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Ditch SNR calcs too.

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This commit is contained in:
Oliver Jowett 2015-01-21 19:10:07 +00:00
parent 00e232cc4f
commit 20456a83fd
1 changed files with 3 additions and 83 deletions
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86
demod_2400.c
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@ -155,7 +155,7 @@ void demodulate2400(uint16_t *m, uint32_t mlen) {
uint32_t j;
unsigned char *bestmsg;
int bestscore, bestphase, bestsnr;
int bestscore, bestphase;
memset(&mm, 0, sizeof(mm));
msg = msg1;
@ -263,11 +263,10 @@ void demodulate2400(uint16_t *m, uint32_t mlen) {
}
Modes.stats_current.valid_preamble++;
bestmsg = NULL; bestscore = -1; bestphase = -1; bestsnr = -1;
bestmsg = NULL; bestscore = -1; bestphase = -1;
for (try_phase = first_phase; try_phase <= last_phase; ++try_phase) {
int sigLevel = base_signal, noiseLevel = base_noise;
uint16_t *pPtr;
int phase, i, snr, score, bytelen;
int phase, i, score, bytelen;
// Decode all the next 112 bits, regardless of the actual message
// size. We'll check the actual message type later
@ -291,21 +290,6 @@ void demodulate2400(uint16_t *m, uint32_t mlen) {
(slice_phase2(pPtr+14) > 0 ? 0x02 : 0) |
(slice_phase4(pPtr+16) > 0 ? 0x01 : 0);
if (theByte & 0x20) {
sigLevel += pPtr[5];
noiseLevel += pPtr[6];
} else {
noiseLevel += pPtr[5];
sigLevel += pPtr[6];
}
if (theByte & 0x01) {
sigLevel += pPtr[17];
noiseLevel += pPtr[18];
} else {
noiseLevel += pPtr[17];
sigLevel += pPtr[18];
}
phase = 1;
pPtr += 19;
@ -322,14 +306,6 @@ void demodulate2400(uint16_t *m, uint32_t mlen) {
(slice_phase3(pPtr+14) > 0 ? 0x02 : 0) |
(slice_phase0(pPtr+17) > 0 ? 0x01 : 0);
if (theByte & 0x08) {
sigLevel += pPtr[10];
noiseLevel += pPtr[11];
} else {
noiseLevel += pPtr[10];
sigLevel += pPtr[11];
}
phase = 2;
pPtr += 19;
break;
@ -345,22 +321,6 @@ void demodulate2400(uint16_t *m, uint32_t mlen) {
(slice_phase4(pPtr+14) > 0 ? 0x02 : 0) |
(slice_phase1(pPtr+17) > 0 ? 0x01 : 0);
if (theByte & 0x40) {
sigLevel += pPtr[3];
noiseLevel += pPtr[4];
} else {
noiseLevel += pPtr[3];
sigLevel += pPtr[4];
}
if (theByte & 0x02) {
sigLevel += pPtr[15];
noiseLevel += pPtr[16];
} else {
noiseLevel += pPtr[15];
sigLevel += pPtr[16];
}
phase = 3;
pPtr += 19;
break;
@ -376,14 +336,6 @@ void demodulate2400(uint16_t *m, uint32_t mlen) {
(slice_phase0(pPtr+15) > 0 ? 0x02 : 0) |
(slice_phase2(pPtr+17) > 0 ? 0x01 : 0);
if (theByte & 0x10) {
sigLevel += pPtr[8];
noiseLevel += pPtr[9];
} else {
noiseLevel += pPtr[8];
sigLevel += pPtr[9];
}
phase = 4;
pPtr += 19;
break;
@ -399,23 +351,6 @@ void demodulate2400(uint16_t *m, uint32_t mlen) {
(slice_phase1(pPtr+15) > 0 ? 0x02 : 0) |
(slice_phase3(pPtr+17) > 0 ? 0x01 : 0);
if (theByte & 0x80) {
sigLevel += pPtr[1];
noiseLevel += pPtr[2];
} else {
noiseLevel += pPtr[1];
sigLevel += pPtr[2];
}
if (theByte & 0x04) {
sigLevel += pPtr[13];
noiseLevel += pPtr[14];
} else {
noiseLevel += pPtr[13];
sigLevel += pPtr[14];
}
phase = 0;
pPtr += 20;
break;
@ -442,25 +377,11 @@ void demodulate2400(uint16_t *m, uint32_t mlen) {
if (score < 0)
continue; // can't decode
// apply the SNR to the score, so less noisy decodes are better,
// all things being equal
// snr = 5 * 20log10(sigLevel / noiseLevel) (in units of 0.2dB)
// = 100log10(sigLevel) - 100log10(noiseLevel)
while (sigLevel > 65535 || noiseLevel > 65535) {
sigLevel >>= 1;
noiseLevel >>= 1;
}
snr = Modes.log10lut[sigLevel] - Modes.log10lut[noiseLevel];
score += snr;
if (score > bestscore) {
// new high score!
bestmsg = msg;
bestscore = score;
bestphase = try_phase;
bestsnr = snr;
// swap to using the other buffer so we don't clobber our demodulated data
// (if we find a better result then we'll swap back, but that's OK because
@ -479,7 +400,6 @@ void demodulate2400(uint16_t *m, uint32_t mlen) {
// Set initial mm structure details
mm.timestampMsg = Modes.timestampBlk + (j*5) + bestphase;
mm.signalLevel = (bestsnr > 255 ? 255 : (uint8_t)bestsnr);
mm.score = bestscore;
mm.bFlags = mm.correctedbits = 0;