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Simple rate 3/4 data decoder.

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This commit is contained in:
Jonathan Naylor
2016-07-12 20:35:03 +01:00
parent 36e2f202c3
commit 83e65173a9
2 changed files with 195 additions and 59 deletions
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242
DMRTrellis.cpp
View File

@@ -13,20 +13,16 @@
#include "DMRTrellis.h"
#include "DMRDefines.h"
#include "Utils.h"
#include "Log.h"
#include <cstdio>
#include <cassert>
const unsigned int INTERLEAVE_TABLE[] = {
0U, 16U, 32U, 48U, 64U, 80U, 96U, 112U, 128U, 144U, 160U, 176U, 192U,
4U, 20U, 36U, 52U, 68U, 84U, 100U, 116U, 132U, 148U, 164U, 180U,
8U, 24U, 40U, 56U, 72U, 88U, 104U, 120U, 136U, 152U, 168U, 184U,
12U, 28U, 44U, 60U, 76U, 92U, 108U, 124U, 140U, 156U, 172U, 188U};
const unsigned char DIBITS_TO_POINT[] = { 11U, 12U, 0U, 7U, 14U, 9U, 5U, 2U, 10U, 13U, 1U, 6U, 15U, 8U, 4U, 3U};
const unsigned char POINT_TO_DIBITS[] = {0x2U, 0xAU, 0x7U, 0xFU, 0xEU, 0x6U, 0xBU, 0x3U, 0xDU, 0x5U, 0x8U, 0x0U, 0x1U, 0x9U, 0x4U, 0xCU};
0U, 1U, 8U, 9U, 16U, 17U, 24U, 25U, 32U, 33U, 40U, 41U, 48U, 49U, 56U, 57U, 64U, 65U, 72U, 73U, 80U, 81U, 88U, 89U, 96U, 97U,
2U, 3U, 10U, 11U, 18U, 19U, 26U, 27U, 34U, 35U, 42U, 43U, 50U, 51U, 58U, 59U, 66U, 67U, 74U, 75U, 82U, 83U, 90U, 91U,
4U, 5U, 12U, 13U, 20U, 21U, 28U, 29U, 36U, 37U, 44U, 45U, 52U, 53U, 60U, 61U, 68U, 69U, 76U, 77U, 84U, 85U, 92U, 93U,
6U, 7U, 14U, 15U, 22U, 23U, 30U, 31U, 38U, 39U, 46U, 47U, 54U, 55U, 62U, 63U, 70U, 71U, 78U, 79U, 86U, 87U, 94U, 95U};
const unsigned char ENCODE_TABLE[] = {
0U, 8U, 4U, 12U, 2U, 10U, 6U, 14U,
@@ -51,19 +47,41 @@ CDMRTrellis::~CDMRTrellis()
{
}
void CDMRTrellis::decode(const unsigned char* data, unsigned char* payload)
bool CDMRTrellis::decode(const unsigned char* data, unsigned char* payload)
{
assert(data != NULL);
assert(payload != NULL);
CUtils::dump(1U, "Payload", data, DMR_FRAME_LENGTH_BYTES);
signed char dibits[98U];
deinterleave(data, dibits);
// unsigned char points[49U];
// deinterleave(data, points);
unsigned char points[49U];
dibitsToPoints(dibits, points);
// unsigned char tribits[49U];
unsigned char tribits[49U];
unsigned char state = 0U;
// fromtribits(tribits, payload);
for (unsigned int i = 0U; i < 49U; i++) {
tribits[i] = 9U;
for (unsigned int j = 0U; j < 8U; j++) {
if (points[i] == ENCODE_TABLE[state * 8U + j]) {
tribits[i] = j;
break;
}
}
if (tribits[i] == 9U) {
LogDebug("Decoding failure at position %u", i);
return false;
}
state = tribits[i];
}
tribitsToBits(tribits, payload);
return true;
}
void CDMRTrellis::encode(const unsigned char* payload, unsigned char* data)
@@ -72,7 +90,7 @@ void CDMRTrellis::encode(const unsigned char* payload, unsigned char* data)
assert(data != NULL);
unsigned char tribits[49U];
totribits(payload, tribits);
bitsToTribits(payload, tribits);
unsigned char points[49U];
unsigned char state = 0U;
@@ -85,68 +103,184 @@ void CDMRTrellis::encode(const unsigned char* payload, unsigned char* data)
state = tribit;
}
interleave(points, data);
signed char dibits[98U];
pointsToDibits(points, dibits);
interleave(dibits, data);
}
void CDMRTrellis::deinterleave(const unsigned char* data, unsigned char* points) const
void CDMRTrellis::deinterleave(const unsigned char* data, signed char* dibits) const
{
for (unsigned int i = 0U; i < 49U; i++) {
unsigned int n = INTERLEAVE_TABLE[i] + 0U;
for (unsigned int i = 0U; i < 98U; i++) {
unsigned int n = i * 2U + 0U;
if (n >= 98U) n += 68U;
bool b1 = READ_BIT(data, n) != 0x00U;
n = INTERLEAVE_TABLE[i] + 1U;
n = i * 2U + 1U;
if (n >= 98U) n += 68U;
bool b2 = READ_BIT(data, n) != 0x00U;
n = INTERLEAVE_TABLE[i] + 2U;
if (n >= 98U) n += 68U;
bool b3 = READ_BIT(data, n) != 0x00U;
signed char dibit;
if (!b1 && b2)
dibit = +3;
else if (!b1 && !b2)
dibit = +1;
else if (b1 && !b2)
dibit = -1;
else
dibit = -3;
n = INTERLEAVE_TABLE[i] + 3U;
if (n >= 98U) n += 68U;
bool b4 = READ_BIT(data, n) != 0x00U;
unsigned int dibits = 0U;
dibits |= b1 ? 8U : 0U;
dibits |= b2 ? 4U : 0U;
dibits |= b3 ? 2U : 0U;
dibits |= b4 ? 1U : 0U;
points[i] = DIBITS_TO_POINT[dibits];
n = INTERLEAVE_TABLE[i];
dibits[n] = dibit;
}
}
void CDMRTrellis::interleave(const unsigned char* points, unsigned char* data) const
void CDMRTrellis::interleave(const signed char* dibits, unsigned char* data) const
{
for (unsigned int i = 0U; i < 49U; i++) {
unsigned char point = points[i];
unsigned char dibits = POINT_TO_DIBITS[point];
for (unsigned int i = 0U; i < 98U; i++) {
unsigned int n = INTERLEAVE_TABLE[i];
bool b1 = (dibits & 0x08U) == 0x08U;
bool b2 = (dibits & 0x04U) == 0x04U;
bool b3 = (dibits & 0x02U) == 0x02U;
bool b4 = (dibits & 0x01U) == 0x01U;
bool b1, b2;
switch (dibits[n]) {
case +3:
b1 = false;
b2 = true;
break;
case +1:
b1 = false;
b2 = false;
break;
case -1:
b1 = true;
b2 = false;
break;
default:
b1 = true;
b2 = true;
break;
}
unsigned int n = INTERLEAVE_TABLE[i] + 0U;
n = i * 2U + 0U;
if (n >= 98U) n += 68U;
WRITE_BIT(data, n, b1);
n = INTERLEAVE_TABLE[i] + 1U;
n = i * 2U + 1U;
if (n >= 98U) n += 68U;
WRITE_BIT(data, n, b2);
n = INTERLEAVE_TABLE[i] + 2U;
if (n >= 98U) n += 68U;
WRITE_BIT(data, n, b3);
n = INTERLEAVE_TABLE[i] + 3U;
if (n >= 98U) n += 68U;
WRITE_BIT(data, n, b4);
}
}
void CDMRTrellis::totribits(const unsigned char* payload, unsigned char* tribits) const
void CDMRTrellis::dibitsToPoints(const signed char* dibits, unsigned char* points) const
{
for (unsigned int i = 0U; i < 49U; i++) {
if (dibits[i * 2U + 0U] == +1 && dibits[i * 2U + 1U] == -1)
points[i] = 0U;
else if (dibits[i * 2U + 0U] == -1 && dibits[i * 2U + 1U] == -1)
points[i] = 1U;
else if (dibits[i * 2U + 0U] == +3 && dibits[i * 2U + 1U] == -3)
points[i] = 2U;
else if (dibits[i * 2U + 0U] == -3 && dibits[i * 2U + 1U] == -3)
points[i] = 3U;
else if (dibits[i * 2U + 0U] == -3 && dibits[i * 2U + 1U] == -1)
points[i] = 4U;
else if (dibits[i * 2U + 0U] == +3 && dibits[i * 2U + 1U] == -1)
points[i] = 5U;
else if (dibits[i * 2U + 0U] == -1 && dibits[i * 2U + 1U] == -3)
points[i] = 6U;
else if (dibits[i * 2U + 0U] == +1 && dibits[i * 2U + 1U] == -3)
points[i] = 7U;
else if (dibits[i * 2U + 0U] == -3 && dibits[i * 2U + 1U] == +3)
points[i] = 8U;
else if (dibits[i * 2U + 0U] == +3 && dibits[i * 2U + 1U] == +3)
points[i] = 9U;
else if (dibits[i * 2U + 0U] == -1 && dibits[i * 2U + 1U] == +1)
points[i] = 10U;
else if (dibits[i * 2U + 0U] == +1 && dibits[i * 2U + 1U] == +1)
points[i] = 11U;
else if (dibits[i * 2U + 0U] == +1 && dibits[i * 2U + 1U] == +3)
points[i] = 12U;
else if (dibits[i * 2U + 0U] == -1 && dibits[i * 2U + 1U] == +3)
points[i] = 13U;
else if (dibits[i * 2U + 0U] == +3 && dibits[i * 2U + 1U] == +1)
points[i] = 14U;
else if (dibits[i * 2U + 0U] == -3 && dibits[i * 2U + 1U] == +1)
points[i] = 15U;
}
}
void CDMRTrellis::pointsToDibits(const unsigned char* points, signed char* dibits) const
{
for (unsigned int i = 0U; i < 49U; i++) {
switch (points[i]) {
case 0U:
dibits[i * 2U + 0U] = +1;
dibits[i * 2U + 1U] = -1;
break;
case 1U:
dibits[i * 2U + 0U] = -1;
dibits[i * 2U + 1U] = -1;
break;
case 2U:
dibits[i * 2U + 0U] = +3;
dibits[i * 2U + 1U] = -3;
break;
case 3U:
dibits[i * 2U + 0U] = -3;
dibits[i * 2U + 1U] = -3;
break;
case 4U:
dibits[i * 2U + 0U] = -3;
dibits[i * 2U + 1U] = -1;
break;
case 5U:
dibits[i * 2U + 0U] = +3;
dibits[i * 2U + 1U] = -1;
break;
case 6U:
dibits[i * 2U + 0U] = -1;
dibits[i * 2U + 1U] = -3;
break;
case 7U:
dibits[i * 2U + 0U] = +1;
dibits[i * 2U + 1U] = -3;
break;
case 8U:
dibits[i * 2U + 0U] = -3;
dibits[i * 2U + 1U] = +3;
break;
case 9U:
dibits[i * 2U + 0U] = +3;
dibits[i * 2U + 1U] = +3;
break;
case 10U:
dibits[i * 2U + 0U] = -1;
dibits[i * 2U + 1U] = +1;
break;
case 11U:
dibits[i * 2U + 0U] = +1;
dibits[i * 2U + 1U] = +1;
break;
case 12U:
dibits[i * 2U + 0U] = +1;
dibits[i * 2U + 1U] = +3;
break;
case 13U:
dibits[i * 2U + 0U] = -1;
dibits[i * 2U + 1U] = +3;
break;
case 14U:
dibits[i * 2U + 0U] = +3;
dibits[i * 2U + 1U] = +1;
break;
default:
dibits[i * 2U + 0U] = -3;
dibits[i * 2U + 1U] = +1;
break;
}
}
}
void CDMRTrellis::bitsToTribits(const unsigned char* payload, unsigned char* tribits) const
{
for (unsigned int i = 0U; i < 48U; i++) {
unsigned int n = 143U - i * 3U;
@@ -168,7 +302,7 @@ void CDMRTrellis::totribits(const unsigned char* payload, unsigned char* tribits
tribits[48U] = 0U;
}
void CDMRTrellis::fromtribits(const unsigned char* tribits, unsigned char* payload) const
void CDMRTrellis::tribitsToBits(const unsigned char* tribits, unsigned char* payload) const
{
for (unsigned int i = 0U; i < 48U; i++) {
unsigned char tribit = tribits[i];

12
DMRTrellis.h
View File

@@ -19,14 +19,16 @@ public:
CDMRTrellis();
~CDMRTrellis();
void decode(const unsigned char* data, unsigned char* payload);
bool decode(const unsigned char* data, unsigned char* payload);
void encode(const unsigned char* payload, unsigned char* data);
private:
void deinterleave(const unsigned char* in, unsigned char* points) const;
void interleave(const unsigned char* points, unsigned char* out) const;
void totribits(const unsigned char* payload, unsigned char* tribits) const;
void fromtribits(const unsigned char* tribits, unsigned char* payload) const;
void deinterleave(const unsigned char* in, signed char* dibits) const;
void interleave(const signed char* dibits, unsigned char* out) const;
void dibitsToPoints(const signed char* dibits, unsigned char* points) const;
void pointsToDibits(const unsigned char* points, signed char* dibits) const;
void bitsToTribits(const unsigned char* payload, unsigned char* tribits) const;
void tribitsToBits(const unsigned char* tribits, unsigned char* payload) const;
};
#endif