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freq_min=125,
freq_max=7600,
**kwargs,
):
super().__init__(**kwargs)
self.frame_length = frame_length
self.frame_step = frame_step
self.fft_length = fft_length
self.sampling_rate = sampling_rate
self.num_mel_channels = num_mel_channels
self.freq_min = freq_min
self.freq_max = freq_max
# Defining mel filter. This filter will be multiplied with the STFT output
self.mel_filterbank = tf.signal.linear_to_mel_weight_matrix(
num_mel_bins=self.num_mel_channels,
num_spectrogram_bins=self.frame_length // 2 + 1,
sample_rate=self.sampling_rate,
lower_edge_hertz=self.freq_min,
upper_edge_hertz=self.freq_max,
)
def call(self, audio, training=True):
# We will only perform the transformation during training.
if training:
# Taking the Short Time Fourier Transform. Ensure that the audio is padded.
# In the paper, the STFT output is padded using the 'REFLECT' strategy.
stft = tf.signal.stft(
tf.squeeze(audio, -1),
self.frame_length,
self.frame_step,
self.fft_length,
pad_end=True,
)
# Taking the magnitude of the STFT output
magnitude = tf.abs(stft)
# Multiplying the Mel-filterbank with the magnitude and scaling it using the db scale
mel = tf.matmul(tf.square(magnitude), self.mel_filterbank)
log_mel_spec = tfio.audio.dbscale(mel, top_db=80)
return log_mel_spec
else:
return audio
def get_config(self):
config = super(MelSpec, self).get_config()
config.update(
{
\"frame_length\": self.frame_length,
\"frame_step\": self.frame_step,
\"fft_length\": self.fft_length,
\"sampling_rate\": self.sampling_rate,
\"num_mel_channels\": self.num_mel_channels,
\"freq_min\": self.freq_min,
\"freq_max\": self.freq_max,
}
)
return config
The residual convolutional block extensively uses dilations and has a total receptive field of 27 timesteps per block. The dilations must grow as a power of the kernel_size to ensure reduction of hissing noise in the output. The network proposed by the paper is as follows:
ConvBlock
# Creating the residual stack block
def residual_stack(input, filters):
\"\"\"Convolutional residual stack with weight normalization.
Args:
filter: int, determines filter size for the residual stack.
Returns:
Residual stack output.
\"\"\"
c1 = addon_layers.WeightNormalization(
layers.Conv1D(filters, 3, dilation_rate=1, padding=\"same\"), data_init=False
)(input)
lrelu1 = layers.LeakyReLU()(c1)
c2 = addon_layers.WeightNormalization(
layers.Conv1D(filters, 3, dilation_rate=1, padding=\"same\"), data_init=False
)(lrelu1)
add1 = layers.Add()([c2, input])
lrelu2 = layers.LeakyReLU()(add1)
c3 = addon_layers.WeightNormalization(
layers.Conv1D(filters, 3, dilation_rate=3, padding=\"same\"), data_init=False
)(lrelu2)
lrelu3 = layers.LeakyReLU()(c3)
c4 = addon_layers.WeightNormalization(
layers.Conv1D(filters, 3, dilation_rate=1, padding=\"same\"), data_init=False
)(lrelu3)
add2 = layers.Add()([add1, c4])
lrelu4 = layers.LeakyReLU()(add2)
c5 = addon_layers.WeightNormalization(
layers.Conv1D(filters, 3, dilation_rate=9, padding=\"same\"), data_init=False
)(lrelu4)
lrelu5 = layers.LeakyReLU()(c5)
c6 = addon_layers.WeightNormalization(
layers.Conv1D(filters, 3, dilation_rate=1, padding=\"same\"), data_init=False