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Copy pathmel.cpp
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165 lines (144 loc) · 5.4 KB
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#include "mel.h"
#include <algorithm>
#include <cmath>
#include <complex>
#include <cstring>
#include <stdexcept>
#include "pocketfft_hdronly.h"
namespace muscriptor {
namespace {
float hz_to_mel_htk(float freq) {
return 2595.f * std::log10(1.f + freq / 700.f);
}
float mel_to_hz_htk(float mel) {
return 700.f * (std::pow(10.f, mel / 2595.f) - 1.f);
}
// PyTorch F.pad(x, (pad, pad), mode='reflect') for 1-D.
std::vector<float> reflect_pad_1d(const float* wav, size_t n, int pad) {
if (n == 0) return {};
if (n == 1) {
return std::vector<float>(n + 2 * static_cast<size_t>(pad), wav[0]);
}
std::vector<float> out(n + 2 * static_cast<size_t>(pad));
std::memcpy(out.data() + pad, wav, n * sizeof(float));
// Left: indices pad-1, pad-2, ... map to wav[1], wav[2], ... (excluding edge)
for (int i = 0; i < pad; ++i) {
int src = static_cast<int>(i + 1);
// Fold if longer than signal interior
int period = static_cast<int>(n) - 1;
while (src < 0 || src >= static_cast<int>(n)) {
if (src < 0) src = -src;
if (src >= static_cast<int>(n)) src = 2 * period - src;
}
out[pad - 1 - i] = wav[src];
}
// Right: wav[n-2], wav[n-3], ...
for (int i = 0; i < pad; ++i) {
int src = static_cast<int>(n) - 2 - i;
int period = static_cast<int>(n) - 1;
while (src < 0 || src >= static_cast<int>(n)) {
if (src < 0) src = -src;
if (src >= static_cast<int>(n)) src = 2 * period - src;
}
out[pad + static_cast<int>(n) + i] = wav[src];
}
return out;
}
} // namespace
std::vector<float> melscale_fbanks(int n_freqs, float f_min, float f_max, int n_mels, int sample_rate) {
std::vector<float> all_freqs(n_freqs);
for (int i = 0; i < n_freqs; ++i) {
all_freqs[i] = static_cast<float>(i) * (sample_rate / 2.f) / static_cast<float>(n_freqs - 1);
}
float m_min = hz_to_mel_htk(f_min);
float m_max = hz_to_mel_htk(f_max);
std::vector<float> f_pts(n_mels + 2);
for (int i = 0; i < n_mels + 2; ++i) {
float m = m_min + (m_max - m_min) * static_cast<float>(i) / static_cast<float>(n_mels + 1);
f_pts[i] = mel_to_hz_htk(m);
}
std::vector<float> f_diff(n_mels + 1);
for (int i = 0; i < n_mels + 1; ++i) f_diff[i] = f_pts[i + 1] - f_pts[i];
std::vector<float> fb(n_freqs * n_mels, 0.f);
for (int i = 0; i < n_freqs; ++i) {
for (int j = 0; j < n_mels; ++j) {
float down = -(f_pts[j] - all_freqs[i]) / f_diff[j];
float up = (f_pts[j + 2] - all_freqs[i]) / f_diff[j + 1];
fb[i * n_mels + j] = std::max(0.f, std::min(down, up));
}
}
return fb;
}
std::vector<float> compute_mel_spectrogram(
const float* wav, size_t n_samples,
const float* window,
const float* fb,
const MelSpectrogramConfig& cfg,
int* out_n_frames) {
const int n_fft = cfg.n_fft;
const int hop = cfg.hop_length;
const int n_freqs = n_fft / 2 + 1;
const int n_mels = cfg.n_mels;
std::vector<float> padded;
const float* signal = wav;
size_t sig_len = n_samples;
if (cfg.center) {
padded = reflect_pad_1d(wav, n_samples, n_fft / 2);
signal = padded.data();
sig_len = padded.size();
}
if (sig_len < static_cast<size_t>(n_fft)) {
if (out_n_frames) *out_n_frames = 0;
return {};
}
int n_frames = 1 + static_cast<int>((sig_len - n_fft) / hop);
if (out_n_frames) *out_n_frames = n_frames;
std::vector<float> mel(static_cast<size_t>(n_frames) * n_mels, 0.f);
std::vector<float> frame(n_fft);
std::vector<std::complex<float>> spectrum(n_freqs);
pocketfft::shape_t shape = {static_cast<size_t>(n_fft)};
pocketfft::stride_t stride_in = {sizeof(float)};
pocketfft::stride_t stride_out = {sizeof(std::complex<float>)};
pocketfft::shape_t axes = {0};
for (int t = 0; t < n_frames; ++t) {
const float* src = signal + static_cast<size_t>(t) * hop;
for (int i = 0; i < n_fft; ++i) {
frame[i] = src[i] * window[i];
}
pocketfft::r2c(shape, stride_in, stride_out, axes, pocketfft::FORWARD,
frame.data(), spectrum.data(), 1.f);
std::vector<float> power(n_freqs);
for (int f = 0; f < n_freqs; ++f) {
float mag = std::abs(spectrum[f]);
power[f] = (cfg.power == 1.f) ? mag : std::pow(mag, cfg.power);
}
for (int m = 0; m < n_mels; ++m) {
float sum = 0.f;
for (int f = 0; f < n_freqs; ++f) {
sum += power[f] * fb[static_cast<size_t>(f) * n_mels + m];
}
if (cfg.log_scale) sum = std::log(sum + cfg.eps);
mel[static_cast<size_t>(t) * n_mels + m] = sum;
}
}
return mel;
}
std::vector<float> mel_project(
const float* mel, int n_frames, int n_mels,
const float* weight,
int dim,
const float* bias) {
std::vector<float> out(static_cast<size_t>(n_frames) * dim, 0.f);
for (int t = 0; t < n_frames; ++t) {
for (int d = 0; d < dim; ++d) {
float sum = bias ? bias[d] : 0.f;
for (int m = 0; m < n_mels; ++m) {
sum += weight[static_cast<size_t>(d) * n_mels + m] *
mel[static_cast<size_t>(t) * n_mels + m];
}
out[static_cast<size_t>(t) * dim + d] = sum;
}
}
return out;
}
} // namespace muscriptor