File size: 4,777 Bytes
17fe826
 
 
 
 
 
 
 
 
 
 
 
 
 
b15b6e4
17fe826
 
 
 
 
 
 
 
 
c2149f9
17fe826
 
 
 
 
 
c2149f9
17fe826
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
"""
Audio processing tools to convert between spectrogram images and waveforms.
"""
import io
import typing as T

import numpy as np
from PIL import Image
import pydub
from scipy.io import wavfile
import torch
import torchaudio


def wav_bytes_from_spectrogram_image(image: Image.Image) -> T.Tuple[io.BytesIO, float]:
    """
    Reconstruct a WAV audio clip from a spectrogram image. Also returns the duration in seconds.
    """

    max_volume = 50
    power_for_image = 0.25
    Sxx = spectrogram_from_image(image, max_volume=max_volume, power_for_image=power_for_image)

    sample_rate = 44100  # [Hz]
    clip_duration_ms = 5000  # [ms]

    bins_per_image = 512
    n_mels = 512

    # FFT parameters
    window_duration_ms = 100  # [ms]
    padded_duration_ms = 400  # [ms]
    step_size_ms = 10  # [ms]

    # Derived parameters
    num_samples = int(image.width / float(bins_per_image) * clip_duration_ms) * sample_rate
    n_fft = int(padded_duration_ms / 1000.0 * sample_rate)
    hop_length = int(step_size_ms / 1000.0 * sample_rate)
    win_length = int(window_duration_ms / 1000.0 * sample_rate)

    samples = waveform_from_spectrogram(
        Sxx=Sxx,
        n_fft=n_fft,
        hop_length=hop_length,
        win_length=win_length,
        num_samples=num_samples,
        sample_rate=sample_rate,
        mel_scale=True,
        n_mels=n_mels,
        max_mel_iters=200,
        num_griffin_lim_iters=32,
    )

    wav_bytes = io.BytesIO()
    wavfile.write(wav_bytes, sample_rate, samples.astype(np.int16))
    wav_bytes.seek(0)

    duration_s = float(len(samples)) / sample_rate

    return wav_bytes, duration_s


def spectrogram_from_image(
    image: Image.Image, max_volume: float = 50, power_for_image: float = 0.25
) -> np.ndarray:
    """
    Compute a spectrogram magnitude array from a spectrogram image.

    TODO(hayk): Add image_from_spectrogram and call this out as the reverse.
    """
    # Convert to a numpy array of floats
    data = np.array(image).astype(np.float32)

    # Flip Y take a single channel
    data = data[::-1, :, 0]

    # Invert
    data = 255 - data

    # Rescale to max volume
    data = data * max_volume / 255

    # Reverse the power curve
    data = np.power(data, 1 / power_for_image)

    return data


def spectrogram_from_waveform(
    waveform: np.ndarray,
    sample_rate: int,
    n_fft: int,
    hop_length: int,
    win_length: int,
    mel_scale: bool = True,
    n_mels: int = 512,
) -> np.ndarray:
    """
    Compute a spectrogram from a waveform.
    """

    spectrogram_func = torchaudio.transforms.Spectrogram(
        n_fft=n_fft,
        power=None,
        hop_length=hop_length,
        win_length=win_length,
    )

    waveform_tensor = torch.from_numpy(waveform.astype(np.float32)).reshape(1, -1)
    Sxx_complex = spectrogram_func(waveform_tensor).numpy()[0]

    Sxx_mag = np.abs(Sxx_complex)

    if mel_scale:
        mel_scaler = torchaudio.transforms.MelScale(
            n_mels=n_mels,
            sample_rate=sample_rate,
            f_min=0,
            f_max=10000,
            n_stft=n_fft // 2 + 1,
            norm=None,
            mel_scale="htk",
        )

        Sxx_mag = mel_scaler(torch.from_numpy(Sxx_mag)).numpy()

    return Sxx_mag


def waveform_from_spectrogram(
    Sxx: np.ndarray,
    n_fft: int,
    hop_length: int,
    win_length: int,
    num_samples: int,
    sample_rate: int,
    mel_scale: bool = True,
    n_mels: int = 512,
    max_mel_iters: int = 200,
    num_griffin_lim_iters: int = 32,
    device: str = "cuda:0",
) -> np.ndarray:
    """
    Reconstruct a waveform from a spectrogram.

    This is an approximate inverse of spectrogram_from_waveform, using the Griffin-Lim algorithm
    to approximate the phase.
    """
    Sxx_torch = torch.from_numpy(Sxx).to(device)

    # TODO(hayk): Make this a class that caches the two things

    if mel_scale:
        mel_inv_scaler = torchaudio.transforms.InverseMelScale(
            n_mels=n_mels,
            sample_rate=sample_rate,
            f_min=0,
            f_max=10000,
            n_stft=n_fft // 2 + 1,
            norm=None,
            mel_scale="htk",
            max_iter=max_mel_iters,
        ).to(device)

        Sxx_torch = mel_inv_scaler(Sxx_torch)

    griffin_lim = torchaudio.transforms.GriffinLim(
        n_fft=n_fft,
        win_length=win_length,
        hop_length=hop_length,
        power=1.0,
        n_iter=num_griffin_lim_iters,
    ).to(device)

    waveform = griffin_lim(Sxx_torch).cpu().numpy()

    return waveform


def mp3_bytes_from_wav_bytes(wav_bytes: io.BytesIO) -> io.BytesIO:
    mp3_bytes = io.BytesIO()
    sound = pydub.AudioSegment.from_wav(wav_bytes)
    sound.export(mp3_bytes, format="mp3")
    mp3_bytes.seek(0)
    return mp3_bytes