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Returns:
Feature Matching Loss.
\"\"\"
fm_loss = []
for i in range(len(fake_pred)):
for j in range(len(fake_pred[i]) - 1):
fm_loss.append(mae(real_pred[i][j], fake_pred[i][j]))
return tf.reduce_mean(fm_loss)
def discriminator_loss(real_pred, fake_pred):
\"\"\"Implements the discriminator loss.
Args:
real_pred: Tensor, output of the ground truth wave passed through the discriminator.
fake_pred: Tensor, output of the generator prediction passed through the discriminator.
Returns:
Discriminator Loss.
\"\"\"
real_loss, fake_loss = [], []
for i in range(len(real_pred)):
real_loss.append(mse(tf.ones_like(real_pred[i][-1]), real_pred[i][-1]))
fake_loss.append(mse(tf.zeros_like(fake_pred[i][-1]), fake_pred[i][-1]))
# Calculating the final discriminator loss after scaling
disc_loss = tf.reduce_mean(real_loss) + tf.reduce_mean(fake_loss)
return disc_loss
Defining the MelGAN model for training. This subclass overrides the train_step() method to implement the training logic.
class MelGAN(keras.Model):
def __init__(self, generator, discriminator, **kwargs):
\"\"\"MelGAN trainer class
Args:
generator: keras.Model, Generator model
discriminator: keras.Model, Discriminator model
\"\"\"
super().__init__(**kwargs)
self.generator = generator
self.discriminator = discriminator
def compile(
self,
gen_optimizer,
disc_optimizer,
generator_loss,
feature_matching_loss,
discriminator_loss,
):
\"\"\"MelGAN compile method.
Args:
gen_optimizer: keras.optimizer, optimizer to be used for training
disc_optimizer: keras.optimizer, optimizer to be used for training
generator_loss: callable, loss function for generator
feature_matching_loss: callable, loss function for feature matching
discriminator_loss: callable, loss function for discriminator
\"\"\"
super().compile()
# Optimizers
self.gen_optimizer = gen_optimizer
self.disc_optimizer = disc_optimizer
# Losses
self.generator_loss = generator_loss
self.feature_matching_loss = feature_matching_loss
self.discriminator_loss = discriminator_loss
# Trackers
self.gen_loss_tracker = keras.metrics.Mean(name=\"gen_loss\")
self.disc_loss_tracker = keras.metrics.Mean(name=\"disc_loss\")
def train_step(self, batch):
x_batch_train, y_batch_train = batch
with tf.GradientTape() as gen_tape, tf.GradientTape() as disc_tape:
# Generating the audio wave
gen_audio_wave = generator(x_batch_train, training=True)
# Generating the features using the discriminator
fake_pred = discriminator(y_batch_train)
real_pred = discriminator(gen_audio_wave)
# Calculating the generator losses
gen_loss = generator_loss(real_pred, fake_pred)
fm_loss = feature_matching_loss(real_pred, fake_pred)
# Calculating final generator loss
gen_fm_loss = gen_loss + 10 * fm_loss
# Calculating the discriminator losses
disc_loss = discriminator_loss(real_pred, fake_pred)
# Calculating and applying the gradients for generator and discriminator
grads_gen = gen_tape.gradient(gen_fm_loss, generator.trainable_weights)
grads_disc = disc_tape.gradient(disc_loss, discriminator.trainable_weights)