8 #define LANCZOS_RADIUS 30
10 #define HYSTERESIS_LIMIT 1000
15 return 1.0f - fabs(x);
22 double weight(double x)
24 if (fabs(x) > LANCZOS_RADIUS) {
27 return sinc(M_PI * x) * sinc(M_PI * x / LANCZOS_RADIUS);
30 double weight(double x)
35 return 1.0f - fabs(x);
39 double interpolate(const std::vector<short> &pcm, double i)
41 int lower = std::max<int>(ceil(i - LANCZOS_RADIUS), 0);
42 int upper = std::min<int>(floor(i + LANCZOS_RADIUS), pcm.size() - 1);
45 for (int x = lower; x <= upper; ++x) {
46 sum += pcm[x] * weight(i - x);
52 double find_zerocrossing(const std::vector<short> &pcm, int x)
57 if (pcm[x + 1] == 0) {
61 assert(pcm[x + 1] > 0);
66 while (upper - lower > 1e-6) {
67 double mid = 0.5f * (upper + lower);
68 if (interpolate(pcm, mid) > 0) {
75 return 0.5f * (upper + lower);
78 int main(int argc, char **argv)
80 std::vector<short> pcm;
82 while (!feof(stdin)) {
84 ssize_t ret = fread(buf, 2, BUFSIZE, stdin);
86 pcm.insert(pcm.end(), buf, buf + ret);
91 for (int i = 0; i < LEN; ++i) {
92 in[i] += rand() % 10000;
97 for (int i = 0; i < LEN; ++i) {
98 printf("%d\n", in[i]);
102 double last_upflank = -1;
103 int last_max_level = 0;
104 for (int i = 0; i < pcm.size(); ++i) {
105 int bit = (pcm[i] > 0) ? 1 : 0;
106 if (bit == 1 && last_bit == 0 && last_max_level > HYSTERESIS_LIMIT) {
108 double t = find_zerocrossing(pcm, i - 1) * (123156.0/44100.0);
109 if (last_upflank > 0) {
110 // fprintf(stderr, "length: %f (0x%x)\n", t - last_upflank, lrintf(t - last_upflank));
111 int len = lrintf(t - last_upflank);
112 printf("0x%x\n", len);
117 last_max_level = std::max(last_max_level, abs(pcm[i]));