Add vanilla DeepSpeech model (#1399)

Co-authored-by: Vincent Quenneville-Belair <vincentqb@gmail.com>

docs/source/models.rst

@@ -17,6 +17,14 @@ The models subpackage contains definitions of models for addressing common audio
   .. automethod:: forward
 
 
+:hidden:`DeepSpeech`
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autoclass:: DeepSpeech
+
+  .. automethod:: forward
+
+
 :hidden:`Wav2Letter`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

test/torchaudio_unittest/models_test.py

@@ -3,7 +3,7 @@ from collections import namedtuple
 
 import torch
 from parameterized import parameterized
-from torchaudio.models import ConvTasNet, Wav2Letter, WaveRNN
+from torchaudio.models import ConvTasNet, DeepSpeech, Wav2Letter, WaveRNN
 from torchaudio.models.wavernn import MelResNet, UpsampleNetwork
 from torchaudio_unittest import common_utils
 
@@ -174,3 +174,20 @@ class TestConvTasNet(common_utils.TorchaudioTestCase):
         output = model(tensor)
 
         assert output.shape == (batch_size, num_sources, num_frames)
+
+
+class TestDeepSpeech(common_utils.TorchaudioTestCase):
+
+    def test_deepspeech(self):
+        n_batch = 2
+        n_feature = 1
+        n_channel = 1
+        n_class = 40
+        n_time = 320
+
+        model = DeepSpeech(n_feature=n_feature, n_class=n_class)
+
+        x = torch.rand(n_batch, n_channel, n_time, n_feature)
+        out = model(x)
+
+        assert out.size() == (n_batch, n_time, n_class)

torchaudio/models/__init__.py

 from .wav2letter import Wav2Letter
 from .wavernn import WaveRNN
 from .conv_tasnet import ConvTasNet
+from .deepspeech import DeepSpeech
 
 __all__ = [
     'Wav2Letter',
     'WaveRNN',
     'ConvTasNet',
+    'DeepSpeech',
 ]

torchaudio/models/deepspeech.py

+import torch
+
+__all__ = ["DeepSpeech"]
+
+
+class FullyConnected(torch.nn.Module):
+    """
+    Args:
+        n_feature: Number of input features
+        n_hidden: Internal hidden unit size.
+    """
+
+    def __init__(self,
+                 n_feature: int,
+                 n_hidden: int,
+                 dropout: float,
+                 relu_max_clip: int = 20) -> None:
+        super(FullyConnected, self).__init__()
+        self.fc = torch.nn.Linear(n_feature, n_hidden, bias=True)
+        self.relu_max_clip = relu_max_clip
+        self.dropout = dropout
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        x = self.fc(x)
+        x = torch.nn.functional.relu(x)
+        x = torch.nn.functional.hardtanh(x, 0, self.relu_max_clip)
+        if self.dropout:
+            x = torch.nn.functional.dropout(x, self.dropout, self.training)
+        return x
+
+
+class DeepSpeech(torch.nn.Module):
+    """
+    DeepSpeech model architecture from
+    `"Deep Speech: Scaling up end-to-end speech recognition"`
+    <https://arxiv.org/abs/1412.5567> paper.
+
+    Args:
+        n_feature: Number of input features
+        n_hidden: Internal hidden unit size.
+        n_class: Number of output classes
+    """
+
+    def __init__(
+        self,
+        n_feature: int,
+        n_hidden: int = 2048,
+        n_class: int = 40,
+        dropout: float = 0.0,
+    ) -> None:
+        super(DeepSpeech, self).__init__()
+        self.n_hidden = n_hidden
+        self.fc1 = FullyConnected(n_feature, n_hidden, dropout)
+        self.fc2 = FullyConnected(n_hidden, n_hidden, dropout)
+        self.fc3 = FullyConnected(n_hidden, n_hidden, dropout)
+        self.bi_rnn = torch.nn.RNN(
+            n_hidden, n_hidden, num_layers=1, nonlinearity="relu", bidirectional=True
+        )
+        self.fc4 = FullyConnected(n_hidden, n_hidden, dropout)
+        self.out = torch.nn.Linear(n_hidden, n_class)
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        """
+        Args:
+            x (torch.Tensor): Tensor of dimension (batch, channel, time, feature).
+        Returns:
+            Tensor: Predictor tensor of dimension (batch, time, class).
+        """
+        # N x C x T x F
+        x = self.fc1(x)
+        # N x C x T x H
+        x = self.fc2(x)
+        # N x C x T x H
+        x = self.fc3(x)
+        # N x C x T x H
+        x = x.squeeze(1)
+        # N x T x H
+        x = x.transpose(0, 1)
+        # T x N x H
+        x, _ = self.bi_rnn(x)
+        # The fifth (non-recurrent) layer takes both the forward and backward units as inputs
+        x = x[:, :, :self.n_hidden] + x[:, :, self.n_hidden:]
+        # T x N x H
+        x = self.fc4(x)
+        # T x N x H
+        x = self.out(x)
+        # T x N x n_class
+        x = x.permute(1, 0, 2)
+        # N x T x n_class
+        x = torch.nn.functional.log_softmax(x, dim=2)
+        # N x T x n_class
+        return x