9 #include "interpolate.h"
13 #define HYSTERESIS_LIMIT 3000
14 #define SAMPLE_RATE 44100
15 #define C64_FREQUENCY 985248
17 #define SYNC_PULSE_START 1000
18 #define SYNC_PULSE_END 15000
19 #define SYNC_PULSE_LENGTH 378.0
20 #define SYNC_TEST_TOLERANCE 1.10
23 double find_zerocrossing(const std::vector<short> &pcm, int x)
28 if (pcm[x + 1] == 0) {
32 assert(pcm[x + 1] < 0);
37 while (lower - upper > 1e-3) {
38 double mid = 0.5f * (upper + lower);
39 if (lanczos_interpolate(pcm, mid) > 0) {
46 return 0.5f * (upper + lower);
50 double time; // in seconds from start
51 double len; // in seconds
54 int main(int argc, char **argv)
56 make_lanczos_weight_table();
57 std::vector<short> pcm;
59 while (!feof(stdin)) {
61 ssize_t ret = fread(buf, 2, BUFSIZE, stdin);
63 pcm.insert(pcm.end(), buf, buf + ret);
68 for (int i = 0; i < LEN; ++i) {
69 in[i] += rand() % 10000;
74 for (int i = 0; i < LEN; ++i) {
75 printf("%d\n", in[i]);
79 std::vector<pulse> pulses; // in seconds
83 double last_downflank = -1;
84 for (unsigned i = 0; i < pcm.size(); ++i) {
85 int bit = (pcm[i] > 0) ? 1 : 0;
86 if (bit == 0 && last_bit == 1) {
87 // Check if we ever go up above HYSTERESIS_LIMIT before we dip down again.
88 bool true_pulse = false;
90 int min_level_after = 32767;
91 for (j = i; j < pcm.size(); ++j) {
92 min_level_after = std::min<int>(min_level_after, pcm[j]);
93 if (pcm[j] > 0) break;
94 if (pcm[j] < -HYSTERESIS_LIMIT) {
102 fprintf(stderr, "Ignored down-flank at %.6f seconds due to hysteresis (%d < %d).\n",
103 double(i) / SAMPLE_RATE, -min_level_after, HYSTERESIS_LIMIT);
110 double t = find_zerocrossing(pcm, i - 1) * (1.0 / SAMPLE_RATE);
111 if (last_downflank > 0) {
114 p.len = t - last_downflank;
122 // Calibrate on the first ~25k pulses (skip a few, just to be sure).
123 double calibration_factor = 1.0f;
124 if (pulses.size() < SYNC_PULSE_END) {
125 fprintf(stderr, "Too few pulses, not calibrating!\n");
128 for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) {
129 sum += pulses[i].len;
131 double mean_length = C64_FREQUENCY * sum / (SYNC_PULSE_END - SYNC_PULSE_START);
132 calibration_factor = SYNC_PULSE_LENGTH / mean_length;
133 fprintf(stderr, "Calibrated sync pulse length: %.2f -> %.2f (change %+.2f%%)\n",
134 mean_length, SYNC_PULSE_LENGTH, 100.0 * (calibration_factor - 1.0));
136 // Check for pulses outside +/- 10% (sign of misdetection).
137 for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) {
138 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
139 if (cycles < SYNC_PULSE_LENGTH / SYNC_TEST_TOLERANCE || cycles > SYNC_PULSE_LENGTH * SYNC_TEST_TOLERANCE) {
140 fprintf(stderr, "Sync cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
141 pulses[i].time, cycles);
145 // Compute the standard deviation (to check for uneven speeds).
147 for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) {
148 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
149 sum2 += (cycles - SYNC_PULSE_LENGTH) * (cycles - SYNC_PULSE_LENGTH);
151 double stddev = sqrt(sum2 / (SYNC_PULSE_END - SYNC_PULSE_START - 1));
152 fprintf(stderr, "Sync pulse length standard deviation: %.2f cycles\n",
156 FILE *fp = fopen("cycles.plot", "w");
157 std::vector<char> tap_data;
158 for (unsigned i = 0; i < pulses.size(); ++i) {
159 double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
160 fprintf(fp, "%f %f\n", pulses[i].time, cycles);
161 int len = lrintf(cycles / TAP_RESOLUTION);
162 if (i > SYNC_PULSE_END && (cycles < 100 || cycles > 800)) {
163 fprintf(stderr, "Cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
164 pulses[i].time, cycles);
167 tap_data.push_back(len);
169 int overflow_len = lrintf(cycles);
170 tap_data.push_back(0);
171 tap_data.push_back(overflow_len & 0xff);
172 tap_data.push_back((overflow_len >> 8) & 0xff);
173 tap_data.push_back(overflow_len >> 16);
179 memcpy(hdr.identifier, "C64-TAPE-RAW", 12);
181 hdr.reserved[0] = hdr.reserved[1] = hdr.reserved[2] = 0;
182 hdr.data_len = tap_data.size();
184 fwrite(&hdr, sizeof(hdr), 1, stdout);
185 fwrite(tap_data.data(), tap_data.size(), 1, stdout);
187 // Output a debug raw file with pulse detection points.
188 fp = fopen("debug.raw", "wb");
191 unsigned pulsenum = 0;
192 for (unsigned i = 0; i < pcm.size(); ++i) {
193 unsigned next_pulse = (pulsenum >= pulses.size()) ? INT_MAX : int(pulses[pulsenum].time * SAMPLE_RATE);
194 if (i >= next_pulse) {
195 fwrite(&one, sizeof(one), 1, fp);
198 fwrite(&zero, sizeof(zero), 1, fp);