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