From 537c8576ecf3da788ef06488359508d06d4cc1bc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Eren=20G=C3=B6lge?= <egolge@coqui.ai>
Date: Wed, 8 Sep 2021 13:35:18 +0000
Subject: [PATCH] Stage `TTS.tts.utils.helpers`

---
 TTS/tts/utils/helpers.py | 111 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 TTS/tts/utils/helpers.py

diff --git a/TTS/tts/utils/helpers.py b/TTS/tts/utils/helpers.py
new file mode 100644
index 00000000..07021786
--- /dev/null
+++ b/TTS/tts/utils/helpers.py
@@ -0,0 +1,111 @@
+import torch
+import numpy as np
+
+
+class StandardScaler:
+    """StandardScaler for mean-std normalization with the given mean and std values.
+    """
+    def __init__(self, mean:np.ndarray=None, std:np.ndarray=None) -> None:
+        self.mean_ = mean
+        self.std_ = std
+
+    def set_stats(self, mean, scale):
+        self.mean_ = mean
+        self.scale_ = scale
+
+    def reset_stats(self):
+        delattr(self, "mean_")
+        delattr(self, "scale_")
+
+    def transform(self, X):
+        X = np.asarray(X)
+        X -= self.mean_
+        X /= self.scale_
+        return X
+
+    def inverse_transform(self, X):
+        X = np.asarray(X)
+        X *= self.scale_
+        X += self.mean_
+        return X
+
+
+# from https://gist.github.com/jihunchoi/f1434a77df9db1bb337417854b398df1
+def sequence_mask(sequence_length, max_len=None):
+    """Create a sequence mask for filtering padding in a sequence tensor.
+
+    Args:
+        sequence_length (torch.tensor): Sequence lengths.
+        max_len (int, Optional): Maximum sequence length. Defaults to None.
+
+    Shapes:
+        - mask: :math:`[B, T_max]`
+    """
+    if max_len is None:
+        max_len = sequence_length.data.max()
+    seq_range = torch.arange(max_len, dtype=sequence_length.dtype, device=sequence_length.device)
+    # B x T_max
+    mask = seq_range.unsqueeze(0) < sequence_length.unsqueeze(1)
+    return mask
+
+
+def segment(x: torch.tensor, segment_indices: torch.tensor, segment_size=4):
+    """Segment each sample in a batch based on the provided segment indices
+
+    Args:
+        x (torch.tensor): Input tensor.
+        segment_indices (torch.tensor): Segment indices.
+        segment_size (int): Expected output segment size.
+    """
+    segments = torch.zeros_like(x[:, :, :segment_size])
+    for i in range(x.size(0)):
+        index_start = segment_indices[i]
+        index_end = index_start + segment_size
+        segments[i] = x[i, :, index_start:index_end]
+    return segments
+
+
+def rand_segments(x: torch.tensor, x_lengths: torch.tensor = None, segment_size=4):
+    """Create random segments based on the input lengths.
+
+    Args:
+        x (torch.tensor): Input tensor.
+        x_lengths (torch.tensor): Input lengths.
+        segment_size (int): Expected output segment size.
+
+    Shapes:
+        - x: :math:`[B, C, T]`
+        - x_lengths: :math:`[B]`
+    """
+    B, _, T = x.size()
+    if x_lengths is None:
+        x_lengths = T
+    max_idxs = x_lengths - segment_size + 1
+    assert all(max_idxs > 0), " [!] At least one sample is shorter than the segment size."
+    segment_indices = (torch.rand([B]).type_as(x) * max_idxs).long()
+    ret = segment(x, segment_indices, segment_size)
+    return ret, segment_indices
+
+def average_over_durations(values, durs):
+    """Average values over durations.
+
+    Shapes:
+        - values: :math:`[B, 1, T_de]`
+        - durs: :math:`[B, T_en]`
+        - avg: :math:`[B, 1, T_en]`
+    """
+    durs_cums_ends = torch.cumsum(durs, dim=1).long()
+    durs_cums_starts = torch.nn.functional.pad(durs_cums_ends[:, :-1], (1, 0))
+    values_nonzero_cums = torch.nn.functional.pad(torch.cumsum(values != 0.0, dim=2), (1, 0))
+    values_cums = torch.nn.functional.pad(torch.cumsum(values, dim=2), (1, 0))
+
+    bs, l = durs_cums_ends.size()
+    n_formants = values.size(1)
+    dcs = durs_cums_starts[:, None, :].expand(bs, n_formants, l)
+    dce = durs_cums_ends[:, None, :].expand(bs, n_formants, l)
+
+    values_sums = (torch.gather(values_cums, 2, dce) - torch.gather(values_cums, 2, dcs)).float()
+    values_nelems = (torch.gather(values_nonzero_cums, 2, dce) - torch.gather(values_nonzero_cums, 2, dcs)).float()
+
+    avg = torch.where(values_nelems == 0.0, values_nelems, values_sums / values_nelems)
+    return avg
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