -1}, {+3, -3}, {-3, -3},
{-3, -1}, {+3, -1}, {-1, -3}, {+1, -3},
{-3, +3}, {+3, +3}, {-1, +1}, {+1, +1},
{+1, +3}, {-1, +3}, {+3, +1}, {-3, +1}
};

/* Table B.9: Interleaving schedule for rate 3⁄4 Trellis code */
static uint8_t rate_34_interleaving_schedule[98] = {
0x00, 0x01, 0x08, 0x09, 0x10, 0x11, 0x18, 0x19, 0x20, 0x21, 0x28, 0x29,
0x30, 0x31, 0x38, 0x39, 0x40, 0x41, 0x48, 0x49, 0x50, 0x51, 0x58, 0x59,
0x60, 0x61, 0x02, 0x03, 0x0a, 0x0b, 0x12, 0x13, 0x1a, 0x1b, 0x22, 0x23,
0x2a, 0x2b, 0x32, 0x33, 0x3a, 0x3b, 0x42, 0x43, 0x4a, 0x4b, 0x52, 0x53,
0x5a, 0x5b, 0x04, 0x05, 0x0c, 0x0d, 0x14, 0x15, 0x1c, 0x1d, 0x24, 0x25,
0x2c, 0x2d, 0x34, 0x35, 0x3c, 0x3d, 0x44, 0x45, 0x4c, 0x4d, 0x54, 0x55,
0x5c, 0x5d, 0x06, 0x07, 0x0e, 0x0f, 0x16, 0x17, 0x1e, 0x1f, 0x26, 0x27,
0x2e, 0x2f, 0x36, 0x37, 0x3e, 0x3f, 0x46, 0x47, 0x4e, 0x4f, 0x56, 0x57,
0x5e, 0x5f
0x00, 0x01, 0x08, 0x09, 0x10, 0x11, 0x18, 0x19, 0x20, 0x21, 0x28, 0x29,
0x30, 0x31, 0x38, 0x39, 0x40, 0x41, 0x48, 0x49, 0x50, 0x51, 0x58, 0x59,
0x60, 0x61, 0x02, 0x03, 0x0a, 0x0b, 0x12, 0x13, 0x1a, 0x1b, 0x22, 0x23,
0x2a, 0x2b, 0x32, 0x33, 0x3a, 0x3b, 0x42, 0x43, 0x4a, 0x4b, 0x52, 0x53,
0x5a, 0x5b, 0x04, 0x05, 0x0c, 0x0d, 0x14, 0x15, 0x1c, 0x1d, 0x24, 0x25,
0x2c, 0x2d, 0x34, 0x35, 0x3c, 0x3d, 0x44, 0x45, 0x4c, 0x4d, 0x54, 0x55,
0x5c, 0x5d, 0x06, 0x07, 0x0e, 0x0f, 0x16, 0x17, 0x1e, 0x1f, 0x26, 0x27,
0x2e, 0x2f, 0x36, 0x37, 0x3e, 0x3f, 0x46, 0x47, 0x4e, 0x4f, 0x56, 0x57,
0x5e, 0x5f
};

int dmr_trellis_rate_34_decode(dmr_packet packet, uint8_t bytes[18])
{
if (packet == NULL || bytes == NULL)
return dmr_error(DMR_EINVAL);
if (packet == NULL || bytes == NULL)
return dmr_error(DMR_EINVAL);

/* Convert payload to bits and extract info bits */
bool bits[DMR_PACKET_BITS], info[196];
dmr_bytes_to_bits(packet, DMR_PACKET_LEN, bits, DMR_PACKET_BITS);
memcpy(info + 0, bits + 0, 98);
memcpy(info + 98, bits + 166, 98);
/* Convert payload to bits and extract info bits */
bool bits[DMR_PACKET_BITS], info[196];
dmr_bytes_to_bits(packet, DMR_PACKET_LEN, bits, DMR_PACKET_BITS);
memcpy(info + 0, bits + 0, 98);
memcpy(info + 98, bits + 166, 98);

/* Convert info bits to dibits */
int8_t dibits[98], deinterleaved_dibits[98];
uint8_t i, j, o;
for (i = 0; i < 196; i += 2) {
o = i / 2;
if (bits[i]) {
if (bits[i + 1]) {
dibits[o] = -3;
} else {
dibits[o] = -1;
}
} else {
if (bits[i + 1]) {
dibits[o] = 3;
} else {
dibits[o] = 1;
}
}
}
/* Convert info bits to dibits */
int8_t dibits[98], deinterleaved_dibits[98];
uint8_t i, j, o;
for (i = 0; i < 196; i += 2) {
o = i / 2;
if (bits[i]) {
if (bits[i + 1]) {
dibits[o] = -3;
} else {
dibits[o] = -1;
}
} else {
if (bits[i + 1]) {
dibits[o] = 3;
} else {
dibits[o] = 1;
}
}
}

/* Table B.9: Interleaving schedule for rate 3⁄4 Trellis code */
for (i = 0; i < 98; i++) {
deinterleaved_dibits[rate_34_interleaving_schedule[i]] = dibits[i];
}
/* Table B.9: Interleaving schedule for rate 3⁄4 Trellis code */
for (i = 0; i < 98; i++) {
deinterleaved_dibits[rate_34_interleaving_schedule[i]] = dibits[i];
}

/* Table B.8: Constellation to dibit pair mapping */
uint8_t points[49];
for (i = 0; i < 98; i += 2) {
o = i / 2;
for (j = 0; j < 16; j++) {
if (dibits[i + 0] == constellation_point_mapping[j][0] &&
dibits[i + 1] == constellation_point_mapping[j][1]) {
points[o] = j;
break;
}
}
}
/* Table B.8: Constellation to dibit pair mapping */
uint8_t points[49];
for (i = 0; i < 98; i += 2) {
o = i / 2;
for (j = 0; j < 16; j++) {
if (deinterleaved_dibits[i + 0] == constellation_point_mapping[j][0] &&
deinterleaved_dibits[i + 1] == constellation_point_mapping[j][1]) {
points[o] = j;
break;
}
}
}

/* Table B.7: Trellis encoder state transition table */
uint8_t tribits[48], last = 0;
bool match = false;
int8_t start;
for (i = 0; i < 48; i++) {
start = last * 8;
match = false;
for (j = start; j < (start + 8); j++) {
/* Check if this constellation point matches an element of this row of the state table */
if (points[i] == state_transition_table[j]) {
match = true;
last = j - start;
tribits[i] = last;
break;
}
}
if (!match) {
return dmr_error_set("trellis: tribit extract error at point %u", i);
}
}
/* Table B.7: Trellis encoder state transition table */
uint8_t tribits[48], last = 0;
bool match = false;
int8_t start;
for (i = 0; i < 48; i++) {
start = last * 8;
match = false;
for (j = start; j < (start + 8); j++) {
/* Check if this constellation point matches an element of this row of the state table */
if (points[i] == state_transition_table[j]) {
match = true;
last = j - start;
tribits[i] = last;
break;
}
}
if (!match) {
return dmr_error_set("trellis: tribit extract error at point %u", i);
}
}

/* Map 48 tribits back to 144 bits */
memset(info, 0, sizeof(info));
for (i = 0; i < 144; i += 3) {
o = i / 3;
if ((tribits[o] & 0x04) > 0) {
bits[i + 0] = true;
}
if ((tribits[o] & 0x02) > 0) {
bits[i + 1] = true;
}
if ((tribits[o] & 0x01) > 0) {
bits[i + 2] = true;
}
}
/* Map 48 tribits back to 144 bits */
memset(info, 0, sizeof(info));
for (i = 0; i < 144; i += 3) {
o = i / 3;
if ((tribits[o] & 0x04) > 0) {
bits[i + 0] = true;
}
if ((tribits[o] & 0x02) > 0) {
bits[i + 1] = true;
}
if ((tribits[o] & 0x01) > 0) {
bits[i + 2] = true;
}
}

/* Map 144 bits back to bytes */
dmr_bits_to_bytes(info, 144, bytes, 18);
/* Map 144 bits back to bytes */
dmr_bits_to_bytes(info, 144, bytes, 18);

return 0;
return 0;
}

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