UKUEHN : Various Improvements
Sorry Ulrich - I can't get Github to resolve the merge errors and preserve your commit notes, so I'll add them here. Improvements on bit error correction, doc update, preparation for program installation/package build Hi, I committed some further improvements on the bit error correction code, updated the readme, and implemented a way to install the program in the linux file system hierarchy (allows for package building). Regards, Ulrich
This commit is contained in:
Malcolm Robb
parent
ee742cf8db
commit
9edba9332a
3 changed files with 107 additions and 58 deletions
124
dump1090.c
124
dump1090.c
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@ -72,6 +72,9 @@
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#define MODES_MSG_SQUELCH_LEVEL 0x02FF /* Average signal strength limit */
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#define MODES_MSG_ENCODER_ERRS 3 /* Maximum number of encoding errors */
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/* When changing, change also fixBitErrors() and modesInitErrorTable() !! */
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#define MODES_MAX_BITERRORS 2 /* Global max for fixable bit erros */
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#define MODEAC_MSG_SAMPLES (25 * 2) /* include up to the SPI bit */
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#define MODEAC_MSG_BYTES 2
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#define MODEAC_MSG_SQUELCH_LEVEL 0x07FF /* Average signal strength limit */
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@ -150,6 +153,10 @@
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#define MODES_CLIENT_BUF_SIZE 1024
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#define MODES_NET_SNDBUF_SIZE (1024*64)
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#ifndef HTMLPATH
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#define HTMLPATH "./public_html" /* default path for gmap.html etc. */
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#endif
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#define MODES_NOTUSED(V) ((void) V)
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/* Structure used to describe a networking client. */
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@ -229,7 +236,7 @@ struct {
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/* Configuration */
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char *filename; /* Input form file, --ifile option. */
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int phase_enhance; /* Enable phase enhancement if true */
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int fix_errors; /* Single bit error correction if true. */
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int fix_errors; /* If > 0 no of bit errors to fix */
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int check_crc; /* Only display messages with good CRC. */
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int raw; /* Raw output format. */
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int beast; /* Beast binary format output. */
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@ -273,8 +280,12 @@ struct {
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unsigned int stat_goodcrc;
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unsigned int stat_badcrc;
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unsigned int stat_fixed;
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unsigned int stat_single_bit_fix;
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unsigned int stat_two_bits_fix;
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/* Histogram of fixed bit errors: index 0 for single bit erros,
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* index 1 for double bit errors etc.
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*/
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unsigned int stat_bit_fix[MODES_MAX_BITERRORS];
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unsigned int stat_http_requests;
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unsigned int stat_sbs_connections;
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unsigned int stat_out_of_phase;
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@ -300,7 +311,8 @@ struct modesMessage {
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int msgtype; // Downlink format #
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int crcok; // True if CRC was valid
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uint32_t crc; // Message CRC
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int correctedbits; // No. of bits corrected
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int correctedbits; // No. of bits corrected
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int corrected[MODES_MAX_BITERRORS]; // corrected bit positions
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uint32_t addr; // ICAO Address from bytes 1 2 and 3
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int phase_corrected; // True if phase correction was applied
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uint64_t timestampMsg; // Timestamp of the message
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@ -341,7 +353,7 @@ void modesSendRawOutput(struct modesMessage *mm);
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void modesSendBeastOutput(struct modesMessage *mm);
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void modesSendSBSOutput(struct modesMessage *mm);
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void useModesMessage(struct modesMessage *mm);
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int fixBitErrors(unsigned char *msg, int bits);
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int fixBitErrors(unsigned char *msg, int bits, int maxfixable, int *bitpos);
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int fixSingleBitErrors(unsigned char *msg, int bits);
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int fixTwoBitsErrors(unsigned char *msg, int bits);
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void modesInitErrorInfo();
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@ -672,7 +684,7 @@ void dumpMagnitudeVector(uint16_t *m, uint32_t offset) {
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/* Produce a raw representation of the message as a Javascript file
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* loadable by debug.html. */
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void dumpRawMessageJS(char *descr, unsigned char *msg,
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uint16_t *m, uint32_t offset, int fixable)
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uint16_t *m, uint32_t offset, int fixable, int *bitpos)
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{
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int padding = 5; /* Show a few samples before the actual start. */
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int start = offset - padding;
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@ -680,6 +692,7 @@ void dumpRawMessageJS(char *descr, unsigned char *msg,
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FILE *fp;
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int j;
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MODES_NOTUSED(fixable);
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if ((fp = fopen("frames.js","a")) == NULL) {
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fprintf(stderr, "Error opening frames.js: %s\n", strerror(errno));
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exit(1);
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@ -690,8 +703,8 @@ void dumpRawMessageJS(char *descr, unsigned char *msg,
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fprintf(fp,"%d", j < 0 ? 0 : m[j]);
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if (j != end) fprintf(fp,",");
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}
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fprintf(fp,"], \"fixed\": %d, \"bits\": %d, \"hex\": \"",
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fixable, modesMessageLenByType(msg[0]>>3));
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fprintf(fp,"], \"fix1\": %d, \"fix2\": %d, \"bits\": %d, \"hex\": \"",
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bitpos[0], bitpos[1] , modesMessageLenByType(msg[0]>>3));
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for (j = 0; j < MODES_LONG_MSG_BYTES; j++)
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fprintf(fp,"\\x%02x",msg[j]);
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fprintf(fp,"\"});\n");
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@ -716,13 +729,18 @@ void dumpRawMessage(char *descr, unsigned char *msg,
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int j;
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int msgtype = msg[0] >> 3;
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int fixable = 0;
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int bitpos[MODES_MAX_BITERRORS];
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for (j = 0; j < MODES_MAX_BITERRORS; j++) {
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bitpos[j] = -1;
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}
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if (msgtype == 17) {
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fixable = fixBitErrors(msg, MODES_LONG_MSG_BITS);
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fixable = fixBitErrors(msg, MODES_LONG_MSG_BITS,
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MODES_MAX_BITERRORS, bitpos);
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}
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if (Modes.debug & MODES_DEBUG_JS) {
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dumpRawMessageJS(descr, msg, m, offset, fixable);
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dumpRawMessageJS(descr, msg, m, offset, fixable, bitpos);
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return;
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}
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@ -1253,8 +1271,8 @@ int fixTwoBitsErrors(unsigned char *msg, int bits) {
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*/
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struct errorinfo {
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uint32_t syndrome; /* CRC syndrome */
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int pos0; /* bit position of first error */
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int pos1; /* bit position of second error, or -1 */
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int bits; /* No of bit positions to fix */
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int pos[MODES_MAX_BITERRORS]; /* bit positions */
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};
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#define NERRORINFO \
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@ -1290,8 +1308,9 @@ void modesInitErrorInfo() {
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msg[bytepos0] ^= mask0; // create error0
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crc = modesChecksum(msg, MODES_LONG_MSG_BITS);
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bitErrorTable[n].syndrome = crc; // single bit error case
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bitErrorTable[n].pos0 = i;
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bitErrorTable[n].pos1 = -1;
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bitErrorTable[n].bits = 1;
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bitErrorTable[n].pos[0] = i;
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bitErrorTable[n].pos[1] = -1;
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n += 1;
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if (Modes.aggressive) {
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@ -1308,9 +1327,10 @@ void modesInitErrorInfo() {
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*/
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break;
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}
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bitErrorTable[n].syndrome = crc; // two bit error case
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bitErrorTable[n].pos0 = i;
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bitErrorTable[n].pos1 = j;
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bitErrorTable[n].syndrome = crc; // two bit error case
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bitErrorTable[n].bits = 2;
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bitErrorTable[n].pos[0] = i;
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bitErrorTable[n].pos[1] = j;
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n += 1;
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msg[bytepos1] ^= mask1; // revert error1
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}
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@ -1362,35 +1382,43 @@ int flipBit(unsigned char *msg, int nbits, int bit) {
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// Search syndrome in table and, if an entry is found, flip the necessary
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// bits. Make sure the indices fit into the array, and for 2-bit errors,
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// are different.
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// Additional parameter: fix only less than maxcorrected bits, and record
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// fixed bit positions in corrected[]. This array can be NULL, otherwise
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// must be of length at least maxcorrected.
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// Return number of fixed bits.
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//
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int fixBitErrors(unsigned char *msg, int bits) {
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int fixBitErrors(unsigned char *msg, int bits,
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int maxfixable, int *fixedbitpos) {
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struct errorinfo *pei;
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struct errorinfo ei;
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int bitpos0, bitpos1, offset, res;
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int bitpos, offset, res, i;
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memset(&ei, 0, sizeof(struct errorinfo));
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ei.syndrome = modesChecksum(msg, bits);
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ei.pos0 = -1;
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ei.pos1 = -1;
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pei = bsearch(&ei, bitErrorTable, NERRORINFO,
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sizeof(struct errorinfo), cmpErrorInfo);
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if (pei == NULL) {
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return 0; // No syndrome found
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}
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if (maxfixable < pei->bits) {
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return 0;
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}
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res = 0;
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offset = MODES_LONG_MSG_BITS-bits;
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bitpos0 = pei->pos0 - offset;
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if ((bitpos0 < 0) || (bitpos0 >= bits)) {
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return 0;
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/* Check that all bit positions are inside message boundaries */
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for (i = 0; i < pei->bits; i++) {
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bitpos = pei->pos[i] - offset;
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if ((bitpos < 0) || (bitpos >= bits)) {
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return 0;
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}
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}
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msg[(bitpos0 >> 3)] ^= (1 << (7 - (bitpos0 & 7)));
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res++;
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if (pei->pos1 >= 0) { /* two-bit error pattern */
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bitpos1 = pei->pos1 - offset;
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if ((bitpos1 < 0) || (bitpos1 >= bits)) {
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return 0;
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}
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msg[(bitpos1 >> 3)] ^= (1 << (7 - (bitpos1 & 7)));
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res++;
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/* Fix the bits */
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for (i = 0; i < pei->bits; i++) {
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bitpos = pei->pos[i] - offset;
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msg[(bitpos >> 3)] ^= (1 << (7 - (bitpos & 7)));
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if (fixedbitpos != NULL) {
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fixedbitpos[res] = bitpos;
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}
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res++;
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}
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return res;
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}
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@ -1492,7 +1520,8 @@ void testAndTimeBitCorrection() {
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inittmsg1();
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gettimeofday(&starttv, NULL);
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for (i = 0; i < MODES_LONG_MSG_BITS; i++) {
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fixBitErrors(&tmsg1[i][0], MODES_LONG_MSG_BITS);
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fixBitErrors(&tmsg1[i][0], MODES_LONG_MSG_BITS,
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MODES_MAX_BITERRORS, NULL);
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}
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gettimeofday(&endtv, NULL);
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printf(" New code: 1-bit errors on %d msgs: %ld usecs\n",
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@ -1511,7 +1540,8 @@ void testAndTimeBitCorrection() {
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inittmsg2();
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gettimeofday(&starttv, NULL);
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for (i = 0; i < NTWOBITS; i++) {
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fixBitErrors(&tmsg2[i][0], MODES_LONG_MSG_BITS);
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fixBitErrors(&tmsg2[i][0], MODES_LONG_MSG_BITS,
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MODES_MAX_BITERRORS, NULL);
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}
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gettimeofday(&endtv, NULL);
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printf(" New code: 2-bit errors on %d msgs: %ld usecs\n",
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@ -1745,7 +1775,8 @@ void decodeModesMessage(struct modesMessage *mm, unsigned char *msg) {
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// using the results. Perhaps check the ICAO against known aircraft, and check
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// IID against known good IID's. That's a TODO.
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//
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mm->correctedbits = fixBitErrors(msg, mm->msgbits);
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mm->correctedbits = fixBitErrors(msg, mm->msgbits,
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Modes.fix_errors, mm->corrected);
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// If we correct, validate ICAO addr to help filter birthday paradox solutions.
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if (mm->correctedbits) {
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uint32_t addr = (msg[1] << 16) | (msg[2] << 8) | (msg[3]);
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@ -2601,11 +2632,10 @@ void detectModeS(uint16_t *m, uint32_t mlen) {
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} else {
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Modes.stat_badcrc++;
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Modes.stat_fixed++;
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if (mm.correctedbits == 1) {
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Modes.stat_single_bit_fix++;
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} else if (mm.correctedbits == 2) {
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Modes.stat_two_bits_fix++;
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Modes.stat_fixed += 1;
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if ((mm.correctedbits > 0) &&
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(mm.correctedbits <= MODES_MAX_BITERRORS)) {
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Modes.stat_bit_fix[mm.correctedbits-1] += 1;
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}
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}
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}
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@ -3858,9 +3888,10 @@ int handleHTTPRequest(struct client *c) {
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}
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if (strlen(url) < 2) {
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snprintf(getFile, sizeof getFile, "./public_html/gmap.html"); // Default file
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snprintf(getFile, sizeof getFile, "%s/%s",
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HTMLPATH, "gmap.html"); // Default file
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} else {
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snprintf(getFile, sizeof getFile, "./public_html%s", url);
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snprintf(getFile, sizeof getFile, "%s/%s", HTMLPATH, url);
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}
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/* Select the content to send, we have just two so far:
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@ -4155,7 +4186,7 @@ int main(int argc, char **argv) {
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Modes.metric = 1;
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} else if (!strcmp(argv[j],"--aggressive")) {
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Modes.aggressive = 1;
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Modes.fix_errors = 1;
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Modes.fix_errors = MODES_MAX_BITERRORS;
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} else if (!strcmp(argv[j],"--interactive")) {
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Modes.interactive = 1;
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} else if (!strcmp(argv[j],"--interactive-rows") && more) {
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@ -4280,8 +4311,9 @@ int main(int argc, char **argv) {
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printf("%d with good crc\n", Modes.stat_goodcrc);
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printf("%d with bad crc\n", Modes.stat_badcrc);
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printf("%d errors corrected\n", Modes.stat_fixed);
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printf("%d single bit errors\n", Modes.stat_single_bit_fix);
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printf("%d two bits errors\n", Modes.stat_two_bits_fix);
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for (j = 0; j < MODES_MAX_BITERRORS; j++) {
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printf(" %d with %d bit %s\n", Modes.stat_bit_fix[j], j+1, (j==0)?"error":"errors");
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}
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printf("%d phase enhancement attempts\n", Modes.stat_out_of_phase);
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printf("%d phase enhanced demodulated with 0 errors\n", Modes.stat_ph_demodulated0);
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printf("%d phase enhanced demodulated with 1 error\n", Modes.stat_ph_demodulated1);
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