mirror of
https://github.com/rtlsdrblog/rtl-sdr-blog.git
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rtl_adsb: sensitivity tweaks
Signed-off-by: Steve Markgraf <steve@steve-m.de>
This commit is contained in:
Kyle Keen
Steve Markgraf
parent
71b254a238
commit
8033414974
@ -50,8 +50,8 @@
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#define ADSB_RATE 2000000
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#define ADSB_FREQ 1090000000
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#define DEFAULT_ASYNC_BUF_NUMBER 32
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#define DEFAULT_BUF_LENGTH (128 * 16384)
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#define DEFAULT_ASYNC_BUF_NUMBER 12
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#define DEFAULT_BUF_LENGTH (16 * 16384)
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#define AUTO_GAIN -100
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static pthread_t demod_thread;
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@ -61,8 +61,9 @@ static rtlsdr_dev_t *dev = NULL;
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/* todo, bundle these up in a struct */
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uint8_t *buffer;
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int raw_output = 0;
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int verbose_output = 0;
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int short_output = 0;
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double quality = 1.0;
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int allowed_errors = 5;
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FILE *file;
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int adsb_frame[14];
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@ -76,16 +77,17 @@ void usage(void)
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"rtl_adsb, a simple ADS-B decoder\n\n"
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"Use:\trtl_adsb [-R] [-g gain] [-p ppm] [output file]\n"
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"\t[-d device_index (default: 0)]\n"
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"\t[-R output raw bitstream (default: off)]\n"
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"\t[-V verbove output (default: off)]\n"
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"\t[-S show short frames (default: off)]\n"
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"\t[-Q quality (0: no sanity checks, 0.5: half bit, 1: one bit (default), 2: two bits)]\n"
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"\t[-e allowed_errors (default: 5)]\n"
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"\t[-g tuner_gain (default: automatic)]\n"
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"\t[-p ppm_error (default: 0)]\n"
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"\tfilename (a '-' dumps samples to stdout)\n"
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"\t (omitting the filename also uses stdout)\n\n"
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"Streaming with netcat:\n"
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"\trtl_adsb -R | netcat -lp 8080\n"
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"\twhile true; do rtl_adsb -R | nc -lp 8080; done\n"
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"\trtl_adsb | netcat -lp 8080\n"
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"\twhile true; do rtl_adsb | nc -lp 8080; done\n"
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"\n");
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exit(1);
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}
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@ -113,23 +115,25 @@ static void sighandler(int signum)
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void display(int *frame, int len)
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{
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int i;
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int i, df;
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if (!short_output && len <= short_frame) {
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return;}
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if (raw_output) {
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fprintf(file, "*");
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for (i=0; i<((len+7)/8); i++) {
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fprintf(file, "%02x", frame[i]);}
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fprintf(file, ";\r\n");
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return;
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}
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fprintf(file, "----------\n");
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fprintf(file, "DF=%x CA=%x\n", (frame[0] >> 3) & 0x1f, frame[0] & 0x07);
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df = (frame[0] >> 3) & 0x1f;
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if (quality == 0.0 && !(df==11 || df==17 || df==18 || df==19)) {
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return;}
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fprintf(file, "*");
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for (i=0; i<((len+7)/8); i++) {
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fprintf(file, "%02x", frame[i]);}
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fprintf(file, ";\r\n");
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if (!verbose_output) {
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return;}
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fprintf(file, "DF=%i CA=%i\n", df, frame[0] & 0x07);
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fprintf(file, "ICAO Address=%06x\n", frame[1] << 16 | frame[2] << 8 | frame[3]);
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if (len <= short_frame) {
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return;}
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fprintf(file, "PI=0x%06x\n", frame[11] << 16 | frame[12] << 8 | frame[13]);
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fprintf(file, "Type Code=%x S.Type/Ant.=%x\n", (frame[4] >> 3) & 0x1f, frame[4] & 0x07);
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fprintf(file, "Type Code=%i S.Type/Ant.=%x\n", (frame[4] >> 3) & 0x1f, frame[4] & 0x07);
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fprintf(file, "--------------\n");
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}
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int magnitute(unsigned char *buf, int len)
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@ -151,6 +155,30 @@ inline unsigned char single_manchester(unsigned char a, unsigned char b, unsigne
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int bit, bit_p;
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bit_p = a > b;
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bit = c > d;
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if (quality == 0.0) {
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return bit;}
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if (quality == 0.5) {
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if ( bit && bit_p && b > c) {
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return 255;}
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if (!bit && !bit_p && b < c) {
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return 255;}
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return bit;
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}
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if (quality == 1.0) {
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if ( bit && bit_p && c > b) {
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return 1;}
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if ( bit && !bit_p && d < b) {
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return 1;}
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if (!bit && bit_p && d > b) {
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return 0;}
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if (!bit && !bit_p && c < b) {
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return 0;}
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return 255;
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}
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if ( bit && bit_p && c > b && d < a) {
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return 1;}
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if ( bit && !bit_p && c > a && d < b) {
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@ -184,10 +212,12 @@ inline int preamble(unsigned char *buf, int len, int i)
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case 2:
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case 7:
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case 9:
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high = min(high, buf[i+i2]);
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//high = min(high, buf[i+i2]);
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high = buf[i+i2];
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break;
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default:
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low = max(low, buf[i+i2]);
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//low = max(low, buf[i+i2]);
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low = buf[i+i2];
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break;
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}
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if (high <= low) {
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@ -215,7 +245,6 @@ void manchester(unsigned char *buf, int len)
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for (i2=0; i2<preamble_len; i2++) {
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buf[i+i2] = 253;}
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i += preamble_len;
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//printf("preamble found\n");
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break;
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}
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i2 = start = i;
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@ -231,7 +260,8 @@ void manchester(unsigned char *buf, int len)
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buf[i2] = 255;
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break;
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} else {
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bit = 0;
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bit = a > b;
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/* these don't have to match the bit */
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a = 0;
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b = 255;
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}
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@ -239,8 +269,6 @@ void manchester(unsigned char *buf, int len)
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buf[i] = buf[i+1] = 254; /* to be overwritten */
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buf[i2] = bit;
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}
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// todo, nuke short segments
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//printf("%i\n", i2 - start);
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}
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}
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@ -263,18 +291,16 @@ void messages(unsigned char *buf, int len)
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adsb_frame[index] |= (unsigned char)(1<<shift);
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}
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if (data_i == 7) {
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//if (adsb_frame[0] == 0) {
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// break;}
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if (adsb_frame[0] == 0) {
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break;}
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if (adsb_frame[0] & 0x80) {
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frame_len = long_frame;}
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else {
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frame_len = short_frame;}
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}
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}
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// todo, check CRC
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if (data_i < (frame_len-1)) {
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continue;}
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//fprintf(file, "bits: %i\n", data_i);
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display(adsb_frame, frame_len);
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fflush(file);
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}
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@ -299,7 +325,6 @@ static void *demod_thread_fn(void *arg)
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len = magnitute(buffer, DEFAULT_BUF_LENGTH);
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manchester(buffer, len);
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messages(buffer, len);
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//fsync(file);
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}
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rtlsdr_cancel_async(dev);
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return 0;
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@ -312,14 +337,14 @@ int main(int argc, char **argv)
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#endif
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char *filename = NULL;
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int n_read, r, opt;
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int i, gain = AUTO_GAIN; // tenths of a dB
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int i, gain = AUTO_GAIN; /* tenths of a dB */
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uint32_t dev_index = 0;
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int device_count;
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int ppm_error = 0;
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char vendor[256], product[256], serial[256];
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sem_init(&data_ready, 0, 0);
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while ((opt = getopt(argc, argv, "g:p:e:RS")) != -1)
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while ((opt = getopt(argc, argv, "d:g:p:e:Q:VS")) != -1)
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{
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switch (opt) {
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case 'd':
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@ -331,8 +356,8 @@ int main(int argc, char **argv)
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case 'p':
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ppm_error = atoi(optarg);
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break;
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case 'R':
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raw_output = 1;
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case 'V':
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verbose_output = 1;
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break;
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case 'S':
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short_output = 1;
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@ -340,6 +365,9 @@ int main(int argc, char **argv)
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case 'e':
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allowed_errors = atoi(optarg);
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break;
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case 'Q':
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quality = atof(optarg);
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break;
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default:
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usage();
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return 0;
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@ -347,7 +375,6 @@ int main(int argc, char **argv)
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}
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if (argc <= optind) {
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//usage();
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filename = "-";
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} else {
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filename = argv[optind];
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