"""Time warp module."""
import torch
from espnet.nets.pytorch_backend.nets_utils import pad_list
DEFAULT_TIME_WARP_MODE = "bicubic"
[docs]def time_warp(x: torch.Tensor, window: int = 80, mode: str = DEFAULT_TIME_WARP_MODE):
"""Time warping using torch.interpolate.
Args:
x: (Batch, Time, Freq)
window: time warp parameter
mode: Interpolate mode
"""
# bicubic supports 4D or more dimension tensor
org_size = x.size()
if x.dim() == 3:
# x: (Batch, Time, Freq) -> (Batch, 1, Time, Freq)
x = x[:, None]
t = x.shape[2]
if t - window <= window:
return x.view(*org_size)
center = torch.randint(window, t - window, (1,))[0]
warped = torch.randint(center - window, center + window, (1,))[0] + 1
# left: (Batch, Channel, warped, Freq)
# right: (Batch, Channel, time - warped, Freq)
left = torch.nn.functional.interpolate(
x[:, :, :center], (warped, x.shape[3]), mode=mode, align_corners=False
)
right = torch.nn.functional.interpolate(
x[:, :, center:], (t - warped, x.shape[3]), mode=mode, align_corners=False
)
if x.requires_grad:
x = torch.cat([left, right], dim=-2)
else:
x[:, :, :warped] = left
x[:, :, warped:] = right
return x.view(*org_size)
[docs]class TimeWarp(torch.nn.Module):
"""Time warping using torch.interpolate.
Args:
window: time warp parameter
mode: Interpolate mode
"""
def __init__(self, window: int = 80, mode: str = DEFAULT_TIME_WARP_MODE):
super().__init__()
self.window = window
self.mode = mode
[docs] def forward(self, x: torch.Tensor, x_lengths: torch.Tensor = None):
"""Forward function.
Args:
x: (Batch, Time, Freq)
x_lengths: (Batch,)
"""
if x_lengths is None or all(le == x_lengths[0] for le in x_lengths):
# Note that applying same warping for each sample
y = time_warp(x, window=self.window, mode=self.mode)
else:
# FIXME(kamo): I have no idea to batchify Timewarp
ys = []
for i in range(x.size(0)):
_y = time_warp(
x[i][None, : x_lengths[i]],
window=self.window,
mode=self.mode,
)[0]
ys.append(_y)
y = pad_list(ys, 0.0)
return y, x_lengths