#define EQUAL_TEMPERAMENT 0
#define WELL_TEMPERED_GUITAR 1
-#define TUNING EQUAL_TEMPERAMENT
+#define TUNING WELL_TEMPERED_GUITAR
int get_dsp_fd();
void read_chunk(int fd, double *in, unsigned num_samples);
void apply_window(double *in, double *out, unsigned num_samples);
std::pair<double, double> find_peak(double *in, unsigned num_samples);
void find_peak_magnitudes(std::complex<double> *in, double *out, unsigned num_samples);
+std::pair<double, double> adjust_for_overtones(std::pair<double, double> base, double *in, unsigned num_samples);
double bin_to_freq(double bin, unsigned num_samples);
+double freq_to_bin(double freq, unsigned num_samples);
std::string freq_to_tonename(double freq);
std::pair<double, double> interpolate_peak(double ym1, double y0, double y1);
void print_spectrogram(double freq, double amp);
in = reinterpret_cast<double *> (fftw_malloc(sizeof(double) * FFT_LENGTH / PAD_FACTOR));
in_windowed = reinterpret_cast<double *> (fftw_malloc(sizeof(double) * FFT_LENGTH));
out = reinterpret_cast<std::complex<double> *> (fftw_malloc(sizeof(std::complex<double>) * (FFT_LENGTH / 2 + 1)));
- bins = reinterpret_cast<double *> (fftw_malloc(sizeof(double) * FFT_LENGTH / 2 + 1));
+ bins = reinterpret_cast<double *> (fftw_malloc(sizeof(double) * (FFT_LENGTH / 2 + 1)));
memset(in, 0, sizeof(double) * FFT_LENGTH / PAD_FACTOR);
fftw_execute(p);
find_peak_magnitudes(out, bins, FFT_LENGTH);
std::pair<double, double> peak = find_peak(bins, FFT_LENGTH);
+ if (peak.first > 0.0)
+ peak = adjust_for_overtones(peak, bins, FFT_LENGTH);
if (peak.first < 50.0 || peak.second - log10(FFT_LENGTH) < 0.0) {
#if TUNING == WELL_TEMPERED_GUITAR
int chan = 1;
ioctl(fd, SOUND_PCM_WRITE_CHANNELS, &chan);
- int rate = 22050;
+ int rate = SAMPLE_RATE;
ioctl(fd, SOUND_PCM_WRITE_RATE, &rate);
+ int max_fragments = 2;
+ int frag_shift = ffs(FFT_LENGTH / OVERLAP) - 1;
+ int fragments = (max_fragments << 16) | frag_shift;
+ ioctl(fd, SNDCTL_DSP_SETFRAGMENT, &fragments);
+
ioctl(3, SNDCTL_DSP_SYNC, 0);
return fd;
best_bin /= i;
// consider sliding one bin up or down
- if (best_bin > 0 && in[best_bin - 1] > in[best_bin] && in[best_bin - 1] > in[best_bin - 2]) {
+ if (best_bin > 1 && in[best_bin - 1] > in[best_bin] && in[best_bin - 1] > in[best_bin - 2]) {
--best_bin;
- } else if (best_bin < num_samples / 2 && in[best_bin + 1] > in[best_bin] && in[best_bin + 1] > in[best_bin + 2]) {
+ } else if (best_bin < num_samples / 2 - 1 && in[best_bin + 1] > in[best_bin] && in[best_bin + 1] > in[best_bin + 2]) {
++best_bin;
}
}
}
+ if (best_bin == 0 || best_bin == num_samples / 2) {
+ return std::make_pair(-1.0, 0.0);
+ }
std::pair<double, double> peak =
interpolate_peak(in[best_bin - 1],
in[best_bin],
return std::make_pair(bin_to_freq(double(best_bin) + peak.first, num_samples), peak.second);
}
+// it's perhaps not ideal to _first_ find the peak and _then_ the harmonics --
+// ideally, one should find the set of all peaks and then determine the likely
+// base from that... something for later. :-)
+std::pair<double, double> adjust_for_overtones(std::pair<double, double> base, double *in, unsigned num_samples)
+{
+ double mu = base.first, var = 1.0 / (base.second * base.second);
+
+ //printf("Base at %.2f (amp=%5.2fdB)\n", base.first, base.second);
+
+ for (unsigned i = 2; i < 10; ++i) {
+ unsigned middle = unsigned(floor(freq_to_bin(base.first, num_samples) * i + 0.5));
+ unsigned lower = middle - (i+1)/2, upper = middle + (i+1)/2;
+
+ if (upper >= num_samples)
+ upper = num_samples - 2;
+
+ // printf("Searching in [%u,%u] = %f..%f\n", lower, upper, bin_to_freq(lower, num_samples), bin_to_freq(upper, num_samples));
+
+ // search for a peak in this interval
+ double best_harmonics_freq = -1.0;
+ double best_harmonics_amp = -1.0;
+ for (unsigned j = lower; j <= upper; ++j) {
+ if (in[j] > in[j-1] && in[j] > in[j+1]) {
+ std::pair<double, double> peak =
+ interpolate_peak(in[j - 1],
+ in[j],
+ in[j + 1]);
+
+ if (peak.second > best_harmonics_amp) {
+ best_harmonics_freq = bin_to_freq(j + peak.first, num_samples);
+ best_harmonics_amp = peak.second;
+ }
+ }
+ }
+
+ if (best_harmonics_amp <= 0.0)
+ continue;
+
+ //printf("Found overtone %u at %.2f (amp=%5.2fdB)\n", i, best_harmonics_freq,
+ // best_harmonics_amp);
+
+ double this_mu = best_harmonics_freq / double(i);
+ double this_var = 1.0 / (best_harmonics_amp * best_harmonics_amp);
+
+ double k = var / (var + this_var);
+ mu = (1.0 - k) * mu + k * this_mu;
+ var *= (1.0 - k);
+ }
+ return std::make_pair(mu, base.second);
+}
+
double bin_to_freq(double bin, unsigned num_samples)
{
return bin * SAMPLE_RATE / double(num_samples);
}
+double freq_to_bin(double freq, unsigned num_samples)
+{
+ return freq * double(num_samples) / double(SAMPLE_RATE);
+}
/*
* Given three bins, find the interpolated real peak based
projects / pitch / blobdiff