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# This module is from [WeNet](https://github.com/wenet-e2e/wenet).
# ## Citations
# ```bibtex
# @inproceedings{yao2021wenet,
# title={WeNet: Production oriented Streaming and Non-streaming End-to-End Speech Recognition Toolkit},
# author={Yao, Zhuoyuan and Wu, Di and Wang, Xiong and Zhang, Binbin and Yu, Fan and Yang, Chao and Peng, Zhendong and Chen, Xiaoyu and Xie, Lei and Lei, Xin},
# booktitle={Proc. Interspeech},
# year={2021},
# address={Brno, Czech Republic },
# organization={IEEE}
# }
# @article{zhang2022wenet,
# title={WeNet 2.0: More Productive End-to-End Speech Recognition Toolkit},
# author={Zhang, Binbin and Wu, Di and Peng, Zhendong and Song, Xingchen and Yao, Zhuoyuan and Lv, Hang and Xie, Lei and Yang, Chao and Pan, Fuping and Niu, Jianwei},
# journal={arXiv preprint arXiv:2203.15455},
# year={2022}
# }
#
"""Subsampling layer definition."""
from typing import Tuple, Union
import torch
from modules.wenet_extractor.transformer.subsampling import BaseSubsampling
class Conv2dSubsampling2(BaseSubsampling):
"""Convolutional 2D subsampling (to 1/4 length).
Args:
idim (int): Input dimension.
odim (int): Output dimension.
dropout_rate (float): Dropout rate.
"""
def __init__(
self, idim: int, odim: int, dropout_rate: float, pos_enc_class: torch.nn.Module
):
"""Construct an Conv2dSubsampling4 object."""
super().__init__()
self.conv = torch.nn.Sequential(torch.nn.Conv2d(1, odim, 3, 2), torch.nn.ReLU())
self.out = torch.nn.Sequential(torch.nn.Linear(odim * ((idim - 1) // 2), odim))
self.pos_enc = pos_enc_class
# The right context for every conv layer is computed by:
# (kernel_size - 1) * frame_rate_of_this_layer
self.subsampling_rate = 2
# 2 = (3 - 1) * 1
self.right_context = 2
def forward(
self,
x: torch.Tensor,
x_mask: torch.Tensor,
offset: Union[int, torch.Tensor] = 0,
) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
"""Subsample x.
Args:
x (torch.Tensor): Input tensor (#batch, time, idim).
x_mask (torch.Tensor): Input mask (#batch, 1, time).
Returns:
torch.Tensor: Subsampled tensor (#batch, time', odim),
where time' = time // 2.
torch.Tensor: Subsampled mask (#batch, 1, time'),
where time' = time // 2.
torch.Tensor: positional encoding
"""
x = x.unsqueeze(1) # (b, c=1, t, f)
x = self.conv(x)
b, c, t, f = x.size()
x = self.out(x.transpose(1, 2).contiguous().view(b, t, c * f))
x, pos_emb = self.pos_enc(x, offset)
return x, pos_emb, x_mask[:, :, :-2:2]
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