_utils.py

import torch.nn as nn


__all__ = ["Conv3DSimple", "Conv2Plus1D", "Conv3DNoTemporal"]


class Conv3DSimple(nn.Conv3d):
    def __init__(self,
                 in_planes,
                 out_planes,
                 midplanes=None,
                 stride=1,
                 padding=1):

        super(Conv3DSimple, self).__init__(
            in_channels=in_planes,
            out_channels=out_planes,
            kernel_size=(3, 3, 3),
            stride=stride,
            padding=padding,
            bias=False)

    @staticmethod
    def get_downsample_stride(stride):
        return (stride, stride, stride)


class Conv2Plus1D(nn.Sequential):

    def __init__(self,
                 in_planes,
                 out_planes,
                 midplanes,
                 stride=1,
                 padding=1):
        conv1 = [
            nn.Conv3d(in_planes, midplanes, kernel_size=(1, 3, 3),
                      stride=(1, stride, stride), padding=(0, padding, padding),
                      bias=False),
            nn.BatchNorm3d(midplanes),
            nn.ReLU(inplace=True),
            nn.Conv3d(midplanes, out_planes, kernel_size=(3, 1, 1),
                      stride=(stride, 1, 1), padding=(padding, 0, 0),
                      bias=False)
        ]
        super(Conv2Plus1D, self).__init__(*conv1)

    @staticmethod
    def get_downsample_stride(stride):
        return (stride, stride, stride)


class Conv3DNoTemporal(nn.Conv3d):

    def __init__(self,
                 in_planes,
                 out_planes,
                 midplanes=None,
                 stride=1,
                 padding=1):

        super(Conv3DNoTemporal, self).__init__(
            in_channels=in_planes,
            out_channels=out_planes,
            kernel_size=(1, 3, 3),
            stride=(1, stride, stride),
            padding=(0, padding, padding),
            bias=False)

    @staticmethod
    def get_downsample_stride(stride):
        return (1, stride, stride)