+
+static struct option long_options[] = {
+ {"no-calibrate", 0, 0, 's' },
+ {"plot-cycles", 0, 0, 'p' },
+ {"hysteresis-limit", required_argument, 0, 'l' },
+ {"filter", required_argument, 0, 'f' },
+ {"output-filtered", 0, 0, 'F' },
+ {"help", 0, 0, 'h' },
+ {0, 0, 0, 0 }
+};
+
+void help()
+{
+ fprintf(stderr, "decode [OPTIONS] AUDIO-FILE > TAP-FILE\n");
+ fprintf(stderr, "\n");
+ fprintf(stderr, " -s, --no-calibrate do not try to calibrate on sync pulse length\n");
+ fprintf(stderr, " -p, --plot-cycles output debugging info to cycles.plot\n");
+ fprintf(stderr, " -l, --hysteresis-limit VAL change amplitude threshold for ignoring pulses (0..32768)\n");
+ fprintf(stderr, " -f, --filter C1:C2:C3:... specify FIR filter (up to %d coefficients)\n", NUM_FILTER_COEFF);
+ fprintf(stderr, " -F, --output-filtered output filtered waveform to filtered.raw\n");
+ fprintf(stderr, " -h, --help display this help, then exit\n");
+ exit(1);
+}
+
+void parse_options(int argc, char **argv)
+{
+ for ( ;; ) {
+ int option_index = 0;
+ int c = getopt_long(argc, argv, "spl:f:Fh", long_options, &option_index);
+ if (c == -1)
+ break;
+
+ switch (c) {
+ case 's':
+ do_calibrate = false;
+ break;
+
+ case 'p':
+ output_cycles_plot = true;
+ break;
+ case 'l':
+ hysteresis_limit = atof(optarg) / 32768.0;
+ break;
+
+ case 'f': {
+ const char *coeffstr = strtok(optarg, ":");
+ int coeff_index = 0;
+ while (coeff_index < NUM_FILTER_COEFF && coeffstr != NULL) {
+ filter_coeff[coeff_index++] = atof(coeffstr);
+ coeffstr = strtok(NULL, ":");
+ }
+ use_filter = true;
+ break;
+ }
+
+ case 'F':
+ output_filtered = true;
+ break;
+
+ case 'h':
+ default:
+ help();
+ exit(1);
+ }
+ }
+}
+
+// TODO: Support AVX here.
+std::vector<float> do_filter(const std::vector<float>& pcm, const float* filter)
+{
+ std::vector<float> filtered_pcm;
+ filtered_pcm.reserve(pcm.size());
+ for (unsigned i = NUM_FILTER_COEFF; i < pcm.size(); ++i) {
+ float s = 0.0f;
+ for (int j = 0; j < NUM_FILTER_COEFF; ++j) {
+ s += filter[j] * pcm[i - j];
+ }
+ filtered_pcm.push_back(s);
+ }
+
+ if (output_filtered) {
+ FILE *fp = fopen("filtered.raw", "wb");
+ fwrite(filtered_pcm.data(), filtered_pcm.size() * sizeof(filtered_pcm[0]), 1, fp);
+ fclose(fp);
+ }
+
+ return filtered_pcm;
+}
+
+int main(int argc, char **argv)
+{
+ parse_options(argc, argv);
+
+ make_lanczos_weight_table();
+ std::vector<float> pcm;
+ int sample_rate;
+ if (!read_audio_file(argv[optind], &pcm, &sample_rate)) {
+ exit(1);
+ }
+
+ if (use_filter) {
+ pcm = do_filter(pcm, filter_coeff);
+ }
+
+#if 0
+ for (int i = 0; i < LEN; ++i) {
+ in[i] += rand() % 10000;
+ }
+#endif
+
+#if 0
+ for (int i = 0; i < LEN; ++i) {
+ printf("%d\n", in[i]);
+ }
+#endif
+
+ std::vector<pulse> pulses; // in seconds
+
+ // Find the flanks.
+ int last_bit = -1;
+ double last_downflank = -1;
+ for (unsigned i = 0; i < pcm.size(); ++i) {
+ int bit = (pcm[i] > 0) ? 1 : 0;
+ if (bit == 0 && last_bit == 1) {
+ // Check if we ever go up above <hysteresis_limit> before we dip down again.
+ bool true_pulse = false;
+ unsigned j;
+ int min_level_after = 32767;
+ for (j = i; j < pcm.size(); ++j) {
+ min_level_after = std::min<int>(min_level_after, pcm[j]);
+ if (pcm[j] > 0) break;
+ if (pcm[j] < -hysteresis_limit) {
+ true_pulse = true;
+ break;
+ }
+ }
+
+ if (!true_pulse) {
+#if 0
+ fprintf(stderr, "Ignored down-flank at %.6f seconds due to hysteresis (%d < %d).\n",
+ double(i) / sample_rate, -min_level_after, hysteresis_limit);
+#endif
+ i = j;
+ continue;
+ }
+
+ // down-flank!
+ double t = find_zerocrossing(pcm, i - 1) * (1.0 / sample_rate);
+ if (last_downflank > 0) {
+ pulse p;
+ p.time = t;
+ p.len = t - last_downflank;
+ pulses.push_back(p);
+ }
+ last_downflank = t;
+ }
+ last_bit = bit;
+ }
+
+ double calibration_factor = 1.0;
+ if (do_calibrate) {
+ calibration_factor = calibrate(pulses);
+ }
+
+ if (output_cycles_plot) {
+ FILE *fp = fopen("cycles.plot", "w");
+ for (unsigned i = 0; i < pulses.size(); ++i) {
+ double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
+ fprintf(fp, "%f %f\n", pulses[i].time, cycles);
+ }
+ fclose(fp);
+ }
+
+ output_tap(pulses, calibration_factor);
+}