10 #include "audioreader.h"
11 #include "interpolate.h"
15 #define C64_FREQUENCY 985248
16 #define SYNC_PULSE_START 1000
17 #define SYNC_PULSE_END 20000
18 #define SYNC_PULSE_LENGTH 378.0
19 #define SYNC_TEST_TOLERANCE 1.10
21 #define NUM_FILTER_COEFF 32
23 static float hysteresis_limit = 3000.0 / 32768.0;
24 static bool do_calibrate = true;
25 static bool output_cycles_plot = false;
26 static bool use_filter = false;
27 static bool do_crop = false;
28 static float crop_start = 0.0f, crop_end = HUGE_VAL;
29 static float filter_coeff[NUM_FILTER_COEFF] = { 1.0f }; // The rest is filled with 0.
30 static bool output_filtered = false;
31 static bool quiet = false;
34 double find_zerocrossing(const std::vector<float> &pcm, int x)
39 if (pcm[x + 1] == 0) {
43 assert(pcm[x + 1] < 0);
48 while (lower - upper > 1e-3) {
49 double mid = 0.5f * (upper + lower);
50 if (lanczos_interpolate(pcm, mid) > 0) {
57 return 0.5f * (upper + lower);
61 double time; // in seconds from start
62 double len; // in seconds
65 // Calibrate on the first ~25k pulses (skip a few, just to be sure).
66 double calibrate(const std::vector<pulse> &pulses) {
67 if (pulses.size() < SYNC_PULSE_END) {
68 fprintf(stderr, "Too few pulses, not calibrating!\n");
72 int sync_pulse_end = -1;
73 double sync_pulse_stddev = -1.0;
75 // Compute the standard deviation (to check for uneven speeds).
76 // If it suddenly skyrockets, we assume that sync ended earlier
77 // than we thought (it should be 25000 cycles), and that we should
78 // calibrate on fewer cycles.
79 for (int try_end : { 2000, 4000, 5000, 7500, 10000, 15000, SYNC_PULSE_END }) {
81 for (int i = SYNC_PULSE_START; i < try_end; ++i) {
82 double cycles = pulses[i].len * C64_FREQUENCY;
83 sum2 += (cycles - SYNC_PULSE_LENGTH) * (cycles - SYNC_PULSE_LENGTH);
85 double stddev = sqrt(sum2 / (try_end - SYNC_PULSE_START - 1));
86 if (sync_pulse_end != -1 && stddev > 5.0 && stddev / sync_pulse_stddev > 1.3) {
87 fprintf(stderr, "Stopping at %d sync pulses because standard deviation would be too big (%.2f cycles); shorter-than-usual trailer?\n",
88 sync_pulse_end, stddev);
91 sync_pulse_end = try_end;
92 sync_pulse_stddev = stddev;
95 fprintf(stderr, "Sync pulse length standard deviation: %.2f cycles\n",
100 for (int i = SYNC_PULSE_START; i < sync_pulse_end; ++i) {
101 sum += pulses[i].len;
103 double mean_length = C64_FREQUENCY * sum / (sync_pulse_end - SYNC_PULSE_START);
104 double calibration_factor = SYNC_PULSE_LENGTH / mean_length;
106 fprintf(stderr, "Calibrated sync pulse length: %.2f -> %.2f (change %+.2f%%)\n",
107 mean_length, SYNC_PULSE_LENGTH, 100.0 * (calibration_factor - 1.0));
110 // Check for pulses outside +/- 10% (sign of misdetection).
111 for (int i = SYNC_PULSE_START; i < sync_pulse_end; ++i) {
112 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
113 if (cycles < SYNC_PULSE_LENGTH / SYNC_TEST_TOLERANCE || cycles > SYNC_PULSE_LENGTH * SYNC_TEST_TOLERANCE) {
114 fprintf(stderr, "Sync cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
115 pulses[i].time, cycles);
119 return calibration_factor;
122 void output_tap(const std::vector<pulse>& pulses, double calibration_factor)
124 std::vector<char> tap_data;
125 for (unsigned i = 0; i < pulses.size(); ++i) {
126 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
127 int len = lrintf(cycles / TAP_RESOLUTION);
128 if (i > SYNC_PULSE_END && (cycles < 100 || cycles > 800)) {
129 fprintf(stderr, "Cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
130 pulses[i].time, cycles);
133 tap_data.push_back(len);
135 int overflow_len = lrintf(cycles);
136 tap_data.push_back(0);
137 tap_data.push_back(overflow_len & 0xff);
138 tap_data.push_back((overflow_len >> 8) & 0xff);
139 tap_data.push_back(overflow_len >> 16);
144 memcpy(hdr.identifier, "C64-TAPE-RAW", 12);
146 hdr.reserved[0] = hdr.reserved[1] = hdr.reserved[2] = 0;
147 hdr.data_len = tap_data.size();
149 fwrite(&hdr, sizeof(hdr), 1, stdout);
150 fwrite(tap_data.data(), tap_data.size(), 1, stdout);
153 static struct option long_options[] = {
154 {"no-calibrate", 0, 0, 's' },
155 {"plot-cycles", 0, 0, 'p' },
156 {"hysteresis-limit", required_argument, 0, 'l' },
157 {"filter", required_argument, 0, 'f' },
158 {"output-filtered", 0, 0, 'F' },
159 {"crop", required_argument, 0, 'c' },
160 {"quiet", 0, 0, 'q' },
161 {"help", 0, 0, 'h' },
167 fprintf(stderr, "decode [OPTIONS] AUDIO-FILE > TAP-FILE\n");
168 fprintf(stderr, "\n");
169 fprintf(stderr, " -s, --no-calibrate do not try to calibrate on sync pulse length\n");
170 fprintf(stderr, " -p, --plot-cycles output debugging info to cycles.plot\n");
171 fprintf(stderr, " -l, --hysteresis-limit VAL change amplitude threshold for ignoring pulses (0..32768)\n");
172 fprintf(stderr, " -f, --filter C1:C2:C3:... specify FIR filter (up to %d coefficients)\n", NUM_FILTER_COEFF);
173 fprintf(stderr, " -F, --output-filtered output filtered waveform to filtered.raw\n");
174 fprintf(stderr, " -c, --crop START[:END] use only the given part of the file\n");
175 fprintf(stderr, " -q, --quiet suppress some informational messages\n");
176 fprintf(stderr, " -h, --help display this help, then exit\n");
180 void parse_options(int argc, char **argv)
183 int option_index = 0;
184 int c = getopt_long(argc, argv, "spl:f:Fc:qh", long_options, &option_index);
190 do_calibrate = false;
194 output_cycles_plot = true;
198 hysteresis_limit = atof(optarg) / 32768.0;
202 const char *coeffstr = strtok(optarg, ":");
204 while (coeff_index < NUM_FILTER_COEFF && coeffstr != NULL) {
205 filter_coeff[coeff_index++] = atof(coeffstr);
206 coeffstr = strtok(NULL, ":");
213 output_filtered = true;
217 const char *cropstr = strtok(optarg, ":");
218 crop_start = atof(cropstr);
219 cropstr = strtok(NULL, ":");
220 if (cropstr == NULL) {
223 crop_end = atof(cropstr);
241 std::vector<float> crop(const std::vector<float>& pcm, float crop_start, float crop_end, int sample_rate)
243 size_t start_sample, end_sample;
244 if (crop_start >= 0.0f) {
245 start_sample = std::min<size_t>(lrintf(crop_start * sample_rate), pcm.size());
247 if (crop_end >= 0.0f) {
248 end_sample = std::min<size_t>(lrintf(crop_end * sample_rate), pcm.size());
250 return std::vector<float>(pcm.begin() + start_sample, pcm.begin() + end_sample);
253 // TODO: Support AVX here.
254 std::vector<float> do_filter(const std::vector<float>& pcm, const float* filter)
256 std::vector<float> filtered_pcm;
257 filtered_pcm.reserve(pcm.size());
258 for (unsigned i = NUM_FILTER_COEFF; i < pcm.size(); ++i) {
260 for (int j = 0; j < NUM_FILTER_COEFF; ++j) {
261 s += filter[j] * pcm[i - j];
263 filtered_pcm.push_back(s);
266 if (output_filtered) {
267 FILE *fp = fopen("filtered.raw", "wb");
268 fwrite(filtered_pcm.data(), filtered_pcm.size() * sizeof(filtered_pcm[0]), 1, fp);
275 std::vector<pulse> detect_pulses(const std::vector<float> &pcm, int sample_rate)
277 std::vector<pulse> pulses;
281 double last_downflank = -1;
282 for (unsigned i = 0; i < pcm.size(); ++i) {
283 int bit = (pcm[i] > 0) ? 1 : 0;
284 if (bit == 0 && last_bit == 1) {
285 // Check if we ever go up above <hysteresis_limit> before we dip down again.
286 bool true_pulse = false;
288 int min_level_after = 32767;
289 for (j = i; j < pcm.size(); ++j) {
290 min_level_after = std::min<int>(min_level_after, pcm[j]);
291 if (pcm[j] > 0) break;
292 if (pcm[j] < -hysteresis_limit) {
300 fprintf(stderr, "Ignored down-flank at %.6f seconds due to hysteresis (%d < %d).\n",
301 double(i) / sample_rate, -min_level_after, hysteresis_limit);
308 double t = find_zerocrossing(pcm, i - 1) * (1.0 / sample_rate) + crop_start;
309 if (last_downflank > 0) {
312 p.len = t - last_downflank;
322 void output_cycle_plot(const std::vector<pulse> &pulses, double calibration_factor)
324 FILE *fp = fopen("cycles.plot", "w");
325 for (unsigned i = 0; i < pulses.size(); ++i) {
326 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
327 fprintf(fp, "%f %f\n", pulses[i].time, cycles);
332 int main(int argc, char **argv)
334 parse_options(argc, argv);
336 make_lanczos_weight_table();
337 std::vector<float> pcm;
339 if (!read_audio_file(argv[optind], &pcm, &sample_rate)) {
344 pcm = crop(pcm, crop_start, crop_end, sample_rate);
348 pcm = do_filter(pcm, filter_coeff);
352 for (int i = 0; i < LEN; ++i) {
353 in[i] += rand() % 10000;
358 for (int i = 0; i < LEN; ++i) {
359 printf("%d\n", in[i]);
363 std::vector<pulse> pulses = detect_pulses(pcm, sample_rate);
365 double calibration_factor = 1.0;
367 calibration_factor = calibrate(pulses);
370 if (output_cycles_plot) {
371 output_cycle_plot(pulses, calibration_factor);
374 output_tap(pulses, calibration_factor);