10 #include "interpolate.h"
13 #define HYSTERESIS_LIMIT 3000
14 #define SAMPLE_RATE 44100
15 #define C64_FREQUENCY 985248
16 #define TAP_RESOLUTION 8
18 #define SYNC_PULSE_START 1000
19 #define SYNC_PULSE_END 15000
20 #define SYNC_PULSE_LENGTH 378.0
21 #define SYNC_TEST_TOLERANCE 1.10
27 unsigned int data_len;
31 double find_zerocrossing(const std::vector<short> &pcm, int x)
36 if (pcm[x + 1] == 0) {
40 assert(pcm[x + 1] < 0);
45 while (upper - lower > 1e-6) {
46 double mid = 0.5f * (upper + lower);
47 if (lanczos_interpolate(pcm, mid) > 0) {
54 return 0.5f * (upper + lower);
58 double time; // in seconds from start
59 double len; // in seconds
62 int main(int argc, char **argv)
64 make_lanczos_weight_table();
65 std::vector<short> pcm;
67 while (!feof(stdin)) {
69 ssize_t ret = fread(buf, 2, BUFSIZE, stdin);
71 pcm.insert(pcm.end(), buf, buf + ret);
76 for (int i = 0; i < LEN; ++i) {
77 in[i] += rand() % 10000;
82 for (int i = 0; i < LEN; ++i) {
83 printf("%d\n", in[i]);
87 std::vector<pulse> pulses; // in seconds
91 double last_downflank = -1;
92 for (unsigned i = 0; i < pcm.size(); ++i) {
93 int bit = (pcm[i] > 0) ? 1 : 0;
94 if (bit == 0 && last_bit == 1) {
95 // Check if we ever go up above HYSTERESIS_LIMIT before we dip down again.
96 bool true_pulse = false;
98 int min_level_after = 32767;
99 for (j = i; j < pcm.size(); ++j) {
100 min_level_after = std::min<int>(min_level_after, pcm[j]);
101 if (pcm[j] > 0) break;
102 if (pcm[j] < -HYSTERESIS_LIMIT) {
110 fprintf(stderr, "Ignored down-flank at %.6f seconds due to hysteresis (%d < %d).\n",
111 double(i) / SAMPLE_RATE, -min_level_after, HYSTERESIS_LIMIT);
118 double t = find_zerocrossing(pcm, i - 1) * (1.0 / SAMPLE_RATE);
119 if (last_downflank > 0) {
122 p.len = t - last_downflank;
130 // Calibrate on the first ~25k pulses (skip a few, just to be sure).
131 double calibration_factor = 1.0f;
132 if (pulses.size() < SYNC_PULSE_END) {
133 fprintf(stderr, "Too few pulses, not calibrating!\n");
136 for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) {
137 sum += pulses[i].len;
139 double mean_length = C64_FREQUENCY * sum / (SYNC_PULSE_END - SYNC_PULSE_START);
140 calibration_factor = SYNC_PULSE_LENGTH / mean_length;
141 fprintf(stderr, "Calibrated sync pulse length: %.2f -> %.2f (change %+.2f%%)\n",
142 mean_length, SYNC_PULSE_LENGTH, 100.0 * (calibration_factor - 1.0));
144 // Check for pulses outside +/- 10% (sign of misdetection).
145 for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) {
146 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
147 if (cycles < SYNC_PULSE_LENGTH / SYNC_TEST_TOLERANCE || cycles > SYNC_PULSE_LENGTH * SYNC_TEST_TOLERANCE) {
148 fprintf(stderr, "Sync cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
149 pulses[i].time, cycles);
153 // Compute the standard deviation (to check for uneven speeds).
155 for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) {
156 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
157 sum2 += (cycles - SYNC_PULSE_LENGTH) * (cycles - SYNC_PULSE_LENGTH);
159 double stddev = sqrt(sum2 / (SYNC_PULSE_END - SYNC_PULSE_START - 1));
160 fprintf(stderr, "Sync pulse length standard deviation: %.2f cycles\n",
164 FILE *fp = fopen("cycles.plot", "w");
165 std::vector<char> tap_data;
166 for (unsigned i = 0; i < pulses.size(); ++i) {
167 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
168 fprintf(fp, "%f %f\n", pulses[i].time, cycles);
169 int len = lrintf(cycles / TAP_RESOLUTION);
170 if (i > SYNC_PULSE_END && (cycles < 100 || cycles > 800)) {
171 fprintf(stderr, "Cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
172 pulses[i].time, cycles);
175 tap_data.push_back(len);
177 int overflow_len = lrintf(cycles);
178 tap_data.push_back(0);
179 tap_data.push_back(overflow_len & 0xff);
180 tap_data.push_back((overflow_len >> 8) & 0xff);
181 tap_data.push_back(overflow_len >> 16);
187 memcpy(hdr.identifier, "C64-TAPE-RAW", 12);
189 hdr.reserved[0] = hdr.reserved[1] = hdr.reserved[2] = 0;
190 hdr.data_len = tap_data.size();
192 fwrite(&hdr, sizeof(hdr), 1, stdout);
193 fwrite(tap_data.data(), tap_data.size(), 1, stdout);
195 // Output a debug raw file with pulse detection points.
196 fp = fopen("debug.raw", "wb");
199 unsigned pulsenum = 0;
200 for (unsigned i = 0; i < pcm.size(); ++i) {
201 unsigned next_pulse = (pulsenum >= pulses.size()) ? INT_MAX : int(pulses[pulsenum].time * SAMPLE_RATE);
202 if (i >= next_pulse) {
203 fwrite(&one, sizeof(one), 1, fp);
206 fwrite(&zero, sizeof(zero), 1, fp);