├── .gitignore ├── LICENSE ├── Makefile ├── README.md └── rtlmic.c /.gitignore: -------------------------------------------------------------------------------- 1 | rtlmic 2 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /Makefile: -------------------------------------------------------------------------------- 1 | PREFIX ?= /usr 2 | CFLAGS ?= -O3 3 | 4 | all: rtlmic 5 | 6 | rtlmic: rtlmic.c 7 | gcc -Wall $(CFLAGS) -o $@ $< -lrtlsdr -lvolk -lm -ljack 8 | 9 | install: rtlmic 10 | install rtlmic $(PREFIX)/bin/rtlmic 11 | 12 | clean: 13 | rm -f rtlmic 14 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # rtlmic: Wireless microphone receiver for RTL-SDR 2 | 3 | rtlmic is a multichannel FM microphone receiver/demodulator for RTL-SDR cards. 4 | It outputs realtime audio to JACK. 5 | 6 | ## Installation 7 | 8 | Dependencies: 9 | 10 | * libjack 11 | * libvolk 12 | * librtlsdr 13 | 14 | To build and install, just use `make && sudo make install`. 15 | 16 | ## Usage 17 | 18 | Basic usage is simply: 19 | 20 | ```shell 21 | $ rtlmic [channel 1 frequency] [channel 2 frequency]... 22 | ``` 23 | 24 | You can capture as many channels as your CPU can handle, as long as they all 25 | fit within the capture bandwidth of the RTL-SDR. 26 | 27 | Use `rtlmic --help` to see all available options. 28 | 29 | In order to get back correct audio, you should know certain parameters about 30 | your microphones: the companding ratio (`-e`), the companding tau (`-E`), the 31 | deemphasis tau (`-M`), and the FM deviation (`-w`). 32 | 33 | Most microphones use 2:1 companding (the default ratio). The companding 34 | tau is usually determined by an R-C filter in the microphone, connected to the 35 | compressor chip. In my case, the component values are 10kΩ and 1µF, which gives 36 | 10kΩ * 1µF = 10ms tau. The deemphasis tau just affects the frequency response: 37 | the higher the tau, the less high-end the microphone will have. If you do not 38 | know the exact values for your microphone, you can just try and see what sounds 39 | best. 40 | 41 | By default, the RTL-SDR will be tuned to the frequency in between the highest 42 | and lowest channel specified. However, if you have a channel near that point 43 | (e.g. if you are only capturing one channel, or an odd number of evenly spaced 44 | channels) then you may experience additional noise, as the RTL-SDR does not 45 | perform well near DC. You can work around this by choosing a different center 46 | frequency with `-f`. 47 | 48 | You may want to play around with other parameters, e.g. adjusting the tuner gain 49 | (`-g`) and squelch threshold (`-s`), as well as the audio gain (`-a`). If your 50 | channels are spaced closely together, lower the transition width (`-t`) and use 51 | a tight deviation (`-w`). Note that lowering the transition width increases CPU 52 | usage significantly. 53 | 54 | If you have persistent buffer over/underrun problems, you should try changing 55 | the buffering settings `-b` and `-B`, as well as the JACK period size in the 56 | JACK server. A few under/overruns on startup are normal, as it takes some time 57 | for rtlmic to lock onto the exact ratio between the true SDR and JACK 58 | frequencies. 59 | -------------------------------------------------------------------------------- /rtlmic.c: -------------------------------------------------------------------------------- 1 | /* 2 | Copyright (C) 2017 Hector Martin "marcan" 3 | 4 | This program is free software: you can redistribute it and/or modify 5 | it under the terms of the GNU General Public License as published by 6 | the Free Software Foundation, version 3. 7 | 8 | This program is distributed in the hope that it will be useful, 9 | but WITHOUT ANY WARRANTY; without even the implied warranty of 10 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 11 | GNU General Public License for more details. 12 | 13 | You should have received a copy of the GNU General Public License 14 | along with this program. If not, see . 15 | */ 16 | 17 | #include 18 | #include 19 | #include 20 | #include 21 | #include 22 | #include 23 | #include 24 | 25 | #include 26 | #include 27 | #include 28 | #include 29 | #include 30 | 31 | struct onepole { 32 | float acc; 33 | float alpha; 34 | }; 35 | 36 | struct channel { 37 | int f; 38 | int df; 39 | 40 | int ntaps; 41 | float complex **taps; 42 | 43 | float complex phase; 44 | float complex phi; 45 | float complex *sample; 46 | float complex last; 47 | 48 | struct onepole squelch_lpf; 49 | float squelch_ctr; 50 | struct onepole dc_lpf; 51 | struct onepole env_lpf; 52 | struct onepole emph_lpf; 53 | 54 | float acc; 55 | int cnt; 56 | float *audio_buf1; 57 | float *p1; 58 | 59 | jack_ringbuffer_t *rb; 60 | int running; 61 | jack_port_t *port; 62 | float history[3]; 63 | float mu; 64 | }; 65 | 66 | struct state { 67 | int verbose; 68 | 69 | // Sampling 70 | int tuner_gain; // Tuner gain in .1dB increments 71 | rtlsdr_dev_t *dev; 72 | int fs; // Sampling frequency 73 | int fc; // Center tuning frequency 74 | 75 | // Buffering 76 | int blockcnt; // Number of outstanding USB transactions 77 | int blocksz; // Buffer size in samples (raw bytes / 2) 78 | int bufpad; // Number of history samples to keep 79 | int bufsz; // Total buffer size 80 | float complex *buffer; 81 | int p; // Current buffer pointer 82 | 83 | // Filtering 84 | struct onepole dc_lpf_i; 85 | struct onepole dc_lpf_q; 86 | int width; // Filter half-width (deviation) 87 | int twidth; // Transition band width 88 | int decimation; // Decimation after filtering 89 | float fi; // Intermediate frequency (fs / decimation) 90 | int ntaps; // Number of filter taps 91 | int align; // Required platform alignment for buffers in bytes 92 | int nalign; // Alignment in complex samples 93 | 94 | // Audio processing 95 | float fa; // Audio sampling frequency 96 | int adecimation; // Decimation before audio processing 97 | float squelch_thr; // Squelch threshold 98 | float squelch_tau; // Squelch LPF tau 99 | float dc_tau; // DC removal LPF tau 100 | float exp_tau; // Expander tau 101 | float exp_ratio; // Expander ratio 102 | float emph_tau; // De-emphasis tau 103 | float audio_gain; // Audio gain factor 104 | 105 | // Audio buffering/resampling 106 | int fjack; // JACK sample rate 107 | int rb_size; // JACK ringbuffer size 108 | int iblock; // Input (SDR) block size at AF frequency; 109 | int pblock; // Output (JACK) block size at AF frequency; 110 | int oblock; // Output (JACK) block size 111 | int low_thresh; // Ring buffer low threshold 112 | int high_thresh; // Ring buffer high threshold 113 | float dmu; // Downsampling factor 114 | struct onepole buf_lpf; // Resampling loop lpf 115 | 116 | // Channels 117 | int nch; 118 | struct channel *ch; 119 | 120 | jack_client_t *client; 121 | int jack_alive; 122 | }; 123 | 124 | struct state st; 125 | 126 | static int compute_ntaps(int transition_width, int sample_rate) 127 | { 128 | float delta_f = transition_width / (float)sample_rate; 129 | return (((int)(3.3f / delta_f + 0.5f)) & ~1) + 1; 130 | } 131 | 132 | static void generate_lpf(float complex *taps, int ntaps, int fs, int width) 133 | { 134 | int M = ntaps / 2; 135 | double fwT0 = 2 * M_PI * width / (double)fs; 136 | 137 | // Sinc function with Hamming window 138 | // Taps are real here but stored as complex for rotation later 139 | taps[M] = fwT0; 140 | float gain = taps[M]; 141 | for (int i = 1; i <= M; i++) { 142 | float c = sin(i * fwT0) / i * (0.54 + 0.46 * cos(M_PI * i / (double)M)); 143 | gain += 2 * c; 144 | taps[M-i] = taps[M+i] = c; 145 | } 146 | 147 | // Normalize 148 | gain = 1.f / gain; 149 | for(int i = 0; i < ntaps; i++) 150 | taps[i] *= gain; 151 | } 152 | 153 | static void init_onepole(struct onepole *filt, float fs, float tau) 154 | { 155 | if (tau == 0) 156 | filt->alpha = 1.0; 157 | else 158 | filt->alpha = 1.0 - expf(-(1.0 / fs) / tau); 159 | filt->acc = 0; 160 | } 161 | 162 | static inline float filter_onepole(struct onepole *filt, float v) 163 | { 164 | filt->acc = filt->acc * (1.f - filt->alpha) + v * filt->alpha; 165 | return filt->acc; 166 | } 167 | 168 | static inline float cubic(float *y, float mu) 169 | { 170 | float a0,a1,a2,mu2; 171 | 172 | mu2 = mu * mu; 173 | a0 = y[3] - y[2] - y[0] + y[1]; 174 | a1 = y[0] - y[1] - a0; 175 | a2 = y[2] - y[0]; 176 | 177 | return a0 * mu * mu2 + a1 * mu2 + a2 * mu + y[1]; 178 | } 179 | 180 | static void init_channel(int c) 181 | { 182 | struct channel *ch = &st.ch[c]; 183 | 184 | ch->df = st.fc - ch->f; 185 | ch->ntaps = st.ntaps; 186 | 187 | ch->taps = malloc(st.nalign * sizeof(float complex *)); 188 | for (int i = 0; i < st.nalign; i++) { 189 | ch->taps[i] = volk_malloc( 190 | sizeof(float complex) * (ch->ntaps + st.nalign), st.align); 191 | memset(ch->taps[i], 0, sizeof(float complex) * ch->ntaps); 192 | } 193 | 194 | generate_lpf(ch->taps[0], st.ntaps, st.fs, st.width); 195 | 196 | // Shift LPF into BPF 197 | double fwT0 = 2 * M_PI * ch->df / (double)st.fs; 198 | for (int i = 0; i < st.ntaps; i++) { 199 | ch->taps[0][i] = ch->taps[0][i] * cexpf(lv_cmake(0, i * fwT0)); 200 | } 201 | // Frequency shifter 202 | ch->phase = lv_cmake(1.f, 0.f); 203 | ch->phi = cexp(lv_cmake(0, fwT0 * st.decimation)); 204 | 205 | // Build offset tap vectors, padded with zeros, for SIMD alignment 206 | for (int i = 1; i < st.nalign; i++) 207 | memcpy(&ch->taps[i][i], ch->taps[0], st.ntaps * sizeof(float complex)); 208 | 209 | // Make sure output sample buffer is aligned too 210 | ch->sample = volk_malloc(sizeof(float complex), st.align); 211 | 212 | init_onepole(&ch->squelch_lpf, st.fi, st.squelch_tau); 213 | init_onepole(&ch->dc_lpf, st.fa, st.dc_tau); 214 | init_onepole(&ch->env_lpf, st.fa, st.exp_tau); 215 | init_onepole(&ch->emph_lpf, st.fa, st.emph_tau); 216 | 217 | ch->audio_buf1 = malloc(st.iblock * sizeof(float)); 218 | ch->p1 = ch->audio_buf1; 219 | 220 | ch->rb = jack_ringbuffer_create(st.rb_size * sizeof(float)); 221 | 222 | char name[16]; 223 | sprintf(name, "channel_%d", c + 1); 224 | ch->port = jack_port_register(st.client, name, JACK_DEFAULT_AUDIO_TYPE, 225 | JackPortIsOutput, 0); 226 | } 227 | 228 | static void process_channel_sample(int c, float complex *buf) 229 | { 230 | struct channel *ch = &st.ch[c]; 231 | 232 | uintptr_t pad = (((uintptr_t)buf) & (st.align - 1)) / sizeof(float complex); 233 | 234 | // Bandpass filter 235 | volk_32fc_x2_dot_prod_32fc_a(ch->sample, buf - pad, ch->taps[pad], 236 | st.ntaps + pad); 237 | // Shift frequency 238 | float complex ss = *ch->sample * ch->phase; 239 | ch->phase *= ch->phi; 240 | // Demodulate FM 241 | float s = cargf(lv_conj(ch->last) * ss); 242 | // Squelch 243 | if (filter_onepole(&ch->squelch_lpf, cabsf(ss)) < st.squelch_thr) { 244 | s = 0; 245 | ch->squelch_ctr = 0; 246 | } else if (ch->squelch_ctr < 1.0) { 247 | s *= ch->squelch_ctr; 248 | ch->squelch_ctr += 0.00005; 249 | } 250 | // Simple boxcar filter for audio decimation 251 | ch->acc += s; 252 | if (++ch->cnt >= st.adecimation) { 253 | *(ch->p1++) = ch->acc / st.adecimation; 254 | ch->cnt = 0; 255 | ch->acc = 0; 256 | } 257 | 258 | ch->last = ss; 259 | } 260 | 261 | static void process_channel_audio(int c) 262 | { 263 | struct channel *ch = &st.ch[c]; 264 | 265 | jack_ringbuffer_data_t wdata[2]; 266 | 267 | jack_ringbuffer_get_write_vector(ch->rb, wdata); 268 | 269 | float *dp = (void*)wdata[0].buf; 270 | int wcnt = wdata[0].len / sizeof(float); 271 | int put = 0; 272 | 273 | float *p = ch->audio_buf1; 274 | while (p != ch->p1) { 275 | if (!wcnt) { 276 | if (wdata[1].len) { 277 | dp = (void*)wdata[1].buf; 278 | wcnt = wdata[1].len / sizeof(float); 279 | wdata[1].len = 0; 280 | } else { 281 | if (c == 0) 282 | fprintf(stderr, "Ring buffer overrun! Left=%d \n", 283 | (int)(ch->p1 - p)); 284 | break; 285 | } 286 | } 287 | 288 | float s = *p++; 289 | // Remove DC 290 | s -= filter_onepole(&ch->dc_lpf, s); 291 | // Expander 292 | s *= powf(filter_onepole(&ch->env_lpf, fabsf(s)), st.exp_ratio - 1.f); 293 | // De-emphasis 294 | s = filter_onepole(&ch->emph_lpf, s); 295 | // Gain 296 | s *= st.audio_gain; 297 | *dp++ = s; 298 | wcnt--; 299 | put++; 300 | } 301 | jack_ringbuffer_write_advance(ch->rb, put * sizeof(float)); 302 | ch->p1 = ch->audio_buf1; 303 | 304 | // Normalize phase to make sure it doesn't go wacky 305 | ch->phase /= cabsf(ch->phase); 306 | } 307 | 308 | 309 | void got_samples(unsigned char *buf, uint32_t len, void *ctx) 310 | { 311 | if (!st.jack_alive) 312 | return; 313 | 314 | if (len != st.blocksz * 2) { 315 | printf("Got %d bytes, expected %d!\n", len, st.blocksz); 316 | exit(1); 317 | } 318 | 319 | memcpy(st.buffer, &st.buffer[st.blocksz], 320 | st.bufpad * sizeof(float complex)); 321 | 322 | float complex *dst = &st.buffer[st.ntaps]; 323 | len /= 2; 324 | 325 | while (len--) { 326 | float i = (buf[0] - 127) / 127.f; 327 | float q = (buf[1] - 127) / 127.f; 328 | i -= filter_onepole(&st.dc_lpf_i, i); 329 | q -= filter_onepole(&st.dc_lpf_q, q); 330 | *dst++ = lv_cmake(i, q); 331 | buf += 2; 332 | } 333 | 334 | int p = st.p; 335 | int max = st.blocksz + st.decimation; 336 | float complex *pbuf = &st.buffer[p]; 337 | for (; p < max; p += st.decimation) 338 | { 339 | for (int i = 0; i < st.nch; i++) 340 | process_channel_sample(i, pbuf); 341 | pbuf += st.decimation; 342 | } 343 | st.p = p - st.blocksz; 344 | 345 | for (int i = 0; i < st.nch; i++) { 346 | process_channel_audio(i); 347 | } 348 | 349 | float fullness = jack_ringbuffer_read_space(st.ch[0].rb) / 350 | sizeof(float) / (float)st.rb_size; 351 | 352 | float f2 = filter_onepole(&st.buf_lpf, fullness); 353 | 354 | st.dmu = st.fa / st.fjack * (1.0 + 0.2 * (f2 - 0.5)); 355 | 356 | if (st.verbose >= 2) 357 | fprintf(stderr, "RB fullness: %.02f (%.02f) AF=%.01f \r", 358 | 100.0f * fullness, 100.0f * f2, st.dmu * st.fjack); 359 | 360 | } 361 | 362 | void jack_shutdown (void *arg) 363 | { 364 | exit (1); 365 | } 366 | 367 | int jack_process (jack_nframes_t nframes, void *arg) 368 | { 369 | st.jack_alive = 1; 370 | for (int c = 0; c < st.nch; c++) { 371 | struct channel *ch = &st.ch[c]; 372 | float *o = (float *)jack_port_get_buffer(ch->port, nframes); 373 | jack_ringbuffer_data_t rvec[2]; 374 | jack_ringbuffer_get_read_vector(ch->rb, rvec); 375 | int avail = (rvec[0].len + rvec[1].len) / sizeof(float); 376 | int left = nframes; 377 | int read = 0; 378 | 379 | if (!ch->running && avail < (st.rb_size / 2)) { 380 | memset(o, 0, nframes * sizeof(float)); 381 | continue; 382 | } 383 | 384 | avail = rvec[0].len / sizeof(float); 385 | float *r = (void *)rvec[0].buf; 386 | ch->running = 1; 387 | 388 | float y[4], mu=ch->mu, dmu=st.dmu; 389 | memcpy(y, ch->history, sizeof(float) * 4); 390 | 391 | while (left--) { 392 | *o++ = cubic(y, ch->mu); 393 | mu += dmu; 394 | while (mu >= 1.f) { 395 | y[0] = y[1]; 396 | y[1] = y[2]; 397 | y[2] = y[3]; 398 | if (!avail) { 399 | if (rvec[1].len) { 400 | avail = rvec[1].len / sizeof(float); 401 | rvec[1].len = 0; 402 | r = (void *)rvec[1].buf; 403 | } else { 404 | if (c == 0) 405 | fprintf(stderr, 406 | "Ring buffer underrun! left=%d \n", 407 | left); 408 | memset(o, 0, sizeof(float) * left); 409 | y[3] = 0; 410 | while (mu >= 1.f) 411 | mu -= 1.f; 412 | ch->running = 0; 413 | goto next_channel; 414 | } 415 | } 416 | y[3] = *r++; 417 | mu -= 1.f; 418 | read++; 419 | avail--; 420 | } 421 | } 422 | next_channel: 423 | jack_ringbuffer_read_advance(ch->rb, read * sizeof(float)); 424 | ch->mu = mu; 425 | memcpy(ch->history, y, sizeof(float) * 4); 426 | } 427 | 428 | return 0; 429 | } 430 | 431 | static struct option long_options[] = 432 | { 433 | {"verbose", no_argument, 0, 'v'}, 434 | {"client-name", required_argument, 0, 'c'}, 435 | {"fc", required_argument, 0, 'f'}, 436 | {"rate", required_argument, 0, 'r'}, 437 | {"tuner-gain", required_argument, 0, 'g'}, 438 | {"blocksize", required_argument, 0, 'b'}, 439 | {"blocks", required_argument, 0, 'n'}, 440 | {"width", required_argument, 0, 'w'}, 441 | {"transition-width", required_argument, 0, 't'}, 442 | {"squelch", required_argument, 0, 's'}, 443 | {"squelch-tau", required_argument, 0, 'S'}, 444 | {"dc-tau", required_argument, 0, 'D'}, 445 | {"expander-ratio", required_argument, 0, 'e'}, 446 | {"expander-tau", required_argument, 0, 'E'}, 447 | {"deemph-tau", required_argument, 0, 'M'}, 448 | {0, 0, 0, 0} 449 | }; 450 | 451 | void usage(void) 452 | { 453 | fprintf(stderr, "Usage: rtlmic [OPTION]... [FREQUENCY]...\n"); 454 | fprintf(stderr, "rtlmic - Demodulate FM microphones using an RTL-SDR\n"); 455 | fprintf(stderr, "\n"); 456 | fprintf(stderr, " -h, --help this help\n"); 457 | fprintf(stderr, " -v, --verbose be verbose\n"); 458 | fprintf(stderr, " -c, --client-name=NAME JACK client name (default: rtlmic)\n"); 459 | fprintf(stderr, " -f, --fc=HZ center frequency to tune to\n"); 460 | fprintf(stderr, " (default: auto)\n"); 461 | fprintf(stderr, " -r, --rate=HZ capture sample rate\n"); 462 | fprintf(stderr, " (default: auto)\n"); 463 | fprintf(stderr, " -g, --tuner-gain=DB tuner gain in dB\n"); 464 | fprintf(stderr, " (default: 10 dB)\n"); 465 | fprintf(stderr, " -b, --blocksize=SIZE capture block size in samples\n"); 466 | fprintf(stderr, " must be a multiple of 256\n"); 467 | fprintf(stderr, " (default: 8192)\n"); 468 | fprintf(stderr, " -n, --blocks=NUMBER number of outstanding transfers\n"); 469 | fprintf(stderr, " (default: 4)\n"); 470 | fprintf(stderr, " -w, --width=HZ filter half-width (FM deviation)\n"); 471 | fprintf(stderr, " (default: 100000 Hz)\n"); 472 | fprintf(stderr, " -t, --transition-width=HZ\n"); 473 | fprintf(stderr, " filter transition bandwidth\n"); 474 | fprintf(stderr, " (default: 50000 Hz)\n"); 475 | fprintf(stderr, " -s, --squelch=DB squelch level in dB\n"); 476 | fprintf(stderr, " (default: -50 dB)\n"); 477 | fprintf(stderr, " -S, --squelch-tau=MS squelch time constant in msec\n"); 478 | fprintf(stderr, " (default: 0.1 ms)\n"); 479 | fprintf(stderr, " -D, --dc-tau=S DC removal time constant in sec\n"); 480 | fprintf(stderr, " (default: 2 s)\n"); 481 | fprintf(stderr, " -e, --expander-ratio=N expander ratio. 1=1:1, 2=2:1, etc.\n"); 482 | fprintf(stderr, " (default: 2 (2:1))\n"); 483 | fprintf(stderr, " -E, --expander-tau=MS expander time constant in msec\n"); 484 | fprintf(stderr, " (default: 10 ms)\n"); 485 | fprintf(stderr, " -M, --deemph-tau=US de-emphasis time constant in usec\n"); 486 | fprintf(stderr, " (default: 75 us)\n"); 487 | fprintf(stderr, " -a, --audio-gain=DB audio gain in dB (default: 0 dB)\n"); 488 | } 489 | 490 | // "Nice" sample rates for RTL-SDR 491 | int sample_rates[] = { 492 | 240000, 300000, 960000, 1152000, 1200000, 1440000, 493 | 1600000, 1800000, 1920000, 2400000, 2880000, 3200000, 494 | 0 495 | }; 496 | 497 | int main(int argc, char **argv) 498 | { 499 | memset(&st, 0, sizeof(st)); 500 | 501 | char *client_name = "rtlmic"; 502 | 503 | int fmin = INT_MAX; 504 | int fmax = 0; 505 | 506 | st.tuner_gain = 100; 507 | st.blocksz = 8192; 508 | st.blockcnt = 4; 509 | st.width = 100000; 510 | st.twidth = 50000; 511 | st.squelch_thr = powf(10.f, -50 / 20.f); 512 | st.squelch_tau = 0.0001f; 513 | st.dc_tau = 2.f; 514 | st.exp_tau = 0.01f; 515 | st.exp_ratio = 2.f; 516 | st.emph_tau = 75e-6; 517 | st.audio_gain = 1.f; 518 | 519 | while (1) { 520 | int c = getopt_long(argc, argv, "vc:f:r:g:b:n:w:t:s:S:D:e:E:M:a:", 521 | long_options, NULL); 522 | if (c == -1) 523 | break; 524 | 525 | switch (c) 526 | { 527 | case 'v': 528 | st.verbose++; 529 | break; 530 | case 'c': 531 | client_name = optarg; 532 | break; 533 | case 'f': 534 | st.fc = atoi(optarg); 535 | break; 536 | case 'r': 537 | st.fs = atoi(optarg); 538 | break; 539 | case 'g': 540 | st.tuner_gain = atoi(optarg) * 10; 541 | break; 542 | case 'b': 543 | st.blocksz = atoi(optarg); 544 | break; 545 | case 'n': 546 | st.blockcnt = atoi(optarg); 547 | break; 548 | case 'w': 549 | st.width = atoi(optarg); 550 | break; 551 | case 't': 552 | st.twidth = atoi(optarg); 553 | break; 554 | case 's': 555 | st.squelch_thr = powf(10.f, atoi(optarg) / 20.f); 556 | break; 557 | case 'S': 558 | st.squelch_tau = atof(optarg) / 1000.f; 559 | break; 560 | case 'D': 561 | st.dc_tau = atof(optarg); 562 | break; 563 | case 'e': 564 | st.exp_ratio = atof(optarg); 565 | break; 566 | case 'E': 567 | st.exp_tau = atof(optarg) / 1000.0; 568 | break; 569 | case 'M': 570 | st.emph_tau = atof(optarg) / 1000000.0; 571 | break; 572 | case 'a': 573 | st.audio_gain = powf(10.f, atoi(optarg) / 20.f); 574 | break; 575 | case 'h': 576 | usage(); 577 | return 1; 578 | default: 579 | usage(); 580 | return 1; 581 | } 582 | } 583 | 584 | if (optind == argc) 585 | { 586 | fprintf(stderr, "No frequencies specified.\n"); 587 | usage(); 588 | return 1; 589 | } 590 | 591 | st.ch = malloc((argc - optind) * sizeof(struct channel)); 592 | memset(st.ch, 0, (argc - optind) * sizeof(struct channel)); 593 | 594 | while (optind < argc) 595 | { 596 | int f = atoi(argv[optind++]); 597 | st.ch[st.nch].f = f; 598 | if (f < fmin) 599 | fmin = f; 600 | if (f > fmax) 601 | fmax = f; 602 | if (st.verbose) 603 | fprintf(stderr, "Channel %d: %d Hz\n", st.nch, f); 604 | st.nch++; 605 | } 606 | //st.nch = 1; 607 | 608 | st.align = volk_get_alignment(); 609 | st.nalign = st.align / sizeof(float complex); 610 | if (st.verbose) 611 | fprintf(stderr, "Platform alignment: %d (%d samples)\n", 612 | st.align, st.nalign); 613 | 614 | if (st.fc == 0) { 615 | st.fc = (fmin + fmax) / 2; 616 | } 617 | if (st.verbose) 618 | fprintf(stderr, "Center frequency: %d Hz\n", st.fc); 619 | 620 | if (st.fs == 0) { 621 | // Give us one extra filter-width worth of padding 622 | int need_rate = (fmax - fmin) + 3 * st.width; 623 | for (int i = 0; st.fs < need_rate; i++) { 624 | if (!sample_rates[i]) { 625 | fprintf(stderr, "Channels are too far apart! " 626 | "Total bandwidth needed is %d Hz\n", need_rate); 627 | return 1; 628 | } 629 | st.fs = sample_rates[i]; 630 | } 631 | } 632 | if (st.verbose) { 633 | fprintf(stderr, "RTL-SDR sample rate: %d Hz\n", st.fs); 634 | fprintf(stderr, "RTL-SDR block size: %d\n", st.blocksz); 635 | } 636 | 637 | jack_status_t jack_status; 638 | 639 | st.client = jack_client_open(client_name, JackNullOption, &jack_status); 640 | if (!st.client) { 641 | fprintf (stderr, "jack server not running?\n"); 642 | return 1; 643 | } 644 | st.fjack = jack_get_sample_rate(st.client); 645 | st.oblock = jack_get_buffer_size(st.client); 646 | if (st.verbose) { 647 | fprintf(stderr, "JACK sample rate: %d Hz\n", st.fjack); 648 | } 649 | 650 | st.decimation = st.fs / (st.width * 2); 651 | st.fi = (float)st.fs / st.decimation; 652 | st.adecimation = (int)st.fi / st.fjack; 653 | st.fa = st.fi / st.adecimation; 654 | 655 | st.ntaps = compute_ntaps(st.twidth, st.fs); 656 | 657 | st.bufpad = st.ntaps + st.decimation; 658 | st.bufsz = st.blocksz + st.bufpad; 659 | st.buffer = volk_malloc(sizeof(float complex) * st.bufsz, st.align); 660 | st.p = st.decimation; 661 | memset(st.buffer, 0, sizeof(float complex) * st.bufsz); 662 | 663 | st.iblock = (st.blocksz / st.decimation + 1) / st.adecimation + 1; 664 | st.pblock = (int)((float)st.oblock / st.fjack * st.fa + 5); 665 | 666 | st.low_thresh = st.iblock; 667 | if (st.pblock < st.iblock) 668 | st.low_thresh = st.pblock; 669 | 670 | st.low_thresh += st.low_thresh / 3; 671 | 672 | st.rb_size = 128; 673 | if (st.rb_size < 3 * st.iblock) 674 | st.rb_size = 3 * st.iblock; 675 | if (st.rb_size < 3 * st.oblock) 676 | st.rb_size = 3 * st.oblock; 677 | 678 | st.high_thresh = st.rb_size - st.low_thresh; 679 | 680 | st.dmu = st.fa / st.fjack; 681 | 682 | if (st.verbose) { 683 | fprintf(stderr, "Decimation: %d\n", st.decimation); 684 | fprintf(stderr, "IF: %.2f Hz\n", st.fi); 685 | fprintf(stderr, "Audio decimation: %d\n", st.adecimation); 686 | fprintf(stderr, "AF: %.2f Hz\n", st.fa); 687 | fprintf(stderr, "Filter taps: %d\n", st.ntaps); 688 | fprintf(stderr, "Buffer sizes: %d/%d/%d -> %d\n", 689 | st.iblock, st.pblock, st.oblock, st.rb_size); 690 | fprintf(stderr, "Buffer low threshold: %d\n", st.low_thresh); 691 | } 692 | 693 | init_onepole(&st.dc_lpf_i, st.fs, 1.); 694 | init_onepole(&st.dc_lpf_q, st.fs, 1.); 695 | 696 | init_onepole(&st.buf_lpf, 1., 200.); 697 | st.buf_lpf.acc = 0.5; 698 | 699 | for (int i = 0; i < st.nch; i++) 700 | init_channel(i); 701 | 702 | int r = rtlsdr_open(&st.dev, 0); 703 | if (r < 0) { 704 | fprintf(stderr, "Failed to open rtlsdr device: error %d.\n", r); 705 | return 1; 706 | } 707 | 708 | rtlsdr_set_offset_tuning(st.dev, 1); 709 | rtlsdr_set_tuner_gain(st.dev, st.tuner_gain); 710 | rtlsdr_set_agc_mode(st.dev, 0); 711 | rtlsdr_reset_buffer(st.dev); 712 | rtlsdr_set_center_freq(st.dev, st.fc); 713 | rtlsdr_set_sample_rate(st.dev, st.fs); 714 | 715 | jack_set_process_callback(st.client, jack_process, NULL); 716 | jack_on_shutdown(st.client, jack_shutdown, NULL); 717 | if (jack_activate(st.client)) { 718 | fprintf(stderr, "cannot activate client"); 719 | return 1; 720 | } 721 | 722 | rtlsdr_read_async(st.dev, got_samples, NULL, st.blockcnt, st.blocksz * 2); 723 | jack_client_close(st.client); 724 | } 725 | --------------------------------------------------------------------------------