TensorFlowTTS/tensorflow_tts/models/tacotron2.py

# -*- coding: utf-8 -*-
# Copyright 2020 The Tacotron-2 Authors, Minh Nguyen (@dathudeptrai), Eren Gölge (@erogol) and Jae Yoo (@jaeyoo)
#
# 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.

"""Tacotron-2 Modules."""

import collections

import numpy as np
import tensorflow as tf

# TODO: once https://github.com/tensorflow/addons/pull/1964 is fixed,
#  uncomment this line.
# from tensorflow_addons.seq2seq import dynamic_decode
from tensorflow_addons.seq2seq import BahdanauAttention, Decoder, Sampler

from tensorflow_tts.utils import dynamic_decode

from tensorflow_tts.models import BaseModel


def get_initializer(initializer_range=0.02):
    """Creates a `tf.initializers.truncated_normal` with the given range.
    Args:
        initializer_range: float, initializer range for stddev.
    Returns:
        TruncatedNormal initializer with stddev = `initializer_range`.
    """
    return tf.keras.initializers.TruncatedNormal(stddev=initializer_range)


def gelu(x):
    """Gaussian Error Linear unit."""
    cdf = 0.5 * (1.0 + tf.math.erf(x / tf.math.sqrt(2.0)))
    return x * cdf


def gelu_new(x):
    """Smoother gaussian Error Linear Unit."""
    cdf = 0.5 * (1.0 + tf.tanh((np.sqrt(2 / np.pi) * (x + 0.044715 * tf.pow(x, 3)))))
    return x * cdf


def swish(x):
    """Swish activation function."""
    return tf.nn.swish(x)


def mish(x):
    return x * tf.math.tanh(tf.math.softplus(x))


ACT2FN = {
    "identity": tf.keras.layers.Activation("linear"),
    "tanh": tf.keras.layers.Activation("tanh"),
    "gelu": tf.keras.layers.Activation(gelu),
    "relu": tf.keras.activations.relu,
    "swish": tf.keras.layers.Activation(swish),
    "gelu_new": tf.keras.layers.Activation(gelu_new),
    "mish": tf.keras.layers.Activation(mish),
}


class TFEmbedding(tf.keras.layers.Embedding):
    """Faster version of embedding."""

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

    def call(self, inputs):
        inputs = tf.cast(tf.expand_dims(inputs, -1), tf.int32)
        outputs = tf.gather_nd(self.embeddings, inputs)
        return outputs


class TFTacotronConvBatchNorm(tf.keras.layers.Layer):
    """Tacotron-2 Convolutional Batchnorm module."""

    def __init__(
        self, filters, kernel_size, dropout_rate, activation=None, name_idx=None
    ):
        super().__init__()
        self.conv1d = tf.keras.layers.Conv1D(
            filters,
            kernel_size,
            kernel_initializer=get_initializer(0.02),
            padding="same",
            name="conv_._{}".format(name_idx),
        )
        self.norm = tf.keras.layers.experimental.SyncBatchNormalization(
            axis=-1, name="batch_norm_._{}".format(name_idx)
        )
        self.dropout = tf.keras.layers.Dropout(
            rate=dropout_rate, name="dropout_._{}".format(name_idx)
        )
        self.act = ACT2FN[activation]

    def call(self, inputs, training=False):
        outputs = self.conv1d(inputs)
        outputs = self.norm(outputs, training=training)
        outputs = self.act(outputs)
        outputs = self.dropout(outputs, training=training)
        return outputs


class TFTacotronEmbeddings(tf.keras.layers.Layer):
    """Construct character/phoneme/positional/speaker embeddings."""

    def __init__(self, config, **kwargs):
        """Init variables."""
        super().__init__(**kwargs)
        self.vocab_size = config.vocab_size
        self.embedding_hidden_size = config.embedding_hidden_size
        self.initializer_range = config.initializer_range
        self.config = config

        if config.n_speakers > 1:
            self.speaker_embeddings = TFEmbedding(
                config.n_speakers,
                config.embedding_hidden_size,
                embeddings_initializer=get_initializer(self.initializer_range),
                name="speaker_embeddings",
            )
            self.speaker_fc = tf.keras.layers.Dense(
                units=config.embedding_hidden_size, name="speaker_fc"
            )

        self.LayerNorm = tf.keras.layers.LayerNormalization(
            epsilon=config.layer_norm_eps, name="LayerNorm"
        )
        self.dropout = tf.keras.layers.Dropout(config.embedding_dropout_prob)

    def build(self, input_shape):
        """Build shared character/phoneme embedding layers."""
        with tf.name_scope("character_embeddings"):
            self.character_embeddings = self.add_weight(
                "weight",
                shape=[self.vocab_size, self.embedding_hidden_size],
                initializer=get_initializer(self.initializer_range),
            )
        super().build(input_shape)

    def call(self, inputs, training=False):
        """Get character embeddings of inputs.
        Args:
            1. character, Tensor (int32) shape [batch_size, length].
            2. speaker_id, Tensor (int32) shape [batch_size]
        Returns:
            Tensor (float32) shape [batch_size, length, embedding_size].
        """
        return self._embedding(inputs, training=training)

    def _embedding(self, inputs, training=False):
        """Applies embedding based on inputs tensor."""
        input_ids, speaker_ids = inputs

        # create embeddings
        inputs_embeds = tf.gather(self.character_embeddings, input_ids)
        embeddings = inputs_embeds

        if self.config.n_speakers > 1:
            speaker_embeddings = self.speaker_embeddings(speaker_ids)
            speaker_features = tf.math.softplus(self.speaker_fc(speaker_embeddings))
            # extended speaker embeddings
            extended_speaker_features = speaker_features[:, tf.newaxis, :]
            # sum all embedding
            embeddings += extended_speaker_features

        # apply layer-norm and dropout for embeddings.
        embeddings = self.LayerNorm(embeddings)
        embeddings = self.dropout(embeddings, training=training)

        return embeddings


class TFTacotronEncoderConvs(tf.keras.layers.Layer):
    """Tacotron-2 Encoder Convolutional Batchnorm module."""

    def __init__(self, config, **kwargs):
        """Init variables."""
        super().__init__(**kwargs)
        self.conv_batch_norm = []
        for i in range(config.n_conv_encoder):
            conv = TFTacotronConvBatchNorm(
                filters=config.encoder_conv_filters,
                kernel_size=config.encoder_conv_kernel_sizes,
                activation=config.encoder_conv_activation,
                dropout_rate=config.encoder_conv_dropout_rate,
                name_idx=i,
            )
            self.conv_batch_norm.append(conv)

    def call(self, inputs, training=False):
        """Call logic."""
        outputs = inputs
        for conv in self.conv_batch_norm:
            outputs = conv(outputs, training=training)
        return outputs


class TFTacotronEncoder(tf.keras.layers.Layer):
    """Tacotron-2 Encoder."""

    def __init__(self, config, **kwargs):
        """Init variables."""
        super().__init__(**kwargs)
        self.embeddings = TFTacotronEmbeddings(config, name="embeddings")
        self.convbn = TFTacotronEncoderConvs(config, name="conv_batch_norm")
        self.bilstm = tf.keras.layers.Bidirectional(
            tf.keras.layers.LSTM(
                units=config.encoder_lstm_units, return_sequences=True
            ),
            name="bilstm",
        )

        if config.n_speakers > 1:
            self.encoder_speaker_embeddings = TFEmbedding(
                config.n_speakers,
                config.embedding_hidden_size,
                embeddings_initializer=get_initializer(config.initializer_range),
                name="encoder_speaker_embeddings",
            )
            self.encoder_speaker_fc = tf.keras.layers.Dense(
                units=config.encoder_lstm_units * 2, name="encoder_speaker_fc"
            )

        self.config = config

    def call(self, inputs, training=False):
        """Call logic."""
        input_ids, speaker_ids, input_mask = inputs

        # create embedding and mask them since we sum
        # speaker embedding to all character embedding.
        input_embeddings = self.embeddings([input_ids, speaker_ids], training=training)

        # pass embeddings to convolution batch norm
        conv_outputs = self.convbn(input_embeddings, training=training)

        # bi-lstm.
        outputs = self.bilstm(conv_outputs, mask=input_mask)

        if self.config.n_speakers > 1:
            encoder_speaker_embeddings = self.encoder_speaker_embeddings(speaker_ids)
            encoder_speaker_features = tf.math.softplus(
                self.encoder_speaker_fc(encoder_speaker_embeddings)
            )
            # extended encoderspeaker embeddings
            extended_encoder_speaker_features = encoder_speaker_features[
                :, tf.newaxis, :
            ]
            # sum to encoder outputs
            outputs += extended_encoder_speaker_features

        return outputs


class Tacotron2Sampler(Sampler):
    """Tacotron2 sampler for Seq2Seq training."""

    def __init__(
        self, config,
    ):
        super().__init__()
        self.config = config
        # create schedule factor.
        # the input of a next decoder cell is calculated by formular:
        # next_inputs = ratio * prev_groundtruth_outputs + (1.0 - ratio) * prev_predicted_outputs.
        self._ratio = tf.constant(1.0, dtype=tf.float32)
        self._reduction_factor = self.config.reduction_factor

    def setup_target(self, targets, mel_lengths):
        """Setup ground-truth mel outputs for decoder."""
        self.mel_lengths = mel_lengths
        self.set_batch_size(tf.shape(targets)[0])
        self.targets = targets[
            :, self._reduction_factor - 1 :: self._reduction_factor, :
        ]
        self.max_lengths = tf.tile([tf.shape(self.targets)[1]], [self._batch_size])

    @property
    def batch_size(self):
        return self._batch_size

    @property
    def sample_ids_shape(self):
        return tf.TensorShape([])

    @property
    def sample_ids_dtype(self):
        return tf.int32

    @property
    def reduction_factor(self):
        return self._reduction_factor

    def initialize(self):
        """Return (Finished, next_inputs)."""
        return (
            tf.tile([False], [self._batch_size]),
            tf.tile([[0.0]], [self._batch_size, self.config.n_mels]),
        )

    def sample(self, time, outputs, state):
        return tf.tile([0], [self._batch_size])

    def next_inputs(
        self,
        time,
        outputs,
        state,
        sample_ids,
        stop_token_prediction,
        training=False,
        **kwargs,
    ):
        if training:
            finished = time + 1 >= self.max_lengths
            next_inputs = (
                self._ratio * self.targets[:, time, :]
                + (1.0 - self._ratio) * outputs[:, -self.config.n_mels :]
            )
            next_state = state
            return (finished, next_inputs, next_state)
        else:
            stop_token_prediction = tf.nn.sigmoid(stop_token_prediction)
            finished = tf.cast(tf.round(stop_token_prediction), tf.bool)
            finished = tf.reduce_all(finished)
            next_inputs = outputs[:, -self.config.n_mels :]
            next_state = state
            return (finished, next_inputs, next_state)

    def set_batch_size(self, batch_size):
        self._batch_size = batch_size


class TFTacotronLocationSensitiveAttention(BahdanauAttention):
    """Tacotron-2 Location Sensitive Attention module."""

    def __init__(
        self,
        config,
        memory,
        mask_encoder=True,
        memory_sequence_length=None,
        is_cumulate=True,
    ):
        """Init variables."""
        memory_length = memory_sequence_length if (mask_encoder is True) else None
        super().__init__(
            units=config.attention_dim,
            memory=memory,
            memory_sequence_length=memory_length,
            probability_fn="softmax",
            name="LocationSensitiveAttention",
        )
        self.location_convolution = tf.keras.layers.Conv1D(
            filters=config.attention_filters,
            kernel_size=config.attention_kernel,
            padding="same",
            use_bias=False,
            name="location_conv",
        )
        self.location_layer = tf.keras.layers.Dense(
            units=config.attention_dim, use_bias=False, name="location_layer"
        )

        self.v = tf.keras.layers.Dense(1, use_bias=True, name="scores_attention")
        self.config = config
        self.is_cumulate = is_cumulate
        self.use_window = False

    def setup_window(self, win_front=2, win_back=4):
        self.win_front = tf.constant(win_front, tf.int32)
        self.win_back = tf.constant(win_back, tf.int32)

        self._indices = tf.expand_dims(tf.range(tf.shape(self.keys)[1]), 0)
        self._indices = tf.tile(
            self._indices, [tf.shape(self.keys)[0], 1]
        )  # [batch_size, max_time]

        self.use_window = True

    def _compute_window_mask(self, max_alignments):
        """Compute window mask for inference.
        Args:
            max_alignments (int): [batch_size]
        """
        expanded_max_alignments = tf.expand_dims(max_alignments, 1)  # [batch_size, 1]
        low = expanded_max_alignments - self.win_front
        high = expanded_max_alignments + self.win_back
        mlow = tf.cast((self._indices < low), tf.float32)
        mhigh = tf.cast((self._indices > high), tf.float32)
        mask = mlow + mhigh
        return mask  # [batch_size, max_length]

    def __call__(self, inputs, training=False):
        query, state, prev_max_alignments = inputs

        processed_query = self.query_layer(query) if self.query_layer else query
        processed_query = tf.expand_dims(processed_query, 1)

        expanded_alignments = tf.expand_dims(state, axis=2)
        f = self.location_convolution(expanded_alignments)
        processed_location_features = self.location_layer(f)

        energy = self._location_sensitive_score(
            processed_query, processed_location_features, self.keys
        )

        # mask energy on inference steps.
        if self.use_window is True:
            window_mask = self._compute_window_mask(prev_max_alignments)
            energy = energy + window_mask * -1e20

        alignments = self.probability_fn(energy, state)

        if self.is_cumulate:
            state = alignments + state
        else:
            state = alignments

        expanded_alignments = tf.expand_dims(alignments, 2)
        context = tf.reduce_sum(expanded_alignments * self.values, 1)

        return context, alignments, state

    def _location_sensitive_score(self, W_query, W_fil, W_keys):
        """Calculate location sensitive energy."""
        return tf.squeeze(self.v(tf.nn.tanh(W_keys + W_query + W_fil)), -1)

    def get_initial_state(self, batch_size, size):
        """Get initial alignments."""
        return tf.zeros(shape=[batch_size, size], dtype=tf.float32)

    def get_initial_context(self, batch_size):
        """Get initial attention."""
        return tf.zeros(
            shape=[batch_size, self.config.encoder_lstm_units * 2], dtype=tf.float32
        )


class TFTacotronPrenet(tf.keras.layers.Layer):
    """Tacotron-2 prenet."""

    def __init__(self, config, **kwargs):
        """Init variables."""
        super().__init__(**kwargs)
        self.prenet_dense = [
            tf.keras.layers.Dense(
                units=config.prenet_units,
                activation=ACT2FN[config.prenet_activation],
                name="dense_._{}".format(i),
            )
            for i in range(config.n_prenet_layers)
        ]
        self.dropout = tf.keras.layers.Dropout(
            rate=config.prenet_dropout_rate, name="dropout"
        )

    def call(self, inputs, training=False):
        """Call logic."""
        outputs = inputs
        for layer in self.prenet_dense:
            outputs = layer(outputs)
            outputs = self.dropout(outputs, training=True)
        return outputs


class TFTacotronPostnet(tf.keras.layers.Layer):
    """Tacotron-2 postnet."""

    def __init__(self, config, **kwargs):
        """Init variables."""
        super().__init__(**kwargs)
        self.conv_batch_norm = []
        for i in range(config.n_conv_postnet):
            conv = TFTacotronConvBatchNorm(
                filters=config.postnet_conv_filters,
                kernel_size=config.postnet_conv_kernel_sizes,
                dropout_rate=config.postnet_dropout_rate,
                activation="identity" if i + 1 == config.n_conv_postnet else "tanh",
                name_idx=i,
            )
            self.conv_batch_norm.append(conv)

    def call(self, inputs, training=False):
        """Call logic."""
        outputs = inputs
        for _, conv in enumerate(self.conv_batch_norm):
            outputs = conv(outputs, training=training)
        return outputs


TFTacotronDecoderCellState = collections.namedtuple(
    "TFTacotronDecoderCellState",
    [
        "attention_lstm_state",
        "decoder_lstms_state",
        "context",
        "time",
        "state",
        "alignment_history",
        "max_alignments",
    ],
)

TFDecoderOutput = collections.namedtuple(
    "TFDecoderOutput", ("mel_output", "token_output", "sample_id")
)


class TFTacotronDecoderCell(tf.keras.layers.AbstractRNNCell):
    """Tacotron-2 custom decoder cell."""

    def __init__(self, config, enable_tflite_convertible=False, **kwargs):
        """Init variables."""
        super().__init__(**kwargs)
        self.enable_tflite_convertible = enable_tflite_convertible
        self.prenet = TFTacotronPrenet(config, name="prenet")

        # define lstm cell on decoder.
        # TODO(@dathudeptrai) switch to zone-out lstm.
        self.attention_lstm = tf.keras.layers.LSTMCell(
            units=config.decoder_lstm_units, name="attention_lstm_cell"
        )
        lstm_cells = []
        for i in range(config.n_lstm_decoder):
            lstm_cell = tf.keras.layers.LSTMCell(
                units=config.decoder_lstm_units, name="lstm_cell_._{}".format(i)
            )
            lstm_cells.append(lstm_cell)
        self.decoder_lstms = tf.keras.layers.StackedRNNCells(
            lstm_cells, name="decoder_lstms"
        )

        # define attention layer.
        if config.attention_type == "lsa":
            # create location-sensitive attention.
            self.attention_layer = TFTacotronLocationSensitiveAttention(
                config,
                memory=None,
                mask_encoder=True,
                memory_sequence_length=None,
                is_cumulate=True,
            )
        else:
            raise ValueError("Only lsa (location-sensitive attention) is supported")

        # frame, stop projection layer.
        self.frame_projection = tf.keras.layers.Dense(
            units=config.n_mels * config.reduction_factor, name="frame_projection"
        )
        self.stop_projection = tf.keras.layers.Dense(
            units=config.reduction_factor, name="stop_projection"
        )

        self.config = config

    def set_alignment_size(self, alignment_size):
        self.alignment_size = alignment_size

    @property
    def output_size(self):
        """Return output (mel) size."""
        return self.frame_projection.units

    @property
    def state_size(self):
        """Return hidden state size."""
        return TFTacotronDecoderCellState(
            attention_lstm_state=self.attention_lstm.state_size,
            decoder_lstms_state=self.decoder_lstms.state_size,
            time=tf.TensorShape([]),
            attention=self.config.attention_dim,
            state=self.alignment_size,
            alignment_history=(),
            max_alignments=tf.TensorShape([1]),
        )

    def get_initial_state(self, batch_size):
        """Get initial states."""
        initial_attention_lstm_cell_states = self.attention_lstm.get_initial_state(
            None, batch_size, dtype=tf.float32
        )
        initial_decoder_lstms_cell_states = self.decoder_lstms.get_initial_state(
            None, batch_size, dtype=tf.float32
        )
        initial_context = tf.zeros(
            shape=[batch_size, self.config.encoder_lstm_units * 2], dtype=tf.float32
        )
        initial_state = self.attention_layer.get_initial_state(
            batch_size, size=self.alignment_size
        )
        if self.enable_tflite_convertible:
            initial_alignment_history = ()
        else:
            initial_alignment_history = tf.TensorArray(
                dtype=tf.float32, size=0, dynamic_size=True
            )
        return TFTacotronDecoderCellState(
            attention_lstm_state=initial_attention_lstm_cell_states,
            decoder_lstms_state=initial_decoder_lstms_cell_states,
            time=tf.zeros([], dtype=tf.int32),
            context=initial_context,
            state=initial_state,
            alignment_history=initial_alignment_history,
            max_alignments=tf.zeros([batch_size], dtype=tf.int32),
        )

    def call(self, inputs, states, training=False):
        """Call logic."""
        decoder_input = inputs

        # 1. apply prenet for decoder_input.
        prenet_out = self.prenet(decoder_input, training=training)  # [batch_size, dim]

        # 2. concat prenet_out and prev context vector
        # then use it as input of attention lstm layer.
        attention_lstm_input = tf.concat([prenet_out, states.context], axis=-1)
        attention_lstm_output, next_attention_lstm_state = self.attention_lstm(
            attention_lstm_input, states.attention_lstm_state
        )

        # 3. compute context, alignment and cumulative alignment.
        prev_state = states.state
        if not self.enable_tflite_convertible:
            prev_alignment_history = states.alignment_history
        prev_max_alignments = states.max_alignments
        context, alignments, state = self.attention_layer(
            [attention_lstm_output, prev_state, prev_max_alignments], training=training,
        )

        # 4. run decoder lstm(s)
        decoder_lstms_input = tf.concat([attention_lstm_output, context], axis=-1)
        decoder_lstms_output, next_decoder_lstms_state = self.decoder_lstms(
            decoder_lstms_input, states.decoder_lstms_state
        )

        # 5. compute frame feature and stop token.
        projection_inputs = tf.concat([decoder_lstms_output, context], axis=-1)
        decoder_outputs = self.frame_projection(projection_inputs)

        stop_inputs = tf.concat([decoder_lstms_output, decoder_outputs], axis=-1)
        stop_tokens = self.stop_projection(stop_inputs)

        # 6. save alignment history to visualize.
        if self.enable_tflite_convertible:
            alignment_history = ()
        else:
            alignment_history = prev_alignment_history.write(states.time, alignments)

        # 7. return new states.
        new_states = TFTacotronDecoderCellState(
            attention_lstm_state=next_attention_lstm_state,
            decoder_lstms_state=next_decoder_lstms_state,
            time=states.time + 1,
            context=context,
            state=state,
            alignment_history=alignment_history,
            max_alignments=tf.argmax(alignments, -1, output_type=tf.int32),
        )

        return (decoder_outputs, stop_tokens), new_states


class TFTacotronDecoder(Decoder):
    """Tacotron-2 Decoder."""

    def __init__(
        self,
        decoder_cell,
        decoder_sampler,
        output_layer=None,
        enable_tflite_convertible=False,
    ):
        """Initial variables."""
        self.cell = decoder_cell
        self.sampler = decoder_sampler
        self.output_layer = output_layer
        self.enable_tflite_convertible = enable_tflite_convertible

    def setup_decoder_init_state(self, decoder_init_state):
        self.initial_state = decoder_init_state

    def initialize(self, **kwargs):
        return self.sampler.initialize() + (self.initial_state,)

    @property
    def output_size(self):
        return TFDecoderOutput(
            mel_output=tf.nest.map_structure(
                lambda shape: tf.TensorShape(shape), self.cell.output_size
            ),
            token_output=tf.TensorShape(self.sampler.reduction_factor),
            sample_id=tf.TensorShape([1])
            if self.enable_tflite_convertible
            else self.sampler.sample_ids_shape,  # tf.TensorShape([])
        )

    @property
    def output_dtype(self):
        return TFDecoderOutput(tf.float32, tf.float32, self.sampler.sample_ids_dtype)

    @property
    def batch_size(self):
        return self.sampler._batch_size

    def step(self, time, inputs, state, training=False):
        (mel_outputs, stop_tokens), cell_state = self.cell(
            inputs, state, training=training
        )
        if self.output_layer is not None:
            mel_outputs = self.output_layer(mel_outputs)
        sample_ids = self.sampler.sample(
            time=time, outputs=mel_outputs, state=cell_state
        )
        (finished, next_inputs, next_state) = self.sampler.next_inputs(
            time=time,
            outputs=mel_outputs,
            state=cell_state,
            sample_ids=sample_ids,
            stop_token_prediction=stop_tokens,
            training=training,
        )

        outputs = TFDecoderOutput(mel_outputs, stop_tokens, sample_ids)
        return (outputs, next_state, next_inputs, finished)


class TFTacotron2(BaseModel):
    """Tensorflow tacotron-2 model."""

    def __init__(self, config, **kwargs):
        """Initalize tacotron-2 layers."""
        enable_tflite_convertible = kwargs.pop("enable_tflite_convertible", False)
        super().__init__(self, **kwargs)
        self.encoder = TFTacotronEncoder(config, name="encoder")
        self.decoder_cell = TFTacotronDecoderCell(
            config,
            name="decoder_cell",
            enable_tflite_convertible=enable_tflite_convertible,
        )
        self.decoder = TFTacotronDecoder(
            self.decoder_cell,
            Tacotron2Sampler(config),
            enable_tflite_convertible=enable_tflite_convertible,
        )
        self.postnet = TFTacotronPostnet(config, name="post_net")
        self.post_projection = tf.keras.layers.Dense(
            units=config.n_mels, name="residual_projection"
        )

        self.use_window_mask = False
        self.maximum_iterations = 4000
        self.enable_tflite_convertible = enable_tflite_convertible
        self.config = config

    def setup_window(self, win_front, win_back):
        """Call only for inference."""
        self.use_window_mask = True
        self.win_front = win_front
        self.win_back = win_back

    def setup_maximum_iterations(self, maximum_iterations):
        """Call only for inference."""
        self.maximum_iterations = maximum_iterations

    def _build(self):
        input_ids = np.array([[1, 2, 3, 4, 5, 6, 7, 8, 9]])
        input_lengths = np.array([9])
        speaker_ids = np.array([0])
        mel_outputs = np.random.normal(size=(1, 50, 80)).astype(np.float32)
        mel_lengths = np.array([50])
        self(
            input_ids,
            input_lengths,
            speaker_ids,
            mel_outputs,
            mel_lengths,
            10,
            training=True,
        )

    def call(
        self,
        input_ids,
        input_lengths,
        speaker_ids,
        mel_gts,
        mel_lengths,
        maximum_iterations=None,
        use_window_mask=False,
        win_front=2,
        win_back=3,
        training=False,
        **kwargs,
    ):
        """Call logic."""
        # create input-mask based on input_lengths
        input_mask = tf.sequence_mask(
            input_lengths,
            maxlen=tf.reduce_max(input_lengths),
            name="input_sequence_masks",
        )

        # Encoder Step.
        encoder_hidden_states = self.encoder(
            [input_ids, speaker_ids, input_mask], training=training
        )

        batch_size = tf.shape(encoder_hidden_states)[0]
        alignment_size = tf.shape(encoder_hidden_states)[1]

        # Setup some initial placeholders for decoder step. Include:
        # 1. mel_gts, mel_lengths for teacher forcing mode.
        # 2. alignment_size for attention size.
        # 3. initial state for decoder cell.
        # 4. memory (encoder hidden state) for attention mechanism.
        self.decoder.sampler.setup_target(targets=mel_gts, mel_lengths=mel_lengths)
        self.decoder.cell.set_alignment_size(alignment_size)
        self.decoder.setup_decoder_init_state(
            self.decoder.cell.get_initial_state(batch_size)
        )
        self.decoder.cell.attention_layer.setup_memory(
            memory=encoder_hidden_states,
            memory_sequence_length=input_lengths,  # use for mask attention.
        )
        if use_window_mask:
            self.decoder.cell.attention_layer.setup_window(
                win_front=win_front, win_back=win_back
            )

        # run decode step.
        (
            (frames_prediction, stop_token_prediction, _),
            final_decoder_state,
            _,
        ) = dynamic_decode(
            self.decoder,
            maximum_iterations=maximum_iterations,
            enable_tflite_convertible=self.enable_tflite_convertible,
            training=training,
        )

        decoder_outputs = tf.reshape(
            frames_prediction, [batch_size, -1, self.config.n_mels]
        )
        stop_token_prediction = tf.reshape(stop_token_prediction, [batch_size, -1])

        residual = self.postnet(decoder_outputs, training=training)
        residual_projection = self.post_projection(residual)

        mel_outputs = decoder_outputs + residual_projection

        if self.enable_tflite_convertible:
            mask = tf.math.not_equal(
                tf.cast(
                    tf.reduce_sum(tf.abs(decoder_outputs), axis=-1), dtype=tf.int32
                ),
                0,
            )
            decoder_outputs = tf.expand_dims(
                tf.boolean_mask(decoder_outputs, mask), axis=0
            )
            mel_outputs = tf.expand_dims(tf.boolean_mask(mel_outputs, mask), axis=0)
            alignment_history = ()
        else:
            alignment_history = tf.transpose(
                final_decoder_state.alignment_history.stack(), [1, 2, 0]
            )

        return decoder_outputs, mel_outputs, stop_token_prediction, alignment_history

    @tf.function(
        experimental_relax_shapes=True,
        input_signature=[
            tf.TensorSpec([None, None], dtype=tf.int32, name="input_ids"),
            tf.TensorSpec([None,], dtype=tf.int32, name="input_lengths"),
            tf.TensorSpec([None,], dtype=tf.int32, name="speaker_ids"),
        ],
    )
    def inference(self, input_ids, input_lengths, speaker_ids, **kwargs):
        """Call logic."""
        # create input-mask based on input_lengths
        input_mask = tf.sequence_mask(
            input_lengths,
            maxlen=tf.reduce_max(input_lengths),
            name="input_sequence_masks",
        )

        # Encoder Step.
        encoder_hidden_states = self.encoder(
            [input_ids, speaker_ids, input_mask], training=False
        )

        batch_size = tf.shape(encoder_hidden_states)[0]
        alignment_size = tf.shape(encoder_hidden_states)[1]

        # Setup some initial placeholders for decoder step. Include:
        # 1. batch_size for inference.
        # 2. alignment_size for attention size.
        # 3. initial state for decoder cell.
        # 4. memory (encoder hidden state) for attention mechanism.
        # 5. window front/back to solve long sentence synthesize problems. (call after setup memory.)
        self.decoder.sampler.set_batch_size(batch_size)
        self.decoder.cell.set_alignment_size(alignment_size)
        self.decoder.setup_decoder_init_state(
            self.decoder.cell.get_initial_state(batch_size)
        )
        self.decoder.cell.attention_layer.setup_memory(
            memory=encoder_hidden_states,
            memory_sequence_length=input_lengths,  # use for mask attention.
        )
        if self.use_window_mask:
            self.decoder.cell.attention_layer.setup_window(
                win_front=self.win_front, win_back=self.win_back
            )

        # run decode step.
        (
            (frames_prediction, stop_token_prediction, _),
            final_decoder_state,
            _,
        ) = dynamic_decode(
            self.decoder, maximum_iterations=self.maximum_iterations, training=False
        )

        decoder_outputs = tf.reshape(
            frames_prediction, [batch_size, -1, self.config.n_mels]
        )
        stop_token_predictions = tf.reshape(stop_token_prediction, [batch_size, -1])

        residual = self.postnet(decoder_outputs, training=False)
        residual_projection = self.post_projection(residual)

        mel_outputs = decoder_outputs + residual_projection

        alignment_historys = tf.transpose(
            final_decoder_state.alignment_history.stack(), [1, 2, 0]
        )

        return decoder_outputs, mel_outputs, stop_token_predictions, alignment_historys

    @tf.function(
        experimental_relax_shapes=True,
        input_signature=[
            tf.TensorSpec([1, None], dtype=tf.int32, name="input_ids"),
            tf.TensorSpec([1,], dtype=tf.int32, name="input_lengths"),
            tf.TensorSpec([1,], dtype=tf.int32, name="speaker_ids"),
        ],
    )
    def inference_tflite(self, input_ids, input_lengths, speaker_ids, **kwargs):
        """Call logic."""
        # create input-mask based on input_lengths
        input_mask = tf.sequence_mask(
            input_lengths,
            maxlen=tf.reduce_max(input_lengths),
            name="input_sequence_masks",
        )

        # Encoder Step.
        encoder_hidden_states = self.encoder(
            [input_ids, speaker_ids, input_mask], training=False
        )

        batch_size = tf.shape(encoder_hidden_states)[0]
        alignment_size = tf.shape(encoder_hidden_states)[1]

        # Setup some initial placeholders for decoder step. Include:
        # 1. batch_size for inference.
        # 2. alignment_size for attention size.
        # 3. initial state for decoder cell.
        # 4. memory (encoder hidden state) for attention mechanism.
        # 5. window front/back to solve long sentence synthesize problems. (call after setup memory.)
        self.decoder.sampler.set_batch_size(batch_size)
        self.decoder.cell.set_alignment_size(alignment_size)
        self.decoder.setup_decoder_init_state(
            self.decoder.cell.get_initial_state(batch_size)
        )
        self.decoder.cell.attention_layer.setup_memory(
            memory=encoder_hidden_states,
            memory_sequence_length=input_lengths,  # use for mask attention.
        )
        if self.use_window_mask:
            self.decoder.cell.attention_layer.setup_window(
                win_front=self.win_front, win_back=self.win_back
            )

        # run decode step.
        (
            (frames_prediction, stop_token_prediction, _),
            final_decoder_state,
            _,
        ) = dynamic_decode(
            self.decoder,
            maximum_iterations=self.maximum_iterations,
            enable_tflite_convertible=self.enable_tflite_convertible,
            training=False,
        )

        decoder_outputs = tf.reshape(
            frames_prediction, [batch_size, -1, self.config.n_mels]
        )
        stop_token_predictions = tf.reshape(stop_token_prediction, [batch_size, -1])

        residual = self.postnet(decoder_outputs, training=False)
        residual_projection = self.post_projection(residual)

        mel_outputs = decoder_outputs + residual_projection

        if self.enable_tflite_convertible:
            mask = tf.math.not_equal(
                tf.cast(
                    tf.reduce_sum(tf.abs(decoder_outputs), axis=-1), dtype=tf.int32
                ),
                0,
            )
            decoder_outputs = tf.expand_dims(
                tf.boolean_mask(decoder_outputs, mask), axis=0
            )
            mel_outputs = tf.expand_dims(tf.boolean_mask(mel_outputs, mask), axis=0)
            alignment_historys = ()
        else:
            alignment_historys = tf.transpose(
                final_decoder_state.alignment_history.stack(), [1, 2, 0]
            )

        return decoder_outputs, mel_outputs, stop_token_predictions, alignment_historys