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# Adapted from https://github.com/junjun3518/alias-free-torch under the Apache License 2.0 | |
# LICENSE is in incl_licenses directory. | |
import torch.nn as nn | |
from torch.nn import functional as F | |
from .filter import LowPassFilter1d | |
from .filter import kaiser_sinc_filter1d | |
class UpSample1d(nn.Module): | |
def __init__(self, ratio=2, kernel_size=None): | |
super().__init__() | |
self.ratio = ratio | |
self.kernel_size = int(6 * ratio // 2) * 2 if kernel_size is None else kernel_size | |
self.stride = ratio | |
self.pad = self.kernel_size // ratio - 1 | |
self.pad_left = self.pad * self.stride + (self.kernel_size - self.stride) // 2 | |
self.pad_right = self.pad * self.stride + (self.kernel_size - self.stride + 1) // 2 | |
filter = kaiser_sinc_filter1d(cutoff=0.5 / ratio, | |
half_width=0.6 / ratio, | |
kernel_size=self.kernel_size) | |
self.register_buffer("filter", filter) | |
# x: [B, C, T] | |
def forward(self, x): | |
_, C, _ = x.shape | |
x = F.pad(x, (self.pad, self.pad), mode='replicate') | |
x = self.ratio * F.conv_transpose1d( | |
x, self.filter.expand(C, -1, -1), stride=self.stride, groups=C) | |
x = x[..., self.pad_left:-self.pad_right] | |
return x | |
class DownSample1d(nn.Module): | |
def __init__(self, ratio=2, kernel_size=None): | |
super().__init__() | |
self.ratio = ratio | |
self.kernel_size = int(6 * ratio // 2) * 2 if kernel_size is None else kernel_size | |
self.lowpass = LowPassFilter1d(cutoff=0.5 / ratio, | |
half_width=0.6 / ratio, | |
stride=ratio, | |
kernel_size=self.kernel_size) | |
def forward(self, x): | |
xx = self.lowpass(x) | |
return xx |