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Made decode functions in M17Viterbi class return the final decode cost

This commit is contained in:
Silvano Seva 2022-07-21 22:03:40 +02:00
parent 1bb574c4fa
commit 54af6bf429
1 changed files with 29 additions and 11 deletions
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40
openrtx/include/protocols/M17/M17Viterbi.hpp
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@ -63,10 +63,11 @@ public:
* *
* @param in: input data. * @param in: input data.
* @param out: destination array where decoded data are written. * @param out: destination array where decoded data are written.
* @return number of bit errors corrected.
*/ */
template < size_t IN, size_t OUT > template < size_t IN, size_t OUT >
void decode(const std::array< uint8_t, IN >& in, uint16_t decode(const std::array< uint8_t, IN >& in,
std::array< uint8_t, OUT >& out) std::array< uint8_t, OUT >& out)
{ {
static_assert(IN*4 < 244, "Input size exceeds max history"); static_assert(IN*4 < 244, "Input size exceeds max history");
@ -83,7 +84,7 @@ public:
pos++; pos++;
} }
chainback(out, pos); return chainback(out, pos) / ((K - 1) >> 1);
} }
/** /**
@ -91,20 +92,22 @@ public:
* *
* @param in: input data. * @param in: input data.
* @param out: destination array where decoded data are written. * @param out: destination array where decoded data are written.
* @return number of bit errors corrected.
*/ */
template < size_t IN, size_t OUT, size_t P > template < size_t IN, size_t OUT, size_t P >
void decodePunctured(const std::array< uint8_t, IN >& in, uint16_t decodePunctured(const std::array< uint8_t, IN >& in,
std::array< uint8_t, OUT >& out, std::array< uint8_t, OUT >& out,
const std::array< uint8_t, P >& punctureMatrix) const std::array< uint8_t, P >& punctureMatrix)
{ {
static_assert(IN*4 < 244, "Input size exceeds max history"); static_assert(IN*4 < 244, "Input size exceeds max history");
currMetricsData.fill(0x00); currMetricsData.fill(0x00);
prevMetricsData.fill(0x00); prevMetricsData.fill(0x00);
size_t histPos = 0; size_t histPos = 0;
size_t punctIndex = 0; size_t punctIndex = 0;
size_t bitPos = 0; size_t bitPos = 0;
uint16_t punctBitCnt = 0;
while(bitPos < IN*8) while(bitPos < IN*8)
{ {
@ -117,6 +120,10 @@ public:
sym[i] = getBit(in, bitPos) ? 2 : 0; sym[i] = getBit(in, bitPos) ? 2 : 0;
bitPos++; bitPos++;
} }
else
{
punctBitCnt++;
}
if(punctIndex >= P) punctIndex = 0; if(punctIndex >= P) punctIndex = 0;
} }
@ -125,7 +132,7 @@ public:
histPos++; histPos++;
} }
chainback(out, histPos); return (chainback(out, histPos) - punctBitCnt) / ((K - 1) >> 1);
} }
private: private:
@ -188,9 +195,10 @@ private:
* *
* @param out: destination byte array for decoded data. * @param out: destination byte array for decoded data.
* @param pos: starting position for the chainback. * @param pos: starting position for the chainback.
* @return minimum Viterbi cost at the end of the decode sequence.
*/ */
template < size_t OUT > template < size_t OUT >
void chainback(std::array< uint8_t, OUT >& out, size_t pos) uint16_t chainback(std::array< uint8_t, OUT >& out, size_t pos)
{ {
uint8_t state = 0; uint8_t state = 0;
size_t bitPos = OUT*8; size_t bitPos = OUT*8;
@ -204,6 +212,16 @@ private:
if(bit) state |= 0x80; if(bit) state |= 0x80;
setBit(out, bitPos, bit); setBit(out, bitPos, bit);
} }
uint16_t cost = (*prevMetrics)[0];
for(size_t i = 0; i < NumStates; i++)
{
uint16_t m = (*prevMetrics)[i];
if(m < cost) cost = m;
}
return cost;
} }