refactor: rename canto-backend → backend, canto-frontend → frontend

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/indextts/utils/maskgct/models/codec/speechtokenizer/modules/lstm.py

@@ -0,0 +1,46 @@
+# Copyright (c) 2023 Amphion.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+# This source file is copied from https://github.com/facebookresearch/encodec
+
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the license found in the
+# LICENSE file in the root directory of this source tree.
+
+"""LSTM layers module."""
+
+from torch import nn
+
+
+class SLSTM(nn.Module):
+    """
+    LSTM without worrying about the hidden state, nor the layout of the data.
+    Expects input as convolutional layout.
+    """
+
+    def __init__(
+        self,
+        dimension: int,
+        num_layers: int = 2,
+        skip: bool = True,
+        bidirectional: bool = False,
+    ):
+        super().__init__()
+        self.bidirectional = bidirectional
+        self.skip = skip
+        self.lstm = nn.LSTM(
+            dimension, dimension, num_layers, bidirectional=bidirectional
+        )
+
+    def forward(self, x):
+        x = x.permute(2, 0, 1)
+        y, _ = self.lstm(x)
+        if self.bidirectional:
+            x = x.repeat(1, 1, 2)
+        if self.skip:
+            y = y + x
+        y = y.permute(1, 2, 0)
+        return y