7 #define LANCZOS_RADIUS 30
9 #define HYSTERESIS_LIMIT 1000
14 return 1.0f - fabs(x);
21 double weight(double x)
23 if (fabs(x) > LANCZOS_RADIUS) {
26 return sinc(M_PI * x) * sinc(M_PI * x / LANCZOS_RADIUS);
29 double weight(double x)
34 return 1.0f - fabs(x);
38 double interpolate(const short *in, double i)
40 int lower = std::max(int(ceil(i - LANCZOS_RADIUS)), 0);
41 int upper = std::min(int(floor(i + LANCZOS_RADIUS)), LEN - 1);
44 for (int x = lower; x <= upper; ++x) {
45 sum += in[x] * weight(i - x);
53 double find_zerocrossing(int x)
62 assert(in[x + 1] > 0);
67 while (upper - lower > 1e-6) {
68 double mid = 0.5f * (upper + lower);
69 if (interpolate(in, mid) > 0) {
76 return 0.5f * (upper + lower);
79 int main(int argc, char **argv)
81 fread(in, LEN*2, 1, stdin);
84 for (int i = 0; i < LEN; ++i) {
85 in[i] += rand() % 10000;
90 for (int i = 0; i < LEN; ++i) {
91 printf("%d\n", in[i]);
95 double last_upflank = -1;
96 int last_max_level = 0;
97 for (int i = 0; i < LEN; ++i) {
98 int bit = (in[i] > 0) ? 1 : 0;
99 if (bit == 1 && last_bit == 0 && last_max_level > HYSTERESIS_LIMIT) {
101 double t = find_zerocrossing(i - 1) * (123156.0/44100.0);
102 if (last_upflank > 0) {
103 // fprintf(stderr, "length: %f (0x%x)\n", t - last_upflank, lrintf(t - last_upflank));
104 int len = lrintf(t - last_upflank);
105 printf("0x%x\n", len);
110 last_max_level = std::max(last_max_level, abs(in[i]));