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# Modified from ESPnet(https://github.com/espnet/espnet)
"""ConvolutionModule definition."""
from typing import Tuple
import torch
from torch import nn
class ConvolutionModule(nn.Module):
"""ConvolutionModule in Conformer model."""
def __init__(self,
channels: int,
kernel_size: int = 15,
activation: nn.Module = nn.ReLU(),
norm: str = "batch_norm",
causal: bool = False,
bias: bool = True):
"""Construct an ConvolutionModule object.
Args:
channels (int): The number of channels of conv layers.
kernel_size (int): Kernel size of conv layers.
causal (int): Whether use causal convolution or not
"""
super().__init__()
self.pointwise_conv1 = nn.Conv1d(
channels,
2 * channels,
kernel_size=1,
stride=1,
padding=0,
bias=bias,
)
# self.lorder is used to distinguish if it's a causal convolution,
# if self.lorder > 0: it's a causal convolution, the input will be
# padded with self.lorder frames on the left in forward.
# else: it's a symmetrical convolution
if causal:
padding = 0
self.lorder = kernel_size - 1
else:
# kernel_size should be an odd number for none causal convolution
assert (kernel_size - 1) % 2 == 0
padding = (kernel_size - 1) // 2
self.lorder = 0
self.depthwise_conv = nn.Conv1d(
channels,
channels,
kernel_size,
stride=1,
padding=padding,
groups=channels,
bias=bias,
)
assert norm in ['batch_norm', 'layer_norm']
if norm == "batch_norm":
self.use_layer_norm = False
self.norm = nn.BatchNorm1d(channels)
else:
self.use_layer_norm = True
self.norm = nn.LayerNorm(channels)
self.pointwise_conv2 = nn.Conv1d(
channels,
channels,
kernel_size=1,
stride=1,
padding=0,
bias=bias,
)
self.activation = activation
def forward(
self,
x: torch.Tensor,
mask_pad: torch.Tensor = torch.ones((0, 0, 0), dtype=torch.bool),
cache: torch.Tensor = torch.zeros((0, 0, 0)),
) -> Tuple[torch.Tensor, torch.Tensor]:
"""Compute convolution module.
Args:
x (torch.Tensor): Input tensor (#batch, time, channels).
mask_pad (torch.Tensor): used for batch padding (#batch, 1, time),
(0, 0, 0) means fake mask.
cache (torch.Tensor): left context cache, it is only
used in causal convolution (#batch, channels, cache_t),
(0, 0, 0) meas fake cache.
Returns:
torch.Tensor: Output tensor (#batch, time, channels).
"""
# exchange the temporal dimension and the feature dimension
x = x.transpose(1, 2) # (#batch, channels, time)
# mask batch padding
if mask_pad.size(2) > 0: # time > 0
x.masked_fill_(~mask_pad, 0.0)
if self.lorder > 0:
if cache.size(2) == 0: # cache_t == 0
x = nn.functional.pad(x, (self.lorder, 0), 'constant', 0.0)
else:
assert cache.size(0) == x.size(0) # equal batch
assert cache.size(1) == x.size(1) # equal channel
x = torch.cat((cache, x), dim=2)
assert (x.size(2) > self.lorder)
new_cache = x[:, :, -self.lorder:]
else:
# It's better we just return None if no cache is required,
# However, for JIT export, here we just fake one tensor instead of
# None.
new_cache = torch.zeros((0, 0, 0), dtype=x.dtype, device=x.device)
# GLU mechanism
x = self.pointwise_conv1(x) # (batch, 2*channel, dim)
x = nn.functional.glu(x, dim=1) # (batch, channel, dim)
# 1D Depthwise Conv
x = self.depthwise_conv(x)
if self.use_layer_norm:
x = x.transpose(1, 2)
x = self.activation(self.norm(x))
if self.use_layer_norm:
x = x.transpose(1, 2)
x = self.pointwise_conv2(x)
# mask batch padding
if mask_pad.size(2) > 0: # time > 0
x.masked_fill_(~mask_pad, 0.0)
return x.transpose(1, 2), new_cache
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