def grad_variance(self):
grad_var_ops = []
tensor_to_avg = []
for t, g in zip(self._tvars, self._grads):
if isinstance(g, ops.IndexedSlices):
tensor_to_avg.append(
tf.reshape(tf.unsorted_segment_sum(g.values, g.indices,
g.dense_shape[0]),
shape=t.get_shape()))
else:
tensor_to_avg.append(g)
avg_op = self._moving_averager.apply(tensor_to_avg)
grad_var_ops.append(avg_op)
with tf.control_dependencies([avg_op]):
self._grad_avg = [
self._moving_averager.average(val) for val in tensor_to_avg
]
self._grad_avg_squared = [tf.square(val) for val in self._grad_avg]
self._grad_var = tf.maximum(
tf.constant(EPS, dtype=self._grad_norm_squared_avg.dtype),
self._grad_norm_squared_avg -
tf.add_n([tf.reduce_sum(val) for val in self._grad_avg_squared]))
if self._sparsity_debias:
self._grad_var *= self._sparsity_avg
return grad_var_ops
def prelu_layer(self, x, name, num_parameters=1, init=0.25):
if num_parameters == 1:
shape = 1
else:
shape = x.get_shape()[-1]
alpha = tf.get_variable(name,
shape=shape,
dtype=x.dtype,
initializer=tf.constant_initializer(init))
return tf.maximum(0.0, x) + alpha * tf.minimum(0.0, x)
def get_mu_tensor(self):
root = self.get_cubic_root()
dr = tf.maximum((self._h_max + EPS) / (self._h_min + EPS), 1.0 + EPS)
mu = tf.maximum(root**2, ((tf.sqrt(dr) - 1) / (tf.sqrt(dr) + 1))**2)
return mu
def compute_mel_filterbank_features(waveforms,
sample_rate=16000,
dither=1.0 / np.iinfo(np.int16).max,
preemphasis=0.97,
frame_length=25,
frame_step=10,
fft_length=None,
window_fn=functools.partial(
tf.signal.hann_window, periodic=True),
lower_edge_hertz=80.0,
upper_edge_hertz=7600.0,
num_mel_bins=80,
log_noise_floor=1e-3,
apply_mask=True):
"""Implement mel-filterbank extraction using tf ops.
Args:
waveforms: float32 tensor with shape [batch_size, max_len]
sample_rate: sampling rate of the waveform
dither: stddev of Gaussian noise added to waveform to prevent quantization
artefacts
preemphasis: waveform high-pass filtering constant
frame_length: frame length in ms
frame_step: frame_Step in ms
fft_length: number of fft bins
window_fn: windowing function
lower_edge_hertz: lowest frequency of the filterbank
upper_edge_hertz: highest frequency of the filterbank
num_mel_bins: filterbank size
log_noise_floor: clip small values to prevent numeric overflow in log
apply_mask: When working on a batch of samples, set padding frames to zero
Returns:
filterbanks: a float32 tensor with shape [batch_size, len, num_bins, 1]
"""
# is a complex64 Tensor representing the short-time Fourier
# Transform of each signal in . Its shape is
# [batch_size, ?, fft_unique_bins]
# where fft_unique_bins = fft_length // 2 + 1
# Find the wave length: the largest index for which the value is !=0
# note that waveforms samples that are exactly 0.0 are quite common, so
# simply doing sum(waveforms != 0, axis=-1) will not work correctly.
wav_lens = tf.reduce_max(
tf.expand_dims(tf.range(tf.shape(waveforms)[1]), 0) *
tf.to_int32(tf.not_equal(waveforms, 0.0)),
axis=-1) + 1
if dither > 0:
waveforms += tf.random_normal(tf.shape(waveforms), stddev=dither)
if preemphasis > 0:
waveforms = waveforms[:, 1:] - preemphasis * waveforms[:, :-1]
wav_lens -= 1
frame_length = int(frame_length * sample_rate / 1e3)
frame_step = int(frame_step * sample_rate / 1e3)
if fft_length is None:
fft_length = int(2**(np.ceil(np.log2(frame_length))))
stfts = tf.signal.stft(waveforms,
frame_length=frame_length,
frame_step=frame_step,
fft_length=fft_length,
window_fn=window_fn,
pad_end=True)
stft_lens = (wav_lens + (frame_step - 1)) // frame_step
masks = tf.to_float(
tf.less_equal(tf.expand_dims(tf.range(tf.shape(stfts)[1]), 0),
tf.expand_dims(stft_lens, 1)))
# An energy spectrogram is the magnitude of the complex-valued STFT.
# A float32 Tensor of shape [batch_size, ?, 257].
magnitude_spectrograms = tf.abs(stfts)
# Warp the linear-scale, magnitude spectrograms into the mel-scale.
num_spectrogram_bins = magnitude_spectrograms.shape[-1].value
linear_to_mel_weight_matrix = (tf.signal.linear_to_mel_weight_matrix(
num_mel_bins, num_spectrogram_bins, sample_rate, lower_edge_hertz,
upper_edge_hertz))
mel_spectrograms = tf.tensordot(magnitude_spectrograms,
linear_to_mel_weight_matrix, 1)
# Note: Shape inference for tensordot does not currently handle this case.
mel_spectrograms.set_shape(magnitude_spectrograms.shape[:-1].concatenate(
linear_to_mel_weight_matrix.shape[-1:]))
log_mel_sgram = tf.log(tf.maximum(log_noise_floor, mel_spectrograms))
if apply_mask:
log_mel_sgram *= tf.expand_dims(tf.to_float(masks), -1)
return tf.expand_dims(log_mel_sgram, -1, name="mel_sgrams")