#include <stdio.h>
#include <string.h>
#include <math.h>
-#include <unistd.h>
#include <assert.h>
+#include <limits.h>
#include <vector>
#include <algorithm>
-#define LANCZOS_RADIUS 30
+#include "interpolate.h"
+
#define BUFSIZE 4096
#define HYSTERESIS_LIMIT 3000
#define SAMPLE_RATE 44100
#define SYNC_PULSE_START 1000
#define SYNC_PULSE_END 15000
-#define SYNC_PULSE_LENGTH 380.0
+#define SYNC_PULSE_LENGTH 378.0
#define SYNC_TEST_TOLERANCE 1.10
struct tap_header {
unsigned int data_len;
};
-double sinc(double x)
-{
- if (fabs(x) < 1e-6) {
- return 1.0f - fabs(x);
- } else {
- return sin(x) / x;
- }
-}
-
-#if 0
-double weight(double x)
-{
- if (fabs(x) > LANCZOS_RADIUS) {
- return 0.0f;
- }
- return sinc(M_PI * x) * sinc(M_PI * x / LANCZOS_RADIUS);
-}
-#else
-double weight(double x)
-{
- if (fabs(x) > 1.0f) {
- return 0.0f;
- }
- return 1.0f - fabs(x);
-}
-#endif
-
-double interpolate(const std::vector<short> &pcm, double i)
-{
- int lower = std::max<int>(ceil(i - LANCZOS_RADIUS), 0);
- int upper = std::min<int>(floor(i + LANCZOS_RADIUS), pcm.size() - 1);
- double sum = 0.0f;
-
- for (int x = lower; x <= upper; ++x) {
- sum += pcm[x] * weight(i - x);
- }
- return sum;
-}
-
// between [x,x+1]
double find_zerocrossing(const std::vector<short> &pcm, int x)
{
return x + 1;
}
- assert(pcm[x + 1] > 0);
- assert(pcm[x] < 0);
+ assert(pcm[x + 1] < 0);
+ assert(pcm[x] > 0);
- double lower = x;
- double upper = x + 1;
- while (upper - lower > 1e-6) {
+ double upper = x;
+ double lower = x + 1;
+ while (lower - upper > 1e-3) {
double mid = 0.5f * (upper + lower);
- if (interpolate(pcm, mid) > 0) {
+ if (lanczos_interpolate(pcm, mid) > 0) {
upper = mid;
} else {
lower = mid;
int main(int argc, char **argv)
{
+ make_lanczos_weight_table();
std::vector<short> pcm;
while (!feof(stdin)) {
// Find the flanks.
int last_bit = -1;
- double last_upflank = -1;
- int last_max_level = 0;
+ double last_downflank = -1;
for (unsigned i = 0; i < pcm.size(); ++i) {
int bit = (pcm[i] > 0) ? 1 : 0;
- if (bit == 1 && last_bit == 0 && last_max_level > HYSTERESIS_LIMIT) {
- // up-flank!
+ 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_upflank > 0) {
+ if (last_downflank > 0) {
pulse p;
p.time = t;
- p.len = t - last_upflank;
+ p.len = t - last_downflank;
pulses.push_back(p);
}
- last_upflank = t;
- last_max_level = 0;
+ last_downflank = t;
}
- last_max_level = std::max(last_max_level, abs(pcm[i]));
last_bit = bit;
}
}
double mean_length = C64_FREQUENCY * sum / (SYNC_PULSE_END - SYNC_PULSE_START);
calibration_factor = SYNC_PULSE_LENGTH / mean_length;
- fprintf(stderr, "Calibrated sync pulse length: %.2f -> 380.0 (change %+.2f%%)\n",
- mean_length, 100.0 * (calibration_factor - 1.0));
+ fprintf(stderr, "Calibrated sync pulse length: %.2f -> %.2f (change %+.2f%%)\n",
+ mean_length, SYNC_PULSE_LENGTH, 100.0 * (calibration_factor - 1.0));
// Check for pulses outside +/- 10% (sign of misdetection).
for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) {
double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
if (cycles < SYNC_PULSE_LENGTH / SYNC_TEST_TOLERANCE || cycles > SYNC_PULSE_LENGTH * SYNC_TEST_TOLERANCE) {
- fprintf(stderr, "Sync cycle with upflank at %.6f was detected at %.0f cycles; misdetect?\n",
+ fprintf(stderr, "Sync cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
pulses[i].time, cycles);
}
}
stddev);
}
+ FILE *fp = fopen("cycles.plot", "w");
std::vector<char> tap_data;
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);
int len = lrintf(cycles / TAP_RESOLUTION);
if (i > SYNC_PULSE_END && (cycles < 100 || cycles > 800)) {
- fprintf(stderr, "Cycle with upflank at %.6f was detected at %.0f cycles; misdetect?\n",
+ fprintf(stderr, "Cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
pulses[i].time, cycles);
}
if (len <= 255) {
tap_data.push_back(overflow_len >> 16);
}
}
+ fclose(fp);
tap_header hdr;
memcpy(hdr.identifier, "C64-TAPE-RAW", 12);
fwrite(&hdr, sizeof(hdr), 1, stdout);
fwrite(tap_data.data(), tap_data.size(), 1, stdout);
+
+ // Output a debug raw file with pulse detection points.
+ fp = fopen("debug.raw", "wb");
+ short one = 32767;
+ short zero = 0;
+ unsigned pulsenum = 0;
+ for (unsigned i = 0; i < pcm.size(); ++i) {
+ unsigned next_pulse = (pulsenum >= pulses.size()) ? INT_MAX : int(pulses[pulsenum].time * SAMPLE_RATE);
+ if (i >= next_pulse) {
+ fwrite(&one, sizeof(one), 1, fp);
+ ++pulsenum;
+ } else {
+ fwrite(&zero, sizeof(zero), 1, fp);
+ }
+ }
+ fclose(fp);
}
projects / c64tapwav / blobdiff