git.sesse.net Git - c64tapwav/blob - decode.cpp

   1 #include <stdio.h>
   2 #include <string.h>
   3 #include <math.h>
   4 #include <assert.h>
   5 #include <limits.h>
   6 #include <getopt.h>
   7 #include <vector>
   8 #include <algorithm>
   9
  10 #include "audioreader.h"
  11 #include "interpolate.h"
  12 #include "level.h"
  13 #include "tap.h"
  14
  15 #define BUFSIZE 4096
  16 #define C64_FREQUENCY 985248
  17 #define SYNC_PULSE_START 1000
  18 #define SYNC_PULSE_END 20000
  19 #define SYNC_PULSE_LENGTH 378.0
  20 #define SYNC_TEST_TOLERANCE 1.10
  21
  22 // SPSA options
  23 #define NUM_FILTER_COEFF 32
  24 #define NUM_ITER 5000
  25 #define A NUM_ITER/10  // approx
  26 #define INITIAL_A 0.005 // A bit of trial and error...
  27 #define INITIAL_C 0.02  // This too.
  28 #define GAMMA 0.166
  29 #define ALPHA 1.0
  30
  31 static float hysteresis_limit = 3000.0 / 32768.0;
  32 static bool do_calibrate = true;
  33 static bool output_cycles_plot = false;
  34 static bool use_filter = false;
  35 static bool do_crop = false;
  36 static float crop_start = 0.0f, crop_end = HUGE_VAL;
  37 static float filter_coeff[NUM_FILTER_COEFF] = { 1.0f };  // The rest is filled with 0.
  38 static bool output_filtered = false;
  39 static bool quiet = false;
  40 static bool do_auto_level = false;
  41 static bool output_leveled = false;
  42 static std::vector<float> train_snap_points;
  43 static bool do_train = false;
  44
  45 // The minimum estimated sound level (for do_auto_level) at any given point.
  46 // If you decrease this, you'll be able to amplify really silent signals
  47 // by more, but you'll also increase the level of silent (ie. noise-only) segments,
  48 // possibly caused misdetected pulses in these segments.
  49 static float min_level = 0.05f;
  50
  51 // between [x,x+1]
  52 double find_zerocrossing(const std::vector<float> &pcm, int x)
  53 {
  54         if (pcm[x] == 0) {
  55                 return x;
  56         }
  57         if (pcm[x + 1] == 0) {
  58                 return x + 1;
  59         }
  60
  61         assert(pcm[x + 1] < 0);
  62         assert(pcm[x] > 0);
  63
  64         double upper = x;
  65         double lower = x + 1;
  66         while (lower - upper > 1e-3) {
  67                 double mid = 0.5f * (upper + lower);
  68                 if (lanczos_interpolate(pcm, mid) > 0) {
  69                         upper = mid;
  70                 } else {
  71                         lower = mid;
  72                 }
  73         }
  74
  75         return 0.5f * (upper + lower);
  76 }
  77
  78 struct pulse {
  79         double time;  // in seconds from start
  80         double len;   // in seconds
  81 };
  82
  83 // Calibrate on the first ~25k pulses (skip a few, just to be sure).
  84 double calibrate(const std::vector<pulse> &pulses) {
  85         if (pulses.size() < SYNC_PULSE_END) {
  86                 fprintf(stderr, "Too few pulses, not calibrating!\n");
  87                 return 1.0;
  88         }
  89
  90         int sync_pulse_end = -1;
  91         double sync_pulse_stddev = -1.0;
  92
  93         // Compute the standard deviation (to check for uneven speeds).
  94         // If it suddenly skyrockets, we assume that sync ended earlier
  95         // than we thought (it should be 25000 cycles), and that we should
  96         // calibrate on fewer cycles.
  97         for (int try_end : { 2000, 4000, 5000, 7500, 10000, 15000, SYNC_PULSE_END }) {
  98                 double sum2 = 0.0;
  99                 for (int i = SYNC_PULSE_START; i < try_end; ++i) {
 100                         double cycles = pulses[i].len * C64_FREQUENCY;
 101                         sum2 += (cycles - SYNC_PULSE_LENGTH) * (cycles - SYNC_PULSE_LENGTH);
 102                 }
 103                 double stddev = sqrt(sum2 / (try_end - SYNC_PULSE_START - 1));
 104                 if (sync_pulse_end != -1 && stddev > 5.0 && stddev / sync_pulse_stddev > 1.3) {
 105                         fprintf(stderr, "Stopping at %d sync pulses because standard deviation would be too big (%.2f cycles); shorter-than-usual trailer?\n",
 106                                 sync_pulse_end, stddev);
 107                         break;
 108                 }
 109                 sync_pulse_end = try_end;
 110                 sync_pulse_stddev = stddev;
 111         }
 112         if (!quiet) {
 113                 fprintf(stderr, "Sync pulse length standard deviation: %.2f cycles\n",
 114                         sync_pulse_stddev);
 115         }
 116
 117         double sum = 0.0;
 118         for (int i = SYNC_PULSE_START; i < sync_pulse_end; ++i) {
 119                 sum += pulses[i].len;
 120         }
 121         double mean_length = C64_FREQUENCY * sum / (sync_pulse_end - SYNC_PULSE_START);
 122         double calibration_factor = SYNC_PULSE_LENGTH / mean_length;
 123         if (!quiet) {
 124                 fprintf(stderr, "Calibrated sync pulse length: %.2f -> %.2f (change %+.2f%%)\n",
 125                         mean_length, SYNC_PULSE_LENGTH, 100.0 * (calibration_factor - 1.0));
 126         }
 127
 128         // Check for pulses outside +/- 10% (sign of misdetection).
 129         for (int i = SYNC_PULSE_START; i < sync_pulse_end; ++i) {
 130                 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
 131                 if (cycles < SYNC_PULSE_LENGTH / SYNC_TEST_TOLERANCE || cycles > SYNC_PULSE_LENGTH * SYNC_TEST_TOLERANCE) {
 132                         fprintf(stderr, "Sync cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
 133                                 pulses[i].time, cycles);
 134                 }
 135         }
 136
 137         return calibration_factor;
 138 }
 139
 140 void output_tap(const std::vector<pulse>& pulses, double calibration_factor)
 141 {
 142         std::vector<char> tap_data;
 143         for (unsigned i = 0; i < pulses.size(); ++i) {
 144                 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
 145                 int len = lrintf(cycles / TAP_RESOLUTION);
 146                 if (i > SYNC_PULSE_END && (cycles < 100 || cycles > 800)) {
 147                         fprintf(stderr, "Cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
 148                                         pulses[i].time, cycles);
 149                 }
 150                 if (len <= 255) {
 151                         tap_data.push_back(len);
 152                 } else {
 153                         int overflow_len = lrintf(cycles);
 154                         tap_data.push_back(0);
 155                         tap_data.push_back(overflow_len & 0xff);
 156                         tap_data.push_back((overflow_len >> 8) & 0xff);
 157                         tap_data.push_back(overflow_len >> 16);
 158                 }
 159         }
 160
 161         tap_header hdr;
 162         memcpy(hdr.identifier, "C64-TAPE-RAW", 12);
 163         hdr.version = 1;
 164         hdr.reserved[0] = hdr.reserved[1] = hdr.reserved[2] = 0;
 165         hdr.data_len = tap_data.size();
 166
 167         fwrite(&hdr, sizeof(hdr), 1, stdout);
 168         fwrite(tap_data.data(), tap_data.size(), 1, stdout);
 169 }
 170
 171 static struct option long_options[] = {
 172         {"auto-level",       0,                 0, 'a' },
 173         {"output-leveled",   0,                 0, 'A' },
 174         {"no-calibrate",     0,                 0, 's' },
 175         {"plot-cycles",      0,                 0, 'p' },
 176         {"hysteresis-limit", required_argument, 0, 'l' },
 177         {"filter",           required_argument, 0, 'f' },
 178         {"output-filtered",  0,                 0, 'F' },
 179         {"crop",             required_argument, 0, 'c' },
 180         {"quiet",            0,                 0, 'q' },
 181         {"help",             0,                 0, 'h' },
 182         {0,                  0,                 0, 0   }
 183 };
 184
 185 void help()
 186 {
 187         fprintf(stderr, "decode [OPTIONS] AUDIO-FILE > TAP-FILE\n");
 188         fprintf(stderr, "\n");
 189         fprintf(stderr, "  -a, --auto-level             automatically adjust amplitude levels throughout the file\n");
 190         fprintf(stderr, "  -A, --output-leveled         output leveled waveform to leveled.raw\n");
 191         fprintf(stderr, "  -m, --min-level              minimum estimated sound level (0..32768) for --auto-level\n");
 192         fprintf(stderr, "  -s, --no-calibrate           do not try to calibrate on sync pulse length\n");
 193         fprintf(stderr, "  -p, --plot-cycles            output debugging info to cycles.plot\n");
 194         fprintf(stderr, "  -l, --hysteresis-limit VAL   change amplitude threshold for ignoring pulses (0..32768)\n");
 195         fprintf(stderr, "  -f, --filter C1:C2:C3:...    specify FIR filter (up to %d coefficients)\n", NUM_FILTER_COEFF);
 196         fprintf(stderr, "  -F, --output-filtered        output filtered waveform to filtered.raw\n");
 197         fprintf(stderr, "  -c, --crop START[:END]       use only the given part of the file\n");
 198         fprintf(stderr, "  -t, --train LEN1:LEN2:...    train a filter for detecting any of the given number of cycles\n");
 199         fprintf(stderr, "                               (implies --no-calibrate and --quiet unless overridden)\n");
 200         fprintf(stderr, "  -q, --quiet                  suppress some informational messages\n");
 201         fprintf(stderr, "  -h, --help                   display this help, then exit\n");
 202         exit(1);
 203 }
 204
 205 void parse_options(int argc, char **argv)
 206 {
 207         for ( ;; ) {
 208                 int option_index = 0;
 209                 int c = getopt_long(argc, argv, "aAm:spl:f:Fc:t:qh", long_options, &option_index);
 210                 if (c == -1)
 211                         break;
 212
 213                 switch (c) {
 214                 case 'a':
 215                         do_auto_level = true;
 216                         break;
 217
 218                 case 'A':
 219                         output_leveled = true;
 220                         break;
 221
 222                 case 'm':
 223                         min_level = atof(optarg) / 32768.0;
 224                         break;
 225
 226                 case 's':
 227                         do_calibrate = false;
 228                         break;
 229
 230                 case 'p':
 231                         output_cycles_plot = true;
 232                         break;
 233
 234                 case 'l':
 235                         hysteresis_limit = atof(optarg) / 32768.0;
 236                         break;
 237
 238                 case 'f': {
 239                         const char *coeffstr = strtok(optarg, ": ");
 240                         int coeff_index = 0;
 241                         while (coeff_index < NUM_FILTER_COEFF && coeffstr != NULL) {
 242                                 filter_coeff[coeff_index++] = atof(coeffstr);
 243                                 coeffstr = strtok(NULL, ": ");
 244                         }
 245                         use_filter = true;
 246                         break;
 247                 }
 248
 249                 case 'F':
 250                         output_filtered = true;
 251                         break;
 252
 253                 case 'c': {
 254                         const char *cropstr = strtok(optarg, ":");
 255                         crop_start = atof(cropstr);
 256                         cropstr = strtok(NULL, ":");
 257                         if (cropstr == NULL) {
 258                                 crop_end = HUGE_VAL;
 259                         } else {
 260                                 crop_end = atof(cropstr);
 261                         }
 262                         do_crop = true;
 263                         break;
 264                 }
 265
 266                 case 't': {
 267                         const char *cyclestr = strtok(optarg, ":");
 268                         while (cyclestr != NULL) {
 269                                 train_snap_points.push_back(atof(cyclestr));
 270                                 cyclestr = strtok(NULL, ":");
 271                         }
 272                         do_train = true;
 273
 274                         // Set reasonable defaults (can be overridden later on the command line).
 275                         do_calibrate = false;
 276                         quiet = true;
 277                         break;
 278                 }
 279
 280                 case 'q':
 281                         quiet = true;
 282                         break;
 283
 284                 case 'h':
 285                 default:
 286                         help();
 287                         exit(1);
 288                 }
 289         }
 290 }
 291
 292 std::vector<float> crop(const std::vector<float>& pcm, float crop_start, float crop_end, int sample_rate)
 293 {
 294         size_t start_sample, end_sample;
 295         if (crop_start >= 0.0f) {
 296                 start_sample = std::min<size_t>(lrintf(crop_start * sample_rate), pcm.size());
 297         }
 298         if (crop_end >= 0.0f) {
 299                 end_sample = std::min<size_t>(lrintf(crop_end * sample_rate), pcm.size());
 300         }
 301         return std::vector<float>(pcm.begin() + start_sample, pcm.begin() + end_sample);
 302 }
 303
 304 // TODO: Support AVX here.
 305 std::vector<float> do_filter(const std::vector<float>& pcm, const float* filter)
 306 {
 307         std::vector<float> filtered_pcm;
 308         filtered_pcm.reserve(pcm.size());
 309         for (unsigned i = NUM_FILTER_COEFF; i < pcm.size(); ++i) {
 310                 float s = 0.0f;
 311                 for (int j = 0; j < NUM_FILTER_COEFF; ++j) {
 312                         s += filter[j] * pcm[i - j];
 313                 }
 314                 filtered_pcm.push_back(s);
 315         }
 316
 317         if (output_filtered) {
 318                 FILE *fp = fopen("filtered.raw", "wb");
 319                 fwrite(filtered_pcm.data(), filtered_pcm.size() * sizeof(filtered_pcm[0]), 1, fp);
 320                 fclose(fp);
 321         }
 322
 323         return filtered_pcm;
 324 }
 325
 326 std::vector<pulse> detect_pulses(const std::vector<float> &pcm, int sample_rate)
 327 {
 328         std::vector<pulse> pulses;
 329
 330         // Find the flanks.
 331         int last_bit = -1;
 332         double last_downflank = -1;
 333         for (unsigned i = 0; i < pcm.size(); ++i) {
 334                 int bit = (pcm[i] > 0) ? 1 : 0;
 335                 if (bit == 0 && last_bit == 1) {
 336                         // Check if we ever go up above <hysteresis_limit> before we dip down again.
 337                         bool true_pulse = false;
 338                         unsigned j;
 339                         int min_level_after = 32767;
 340                         for (j = i; j < pcm.size(); ++j) {
 341                                 min_level_after = std::min<int>(min_level_after, pcm[j]);
 342                                 if (pcm[j] > 0) break;
 343                                 if (pcm[j] < -hysteresis_limit) {
 344                                         true_pulse = true;
 345                                         break;
 346                                 }
 347                         }
 348
 349                         if (!true_pulse) {
 350 #if 0
 351                                 fprintf(stderr, "Ignored down-flank at %.6f seconds due to hysteresis (%d < %d).\n",
 352                                         double(i) / sample_rate, -min_level_after, hysteresis_limit);
 353 #endif
 354                                 i = j;
 355                                 continue;
 356                         }
 357
 358                         // down-flank!
 359                         double t = find_zerocrossing(pcm, i - 1) * (1.0 / sample_rate) + crop_start;
 360                         if (last_downflank > 0) {
 361                                 pulse p;
 362                                 p.time = t;
 363                                 p.len = t - last_downflank;
 364                                 pulses.push_back(p);
 365                         }
 366                         last_downflank = t;
 367                 }
 368                 last_bit = bit;
 369         }
 370         return pulses;
 371 }
 372
 373 void output_cycle_plot(const std::vector<pulse> &pulses, double calibration_factor)
 374 {
 375         FILE *fp = fopen("cycles.plot", "w");
 376         for (unsigned i = 0; i < pulses.size(); ++i) {
 377                 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
 378                 fprintf(fp, "%f %f\n", pulses[i].time, cycles);
 379         }
 380         fclose(fp);
 381 }
 382
 383 float eval_badness(const std::vector<pulse>& pulses, double calibration_factor)
 384 {
 385         double sum_badness = 0.0;
 386         for (unsigned i = 0; i < pulses.size(); ++i) {
 387                 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
 388                 if (cycles > 2000.0) cycles = 2000.0;  // Don't make pauses arbitrarily bad.
 389                 double badness = (cycles - train_snap_points[0]) * (cycles - train_snap_points[0]);
 390                 for (unsigned j = 1; j < train_snap_points.size(); ++j) {
 391                         badness = std::min(badness, (cycles - train_snap_points[j]) * (cycles - train_snap_points[j]));
 392                 }
 393                 sum_badness += badness;
 394         }
 395         return sqrt(sum_badness / (pulses.size() - 1));
 396 }
 397
 398 void spsa_train(std::vector<float> &pcm, int sample_rate)
 399 {
 400         // Train!
 401         float filter[NUM_FILTER_COEFF] = { 1.0f };  // The rest is filled with 0.
 402
 403         float start_c = INITIAL_C;
 404         double best_badness = HUGE_VAL;
 405
 406         for (int n = 1; n < NUM_ITER; ++n) {
 407                 float a = INITIAL_A * pow(n + A, -ALPHA);
 408                 float c = start_c * pow(n, -GAMMA);
 409
 410                 // find a random perturbation
 411                 float p[NUM_FILTER_COEFF];
 412                 float filter1[NUM_FILTER_COEFF], filter2[NUM_FILTER_COEFF];
 413                 for (int i = 0; i < NUM_FILTER_COEFF; ++i) {
 414                         p[i] = (rand() % 2) ? 1.0 : -1.0;
 415                         filter1[i] = std::max(std::min(filter[i] - c * p[i], 1.0f), -1.0f);
 416                         filter2[i] = std::max(std::min(filter[i] + c * p[i], 1.0f), -1.0f);
 417                 }
 418
 419                 std::vector<pulse> pulses1 = detect_pulses(do_filter(pcm, filter1), sample_rate);
 420                 std::vector<pulse> pulses2 = detect_pulses(do_filter(pcm, filter2), sample_rate);
 421                 float badness1 = eval_badness(pulses1, 1.0);
 422                 float badness2 = eval_badness(pulses2, 1.0);
 423
 424                 // Find the gradient estimator
 425                 float g[NUM_FILTER_COEFF];
 426                 for (int i = 0; i < NUM_FILTER_COEFF; ++i) {
 427                         g[i] = (badness2 - badness1) / (2.0 * c * p[i]);
 428                         filter[i] -= a * g[i];
 429                         filter[i] = std::max(std::min(filter[i], 1.0f), -1.0f);
 430                 }
 431                 if (badness2 < badness1) {
 432                         std::swap(badness1, badness2);
 433                         std::swap(filter1, filter2);
 434                         std::swap(pulses1, pulses2);
 435                 }
 436                 if (badness1 < best_badness) {
 437                         printf("\nNew best filter (badness=%f):", badness1);
 438                         for (int i = 0; i < NUM_FILTER_COEFF; ++i) {
 439                                 printf(" %.5f", filter1[i]);
 440                         }
 441                         best_badness = badness1;
 442                         printf("\n");
 443
 444                         if (output_cycles_plot) {
 445                                 output_cycle_plot(pulses1, 1.0);
 446                         }
 447                 }
 448                 printf("%d ", n);
 449                 fflush(stdout);
 450         }
 451 }
 452
 453 int main(int argc, char **argv)
 454 {
 455         parse_options(argc, argv);
 456
 457         make_lanczos_weight_table();
 458         std::vector<float> pcm;
 459         int sample_rate;
 460         if (!read_audio_file(argv[optind], &pcm, &sample_rate)) {
 461                 exit(1);
 462         }
 463
 464         if (do_crop) {
 465                 pcm = crop(pcm, crop_start, crop_end, sample_rate);
 466         }
 467
 468         if (use_filter) {
 469                 pcm = do_filter(pcm, filter_coeff);
 470         }
 471
 472         if (do_auto_level) {
 473                 pcm = level_samples(pcm, min_level, sample_rate);
 474                 if (output_leveled) {
 475                         FILE *fp = fopen("leveled.raw", "wb");
 476                         fwrite(pcm.data(), pcm.size() * sizeof(pcm[0]), 1, fp);
 477                         fclose(fp);
 478                 }
 479         }
 480
 481 #if 0
 482         for (int i = 0; i < LEN; ++i) {
 483                 in[i] += rand() % 10000;
 484         }
 485 #endif
 486
 487 #if 0
 488         for (int i = 0; i < LEN; ++i) {
 489                 printf("%d\n", in[i]);
 490         }
 491 #endif
 492
 493         if (do_train) {
 494                 spsa_train(pcm, sample_rate);
 495                 exit(0);
 496         }
 497
 498         std::vector<pulse> pulses = detect_pulses(pcm, sample_rate);
 499
 500         double calibration_factor = 1.0;
 501         if (do_calibrate) {
 502                 calibration_factor = calibrate(pulses);
 503         }
 504
 505         if (output_cycles_plot) {
 506                 output_cycle_plot(pulses, calibration_factor);
 507         }
 508
 509         output_tap(pulses, calibration_factor);
 510 }