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import torch
import torch.nn.functional as F
from torch import nn
class GST(nn.Module):
"""Global Style Token Module for factorizing prosody in speech.
See https://arxiv.org/pdf/1803.09017"""
def __init__(self, num_mel, num_heads, num_style_tokens, gst_embedding_dim, embedded_speaker_dim=None):
super().__init__()
self.encoder = ReferenceEncoder(num_mel, gst_embedding_dim)
self.style_token_layer = StyleTokenLayer(num_heads, num_style_tokens, gst_embedding_dim, embedded_speaker_dim)
def forward(self, inputs, speaker_embedding=None):
enc_out = self.encoder(inputs)
# concat speaker_embedding
if speaker_embedding is not None:
enc_out = torch.cat([enc_out, speaker_embedding], dim=-1)
style_embed = self.style_token_layer(enc_out)
return style_embed
class ReferenceEncoder(nn.Module):
"""NN module creating a fixed size prosody embedding from a spectrogram.
inputs: mel spectrograms [batch_size, num_spec_frames, num_mel]
outputs: [batch_size, embedding_dim]
"""
def __init__(self, num_mel, embedding_dim):
super().__init__()
self.num_mel = num_mel
filters = [1] + [32, 32, 64, 64, 128, 128]
num_layers = len(filters) - 1
convs = [
nn.Conv2d(
in_channels=filters[i], out_channels=filters[i + 1], kernel_size=(3, 3), stride=(2, 2), padding=(1, 1)
)
for i in range(num_layers)
]
self.convs = nn.ModuleList(convs)
self.bns = nn.ModuleList([nn.BatchNorm2d(num_features=filter_size) for filter_size in filters[1:]])
post_conv_height = self.calculate_post_conv_height(num_mel, 3, 2, 1, num_layers)
self.recurrence = nn.GRU(
input_size=filters[-1] * post_conv_height, hidden_size=embedding_dim // 2, batch_first=True
)
def forward(self, inputs):
batch_size = inputs.size(0)
x = inputs.view(batch_size, 1, -1, self.num_mel)
# x: 4D tensor [batch_size, num_channels==1, num_frames, num_mel]
for conv, bn in zip(self.convs, self.bns):
x = conv(x)
x = bn(x)
x = F.relu(x)
x = x.transpose(1, 2)
# x: 4D tensor [batch_size, post_conv_width,
# num_channels==128, post_conv_height]
post_conv_width = x.size(1)
x = x.contiguous().view(batch_size, post_conv_width, -1)
# x: 3D tensor [batch_size, post_conv_width,
# num_channels*post_conv_height]
self.recurrence.flatten_parameters()
_, out = self.recurrence(x)
# out: 3D tensor [seq_len==1, batch_size, encoding_size=128]
return out.squeeze(0)
@staticmethod
def calculate_post_conv_height(height, kernel_size, stride, pad, n_convs):
"""Height of spec after n convolutions with fixed kernel/stride/pad."""
for _ in range(n_convs):
height = (height - kernel_size + 2 * pad) // stride + 1
return height
class StyleTokenLayer(nn.Module):
"""NN Module attending to style tokens based on prosody encodings."""
def __init__(self, num_heads, num_style_tokens, gst_embedding_dim, d_vector_dim=None):
super().__init__()
self.query_dim = gst_embedding_dim // 2
if d_vector_dim:
self.query_dim += d_vector_dim
self.key_dim = gst_embedding_dim // num_heads
self.style_tokens = nn.Parameter(torch.FloatTensor(num_style_tokens, self.key_dim))
nn.init.normal_(self.style_tokens, mean=0, std=0.5)
self.attention = MultiHeadAttention(
query_dim=self.query_dim, key_dim=self.key_dim, num_units=gst_embedding_dim, num_heads=num_heads
)
def forward(self, inputs):
batch_size = inputs.size(0)
prosody_encoding = inputs.unsqueeze(1)
# prosody_encoding: 3D tensor [batch_size, 1, encoding_size==128]
tokens = torch.tanh(self.style_tokens).unsqueeze(0).expand(batch_size, -1, -1)
# tokens: 3D tensor [batch_size, num tokens, token embedding size]
style_embed = self.attention(prosody_encoding, tokens)
return style_embed
class MultiHeadAttention(nn.Module):
"""
input:
query --- [N, T_q, query_dim]
key --- [N, T_k, key_dim]
output:
out --- [N, T_q, num_units]
"""
def __init__(self, query_dim, key_dim, num_units, num_heads):
super().__init__()
self.num_units = num_units
self.num_heads = num_heads
self.key_dim = key_dim
self.W_query = nn.Linear(in_features=query_dim, out_features=num_units, bias=False)
self.W_key = nn.Linear(in_features=key_dim, out_features=num_units, bias=False)
self.W_value = nn.Linear(in_features=key_dim, out_features=num_units, bias=False)
def forward(self, query, key):
queries = self.W_query(query) # [N, T_q, num_units]
keys = self.W_key(key) # [N, T_k, num_units]
values = self.W_value(key)
split_size = self.num_units // self.num_heads
queries = torch.stack(torch.split(queries, split_size, dim=2), dim=0) # [h, N, T_q, num_units/h]
keys = torch.stack(torch.split(keys, split_size, dim=2), dim=0) # [h, N, T_k, num_units/h]
values = torch.stack(torch.split(values, split_size, dim=2), dim=0) # [h, N, T_k, num_units/h]
# score = softmax(QK^T / (d_k**0.5))
scores = torch.matmul(queries, keys.transpose(2, 3)) # [h, N, T_q, T_k]
scores = scores / (self.key_dim**0.5)
scores = F.softmax(scores, dim=3)
# out = score * V
out = torch.matmul(scores, values) # [h, N, T_q, num_units/h]
out = torch.cat(torch.split(out, 1, dim=0), dim=3).squeeze(0) # [N, T_q, num_units]
return out
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