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 #define NUM_FILTER_COEFF 32
  23
  24 static float hysteresis_limit = 3000.0 / 32768.0;
  25 static bool do_calibrate = true;
  26 static bool output_cycles_plot = false;
  27 static bool use_filter = false;
  28 static bool do_crop = false;
  29 static float crop_start = 0.0f, crop_end = HUGE_VAL;
  30 static float filter_coeff[NUM_FILTER_COEFF] = { 1.0f };  // The rest is filled with 0.
  31 static bool output_filtered = false;
  32 static bool quiet = false;
  33 static bool do_auto_level = false;
  34 static bool output_leveled = false;
  35
  36 // between [x,x+1]
  37 double find_zerocrossing(const std::vector<float> &pcm, int x)
  38 {
  39         if (pcm[x] == 0) {
  40                 return x;
  41         }
  42         if (pcm[x + 1] == 0) {
  43                 return x + 1;
  44         }
  45
  46         assert(pcm[x + 1] < 0);
  47         assert(pcm[x] > 0);
  48
  49         double upper = x;
  50         double lower = x + 1;
  51         while (lower - upper > 1e-3) {
  52                 double mid = 0.5f * (upper + lower);
  53                 if (lanczos_interpolate(pcm, mid) > 0) {
  54                         upper = mid;
  55                 } else {
  56                         lower = mid;
  57                 }
  58         }
  59
  60         return 0.5f * (upper + lower);
  61 }
  62
  63 struct pulse {
  64         double time;  // in seconds from start
  65         double len;   // in seconds
  66 };
  67
  68 // Calibrate on the first ~25k pulses (skip a few, just to be sure).
  69 double calibrate(const std::vector<pulse> &pulses) {
  70         if (pulses.size() < SYNC_PULSE_END) {
  71                 fprintf(stderr, "Too few pulses, not calibrating!\n");
  72                 return 1.0;
  73         }
  74
  75         int sync_pulse_end = -1;
  76         double sync_pulse_stddev = -1.0;
  77
  78         // Compute the standard deviation (to check for uneven speeds).
  79         // If it suddenly skyrockets, we assume that sync ended earlier
  80         // than we thought (it should be 25000 cycles), and that we should
  81         // calibrate on fewer cycles.
  82         for (int try_end : { 2000, 4000, 5000, 7500, 10000, 15000, SYNC_PULSE_END }) {
  83                 double sum2 = 0.0;
  84                 for (int i = SYNC_PULSE_START; i < try_end; ++i) {
  85                         double cycles = pulses[i].len * C64_FREQUENCY;
  86                         sum2 += (cycles - SYNC_PULSE_LENGTH) * (cycles - SYNC_PULSE_LENGTH);
  87                 }
  88                 double stddev = sqrt(sum2 / (try_end - SYNC_PULSE_START - 1));
  89                 if (sync_pulse_end != -1 && stddev > 5.0 && stddev / sync_pulse_stddev > 1.3) {
  90                         fprintf(stderr, "Stopping at %d sync pulses because standard deviation would be too big (%.2f cycles); shorter-than-usual trailer?\n",
  91                                 sync_pulse_end, stddev);
  92                         break;
  93                 }
  94                 sync_pulse_end = try_end;
  95                 sync_pulse_stddev = stddev;
  96         }
  97         if (!quiet) {
  98                 fprintf(stderr, "Sync pulse length standard deviation: %.2f cycles\n",
  99                         sync_pulse_stddev);
 100         }
 101
 102         double sum = 0.0;
 103         for (int i = SYNC_PULSE_START; i < sync_pulse_end; ++i) {
 104                 sum += pulses[i].len;
 105         }
 106         double mean_length = C64_FREQUENCY * sum / (sync_pulse_end - SYNC_PULSE_START);
 107         double calibration_factor = SYNC_PULSE_LENGTH / mean_length;
 108         if (!quiet) {
 109                 fprintf(stderr, "Calibrated sync pulse length: %.2f -> %.2f (change %+.2f%%)\n",
 110                         mean_length, SYNC_PULSE_LENGTH, 100.0 * (calibration_factor - 1.0));
 111         }
 112
 113         // Check for pulses outside +/- 10% (sign of misdetection).
 114         for (int i = SYNC_PULSE_START; i < sync_pulse_end; ++i) {
 115                 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
 116                 if (cycles < SYNC_PULSE_LENGTH / SYNC_TEST_TOLERANCE || cycles > SYNC_PULSE_LENGTH * SYNC_TEST_TOLERANCE) {
 117                         fprintf(stderr, "Sync cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
 118                                 pulses[i].time, cycles);
 119                 }
 120         }
 121
 122         return calibration_factor;
 123 }
 124
 125 void output_tap(const std::vector<pulse>& pulses, double calibration_factor)
 126 {
 127         std::vector<char> tap_data;
 128         for (unsigned i = 0; i < pulses.size(); ++i) {
 129                 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
 130                 int len = lrintf(cycles / TAP_RESOLUTION);
 131                 if (i > SYNC_PULSE_END && (cycles < 100 || cycles > 800)) {
 132                         fprintf(stderr, "Cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
 133                                         pulses[i].time, cycles);
 134                 }
 135                 if (len <= 255) {
 136                         tap_data.push_back(len);
 137                 } else {
 138                         int overflow_len = lrintf(cycles);
 139                         tap_data.push_back(0);
 140                         tap_data.push_back(overflow_len & 0xff);
 141                         tap_data.push_back((overflow_len >> 8) & 0xff);
 142                         tap_data.push_back(overflow_len >> 16);
 143                 }
 144         }
 145
 146         tap_header hdr;
 147         memcpy(hdr.identifier, "C64-TAPE-RAW", 12);
 148         hdr.version = 1;
 149         hdr.reserved[0] = hdr.reserved[1] = hdr.reserved[2] = 0;
 150         hdr.data_len = tap_data.size();
 151
 152         fwrite(&hdr, sizeof(hdr), 1, stdout);
 153         fwrite(tap_data.data(), tap_data.size(), 1, stdout);
 154 }
 155
 156 static struct option long_options[] = {
 157         {"auto-level",       0,                 0, 'a' },
 158         {"no-calibrate",     0,                 0, 's' },
 159         {"plot-cycles",      0,                 0, 'p' },
 160         {"hysteresis-limit", required_argument, 0, 'l' },
 161         {"filter",           required_argument, 0, 'f' },
 162         {"output-filtered",  0,                 0, 'F' },
 163         {"crop",             required_argument, 0, 'c' },
 164         {"quiet",            0,                 0, 'q' },
 165         {"help",             0,                 0, 'h' },
 166         {0,                  0,                 0, 0   }
 167 };
 168
 169 void help()
 170 {
 171         fprintf(stderr, "decode [OPTIONS] AUDIO-FILE > TAP-FILE\n");
 172         fprintf(stderr, "\n");
 173         fprintf(stderr, "  -a, --auto-level             automatically adjust amplitude levels throughout the file\n");
 174         fprintf(stderr, "  -A, --output-leveled         output leveled waveform to leveled.raw\n");
 175         fprintf(stderr, "  -s, --no-calibrate           do not try to calibrate on sync pulse length\n");
 176         fprintf(stderr, "  -p, --plot-cycles            output debugging info to cycles.plot\n");
 177         fprintf(stderr, "  -l, --hysteresis-limit VAL   change amplitude threshold for ignoring pulses (0..32768)\n");
 178         fprintf(stderr, "  -f, --filter C1:C2:C3:...    specify FIR filter (up to %d coefficients)\n", NUM_FILTER_COEFF);
 179         fprintf(stderr, "  -F, --output-filtered        output filtered waveform to filtered.raw\n");
 180         fprintf(stderr, "  -c, --crop START[:END]       use only the given part of the file\n");
 181         fprintf(stderr, "  -q, --quiet                  suppress some informational messages\n");
 182         fprintf(stderr, "  -h, --help                   display this help, then exit\n");
 183         exit(1);
 184 }
 185
 186 void parse_options(int argc, char **argv)
 187 {
 188         for ( ;; ) {
 189                 int option_index = 0;
 190                 int c = getopt_long(argc, argv, "aAspl:f:Fc:qh", long_options, &option_index);
 191                 if (c == -1)
 192                         break;
 193
 194                 switch (c) {
 195                 case 'a':
 196                         do_auto_level = true;
 197                         break;
 198
 199                 case 'A':
 200                         output_leveled = true;
 201                         break;
 202
 203                 case 's':
 204                         do_calibrate = false;
 205                         break;
 206
 207                 case 'p':
 208                         output_cycles_plot = true;
 209                         break;
 210
 211                 case 'l':
 212                         hysteresis_limit = atof(optarg) / 32768.0;
 213                         break;
 214
 215                 case 'f': {
 216                         const char *coeffstr = strtok(optarg, ":");
 217                         int coeff_index = 0;
 218                         while (coeff_index < NUM_FILTER_COEFF && coeffstr != NULL) {
 219                                 filter_coeff[coeff_index++] = atof(coeffstr);
 220                                 coeffstr = strtok(NULL, ":");
 221                         }
 222                         use_filter = true;
 223                         break;
 224                 }
 225
 226                 case 'F':
 227                         output_filtered = true;
 228                         break;
 229
 230                 case 'c': {
 231                         const char *cropstr = strtok(optarg, ":");
 232                         crop_start = atof(cropstr);
 233                         cropstr = strtok(NULL, ":");
 234                         if (cropstr == NULL) {
 235                                 crop_end = HUGE_VAL;
 236                         } else {
 237                                 crop_end = atof(cropstr);
 238                         }
 239                         do_crop = true;
 240                         break;
 241                 }
 242
 243                 case 'q':
 244                         quiet = true;
 245                         break;
 246
 247                 case 'h':
 248                 default:
 249                         help();
 250                         exit(1);
 251                 }
 252         }
 253 }
 254
 255 std::vector<float> crop(const std::vector<float>& pcm, float crop_start, float crop_end, int sample_rate)
 256 {
 257         size_t start_sample, end_sample;
 258         if (crop_start >= 0.0f) {
 259                 start_sample = std::min<size_t>(lrintf(crop_start * sample_rate), pcm.size());
 260         }
 261         if (crop_end >= 0.0f) {
 262                 end_sample = std::min<size_t>(lrintf(crop_end * sample_rate), pcm.size());
 263         }
 264         return std::vector<float>(pcm.begin() + start_sample, pcm.begin() + end_sample);
 265 }
 266
 267 // TODO: Support AVX here.
 268 std::vector<float> do_filter(const std::vector<float>& pcm, const float* filter)
 269 {
 270         std::vector<float> filtered_pcm;
 271         filtered_pcm.reserve(pcm.size());
 272         for (unsigned i = NUM_FILTER_COEFF; i < pcm.size(); ++i) {
 273                 float s = 0.0f;
 274                 for (int j = 0; j < NUM_FILTER_COEFF; ++j) {
 275                         s += filter[j] * pcm[i - j];
 276                 }
 277                 filtered_pcm.push_back(s);
 278         }
 279
 280         if (output_filtered) {
 281                 FILE *fp = fopen("filtered.raw", "wb");
 282                 fwrite(filtered_pcm.data(), filtered_pcm.size() * sizeof(filtered_pcm[0]), 1, fp);
 283                 fclose(fp);
 284         }
 285
 286         return filtered_pcm;
 287 }
 288
 289 std::vector<pulse> detect_pulses(const std::vector<float> &pcm, int sample_rate)
 290 {
 291         std::vector<pulse> pulses;
 292
 293         // Find the flanks.
 294         int last_bit = -1;
 295         double last_downflank = -1;
 296         for (unsigned i = 0; i < pcm.size(); ++i) {
 297                 int bit = (pcm[i] > 0) ? 1 : 0;
 298                 if (bit == 0 && last_bit == 1) {
 299                         // Check if we ever go up above <hysteresis_limit> before we dip down again.
 300                         bool true_pulse = false;
 301                         unsigned j;
 302                         int min_level_after = 32767;
 303                         for (j = i; j < pcm.size(); ++j) {
 304                                 min_level_after = std::min<int>(min_level_after, pcm[j]);
 305                                 if (pcm[j] > 0) break;
 306                                 if (pcm[j] < -hysteresis_limit) {
 307                                         true_pulse = true;
 308                                         break;
 309                                 }
 310                         }
 311
 312                         if (!true_pulse) {
 313 #if 0
 314                                 fprintf(stderr, "Ignored down-flank at %.6f seconds due to hysteresis (%d < %d).\n",
 315                                         double(i) / sample_rate, -min_level_after, hysteresis_limit);
 316 #endif
 317                                 i = j;
 318                                 continue;
 319                         }
 320
 321                         // down-flank!
 322                         double t = find_zerocrossing(pcm, i - 1) * (1.0 / sample_rate) + crop_start;
 323                         if (last_downflank > 0) {
 324                                 pulse p;
 325                                 p.time = t;
 326                                 p.len = t - last_downflank;
 327                                 pulses.push_back(p);
 328                         }
 329                         last_downflank = t;
 330                 }
 331                 last_bit = bit;
 332         }
 333         return pulses;
 334 }
 335
 336 void output_cycle_plot(const std::vector<pulse> &pulses, double calibration_factor)
 337 {
 338         FILE *fp = fopen("cycles.plot", "w");
 339         for (unsigned i = 0; i < pulses.size(); ++i) {
 340                 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
 341                 fprintf(fp, "%f %f\n", pulses[i].time, cycles);
 342         }
 343         fclose(fp);
 344 }
 345
 346 int main(int argc, char **argv)
 347 {
 348         parse_options(argc, argv);
 349
 350         make_lanczos_weight_table();
 351         std::vector<float> pcm;
 352         int sample_rate;
 353         if (!read_audio_file(argv[optind], &pcm, &sample_rate)) {
 354                 exit(1);
 355         }
 356
 357         if (do_crop) {
 358                 pcm = crop(pcm, crop_start, crop_end, sample_rate);
 359         }
 360
 361         if (use_filter) {
 362                 pcm = do_filter(pcm, filter_coeff);
 363         }
 364
 365         if (do_auto_level) {
 366                 pcm = level_samples(pcm, sample_rate);
 367                 if (output_leveled) {
 368                         FILE *fp = fopen("leveled.raw", "wb");
 369                         fwrite(pcm.data(), pcm.size() * sizeof(pcm[0]), 1, fp);
 370                         fclose(fp);
 371                 }
 372         }
 373
 374 #if 0
 375         for (int i = 0; i < LEN; ++i) {
 376                 in[i] += rand() % 10000;
 377         }
 378 #endif
 379
 380 #if 0
 381         for (int i = 0; i < LEN; ++i) {
 382                 printf("%d\n", in[i]);
 383         }
 384 #endif
 385
 386         std::vector<pulse> pulses = detect_pulses(pcm, sample_rate);
 387
 388         double calibration_factor = 1.0;
 389         if (do_calibrate) {
 390                 calibration_factor = calibrate(pulses);
 391         }
 392
 393         if (output_cycles_plot) {
 394                 output_cycle_plot(pulses, calibration_factor);
 395         }
 396
 397         output_tap(pulses, calibration_factor);
 398 }