code: """
  single channel speech enhancement for wind noise reduction.
  
  refer to
      "A Convolutional Recurrent Neural Network for Real-Time Speech Enhancement" .
  
  Authors
   * Wang Wei 2021
  """
  import torch
  import torch.nn as nn
  
  class CNN_Block(torch.nn.Module):
      def __init__(self,
          in_channels,
          out_channels,
          kernel_size=[3, 3],
          stride=(1,2),
          padding=(1,0)) -> None:
          super().__init__()
          self.layers = torch.nn.ModuleList()
  
          self.layers.append(nn.Conv2d(in_channels, out_channels, kernel_size, stride=stride, padding=padding))
          self.layers.append(nn.BatchNorm2d(out_channels))
          self.layers.append(nn.ELU())
  
      def forward(self, x):
          for layer in self.layers:
              x = layer(x)
  
          return x
  
  class RNN_Block(torch.nn.Module):
      def __init__(self,
          input_size=1792,
          hidden_size=1792,
          num_layers=2,
          rnn_type='LSTM',
          dropout=0.2) -> None:
          super().__init__()
  
          self.rnn_type = rnn_type
          self.input_size = input_size
          self.hidden_size = hidden_size
          self.num_layers = num_layers
          self.dropout = dropout
  
          if self.rnn_type in ['LSTM', 'GRU']:
              self.rnn = getattr(nn, rnn_type)(self.input_size,
                                               self.hidden_size, self.num_layers,
                                               batch_first=True, dropout=self.dropout)
          else:
              try:
                  nonlinearity = {'RNN_TANH': 'tanh', 'RNN_RELU': 'relu'}[rnn_type]
              except KeyError:
                  raise ValueError("""An invalid option for `--model` was supplied,
                                   options are ['LSTM', 'GRU', 'RNN_TANH' or 'RNN_RELU']""")
              self.rnn = nn.RNN(self.input_size, self.hidden_size, self.num_layers, nonlinearity=nonlinearity, dropout=self.dropout)
  
          # self.hidden = self.init_hidden(batch_size)
  
      def init_hidden(self, batch_size=1):
          if self.rnn_type == 'GRU':
              return torch.zeros(self.num_layers * self.directions_count, batch_size, self.hidden_dim).to(self.device)
          elif self.rnn_type == 'LSTM':
              return (
                      torch.zeros(self.num_layers * self.directions_count, batch_size, self.hidden_dim).to(self.device),
                      torch.zeros(self.num_layers * self.directions_count, batch_size, self.hidden_dim).to(self.device))
          else:
              raise Exception('Unknown rnn_type. Valid options: "gru", "lstm"')
  
      def forward(self, x):
          self.rnn.flatten_parameters()
          x, _ = self.rnn(x)
  
          return x
  
  class DeCNN_Block(torch.nn.Module):
      def __init__(self,
          in_channels,
          out_channels,
          kernel_size=[3, 3],
          stride=(1,2),
          padding=(1,0),
          output_padding=0) -> None:
          super().__init__()
          self.layers = torch.nn.ModuleList()
  
          self.layers.append(
              nn.ConvTranspose2d(
                  in_channels,
                  out_channels,
                  kernel_size=kernel_size,
                  stride=stride,
                  padding=padding,
                  output_padding=output_padding))
          self.layers.append(nn.BatchNorm2d(out_channels))
          self.layers.append(nn.ELU())
  
      def forward(self, x):
          for layer in self.layers:
              x = layer(x)
  
          return x
  
  
  class Encoder(torch.nn.Module):
      def __init__(self, in_channels=1, channels=16, layers=5, scale=2) -> None:
          super().__init__()
  
          self.cnn_b1 = CNN_Block(1, channels)
          self.cnn_b2 = CNN_Block(channels, channels*2)
          self.cnn_b3 = CNN_Block(channels*2, channels*4)
          self.cnn_b4 = CNN_Block(channels*4, channels*8)
          self.cnn_b5 = CNN_Block(channels*8, channels*16)
  
      def forward(self, x):
          o1 = self.cnn_b1(x)
          o2 = self.cnn_b2(o1)
          o3 = self.cnn_b3(o2)
          o4 = self.cnn_b4(o3)
          o5 = self.cnn_b5(o4)
  
          return o1, o2, o3, o4, o5
  
  
  class Decoder(torch.nn.Module):
      def __init__(self, in_channels=512, layers=5, scale=2) -> None:
          super().__init__()
  
          self.decnn_b5 = DeCNN_Block(512, 128)
          self.decnn_b4 = DeCNN_Block(256, 64)
          self.decnn_b3 = DeCNN_Block(128, 32)
          self.decnn_b2 = DeCNN_Block(64, 16, output_padding=(0,1))
          self.decnn_b1 = DeCNN_Block(32, 1)
  
      def forward(self, x, decoder_o5, decoder_o4, decoder_o3, decoder_o2, decoder_o1):
          o5 = self.decnn_b5(torch.cat((x, decoder_o5), 1))
          o4 = self.decnn_b4(torch.cat((o5, decoder_o4), 1))
          o3 = self.decnn_b3(torch.cat((o4, decoder_o3), 1))
          o2 = self.decnn_b2(torch.cat((o3, decoder_o2), 1))
          o = self.decnn_b1(torch.cat((o2, decoder_o1), 1))
  
          return o
  
  
  
  class crn(torch.nn.Module):
      """Basic RNN model with projection layers between RNN layers.
  
      Arguments
      ---------
      input_size : int
          Size of the expected input in the 3rd dimension.
      rnn_size : int
          Number of neurons to use in rnn (for each direction -> and <-).
      projection : int
          Number of neurons in projection layer.
      layers : int
          Number of RNN layers to use.
      """
  
      def __init__(self, input_size=161, contex=0, bidir=False, rnn_size=128, projection=64, layers=2):
          super().__init__()
          self.layers = torch.nn.ModuleList()
  
          if input_size == 257:
              rnn_size = 1792
          elif input_size == 161:
              rnn_size = 1024
  
          self.encoder = Encoder()
          self.rnn = RNN_Block(input_size=rnn_size, hidden_size=rnn_size)
          self.decoder = Decoder()
  
      def forward(self, x: torch.Tensor):
          """model forward
  
          Args:
              x (tensor): input tenosr, [N,T,F]
  
          Returns:
              [type]: [description]
          """
          # N, T, F = x.size()
          if len(x.shape)==3:
              x = x.unsqueeze(1)       # [N,T,F] to [N, 1, T, F]
  
          N, C, T, F = x.size()
  
          o1, o2, o3, o4, o5 = self.encoder(x)
  
          embeded_ch = o5.size(1)
  
          rnn_in = o5.transpose(1, 2)
          rnn_in = rnn_in.reshape(N, T, -1)
          rnn_out = self.rnn(rnn_in)
          rnn_out = rnn_out.unsqueeze(1)
  
          decoder_in = rnn_out.reshape(N, embeded_ch, T, -1)
  
          decoder_out = self.decoder(decoder_in, o5, o4, o3, o2, o1)
  
          return decoder_out.squeeze(1)
  
  if __name__ == "__main__":
      N, C, T, F = 10, 1, 100, 257
      data = torch.rand((N, T,F))
      print(data.shape)
      model = crn(input_size=F)
      output = model(data)
      print(output.shape)
      # input_size = 257
      # contex = 3
      # model = CustomModel(input_size, contex=contex)
      # # input_data = torch.rand(100, 20, input_size)
      from torchsummary import summary
      summary(model, (1, 100, 257))
  
apis: torch.nn.BatchNorm2d torch.rand torch.nn.ModuleList torch.nn.Conv2d torch.nn.RNN torch.zeros torch.nn.ELU torch.cat torch.nn.ConvTranspose2d