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An implementation of “Signal reconstruction from melspectrogram based on bi-level consistency of full-band magnitude and phase" (iPALM-based mel-spectrogram inversion) in Python.
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# -*- coding: utf-8 -*- | |
"""Demonstration script for Mel-Spectrogram Inversion via iPALM. | |
Copyright (C) 2025 by Akira TAMAMORI | |
Permission is hereby granted, free of charge, to any person obtaining a copy | |
of this software and associated documentation files (the "Software"), to deal | |
in the Software without restriction, including without limitation the rights | |
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
copies of the Software, and to permit persons to whom the Software is | |
furnished to do so, subject to the following conditions: | |
The above copyright notice and this permission notice shall be included in all | |
copies or substantial portions of the Software. | |
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | |
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | |
SOFTWARE. | |
""" | |
import argparse | |
from typing import NamedTuple | |
< 8000 /td> | import librosa |
import numpy as np | |
import numpy.typing as npt | |
import soundfile as sf | |
from librosa.core.spectrum import istft, stft | |
from librosa.feature.spectral import melspectrogram | |
from pesq import pesq | |
from pystoi.stoi import stoi | |
from tqdm.auto import tqdm | |
class Arguments(NamedTuple): | |
"""Defines a class for miscellaneous configurations.""" | |
in_file: str # input wav file | |
out_file: str # output (reconstructed) wav file | |
class FeatureConfig(NamedTuple): | |
"""Defines a class for configurations of feature extraction.""" | |
n_mels: int # Number of Mel bins | |
n_fft: int = 1024 # FFT points | |
hop_length: int = 256 # Hop length | |
window: str = "hann" # Window type | |
class IPALMConfig(NamedTuple): | |
"""Defines a class for iPALM configurations.""" | |
n_steps: int # Number of optimization steps | |
lambd: float # iPALM parameter | |
alpha: float # iPALM parameter | |
def parse_args() -> tuple[Arguments, FeatureConfig, IPALMConfig]: | |
"""Parse command line arguments. | |
Returns: | |
arguments (Arguments): Miscellaneous configurations. | |
feat_config (FeatureConfig): Configurations of feature extraction. | |
ipalm_config (IPALMConfig): Configurations of iPALM. | |
""" | |
parser = argparse.ArgumentParser( | |
description="Demonstration script of iPALM-based mel-spectrogram inversion" | |
) | |
parser.add_argument("--in_file", type=str, default="in.wav", help="Input wav file") | |
parser.add_argument( | |
"--out_file", | |
type=str, | |
default="out.wav", | |
help="output (reconstructed) wav file", | |
) | |
parser.add_argument("--n_mels", type=int, default="80", help="Number of Mel bins") | |
parser.add_argument( | |
"--n_steps", type=int, default="500", help="Number of optimization steps" | |
) | |
parser.add_argument("--lambd", type=float, default="10", help="iPALM parameter") | |
parser.add_argument("--alpha", type=float, default="0.9", help="iPALM parameter") | |
args = parser.parse_args() | |
arguments = Arguments(in_file=args.in_file, out_file=args.out_file) | |
feat_config = FeatureConfig(n_mels=args.n_mels) | |
ipalm_config = IPALMConfig(n_steps=args.n_steps, lambd=args.lambd, alpha=args.alpha) | |
return arguments, feat_config, ipalm_config | |
def update_x( | |
z: npt.NDArray[np.complex128], y: npt.NDArray[np.float64] | |
) -> npt.NDArray[np.complex128]: | |
"""Update X using the proximity operator. | |
Args: | |
z (npt.NDArray[np.complex128]): Complex STFT coefficients (Z). | |
y (npt.NDArray[np.float64]): Full band magnitude (Y). | |
Returns: | |
x_new (npt.NDArray[np.complex128]): Updated complex STFT coefficients (X). | |
""" | |
abs_z = np.abs(z) | |
abs_z = np.where(abs_z == 0, 1e-8, abs_z) | |
x_new: npt.NDArray[np.complex128] = y * z / abs_z | |
return x_new | |
def update_w( | |
e_pinv_e: npt.NDArray[np.float64], | |
e_pinv_m: npt.NDArray[np.float64], | |
y: npt.NDArray[np.float64], | |
) -> npt.NDArray[np.float64]: | |
"""Update W using the proximity operator. | |
Args: | |
e_pinv_e (npt.NDArray[np.float64]): Product of E and Moore-Penrose | |
pseudo-inverse of E (E^{†} @ E). | |
e_pinv_m (npt.NDArray[np.float64]): Product of M and Moore-Penrose | |
pseudo-inverse of E (E^{†} @ M). | |
y (npt.NDArray[np.complex128]): Full band magnitude (Y). | |
Returns: | |
w_new (npt.NDArray[np.float64]): Updated Full band magnitude (W). | |
""" | |
w_new: npt.NDArray[np.float64] = y - e_pinv_e @ y + e_pinv_m | |
return w_new | |
def update_z( | |
x: npt.NDArray[np.complex128], n_fft: int, hop_length: int, window: str | |
) -> npt.NDArray[np.complex128]: | |
"""Update Z by projecting onto the STFT domain. | |
Args: | |
8000 | x (npt.NDArray[np.complex128]): Complex STFT coefficients (X). |
n_fft (int): FFT window size. | |
hop_length (int): Hop length. | |
window (str): Window type. | |
Returns: | |
z_new (npt.NDArray[np.complex128]): Updated complex STFT coefficients (Z). | |
""" | |
z_new = stft( | |
istft(x, hop_length=hop_length, window=window), | |
n_fft=n_fft, | |
hop_length=hop_length, | |
window=window, | |
) | |
return z_new | |
def update_y( | |
z: npt.NDArray[np.complex128], w: npt.NDArray[np.float64], lambd: float | |
) -> npt.NDArray[np.float64]: | |
"""Update Y using the proximity operator. | |
Args: | |
z (npt.NDArray[np.complex128]): Complex STFT coefficients (Z). | |
w (npt.NDArray[np.float64]): Full band magnitude (W). | |
lambd (float): iPALM parameter. | |
Returns: | |
y_new (npt.NDArray[np.float64]): Updated Full band magnitude (Y). | |
""" | |
y_new: npt.NDArray[np.float64] = np.maximum((np.abs(z) + lambd * w), 0) | |
y_new = y_new / (1 + lambd) | |
return y_new | |
def initialize_stft_from_mel( | |
mel_spec: npt.NDArray[np.float64], sr: int, n_fft: int | |
) -> npt.NDArray[np.complex128]: | |
"""Initialize STFT coefficients from mel-spectrogram using librosa.mel_to_stft. | |
Args: | |
mel_spec (npt.NDArray[np.float64]): Mel-spectrogram. | |
sr (int): Sampling rate. | |
n_fft (int): FFT size. | |
Returns: | |
npt.NDArray[np.complex128]: Initialized complex STFT coefficients. | |
""" | |
stft_coeffs: npt.NDArray[np.complex128] = librosa.feature.inverse.mel_to_stft( | |
mel_spec, sr=sr, n_fft=n_fft, power=1.0 | |
) | |
random_phase = np.random.uniform(-np.pi, np.pi, stft_coeffs.shape) | |
random_complex: npt.NDArray[np.complex128] = np.exp(1j * random_phase) | |
return np.abs(stft_coeffs) * random_complex | |
def ipalm_mel_inversion( | |
mel_spec: npt.NDArray[np.float64], | |
sr: int, | |
feat_config: FeatureConfig, | |
ipalm_config: IPALMConfig, | |
) -> npt.NDArray[np.float64]: | |
"""Perform iPALM-based mel-spectrogram inversion. | |
This function implements mel-spectrogram inversion using the inertial Proximal | |
Alternating Linearized Minimization (iPALM) algorithm, as described in the | |
following paper: | |
"Signal reconstruction from mel-spectrogram based on bi-level consistency of | |
full-band magnitude and phase" | |
Yoshiki Masuyama, Natsuki Ueno, and Nobutaka Ono | |
In Proc. IEEE Workshop Appl. Signal Process. Audio Acoust. (WASPAA), Oct. 2023 | |
Args: | |
mel_spec (npt.NDArray[np.float64]): Mel-spectrogram (M). | |
sr (int): Sampling rate. | |
feat_config (FeatureConfig): Configurations of feature extraction. | |
ipalm_config (IPALMConfig): Configurations of iPALM. | |
Returns: | |
reconstructed (npt.NDArray[np.float64]): Reconstructed time-domain signal. | |
""" | |
n_mels = mel_spec.shape[0] | |
mel_fbank = librosa.filters.mel( | |
sr=sr, n_fft=feat_config.n_fft, n_mels=n_mels | |
) # Mel-filterbank (E) | |
mel_fbank_pinv = np.linalg.pinv( | |
mel_fbank | |
) # Moore-Penrose pseudo-inverse of E (E^{†}) | |
e_pinv_e = mel_fbank_pinv @ mel_fbank # E^{†} @ E | |
e_pinv_m = mel_fbank_pinv @ mel_spec # E^{†} @ M | |
z = initialize_stft_from_mel(mel_spec, sr, feat_config.n_fft) | |
z_old = z | |
y = np.abs(z) | |
for _ in tqdm( | |
range(ipalm_config.n_steps), | |
bar_format="{desc}: {percentage:3.0f}% ({n_fmt} of {total_fmt}) |{bar}|" | |
+ " Elapsed Time: {elapsed} ETA: {remaining} ", | |
ascii=" #", | |
): | |
x = update_x(z + ipalm_config.alpha * (z - z_old), y) | |
w = update_w(e_pinv_e, e_pinv_m, y) | |
z_old = z | |
z = update_z(x, feat_config.n_fft, feat_config.hop_length, feat_config.window) | |
y = update_y(z, w, ipalm_config.lambd) | |
return istft(z, hop_length=feat_config.hop_length, window=feat_config.window) | |
def calculate_estoi( | |
orig_signal: npt.NDArray[np.float64], | |
reconst_signal: npt.NDArray[np.float64], | |
sr: int, | |
) -> float: | |
"""Calculate Extended Short-Time Objective Intelligibility (ESTOI). | |
Args: | |
orig_signal (npt.NDArray[np.float64]): Original time-domain signal. | |
reconst_signal (npt.NDArray[np.float64]): Reconstructed time-domain signal. | |
sr (int): Sampling rate. | |
Returns: | |
float: ESTOI score. | |
""" | |
if orig_signal.size > reconst_signal.size: | |
orig_signal = orig_signal[: reconst_signal.size] | |
else: | |
reconst_signal = reconst_signal[: orig_signal.size] | |
estoi_score: float = stoi(orig_signal, reconst_signal, sr, extended=True) | |
return estoi_score | |
def calculate_pesq( | |
orig_signal: npt.NDArray[np.float64], | |
reconst_signal: npt.NDArray[np.float64], | |
sr: int, | |
) -> float: | |
"""Calculate Perceptual Evaluation of Speech Quality (PESQ). | |
Args: | |
orig_signal (npt.NDArray[np.float64]): Original time-domain signal. | |
reconst_signal (npt.NDArray[np.float64]): Reconstructed time-domain signal. | |
sr (int): Sampling rate. | |
Returns: | |
float: PESQ score. | |
""" | |
pesq_score: float = pesq(sr, orig_signal, reconst_signal, "wb") | |
return pesq_score | |
def calculate_scm( | |
orig_spec: npt.NDArray[np.float64], | |
reconst_spec: npt.NDArray[np.float64], | |
) -> float: | |
"""Calculate Spectral Convergence Measure (SCM). | |
Args: | |
orig_spec (npt.NDArray[np.float64]): Original mel-spectrogram. | |
reconst_spec (npt.NDArray[np.float64]): Reconstructed mel-spectrogram. | |
Returns: | |
scm_score (float): SCM value in dB. | |
""" | |
numerator = np.linalg.norm(np.abs(reconst_spec) - orig_spec) | |
denominator = np.linalg.norm(orig_spec) | |
if denominator == 0: | |
return -float("inf") | |
scm_score: float = 20 * np.log10(numerator / denominator) | |
return scm_score | |
def main() -> None: | |
"""Perform demonstration.""" | |
args, feat_config, ipalm_config = parse_args() | |
orig_signal, sr = sf.read(args.in_file) | |
mel_spec = melspectrogram( | |
y=orig_signal, | |
sr=sr, | |
n_fft=feat_config.n_fft, | |
hop_length=feat_config.hop_length, | |
window=feat_config.window, | |
power=1.0, | |
) | |
reconst_signal = ipalm_mel_inversion(mel_spec, sr, feat_config, ipalm_config) | |
sf.write(args.out_file, reconst_signal, sr) | |
reconst_mel_spec = melspectrogram( | |
y=reconst_signal, | |
sr=sr, | |
n_fft=feat_config.n_fft, | |
hop_length=feat_config.hop_length, | |
window=feat_config.window, | |
power=1.0, | |
) | |
estoi_score = calculate_estoi(orig_signal, reconst_signal, sr) | |
pesq_score = calculate_pesq(orig_signal, reconst_signal, sr) | |
scm_score = calculate_scm(mel_spec, reconst_mel_spec) | |
print( | |
f"ESTOI = {estoi_score:.6f}, " | |
+ f"PESQ = {pesq_score:.6f}, " | |
+ f"SCM [dB] = {scm_score:.6f}" | |
) | |
if __name__ == "__main__": | |
main() |
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