Lots of refactoring to move the SDR-type-specific bits out of the

main code and make them optionally buildable.

Makefile

@@ -27,7 +27,7 @@ all: dump1090 view1090
 %.o: %.c *.h
 	$(CC) $(CPPFLAGS) $(CFLAGS) -c $< -o $@
 
-dump1090: dump1090.o anet.o interactive.o mode_ac.o mode_s.o net_io.o crc.o demod_2400.o stats.o cpr.o icao_filter.o track.o util.o convert.o $(COMPAT)
+dump1090: dump1090.o anet.o interactive.o mode_ac.o mode_s.o net_io.o crc.o demod_2400.o stats.o cpr.o icao_filter.o track.o util.o convert.o sdr_ifile.o sdr_rtlsdr.o sdr.o $(COMPAT)
 	$(CC) -g -o $@ $^ $(LDFLAGS) $(LIBS) $(LIBS_RTLSDR) -lncurses
 
 view1090: view1090.o anet.o interactive.o mode_ac.o mode_s.o net_io.o crc.o stats.o cpr.o icao_filter.o track.o util.o $(COMPAT)

dump1090.c

@@ -49,12 +49,8 @@
 
 #include "dump1090.h"
 
-#include <rtl-sdr.h>
-
 #include <stdarg.h>
 
-static int verbose_device_search(char *s);
-
 //
 // ============================= Utility functions ==========================
 //
@@ -113,7 +109,6 @@ void modesInitConfig(void) {
     // Now initialise things that should not be 0/NULL to their defaults
     Modes.gain                    = MODES_MAX_GAIN;
     Modes.freq                    = MODES_DEFAULT_FREQ;
-    Modes.ppm_error               = MODES_DEFAULT_PPM;
     Modes.check_crc               = 1;
     Modes.net_heartbeat_interval  = MODES_NET_HEARTBEAT_INTERVAL;
     Modes.net_input_raw_ports     = strdup("30001");
@@ -127,6 +122,8 @@ void modesInitConfig(void) {
     Modes.json_location_accuracy  = 1;
     Modes.maxRange                = 1852 * 300; // 300NM default max range
     Modes.mode_ac_auto            = 1;
+
+    sdrInitConfig();
 }
 //
 //=========================================================================
@@ -212,138 +209,11 @@ void modesInit(void) {
     modesChecksumInit(Modes.nfix_crc);
     icaoFilterInit();
     modeACInit();
-    interactiveInit();
 
     if (Modes.show_only)
         icaoFilterAdd(Modes.show_only);
-
-    // Prepare sample conversion
-    if (!Modes.net_only) {
-        if (Modes.filename == NULL) // using a real RTLSDR, use UC8 input always
-            Modes.input_format = INPUT_UC8;
-
-        Modes.converter_function = init_converter(Modes.input_format,
-                                                  Modes.sample_rate,
-                                                  Modes.dc_filter,
-                                                  &Modes.converter_state);
-        if (!Modes.converter_function) {
-            fprintf(stderr, "Can't initialize sample converter, giving up.\n");
-            exit(1);
-        }
-    }
 }
 
-static void convert_samples(void *iq,
-                            uint16_t *mag,
-                            unsigned nsamples,
-                            double *mean_level,
-                            double *mean_power)
-{
-    Modes.converter_function(iq, mag, nsamples, Modes.converter_state, mean_level, mean_power);
-}
-
-//
-// =============================== RTLSDR handling ==========================
-//
-int modesInitRTLSDR(void) {
-    int j;
-    int device_count, dev_index = 0;
-    char vendor[256], product[256], serial[256];
-
-    if (Modes.dev_name) {
-        if ( (dev_index = verbose_device_search(Modes.dev_name)) < 0 )
-            return -1;
-    }
-
-    device_count = rtlsdr_get_device_count();
-    if (!device_count) {
-        fprintf(stderr, "No supported RTLSDR devices found.\n");
-        return -1;
-    }
-
-    fprintf(stderr, "Found %d device(s):\n", device_count);
-    for (j = 0; j < device_count; j++) {
-        if (rtlsdr_get_device_usb_strings(j, vendor, product, serial) != 0) {
-            fprintf(stderr, "%d: unable to read device details\n", j);
-        } else {
-            fprintf(stderr, "%d: %s, %s, SN: %s %s\n", j, vendor, product, serial,
-                    (j == dev_index) ? "(currently selected)" : "");
-        }
-    }
-
-    if (rtlsdr_open(&Modes.dev, dev_index) < 0) {
-        fprintf(stderr, "Error opening the RTLSDR device: %s\n",
-            strerror(errno));
-        return -1;
-    }
-
-    // Set gain, frequency, sample rate, and reset the device
-    rtlsdr_set_tuner_gain_mode(Modes.dev,
-        (Modes.gain == MODES_AUTO_GAIN) ? 0 : 1);
-    if (Modes.gain != MODES_AUTO_GAIN) {
-        int *gains;
-        int numgains;
-
-        numgains = rtlsdr_get_tuner_gains(Modes.dev, NULL);
-        if (numgains <= 0) {
-            fprintf(stderr, "Error getting tuner gains\n");
-            return -1;
-        }
-
-        gains = malloc(numgains * sizeof(int));
-        if (rtlsdr_get_tuner_gains(Modes.dev, gains) != numgains) {
-            fprintf(stderr, "Error getting tuner gains\n");
-            free(gains);
-            return -1;
-        }
-        
-        if (Modes.gain == MODES_MAX_GAIN) {
-            int highest = -1;
-            int i;
-
-            for (i = 0; i < numgains; ++i) {
-                if (gains[i] > highest)
-                    highest = gains[i];
-            }
-
-            Modes.gain = highest;
-            fprintf(stderr, "Max available gain is: %.2f dB\n", Modes.gain/10.0);
-        } else {
-            int closest = -1;
-            int i;
-
-            for (i = 0; i < numgains; ++i) {
-                if (closest == -1 || abs(gains[i] - Modes.gain) < abs(closest - Modes.gain))
-                    closest = gains[i];
-            }
-
-            if (closest != Modes.gain) {
-                Modes.gain = closest;
-                fprintf(stderr, "Closest available gain: %.2f dB\n", Modes.gain/10.0);
-            }
-        }
-
-        free(gains);
-
-        fprintf(stderr, "Setting gain to: %.2f dB\n", Modes.gain/10.0);
-        if (rtlsdr_set_tuner_gain(Modes.dev, Modes.gain) < 0) {
-            fprintf(stderr, "Error setting tuner gains\n");
-            return -1;
-        }
-    } else {
-        fprintf(stderr, "Using automatic gain control.\n");
-    }
-    rtlsdr_set_freq_correction(Modes.dev, Modes.ppm_error);
-    if (Modes.enable_agc) rtlsdr_set_agc_mode(Modes.dev, 1);
-    rtlsdr_set_center_freq(Modes.dev, Modes.freq);
-    rtlsdr_set_sample_rate(Modes.dev, (unsigned)Modes.sample_rate);
-
-    rtlsdr_reset_buffer(Modes.dev);
-    fprintf(stderr, "Gain reported by device: %.2f dB\n",
-        rtlsdr_get_tuner_gain(Modes.dev)/10.0);
-
-    return 0;
-}
 //
 //=========================================================================
 //
@@ -356,208 +226,6 @@ int modesInitRTLSDR(void) {
 // A Mutex is used to avoid races with the decoding thread.
 //
 
-static struct timespec reader_thread_start;
-
-void rtlsdrCallback(unsigned char *buf, uint32_t len, void *ctx) {
-    struct mag_buf *outbuf;
-    struct mag_buf *lastbuf;
-    uint32_t slen;
-    unsigned next_free_buffer;
-    unsigned free_bufs;
-    unsigned block_duration;
-
-    static int was_odd = 0; // paranoia!!
-    static int dropping = 0;
-
-    MODES_NOTUSED(ctx);
-
-    // Lock the data buffer variables before accessing them
-    pthread_mutex_lock(&Modes.data_mutex);
-    if (Modes.exit) {
-        rtlsdr_cancel_async(Modes.dev); // ask our caller to exit
-    }
-
-    next_free_buffer = (Modes.first_free_buffer + 1) % MODES_MAG_BUFFERS;
-    outbuf = &Modes.mag_buffers[Modes.first_free_buffer];
-    lastbuf = &Modes.mag_buffers[(Modes.first_free_buffer + MODES_MAG_BUFFERS - 1) % MODES_MAG_BUFFERS];
-    free_bufs = (Modes.first_filled_buffer - next_free_buffer + MODES_MAG_BUFFERS) % MODES_MAG_BUFFERS;
-
-    // Paranoia! Unlikely, but let's go for belt and suspenders here
-
-    if (len != MODES_RTL_BUF_SIZE) {
-        fprintf(stderr, "weirdness: rtlsdr gave us a block with an unusual size (got %u bytes, expected %u bytes)\n",
-                (unsigned)len, (unsigned)MODES_RTL_BUF_SIZE);
-
-        if (len > MODES_RTL_BUF_SIZE) {
-            // wat?! Discard the start.
-            unsigned discard = (len - MODES_RTL_BUF_SIZE + 1) / 2;
-            outbuf->dropped += discard;
-            buf += discard*2;
-            len -= discard*2;
-        }
-    }
-
-    if (was_odd) {
-        // Drop a sample so we are in sync with I/Q samples again (hopefully)
-        ++buf;
-        --len;
-        ++outbuf->dropped;
-    }
-
-    was_odd = (len & 1);
-    slen = len/2;
-
-    if (free_bufs == 0 || (dropping && free_bufs < MODES_MAG_BUFFERS/2)) {
-        // FIFO is full. Drop this block.
-        dropping = 1;
-        outbuf->dropped += slen;
-        pthread_mutex_unlock(&Modes.data_mutex);
-        return;
-    }
-
-    dropping = 0;
-    pthread_mutex_unlock(&Modes.data_mutex);
-
-    // Compute the sample timestamp and system timestamp for the start of the block
-    outbuf->sampleTimestamp = lastbuf->sampleTimestamp + 12e6 * (lastbuf->length + outbuf->dropped) / Modes.sample_rate;
-    block_duration = 1e9 * slen / Modes.sample_rate;
-
-    // Get the approx system time for the start of this block
-    clock_gettime(CLOCK_REALTIME, &outbuf->sysTimestamp);
-    outbuf->sysTimestamp.tv_nsec -= block_duration;
-    normalize_timespec(&outbuf->sysTimestamp);
-
-    // Copy trailing data from last block (or reset if not valid)
-    if (outbuf->dropped == 0 && lastbuf->length >= Modes.trailing_samples) {
-        memcpy(outbuf->data, lastbuf->data + lastbuf->length - Modes.trailing_samples, Modes.trailing_samples * sizeof(uint16_t));
-    } else {
-        memset(outbuf->data, 0, Modes.trailing_samples * sizeof(uint16_t));
-    }
-
-    // Convert the new data
-    outbuf->length = slen;
-    convert_samples(buf, &outbuf->data[Modes.trailing_samples], slen, &outbuf->mean_level, &outbuf->mean_power);
-
-    // Push the new data to the demodulation thread
-    pthread_mutex_lock(&Modes.data_mutex);
-
-    Modes.mag_buffers[next_free_buffer].dropped = 0;
-    Modes.mag_buffers[next_free_buffer].length = 0;  // just in case
-    Modes.first_free_buffer = next_free_buffer;
-
-    // accumulate CPU while holding the mutex, and restart measurement
-    end_cpu_timing(&reader_thread_start, &Modes.reader_cpu_accumulator);
-    start_cpu_timing(&reader_thread_start);
-
-    pthread_cond_signal(&Modes.data_cond);
-    pthread_mutex_unlock(&Modes.data_mutex);
-}
-//
-//=========================================================================
-//
-// This is used when --ifile is specified in order to read data from file
-// instead of using an RTLSDR device
-//
-void readDataFromFile(void) {
-    int eof = 0;
-    struct timespec next_buffer_delivery;
-    void *readbuf;
-    int bytes_per_sample = 0;
-
-    switch (Modes.input_format) {
-    case INPUT_UC8:
-        bytes_per_sample = 2;
-        break;
-    case INPUT_SC16:
-    case INPUT_SC16Q11:
-        bytes_per_sample = 4;
-        break;
-    }
-
-    if (!(readbuf = malloc(MODES_MAG_BUF_SAMPLES * bytes_per_sample))) {
-        fprintf(stderr, "failed to allocate read buffer\n");
-        exit(1);
-    }
-
-    clock_gettime(CLOCK_MONOTONIC, &next_buffer_delivery);
-
-    pthread_mutex_lock(&Modes.data_mutex);
-    while (!Modes.exit && !eof) {
-        ssize_t nread, toread;
-        void *r;
-        struct mag_buf *outbuf, *lastbuf;
-        unsigned next_free_buffer;
-        unsigned slen;
-
-        next_free_buffer = (Modes.first_free_buffer + 1) % MODES_MAG_BUFFERS;
-        if (next_free_buffer == Modes.first_filled_buffer) {
-            // no space for output yet
-            pthread_cond_wait(&Modes.data_cond, &Modes.data_mutex);
-            continue;
-        }
-
-        outbuf = &Modes.mag_buffers[Modes.first_free_buffer];
-        lastbuf = &Modes.mag_buffers[(Modes.first_free_buffer + MODES_MAG_BUFFERS - 1) % MODES_MAG_BUFFERS];
-        pthread_mutex_unlock(&Modes.data_mutex);
-
-        // Compute the sample timestamp and system timestamp for the start of the block
-        outbuf->sampleTimestamp = lastbuf->sampleTimestamp + 12e6 * lastbuf->length / Modes.sample_rate;
-
-        // Copy trailing data from last block (or reset if not valid)
-        if (lastbuf->length >= Modes.trailing_samples) {
-            memcpy(outbuf->data, lastbuf->data + lastbuf->length - Modes.trailing_samples, Modes.trailing_samples * sizeof(uint16_t));
-        } else {
-            memset(outbuf->data, 0, Modes.trailing_samples * sizeof(uint16_t));
-        }
-
-        // Get the system time for the start of this block
-        clock_gettime(CLOCK_REALTIME, &outbuf->sysTimestamp);
-
-        toread = MODES_MAG_BUF_SAMPLES * bytes_per_sample;
-        r = readbuf;
-        while (toread) {
-            nread = read(Modes.fd, r, toread);
-            if (nread <= 0) {
-                // Done.
-                eof = 1;
-                break;
-            }
-            r += nread;
-            toread -= nread;
-        }
-
-        slen = outbuf->length = MODES_MAG_BUF_SAMPLES - toread/bytes_per_sample;
-
-        // Convert the new data
-        convert_samples(readbuf, &outbuf->data[Modes.trailing_samples], slen, &outbuf->mean_level, &outbuf->mean_power);
-
-        if (Modes.throttle) {
-            // Wait until we are allowed to release this buffer to the main thread
-            while (clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &next_buffer_delivery, NULL) == EINTR)
-                ;
-
-            // compute the time we can deliver the next buffer.
-            next_buffer_delivery.tv_nsec += outbuf->length * 1e9 / Modes.sample_rate;
-            normalize_timespec(&next_buffer_delivery);
-        }
-
-        // Push the new data to the main thread
-        pthread_mutex_lock(&Modes.data_mutex);
-        Modes.first_free_buffer = next_free_buffer;
-        // accumulate CPU while holding the mutex, and restart measurement
-        end_cpu_timing(&reader_thread_start, &Modes.reader_cpu_accumulator);
-        start_cpu_timing(&reader_thread_start);
-        pthread_cond_signal(&Modes.data_cond);
-    }
-
-    free(readbuf);
-
-    // Wait for the main thread to consume all data
-    while (!Modes.exit && Modes.first_filled_buffer != Modes.first_free_buffer)
-        pthread_cond_wait(&Modes.data_cond, &Modes.data_mutex);
-
-    pthread_mutex_unlock(&Modes.data_mutex);
-}
 //
 //=========================================================================
 //
@@ -565,36 +233,11 @@ void readDataFromFile(void) {
 // without caring about data acquisition
 //
 
-void *readerThreadEntryPoint(void *arg) {
+void *readerThreadEntryPoint(void *arg)
+{
     MODES_NOTUSED(arg);
 
-    start_cpu_timing(&reader_thread_start); // we accumulate in rtlsdrCallback() or readDataFromFile()
+    sdrRun();
-
-    if (Modes.filename == NULL) {
-        while (!Modes.exit) {
-            rtlsdr_read_async(Modes.dev, rtlsdrCallback, NULL,
-                              MODES_RTL_BUFFERS,
-                              MODES_RTL_BUF_SIZE);
-
-            if (!Modes.exit) {
-                log_with_timestamp("Warning: lost the connection to the RTLSDR device.");
-                rtlsdr_close(Modes.dev);
-                Modes.dev = NULL;
-
-                do {
-                    sleep(5);
-                    log_with_timestamp("Trying to reconnect to the RTLSDR device..");
-                } while (!Modes.exit && modesInitRTLSDR() < 0);
-            }
-        }
-
-        if (Modes.dev != NULL) {
-            rtlsdr_close(Modes.dev);
-            Modes.dev = NULL;
-        }
-    } else {
-        readDataFromFile();
-    }
 
     // Wake the main thread (if it's still waiting)
     pthread_mutex_lock(&Modes.data_mutex);
@@ -634,16 +277,18 @@ void snipMode(int level) {
 //
 void showHelp(void) {
     printf(
-"-----------------------------------------------------------------------------\n"
+           "-----------------------------------------------------------------------------\n"
-"| dump1090 ModeS Receiver     %45s |\n"
+           "| dump1090 ModeS Receiver     %45s |\n"
-"-----------------------------------------------------------------------------\n"
+           "-----------------------------------------------------------------------------\n",
-"--device-index <index>   Select RTL device (default: 0)\n"
+           MODES_DUMP1090_VARIANT " " MODES_DUMP1090_VERSION);
+
+    sdrShowHelp();
+
+    printf(
+"      Common options\n"
+"\n"
 "--gain <db>              Set gain (default: max gain. Use -10 for auto-gain)\n"
-"--enable-agc             Enable the Automatic Gain Control (default: off)\n"
 "--freq <hz>              Set frequency (default: 1090 Mhz)\n"
-"--ifile <filename>       Read data from file (use '-' for stdin)\n"
-"--iformat <format>       Sample format for --ifile: UC8 (default), SC16, or SC16Q11\n"
-"--throttle               When reading from a file, play back in realtime, not at max speed\n"
 "--interactive            Interactive mode refreshing data on screen. Implies --throttle\n"
 "--interactive-ttl <sec>  Remove from list if idle for <sec> (default: 60)\n"
 "--raw                    Show only messages hex values\n"
@@ -683,12 +328,11 @@ void showHelp(void) {
 "--debug <flags>          Debug mode (verbose), see README for details\n"
 "--quiet                  Disable output to stdout. Use for daemon applications\n"
 "--show-only <addr>       Show only messages from the given ICAO on stdout\n"
-"--ppm <error>            Set receiver error in parts per million (default 0)\n"
 "--html-dir <dir>         Use <dir> as base directory for the internal HTTP server. Defaults to " HTMLPATH "\n"
 "--write-json <dir>       Periodically write json output to <dir> (for serving by a separate webserver)\n"
 "--write-json-every <t>   Write json output every t seconds (default 1)\n"
 "--json-location-accuracy <n>  Accuracy of receiver location in json metadata: 0=no location, 1=approximate, 2=exact\n"
-"--dcfilter               Apply a 1Hz DC filter to input data (requires lots more CPU)\n"
+"--dcfilter               Apply a 1Hz DC filter to input data (requires more CPU)\n"
 "--help                   Show this help\n"
 "\n"
 "Debug mode flags: d = Log frames decoded with errors\n"
@@ -697,8 +341,7 @@ void showHelp(void) {
 "                  C = Log frames with good CRC\n"
 "                  p = Log frames with bad preamble\n"
 "                  n = Log network debugging info\n"
-"                  j = Log frames to frames.js, loadable by debug.html\n",
+"                  j = Log frames to frames.js, loadable by debug.html\n"
-MODES_DUMP1090_VARIANT " " MODES_DUMP1090_VERSION
     );
 }
 
@@ -815,68 +458,6 @@ void backgroundTasks(void) {
 //
 //=========================================================================
 //
-int verbose_device_search(char *s)
-{
-	int i, device_count, device, offset;
-	char *s2;
-	char vendor[256], product[256], serial[256];
-	device_count = rtlsdr_get_device_count();
-	if (!device_count) {
-		fprintf(stderr, "No supported devices found.\n");
-		return -1;
-	}
-	fprintf(stderr, "Found %d device(s):\n", device_count);
-	for (i = 0; i < device_count; i++) {
-            if (rtlsdr_get_device_usb_strings(i, vendor, product, serial) != 0) {
-                fprintf(stderr, "  %d:  unable to read device details\n", i);
-            } else {
-                fprintf(stderr, "  %d:  %s, %s, SN: %s\n", i, vendor, product, serial);
-            }
-	}
-	fprintf(stderr, "\n");
-	/* does string look like raw id number */
-	device = (int)strtol(s, &s2, 0);
-	if (s2[0] == '\0' && device >= 0 && device < device_count) {
-		fprintf(stderr, "Using device %d: %s\n",
-			device, rtlsdr_get_device_name((uint32_t)device));
-		return device;
-	}
-	/* does string exact match a serial */
-	for (i = 0; i < device_count; i++) {
-		rtlsdr_get_device_usb_strings(i, vendor, product, serial);
-		if (strcmp(s, serial) != 0) {
-			continue;}
-		device = i;
-		fprintf(stderr, "Using device %d: %s\n",
-			device, rtlsdr_get_device_name((uint32_t)device));
-		return device;
-	}
-	/* does string prefix match a serial */
-	for (i = 0; i < device_count; i++) {
-		rtlsdr_get_device_usb_strings(i, vendor, product, serial);
-		if (strncmp(s, serial, strlen(s)) != 0) {
-			continue;}
-		device = i;
-		fprintf(stderr, "Using device %d: %s\n",
-			device, rtlsdr_get_device_name((uint32_t)device));
-		return device;
-	}
-	/* does string suffix match a serial */
-	for (i = 0; i < device_count; i++) {
-		rtlsdr_get_device_usb_strings(i, vendor, product, serial);
-		offset = strlen(serial) - strlen(s);
-		if (offset < 0) {
-			continue;}
-		if (strncmp(s, serial+offset, strlen(s)) != 0) {
-			continue;}
-		device = i;
-		fprintf(stderr, "Using device %d: %s\n",
-			device, rtlsdr_get_device_name((uint32_t)device));
-		return device;
-	}
-	fprintf(stderr, "No matching devices found.\n");
-	return -1;
-}
 //
 //=========================================================================
 //
@@ -894,29 +475,12 @@ int main(int argc, char **argv) {
     for (j = 1; j < argc; j++) {
         int more = j+1 < argc; // There are more arguments
 
-        if (!strcmp(argv[j],"--device-index") && more) {
+        if (!strcmp(argv[j],"--freq") && more) {
+            Modes.freq = (int) strtoll(argv[++j],NULL,10);
+        } else if ( (!strcmp(argv[j], "--device") || !strcmp(argv[j], "--device-index")) && more) {
             Modes.dev_name = strdup(argv[++j]);
         } else if (!strcmp(argv[j],"--gain") && more) {
             Modes.gain = (int) (atof(argv[++j])*10); // Gain is in tens of DBs
-        } else if (!strcmp(argv[j],"--enable-agc")) {
-            Modes.enable_agc++;
-        } else if (!strcmp(argv[j],"--freq") && more) {
-            Modes.freq = (int) strtoll(argv[++j],NULL,10);
-        } else if (!strcmp(argv[j],"--ifile") && more) {
-            Modes.filename = strdup(argv[++j]);
-        } else if (!strcmp(argv[j],"--iformat") && more) {
-            ++j;
-            if (!strcasecmp(argv[j], "uc8")) {
-                Modes.input_format = INPUT_UC8;
-            } else if (!strcasecmp(argv[j], "sc16")) {
-                Modes.input_format = INPUT_SC16;
-            } else if (!strcasecmp(argv[j], "sc16q11")) {
-                Modes.input_format = INPUT_SC16Q11;
-            } else {
-                fprintf(stderr, "Input format '%s' not understood (supported values: UC8, SC16, SC16Q11)\n",
-                        argv[j]);
-                exit(1);
-            }
         } else if (!strcmp(argv[j],"--dcfilter")) {
             Modes.dc_filter = 1;
         } else if (!strcmp(argv[j],"--measure-noise")) {
@@ -942,7 +506,7 @@ int main(int argc, char **argv) {
             fprintf(stderr, "--net-beast ignored, use --net-bo-port to control where Beast output is generated\n");
         } else if (!strcmp(argv[j],"--net-only")) {
             Modes.net = 1;
-            Modes.net_only = 1;
+            Modes.sdr_type = SDR_NONE;
        } else if (!strcmp(argv[j],"--net-heartbeat") && more) {
             Modes.net_heartbeat_interval = (uint64_t)(1000 * atof(argv[++j]));
        } else if (!strcmp(argv[j],"--net-ro-size") && more) {
@@ -992,9 +556,7 @@ int main(int argc, char **argv) {
             fprintf(stderr, "warning: --aggressive not supported in this build, option ignored.\n");
 #endif
         } else if (!strcmp(argv[j],"--interactive")) {
-            Modes.interactive = Modes.throttle = 1;
+            Modes.interactive = 1;
-        } else if (!strcmp(argv[j],"--throttle")) {
-            Modes.throttle = 1;
         } else if (!strcmp(argv[j],"--interactive-ttl") && more) {
             Modes.interactive_display_ttl = (uint64_t)(1000 * atof(argv[++j]));
         } else if (!strcmp(argv[j],"--lat") && more) {
@@ -1034,8 +596,6 @@ int main(int argc, char **argv) {
         } else if (!strcmp(argv[j],"--help")) {
             showHelp();
             exit(0);
-        } else if (!strcmp(argv[j],"--ppm") && more) {
-            Modes.ppm_error = atoi(argv[++j]);
         } else if (!strcmp(argv[j],"--quiet")) {
             Modes.quiet = 1;
         } else if (!strcmp(argv[j],"--show-only") && more) {
@@ -1056,6 +616,8 @@ int main(int argc, char **argv) {
         } else if (!strcmp(argv[j], "--json-location-accuracy") && more) {
             Modes.json_location_accuracy = atoi(argv[++j]);
 #endif
+        } else if (sdrHandleOption(argc, argv, &j)) {
+            /* handled */
         } else {
             fprintf(stderr,
                 "Unknown or not enough arguments for option '%s'.\n\n",
@@ -1074,27 +636,13 @@ int main(int argc, char **argv) {
     log_with_timestamp("%s %s starting up.", MODES_DUMP1090_VARIANT, MODES_DUMP1090_VERSION);
     modesInit();
 
-    if (Modes.net_only) {
+    if (!sdrOpen()) {
-        fprintf(stderr,"Net-only mode, no RTL device or file open.\n");
+        exit(1);
-    } else if (Modes.filename == NULL) {
+    }
-        if (modesInitRTLSDR() < 0) {
+
-            exit(1);
+    if (Modes.net) {
-        }
+        modesInitNet();
-    } else {
-        if (Modes.filename[0] == '-' && Modes.filename[1] == '\0') {
-            Modes.fd = STDIN_FILENO;
-        } else if ((Modes.fd = open(Modes.filename,
-#ifdef _WIN32
-                                    (O_RDONLY | O_BINARY)
-#else
-                                    (O_RDONLY)
-#endif
-                                    )) == -1) {
-            perror("Opening data file");
-            exit(1);
-        }
     }
-    if (Modes.net) modesInitNet();
 
     // init stats:
     Modes.stats_current.start = Modes.stats_current.end =
@@ -1111,9 +659,11 @@ int main(int argc, char **argv) {
     writeJsonToFile("stats.json", generateStatsJson);
     writeJsonToFile("aircraft.json", generateAircraftJson);
 
+    interactiveInit();
+
     // If the user specifies --net-only, just run in order to serve network
     // clients without reading data from the RTL device
-    if (Modes.net_only) {
+    if (Modes.sdr_type == SDR_NONE) {
         while (!Modes.exit) {
             struct timespec start_time;
 
@@ -1130,7 +680,7 @@ int main(int argc, char **argv) {
         pthread_mutex_lock(&Modes.data_mutex);
         pthread_create(&Modes.reader_thread, NULL, readerThreadEntryPoint, NULL);
 
-        while (Modes.exit == 0) {
+        while (!Modes.exit) {
             struct timespec start_time;
 
             if (Modes.first_free_buffer == Modes.first_filled_buffer) {
@@ -1186,7 +736,7 @@ int main(int argc, char **argv) {
                 // Nothing to process this time around.
                 pthread_mutex_unlock(&Modes.data_mutex);
                 if (--watchdogCounter <= 0) {
-                    log_with_timestamp("No data received from the dongle for a long time, it may have wedged");
+                    log_with_timestamp("No data received from the SDR for a long time, it may have wedged");
                     watchdogCounter = 600;
                 }
             }
@@ -1213,9 +763,10 @@ int main(int argc, char **argv) {
         display_total_stats();
     }
 
-    cleanup_converter(Modes.converter_state);
     log_with_timestamp("Normal exit.");
 
+    sdrClose();
+
 #ifndef _WIN32
     pthread_exit(0);
 #else

dump1090.h

@@ -65,6 +65,7 @@
     #include <stdio.h>
     #include <string.h>
     #include <stdlib.h>
+    #include <stdbool.h>
     #include <pthread.h>
     #include <stdint.h>
     #include <errno.h>
@@ -84,12 +85,8 @@
 
 #include "compat/compat.h"
 
-// Avoid a dependency on rtl-sdr except where it's really needed.
-typedef struct rtlsdr_dev rtlsdr_dev_t;
-
 // ============================= #defines ===============================
 
-#define MODES_DEFAULT_PPM          52
 #define MODES_DEFAULT_FREQ         1090000000
 #define MODES_DEFAULT_WIDTH        1000
 #define MODES_DEFAULT_HEIGHT       700
@@ -245,9 +242,14 @@ typedef enum {
 #include "cpr.h"
 #include "icao_filter.h"
 #include "convert.h"
+#include "sdr.h"
 
 //======================== structure declarations =========================
 
+typedef enum {
+    SDR_NONE, SDR_IFILE, SDR_RTLSDR
+} sdr_type_t;
+
 // Structure representing one magnitude buffer
 struct mag_buf {
     uint16_t       *data;            // Magnitude data. Starts with Modes.trailing_samples worth of overlap from the previous block
@@ -274,24 +276,17 @@ struct {                             // Internal state
     unsigned        trailing_samples;                     // extra trailing samples in magnitude buffers
     double          sample_rate;                          // actual sample rate in use (in hz)
 
-    int             fd;              // --ifile option file descriptor
-    input_format_t  input_format;    // --iformat option
     uint16_t       *maglut;          // I/Q -> Magnitude lookup table
     uint16_t       *log10lut;        // Magnitude -> log10 lookup table
     int             exit;            // Exit from the main loop when true
 
     // Sample conversion
     int            dc_filter;        // should we apply a DC filter?
-    iq_convert_fn  converter_function;
-    struct converter_state *converter_state;
 
     // RTLSDR
     char *        dev_name;
     int           gain;
-    int           enable_agc;
-    rtlsdr_dev_t *dev;
     int           freq;
-    int           ppm_error;
 
     // Networking
     char           aneterr[ANET_ERR_LEN];
@@ -308,7 +303,7 @@ struct {                             // Internal state
 #endif
 
     // Configuration
-    char *filename;                  // Input form file, --ifile option
+    sdr_type_t sdr_type;             // where are we getting data from?
     int   nfix_crc;                  // Number of crc bit error(s) to correct
     int   check_crc;                 // Only display messages with good CRC
     int   raw;                       // Raw output format
@@ -343,7 +338,6 @@ struct {                             // Internal state
     uint64_t json_interval;          // Interval between rewriting the json aircraft file, in milliseconds; also the advertised map refresh interval
     char *html_dir;                  // Path to www base directory.
     int   json_location_accuracy;    // Accuracy of location metadata: 0=none, 1=approx, 2=exact
-    int   throttle;                  // When reading from a file, throttle file playback to realtime?
 
     int   json_aircraft_history_next;
     struct {

sdr.c

@@ -0,0 +1,145 @@
+#include "dump1090.h"
+#include "sdr.h"
+
+#define ENABLE_RTLSDR
+
+#include "sdr_ifile.h"
+#ifdef ENABLE_RTLSDR
+#  include "sdr_rtlsdr.h"
+#endif
+
+typedef struct {
+    const char *name;
+    sdr_type_t sdr_type;
+    void (*initConfig)();
+    void (*showHelp)();
+    bool (*handleOption)(int, char**, int*);
+    bool (*open)();
+    void (*run)();
+    void (*close)();
+} sdr_handler;
+
+static void noInitConfig()
+{
+}
+
+static void noShowHelp()
+{
+}
+
+static bool noHandleOption(int argc, char **argv, int *jptr)
+{
+    MODES_NOTUSED(argc);
+    MODES_NOTUSED(argv);
+    MODES_NOTUSED(jptr);
+
+    return false;
+}
+
+static bool noOpen()
+{
+    fprintf(stderr, "Net-only mode, no SDR device or file open.\n");
+    return true;
+}
+
+static void noRun()
+{
+}
+
+static void noClose()
+{
+}
+
+static bool unsupportedOpen()
+{
+    fprintf(stderr, "Support for this SDR type was not enabled in this build.\n");
+    return false;
+}
+
+static sdr_handler sdr_handlers[] = {
+#ifdef ENABLE_RTLSDR
+    { "rtlsdr", SDR_RTLSDR, rtlsdrInitConfig, rtlsdrShowHelp, rtlsdrHandleOption, rtlsdrOpen, rtlsdrRun, rtlsdrClose },
+#endif
+
+    { "ifile", SDR_IFILE, ifileInitConfig, ifileShowHelp, ifileHandleOption, ifileOpen, ifileRun, ifileClose },
+    { "none", SDR_NONE, noInitConfig, noShowHelp, noHandleOption, noOpen, noRun, noClose },
+
+    { NULL, SDR_NONE, NULL, NULL, NULL, NULL, NULL, NULL } /* must come last */
+};
+
+void sdrInitConfig()
+{
+    // Default SDR is the first type available in the handlers array.
+    Modes.sdr_type = sdr_handlers[0].sdr_type;
+
+    for (int i = 0; sdr_handlers[i].name; ++i) {
+        sdr_handlers[i].initConfig();
+    }
+}
+
+void sdrShowHelp()
+{
+    printf("--device-type <type>     Select SDR type (default: %s)\n", sdr_handlers[0].name);
+    printf("\n");
+
+    for (int i = 0; sdr_handlers[i].name; ++i) {
+        sdr_handlers[i].showHelp();
+    }
+}
+
+bool sdrHandleOption(int argc, char **argv, int *jptr)
+{
+    int j = *jptr;
+    if (!strcmp(argv[j], "--device-type") && (j+1) < argc) {
+        ++j;
+        for (int i = 0; sdr_handlers[i].name; ++i) {
+            if (!strcasecmp(sdr_handlers[i].name, argv[j])) {
+                Modes.sdr_type = sdr_handlers[i].sdr_type;
+                *jptr = j;
+                return true;
+            }
+        }
+
+        fprintf(stderr, "SDR type '%s' not recognized; supported SDR types are:\n", argv[j]);
+        for (int i = 0; sdr_handlers[i].name; ++i) {
+            fprintf(stderr, "  %s\n", sdr_handlers[i].name);
+        }
+
+        return false;
+    }
+
+    for (int i = 0; sdr_handlers[i].name; ++i) {
+        if (sdr_handlers[i].handleOption(argc, argv, jptr))
+            return true;
+    }
+
+    return false;
+}
+
+static sdr_handler *current_handler()
+{
+    static sdr_handler unsupported_handler = { "unsupported", SDR_NONE, noInitConfig, noShowHelp, noHandleOption, unsupportedOpen, noRun, noClose };
+
+    for (int i = 0; sdr_handlers[i].name; ++i) {
+        if (Modes.sdr_type == sdr_handlers[i].sdr_type) {
+            return &sdr_handlers[i];
+        }
+    }
+
+    return &unsupported_handler;
+}
+
+bool sdrOpen()
+{
+    return current_handler()->open();
+}
+
+void sdrRun()
+{
+    return current_handler()->run();
+}
+
+void sdrClose()
+{
+    current_handler()->close();
+}

sdr.h

@@ -0,0 +1,13 @@
+#ifndef SDR_H
+#define SDR_H
+
+// Common interface to different SDR inputs.
+
+void sdrInitConfig();
+void sdrShowHelp();
+bool sdrHandleOption(int argc, char **argv, int *jptr);
+bool sdrOpen();
+void sdrRun();
+void sdrClose();
+
+#endif

sdr_ifile.c

@@ -0,0 +1,236 @@
+#include "dump1090.h"
+#include "sdr_ifile.h"
+
+static struct {
+    const char *filename;
+    input_format_t input_format;
+    bool throttle;
+
+    int fd;
+    unsigned bytes_per_sample;
+    void *readbuf;
+    iq_convert_fn converter;
+    struct converter_state *converter_state;
+} ifile;
+
+void ifileInitConfig(void)
+{
+    ifile.filename = NULL;
+    ifile.input_format = INPUT_UC8;
+    ifile.throttle = false;
+    ifile.fd = -1;
+    ifile.bytes_per_sample = 0;
+    ifile.readbuf = NULL;
+    ifile.converter = NULL;
+    ifile.converter_state = NULL;
+}
+
+void ifileShowHelp()
+{
+    printf("      ifile-specific options (use with --ifile)\n");
+    printf("\n");
+    printf("--ifile <path>           read samples from given file ('-' for stdin)\n");
+    printf("--iformat <type>         set sample format (UC8, SC16, SC16Q11)\n");
+    printf("--throttle               process samples at the original capture speed\n");
+    printf("\n");
+}
+
+bool ifileHandleOption(int argc, char **argv, int *jptr)
+{
+    int j = *jptr;
+    bool more = (j +1  < argc);
+
+    if (!strcmp(argv[j], "--ifile") && more) {
+        // implies --device-type ifile
+        ifile.filename = strdup(argv[++j]);
+        Modes.sdr_type = SDR_IFILE;
+    } else if (!strcmp(argv[j],"--iformat") && more) {
+        ++j;
+        if (!strcasecmp(argv[j], "uc8")) {
+            ifile.input_format = INPUT_UC8;
+        } else if (!strcasecmp(argv[j], "sc16")) {
+            ifile.input_format = INPUT_SC16;
+        } else if (!strcasecmp(argv[j], "sc16q11")) {
+            ifile.input_format = INPUT_SC16Q11;
+        } else {
+            fprintf(stderr, "Input format '%s' not understood (supported values: UC8, SC16, SC16Q11)\n",
+                    argv[j]);
+            return false;
+        }
+    } else if (!strcmp(argv[j],"--throttle")) {
+        ifile.throttle = true;
+    } else {
+        return false;
+    }
+
+    *jptr = j;
+    return true;
+}
+
+//
+//=========================================================================
+//
+// This is used when --ifile is specified in order to read data from file
+// instead of using an RTLSDR device
+//
+bool ifileOpen(void)
+{
+    if (!ifile.filename) {
+        fprintf(stderr, "SDR type 'ifile' requires an --ifile argument\n");
+        return false;
+    }
+
+    if (!strcmp(ifile.filename, "-")) {
+        ifile.fd = STDIN_FILENO;
+    } else if ((ifile.fd = open(ifile.filename, O_RDONLY)) < 0) {
+        fprintf(stderr, "ifile: could not open %s: %s\n",
+                ifile.filename, strerror(errno));
+        return false;
+    }
+
+    switch (ifile.input_format) {
+    case INPUT_UC8:
+        ifile.bytes_per_sample = 2;
+        break;
+    case INPUT_SC16:
+    case INPUT_SC16Q11:
+        ifile.bytes_per_sample = 4;
+        break;
+    default:
+        fprintf(stderr, "ifile: unhandled input format\n");
+        ifileClose();
+        return false;
+    }
+
+    if (!(ifile.readbuf = malloc(MODES_MAG_BUF_SAMPLES * ifile.bytes_per_sample))) {
+        fprintf(stderr, "ifile: failed to allocate read buffer\n");
+        ifileClose();
+        return false;
+    }
+
+    ifile.converter = init_converter(ifile.input_format,
+                                     Modes.sample_rate,
+                                     Modes.dc_filter,
+                                     &ifile.converter_state);
+    if (!ifile.converter) {
+        fprintf(stderr, "ifile: can't initialize sample converter\n");
+        ifileClose();
+        return false;
+    }
+
+    return true;
+}
+
+void ifileRun()
+{
+    if (ifile.fd < 0)
+        return;
+
+    int eof = 0;
+    struct timespec next_buffer_delivery;
+
+    struct timespec thread_cpu;
+    start_cpu_timing(&thread_cpu);
+
+    uint64_t sampleCounter = 0;
+
+    clock_gettime(CLOCK_MONOTONIC, &next_buffer_delivery);
+
+    pthread_mutex_lock(&Modes.data_mutex);
+    while (!Modes.exit && !eof) {
+        ssize_t nread, toread;
+        void *r;
+        struct mag_buf *outbuf, *lastbuf;
+        unsigned next_free_buffer;
+        unsigned slen;
+
+        next_free_buffer = (Modes.first_free_buffer + 1) % MODES_MAG_BUFFERS;
+        if (next_free_buffer == Modes.first_filled_buffer) {
+            // no space for output yet
+            pthread_cond_wait(&Modes.data_cond, &Modes.data_mutex);
+            continue;
+        }
+
+        outbuf = &Modes.mag_buffers[Modes.first_free_buffer];
+        lastbuf = &Modes.mag_buffers[(Modes.first_free_buffer + MODES_MAG_BUFFERS - 1) % MODES_MAG_BUFFERS];
+        pthread_mutex_unlock(&Modes.data_mutex);
+
+        // Compute the sample timestamp for the start of the block
+        outbuf->sampleTimestamp = sampleCounter * 12e6 / Modes.sample_rate;
+        sampleCounter += MODES_MAG_BUF_SAMPLES;
+
+        // Copy trailing data from last block (or reset if not valid)
+        if (lastbuf->length >= Modes.trailing_samples) {
+            memcpy(outbuf->data, lastbuf->data + lastbuf->length, Modes.trailing_samples * sizeof(uint16_t));
+        } else {
+            memset(outbuf->data, 0, Modes.trailing_samples * sizeof(uint16_t));
+        }
+
+        // Get the system time for the start of this block
+        clock_gettime(CLOCK_REALTIME, &outbuf->sysTimestamp);
+
+        toread = MODES_MAG_BUF_SAMPLES * ifile.bytes_per_sample;
+        r = ifile.readbuf;
+        while (toread) {
+            nread = read(ifile.fd, r, toread);
+            if (nread <= 0) {
+                if (nread < 0) {
+                    fprintf(stderr, "ifile: error reading input file: %s\n", strerror(errno));
+                }
+                // Done.
+                eof = 1;
+                break;
+            }
+            r += nread;
+            toread -= nread;
+        }
+
+        slen = outbuf->length = MODES_MAG_BUF_SAMPLES - toread / ifile.bytes_per_sample;
+
+        // Convert the new data
+        ifile.converter(ifile.readbuf, &outbuf->data[Modes.trailing_samples], slen, ifile.converter_state, &outbuf->mean_level, &outbuf->mean_power);
+
+        if (ifile.throttle || Modes.interactive) {
+            // Wait until we are allowed to release this buffer to the main thread
+            while (clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &next_buffer_delivery, NULL) == EINTR)
+                ;
+
+            // compute the time we can deliver the next buffer.
+            next_buffer_delivery.tv_nsec += outbuf->length * 1e9 / Modes.sample_rate;
+            normalize_timespec(&next_buffer_delivery);
+        }
+
+        // Push the new data to the main thread
+        pthread_mutex_lock(&Modes.data_mutex);
+        Modes.first_free_buffer = next_free_buffer;
+        // accumulate CPU while holding the mutex, and restart measurement
+        end_cpu_timing(&thread_cpu, &Modes.reader_cpu_accumulator);
+        start_cpu_timing(&thread_cpu);
+        pthread_cond_signal(&Modes.data_cond);
+    }
+
+    // Wait for the main thread to consume all data
+    while (!Modes.exit && Modes.first_filled_buffer != Modes.first_free_buffer)
+        pthread_cond_wait(&Modes.data_cond, &Modes.data_mutex);
+
+    pthread_mutex_unlock(&Modes.data_mutex);
+}
+
+void ifileClose()
+{
+    if (ifile.converter) {
+        cleanup_converter(ifile.converter_state);
+        ifile.converter = NULL;
+        ifile.converter_state = NULL;
+    }
+
+    if (ifile.readbuf) {
+        free(ifile.readbuf);
+        ifile.readbuf = NULL;
+    }
+
+    if (ifile.fd >= 0 && ifile.fd != STDIN_FILENO) {
+        close(ifile.fd);
+        ifile.fd = -1;
+    }
+}

sdr_ifile.h

@@ -0,0 +1,13 @@
+#ifndef SDR_IFILE_H
+#define SDR_IFILE_H
+
+// Pseudo-SDR that reads from a sample file
+
+void ifileInitConfig();
+void ifileShowHelp();
+bool ifileHandleOption(int argc, char **argv, int *jptr);
+bool ifileOpen();
+void ifileRun();
+void ifileClose();
+
+#endif

sdr_rtlsdr.c

@@ -0,0 +1,335 @@
+#include "dump1090.h"
+#include "sdr_rtlsdr.h"
+
+#include <rtl-sdr.h>
+
+static struct {
+    rtlsdr_dev_t *dev;
+    bool digital_agc;
+    int ppm_error;
+
+    iq_convert_fn converter;
+    struct converter_state *converter_state;
+} RTLSDR;
+
+//
+// =============================== RTLSDR handling ==========================
+//
+
+void rtlsdrInitConfig()
+{
+    RTLSDR.dev = NULL;
+    RTLSDR.digital_agc = false;
+    RTLSDR.ppm_error = 0;
+    RTLSDR.converter = NULL;
+    RTLSDR.converter_state = NULL;
+}
+
+static void show_rtlsdr_devices()
+{
+    int device_count = rtlsdr_get_device_count();
+    fprintf(stderr, "rtlsdr: found %d device(s):\n", device_count);
+    for (int i = 0; i < device_count; i++) {
+        char vendor[256], product[256], serial[256];
+
+        if (rtlsdr_get_device_usb_strings(i, vendor, product, serial) != 0) {
+            fprintf(stderr, "  %d:  unable to read device details\n", i);
+        } else {
+            fprintf(stderr, "  %d:  %s, %s, SN: %s\n", i, vendor, product, serial);
+        }
+    }
+}
+
+static int find_device_index(char *s)
+{
+    int device_count = rtlsdr_get_device_count();
+    if (!device_count) {
+        return -1;
+    }
+
+    /* does string look like raw id number */
+    if (!strcmp(s, "0")) {
+        return 0;
+    } else if (s[0] != '0') {
+        char *s2;
+        int device = (int)strtol(s, &s2, 10);
+        if (s2[0] == '\0' && device >= 0 && device < device_count) {
+            return device;
+        }
+    }
+
+    /* does string exact match a serial */
+    for (int i = 0; i < device_count; i++) {
+        char serial[256];
+        if (rtlsdr_get_device_usb_strings(i, NULL, NULL, serial) == 0 && !strcmp(s, serial)) {
+            return i;
+        }
+    }
+
+    /* does string prefix match a serial */
+    for (int i = 0; i < device_count; i++) {
+        char serial[256];
+        if (rtlsdr_get_device_usb_strings(i, NULL, NULL, serial) == 0 && !strncmp(s, serial, strlen(s))) {
+            return i;
+        }
+    }
+
+    /* does string suffix match a serial */
+    for (int i = 0; i < device_count; i++) {
+        char serial[256];
+        if (rtlsdr_get_device_usb_strings(i, NULL, NULL, serial) == 0 && strlen(s) < strlen(serial) && !strcmp(serial + strlen(serial) - strlen(s), s)) {
+            return i;
+        }
+    }
+
+    return -1;
+}
+
+void rtlsdrShowHelp()
+{
+    printf("      rtlsdr-specific options (use with --device-type rtlsdr)\n");
+    printf("\n");
+    printf("--device <index|serial>  select device by index or serial number\n");
+    printf("--enable-agc             enable digital AGC (not tuner AGC!)\n");
+    printf("--ppm <correction>       set oscillator frequency correction in PPM\n");
+    printf("\n");
+}
+
+bool rtlsdrHandleOption(int argc, char **argv, int *jptr)
+{
+    int j = *jptr;
+    bool more = (j +1  < argc);
+
+    if (!strcmp(argv[j], "--enable-agc")) {
+        RTLSDR.digital_agc = true;
+    } else if (!strcmp(argv[j], "--ppm") && more) {
+        RTLSDR.ppm_error = atoi(argv[++j]);
+    } else {
+        return false;
+    }
+
+    *jptr = j;
+    return true;
+}
+
+bool rtlsdrOpen(void) {
+    if (!rtlsdr_get_device_count()) {
+        fprintf(stderr, "rtlsdr: no supported devices found.\n");
+        return false;
+    }
+
+    int dev_index = 0;
+    if (Modes.dev_name) {
+        if ((dev_index = find_device_index(Modes.dev_name)) < 0) {
+            fprintf(stderr, "rtlsdr: no device matching '%s' found.\n", Modes.dev_name);
+            show_rtlsdr_devices();
+            return false;
+        }
+    }
+
+    char manufacturer[256];
+    char product[256];
+    char serial[256];
+    if (rtlsdr_get_device_usb_strings(dev_index, manufacturer, product, serial) < 0) {
+        fprintf(stderr, "rtlsdr: error querying device #%d: %s\n", dev_index, strerror(errno));
+        return false;
+    }
+
+    fprintf(stderr, "rtlsdr: using device #%d: %s (%s, %s, SN %s)\n",
+            dev_index, rtlsdr_get_device_name(dev_index),
+            manufacturer, product, serial);
+
+    if (rtlsdr_open(&RTLSDR.dev, dev_index) < 0) {
+        fprintf(stderr, "rtlsdr: error opening the RTLSDR device: %s\n",
+            strerror(errno));
+        return false;
+    }
+
+    // Set gain, frequency, sample rate, and reset the device
+    if (Modes.gain == MODES_AUTO_GAIN) {
+        fprintf(stderr, "rtlsdr: enabling tuner AGC\n");
+        rtlsdr_set_tuner_gain_mode(RTLSDR.dev, 1);
+    } else {
+        int *gains;
+        int numgains;
+
+        numgains = rtlsdr_get_tuner_gains(RTLSDR.dev, NULL);
+        if (numgains <= 0) {
+            fprintf(stderr, "rtlsdr: error getting tuner gains\n");
+            return false;
+        }
+
+        gains = malloc(numgains * sizeof(int));
+        if (rtlsdr_get_tuner_gains(RTLSDR.dev, gains) != numgains) {
+            fprintf(stderr, "rtlsdr: error getting tuner gains\n");
+            free(gains);
+            return false;
+        }
+
+        int target = (Modes.gain == MODES_MAX_GAIN ? 9999 : Modes.gain);
+        int closest = -1;
+
+        for (int i = 0; i < numgains; ++i) {
+            if (closest == -1 || abs(gains[i] - target) < abs(gains[closest] - target))
+                closest = i;
+        }
+
+        free(gains);
+
+        rtlsdr_set_tuner_gain(RTLSDR.dev, gains[closest]);
+        fprintf(stderr, "rtlsdr: tuner gain set to %.1f dB\n",
+                rtlsdr_get_tuner_gain(RTLSDR.dev)/10.0);
+    }
+
+    if (RTLSDR.digital_agc) {
+        fprintf(stderr, "rtlsdr: enabling digital AGC\n");
+        rtlsdr_set_agc_mode(RTLSDR.dev, 1);
+    }
+
+    rtlsdr_set_freq_correction(RTLSDR.dev, RTLSDR.ppm_error);
+    rtlsdr_set_center_freq(RTLSDR.dev, Modes.freq);
+    rtlsdr_set_sample_rate(RTLSDR.dev, (unsigned)Modes.sample_rate);
+
+    rtlsdr_reset_buffer(RTLSDR.dev);
+
+    RTLSDR.converter = init_converter(INPUT_UC8,
+                                      Modes.sample_rate,
+                                      Modes.dc_filter,
+                                      &RTLSDR.converter_state);
+    if (!RTLSDR.converter) {
+        fprintf(stderr, "rtlsdr: can't initialize sample converter\n");
+        rtlsdrClose();
+        return false;
+    }
+
+    return true;
+}
+
+static struct timespec rtlsdr_thread_cpu;
+
+void rtlsdrCallback(unsigned char *buf, uint32_t len, void *ctx) {
+    struct mag_buf *outbuf;
+    struct mag_buf *lastbuf;
+    uint32_t slen;
+    unsigned next_free_buffer;
+    unsigned free_bufs;
+    unsigned block_duration;
+
+    static int was_odd = 0; // paranoia!!
+    static int dropping = 0;
+    static uint64_t sampleCounter = 0;
+
+    MODES_NOTUSED(ctx);
+
+    // Lock the data buffer variables before accessing them
+    pthread_mutex_lock(&Modes.data_mutex);
+    if (Modes.exit) {
+        rtlsdr_cancel_async(RTLSDR.dev); // ask our caller to exit
+    }
+
+    next_free_buffer = (Modes.first_free_buffer + 1) % MODES_MAG_BUFFERS;
+    outbuf = &Modes.mag_buffers[Modes.first_free_buffer];
+    lastbuf = &Modes.mag_buffers[(Modes.first_free_buffer + MODES_MAG_BUFFERS - 1) % MODES_MAG_BUFFERS];
+    free_bufs = (Modes.first_filled_buffer - next_free_buffer + MODES_MAG_BUFFERS) % MODES_MAG_BUFFERS;
+
+    // Paranoia! Unlikely, but let's go for belt and suspenders here
+
+    if (len != MODES_RTL_BUF_SIZE) {
+        fprintf(stderr, "weirdness: rtlsdr gave us a block with an unusual size (got %u bytes, expected %u bytes)\n",
+                (unsigned)len, (unsigned)MODES_RTL_BUF_SIZE);
+
+        if (len > MODES_RTL_BUF_SIZE) {
+            // wat?! Discard the start.
+            unsigned discard = (len - MODES_RTL_BUF_SIZE + 1) / 2;
+            outbuf->dropped += discard;
+            buf += discard*2;
+            len -= discard*2;
+        }
+    }
+
+    if (was_odd) {
+        // Drop a sample so we are in sync with I/Q samples again (hopefully)
+        ++buf;
+        --len;
+        ++outbuf->dropped;
+    }
+
+    was_odd = (len & 1);
+    slen = len/2;
+
+    if (free_bufs == 0 || (dropping && free_bufs < MODES_MAG_BUFFERS/2)) {
+        // FIFO is full. Drop this block.
+        dropping = 1;
+        outbuf->dropped += slen;
+        sampleCounter += slen;
+        pthread_mutex_unlock(&Modes.data_mutex);
+        return;
+    }
+
+    dropping = 0;
+    pthread_mutex_unlock(&Modes.data_mutex);
+
+    // Compute the sample timestamp and system timestamp for the start of the block
+    outbuf->sampleTimestamp = sampleCounter * 12e6 / Modes.sample_rate;
+    sampleCounter += slen;
+    block_duration = 1e9 * slen / Modes.sample_rate;
+
+    // Get the approx system time for the start of this block
+    clock_gettime(CLOCK_REALTIME, &outbuf->sysTimestamp);
+    outbuf->sysTimestamp.tv_nsec -= block_duration;
+    normalize_timespec(&outbuf->sysTimestamp);
+
+    // Copy trailing data from last block (or reset if not valid)
+    if (outbuf->dropped == 0) {
+        memcpy(outbuf->data, lastbuf->data + lastbuf->length, Modes.trailing_samples * sizeof(uint16_t));
+    } else {
+        memset(outbuf->data, 0, Modes.trailing_samples * sizeof(uint16_t));
+    }
+
+    // Convert the new data
+    outbuf->length = slen;
+    RTLSDR.converter(buf, &outbuf->data[Modes.trailing_samples], slen, RTLSDR.converter_state, &outbuf->mean_level, &outbuf->mean_power);
+
+    // Push the new data to the demodulation thread
+    pthread_mutex_lock(&Modes.data_mutex);
+
+    Modes.mag_buffers[next_free_buffer].dropped = 0;
+    Modes.mag_buffers[next_free_buffer].length = 0;  // just in case
+    Modes.first_free_buffer = next_free_buffer;
+
+    // accumulate CPU while holding the mutex, and restart measurement
+    end_cpu_timing(&rtlsdr_thread_cpu, &Modes.reader_cpu_accumulator);
+    start_cpu_timing(&rtlsdr_thread_cpu);
+
+    pthread_cond_signal(&Modes.data_cond);
+    pthread_mutex_unlock(&Modes.data_mutex);
+}
+
+void rtlsdrRun()
+{
+    if (!RTLSDR.dev) {
+        return;
+    }
+
+    start_cpu_timing(&rtlsdr_thread_cpu);
+
+    while (!Modes.exit) {
+        rtlsdr_read_async(RTLSDR.dev, rtlsdrCallback, NULL,
+                          /* MODES_RTL_BUFFERS */ 4,
+                          MODES_RTL_BUF_SIZE);
+    }
+}
+
+void rtlsdrClose()
+{
+    if (RTLSDR.dev) {
+        rtlsdr_close(RTLSDR.dev);
+        RTLSDR.dev = NULL;
+    }
+
+    if (RTLSDR.converter) {
+        cleanup_converter(RTLSDR.converter_state);
+        RTLSDR.converter = NULL;
+        RTLSDR.converter_state = NULL;
+    }
+}

sdr_rtlsdr.h

@@ -0,0 +1,13 @@
+#ifndef SDR_RTLSDR_H
+#define SDR_RTLSDR_H
+
+// Support for DVB-T dongles in SDR mode via librtlsdr
+
+void rtlsdrInitConfig();
+void rtlsdrShowHelp();
+bool rtlsdrOpen();
+void rtlsdrRun();
+void rtlsdrClose();
+bool rtlsdrHandleOption(int argc, char **argv, int *jptr);
+
+#endif