youtube-music-transcribe / mt3 /spectrograms.py
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# Copyright 2022 The MT3 Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Audio spectrogram functions."""
import dataclasses
from ddsp import spectral_ops
import tensorflow as tf
# defaults for spectrogram config
DEFAULT_SAMPLE_RATE = 16000
DEFAULT_HOP_WIDTH = 128
DEFAULT_NUM_MEL_BINS = 512
# fixed constants; add these to SpectrogramConfig before changing
FFT_SIZE = 2048
MEL_LO_HZ = 20.0
@dataclasses.dataclass
class SpectrogramConfig:
"""Spectrogram configuration parameters."""
sample_rate: int = DEFAULT_SAMPLE_RATE
hop_width: int = DEFAULT_HOP_WIDTH
num_mel_bins: int = DEFAULT_NUM_MEL_BINS
@property
def abbrev_str(self):
s = ''
if self.sample_rate != DEFAULT_SAMPLE_RATE:
s += 'sr%d' % self.sample_rate
if self.hop_width != DEFAULT_HOP_WIDTH:
s += 'hw%d' % self.hop_width
if self.num_mel_bins != DEFAULT_NUM_MEL_BINS:
s += 'mb%d' % self.num_mel_bins
return s
@property
def frames_per_second(self):
return self.sample_rate / self.hop_width
def split_audio(samples, spectrogram_config):
"""Split audio into frames."""
return tf.signal.frame(
samples,
frame_length=spectrogram_config.hop_width,
frame_step=spectrogram_config.hop_width,
pad_end=True)
def compute_spectrogram(samples, spectrogram_config):
"""Compute a mel spectrogram."""
overlap = 1 - (spectrogram_config.hop_width / FFT_SIZE)
return spectral_ops.compute_logmel(
samples,
bins=spectrogram_config.num_mel_bins,
lo_hz=MEL_LO_HZ,
overlap=overlap,
fft_size=FFT_SIZE,
sample_rate=spectrogram_config.sample_rate)
def flatten_frames(frames):
"""Convert frames back into a flat array of samples."""
return tf.reshape(frames, [-1])
def input_depth(spectrogram_config):
return spectrogram_config.num_mel_bins