Decoder cleanups from experimental branch.

demod_2000.c

@@ -317,6 +317,7 @@ void demodulate2000(uint16_t *m, uint32_t mlen) {
  int msglen, scanlen;
  uint32_t sigLevel, noiseLevel;
  uint16_t snr;
+ int message_ok;
 
  pPreamble = &m[j];
  pPayload = &m[j+MODES_PREAMBLE_SAMPLES];
@@ -325,7 +326,6 @@ void demodulate2000(uint16_t *m, uint32_t mlen) {
  // is required for every bit of the input stream, and we don't want to be memset-ing the whole
  // modesMessage structure two million times per second if we don't have to..
  mm.bFlags =
- mm.crcok = 
  mm.correctedbits = 0;
 
  if (!use_correction) // This is not a re-try with phase correction
@@ -544,7 +544,7 @@ void demodulate2000(uint16_t *m, uint32_t mlen) {
  mm.phase_corrected = use_correction;
 
  // Decode the received message
- decodeModesMessage(&mm, msg);
+ message_ok = (decodeModesMessage(&mm, msg) >= 0);
 
  // Update statistics
  if (Modes.stats) {
@@ -557,16 +557,16 @@ void demodulate2000(uint16_t *m, uint32_t mlen) {
  default: dstats->demodulated3++; break;
  }
 
- if (mm.crcok) {
+ if (!message_ok) {
+ dstats->badcrc++;
+ } else if (mm.correctedbits == 0) {
  dstats->goodcrc++;
  dstats->goodcrc_byphase[0]++;
- } else if (mm.correctedbits > 0) {
+ } else {
  dstats->badcrc++; 
  dstats->fixed++;
  if (mm.correctedbits <= MODES_MAX_BITERRORS)
  dstats->bit_fix[mm.correctedbits-1] += 1;
- } else {
- dstats->badcrc++;
  }
  }
 
@@ -576,30 +576,31 @@ void demodulate2000(uint16_t *m, uint32_t mlen) {
  dumpRawMessage("Demodulated with 0 errors", msg, m, j);
  else if (Modes.debug & MODES_DEBUG_BADCRC &&
  mm.msgtype == 17 &&
- (!mm.crcok || mm.correctedbits != 0))
+ (!message_ok || mm.correctedbits > 0))
  dumpRawMessage("Decoded with bad CRC", msg, m, j);
- else if (Modes.debug & MODES_DEBUG_GOODCRC && mm.crcok &&
+ else if (Modes.debug & MODES_DEBUG_GOODCRC &&
+ message_ok && 
  mm.correctedbits == 0)
  dumpRawMessage("Decoded with good CRC", msg, m, j);
  }
 
  // Skip this message if we are sure it's fine
- if (mm.crcok || mm.correctedbits) {
+ if (message_ok) {
  j += (MODES_PREAMBLE_US+msglen)*2 - 1;
- }
-
- // Pass data to the next layer
- useModesMessage(&mm);
 
+ // Pass data to the next layer
+ useModesMessage(&mm);
+ }
  } else {
+ message_ok = 0;
  if (Modes.debug & MODES_DEBUG_DEMODERR && use_correction) {
  printf("The following message has %d demod errors\n", errors);
  dumpRawMessage("Demodulated with errors", msg, m, j);
  }
  }
 
  // Retry with phase correction if enabled, necessary and possible.
- if (Modes.phase_enhance && !mm.crcok && !mm.correctedbits && !use_correction && j && detectOutOfPhase(pPreamble)) {
+ if (Modes.phase_enhance && (!message_ok || mm.correctedbits > 0) && !use_correction && j && detectOutOfPhase(pPreamble)) {
  use_correction = 1; j--;
  } else {
  use_correction = 0; 

demod_2400.c

@@ -273,7 +273,6 @@ void demodulate2400(uint16_t *m, uint32_t mlen)
  // is required for every possible preamble, and we don't want to be memset-ing the whole
  // modesMessage structure if we don't have to..
  mm.bFlags =
- mm.crcok = 
  mm.correctedbits = 0;
 
  // Decode all the next 112 bits, regardless of the actual message
@@ -456,13 +455,15 @@ void demodulate2400(uint16_t *m, uint32_t mlen)
  if ( (msglen) 
  // && ((2 * snr) > (int) (MODES_MSG_SQUELCH_DB * 10))
  && (errors <= MODES_MSG_ENCODER_ERRS) ) {
+ int message_ok;
+
  // Set initial mm structure details
  mm.timestampMsg = Modes.timestampBlk + (j*5) + try_phase;
  mm.signalLevel = (snr > 255 ? 255 : (uint8_t)snr);
  mm.phase_corrected = (initial_phase != try_phase);
 
  // Decode the received message
- decodeModesMessage(&mm, msg);
+ message_ok = (decodeModesMessage(&mm, msg) >= 0);
 
  // Update statistics
  if (Modes.stats) {
@@ -475,16 +476,16 @@ void demodulate2400(uint16_t *m, uint32_t mlen)
  default: dstats->demodulated3++; break;
  }
 
- if (mm.crcok) {
- dstats->goodcrc++;
- dstats->goodcrc_byphase[try_phase%MODES_MAX_PHASE_STATS]++;
+ if (!message_ok) {
+ dstats->badcrc++;
  } else if (mm.correctedbits > 0) {
  dstats->badcrc++; 
  dstats->fixed++;
  if (mm.correctedbits <= MODES_MAX_BITERRORS)
  dstats->bit_fix[mm.correctedbits-1] += 1;
  } else {
- dstats->badcrc++;
+ dstats->goodcrc++;
+ dstats->goodcrc_byphase[try_phase%MODES_MAX_PHASE_STATS]++;
  }
  }
 
@@ -494,7 +495,7 @@ void demodulate2400(uint16_t *m, uint32_t mlen)
  // where the preamble of the second message clobbered the last
  // few bits of the first message, but the message bits didn't
  // overlap)
- if (mm.crcok || mm.correctedbits) {
+ if (message_ok) {
  j += (8 + msglen - 8)*12/5 - 1;
  }
 
@@ -506,7 +507,7 @@ void demodulate2400(uint16_t *m, uint32_t mlen)
  // where trying different phases actually helps, and is much
  // cheaper than trying it on every single candidate that passes
  // peak detection
- if (Modes.phase_enhance && !mm.crcok && !mm.correctedbits) {
+ if (Modes.phase_enhance && !message_ok) {
  if (try_phase == initial_phase)
  ++Modes.stats_current.out_of_phase;
  try_phase++;

dump1090.h

@@ -406,7 +406,6 @@ struct modesMessage {
  unsigned char msg[MODES_LONG_MSG_BYTES]; // Binary message.
  int msgbits; // Number of bits in message 
  int msgtype; // Downlink format #
- int crcok; // True if CRC was valid
  uint32_t crc; // Message CRC
  int correctedbits; // No. of bits corrected 
  char corrected[MODES_MAX_BITERRORS]; // corrected bit positions
@@ -416,7 +415,7 @@ struct modesMessage {
  int remote; // If set this message is from a remote station
  unsigned char signalLevel; // Signal Amplitude
 
- // DF 11
+ // DF 11, DF 17
  int ca; // Responder capabilities
  int iid;
 
@@ -434,10 +433,16 @@ struct modesMessage {
  int vert_rate; // Vertical rate.
  int velocity; // Reported by aircraft, or computed from from EW and NS velocity
 
+ // DF 18
+ int cf; // Control Field
+
  // DF4, DF5, DF20, DF21
  int fs; // Flight status for DF4,5,20,21
  int modeA; // 13 bits identity (Squawk).
 
+ // DF20, DF21
+ int bds; // BDS value implied if overlay control was used
+
  // Fields used by multiple message types.
  int altitude;
  int unit; 
@@ -462,7 +467,7 @@ int ModeAToModeC (unsigned int ModeA);
 //
 int modesMessageLenByType(int type);
 void detectModeS_oversample (uint16_t *m, uint32_t mlen);
-void decodeModesMessage (struct modesMessage *mm, unsigned char *msg);
+int decodeModesMessage (struct modesMessage *mm, unsigned char *msg);
 void displayModesMessage(struct modesMessage *mm);
 void useModesMessage (struct modesMessage *mm);
 void computeMagnitudeVector(uint16_t *pData);

icao_filter.c

@@ -26,7 +26,7 @@
 #define MODES_ICAO_FILTER_TTL 60
 
 // Open-addressed hash table with linear probing.
-// We store each address twice to handle Address/Parity and Data/Parity
+// We store each address twice to handle Data/Parity
 // which need to match on a partial address (top 16 bits only).
 
 // Maintain two tables and switch between them to age out entries.

interactive.c

@@ -380,13 +380,7 @@ static void updatePosition(struct aircraft *a, struct modesMessage *mm, time_t n
 
 struct aircraft *interactiveReceiveData(struct modesMessage *mm) {
  struct aircraft *a, *aux;
- time_t now;
-
- // Return if (checking crc) AND (not crcok) AND (not fixed)
- if (Modes.check_crc && (mm->crcok == 0) && (mm->correctedbits == 0))
- return NULL;
-
- now = time(NULL);
+ time_t now = time(NULL);
 
  // Lookup our aircraft or create a new one
  a = interactiveFindAircraft(mm->addr);

mode_ac.c

@@ -385,7 +385,6 @@ void decodeModeAMessage(struct modesMessage *mm, int ModeA)
 
  // Not much else we can tell from a Mode A/C reply.
  // Just fudge up a few bits to keep other code happy
- mm->crcok = 1;
  mm->correctedbits = 0;
  }
 //