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'''
Exploring Temporal Coherence for More General Video Face Forgery Detection @ ICCV'2021
Copyright (c) Xiamen University and its affiliates.
Modified by Yinglin Zheng from https://github.com/yinglinzheng/FTCN
'''
import torch
from torch import nn, einsum
import torch.nn.functional as F
from einops import rearrange, repeat
from einops.layers.torch import Rearrange
class Residual(nn.Module):
def __init__(self, fn):
super().__init__()
self.fn = fn
def forward(self, x, **kwargs):
return self.fn(x, **kwargs) + x
class PreNorm(nn.Module):
def __init__(self, dim, fn):
super().__init__()
self.norm = nn.LayerNorm(dim)
self.fn = fn
def forward(self, x, **kwargs):
return self.fn(self.norm(x), **kwargs)
class FeedForward(nn.Module):
def __init__(self, dim, hidden_dim, dropout = 0.):
super().__init__()
self.net = nn.Sequential(
nn.Linear(dim, hidden_dim),
nn.GELU(),
nn.Dropout(dropout),
nn.Linear(hidden_dim, dim),
nn.Dropout(dropout)
)
def forward(self, x):
return self.net(x)
class Attention(nn.Module):
def __init__(self, dim, heads = 8, dim_head = 64, dropout = 0.):
super().__init__()
inner_dim = dim_head * heads
project_out = not (heads == 1 and dim_head == dim)
self.heads = heads
self.scale = dim_head ** -0.5
self.to_qkv = nn.Linear(dim, inner_dim * 3, bias = False)
self.to_out = nn.Sequential(
nn.Linear(inner_dim, dim),
nn.Dropout(dropout)
) if project_out else nn.Identity()
def forward(self, x, mask = None):
b, n, _, h = *x.shape, self.heads
qkv = self.to_qkv(x).chunk(3, dim = -1)
q, k, v = map(lambda t: rearrange(t, 'b n (h d) -> b h n d', h = h), qkv)
dots = einsum('b h i d, b h j d -> b h i j', q, k) * self.scale
mask_value = -torch.finfo(dots.dtype).max
if mask is not None:
mask = F.pad(mask.flatten(1), (1, 0), value = True)
assert mask.shape[-1] == dots.shape[-1], 'mask has incorrect dimensions'
mask = rearrange(mask, 'b i -> b () i ()') * rearrange(mask, 'b j -> b () () j')
dots.masked_fill_(~mask, mask_value)
del mask
attn = dots.softmax(dim=-1)
out = einsum('b h i j, b h j d -> b h i d', attn, v)
out = rearrange(out, 'b h n d -> b n (h d)')
out = self.to_out(out)
return out
class Transformer(nn.Module):
def __init__(self, dim, depth, heads, dim_head, mlp_dim, dropout = 0.):
super().__init__()
self.layers = nn.ModuleList([])
for _ in range(depth):
self.layers.append(nn.ModuleList([
Residual(PreNorm(dim, Attention(dim, heads = heads, dim_head = dim_head, dropout = dropout))),
Residual(PreNorm(dim, FeedForward(dim, mlp_dim, dropout = dropout)))
]))
def forward(self, x, mask = None):
for attn, ff in self.layers:
x = attn(x, mask = mask)
x = ff(x)
return x
class ViT(nn.Module):
def __init__(self, *, image_size, patch_size, num_classes, dim, depth, heads, mlp_dim, pool = 'cls', channels = 3, dim_head = 64, dropout = 0., emb_dropout = 0.):
super().__init__()
assert image_size % patch_size == 0, 'Image dimensions must be divisible by the patch size.'
num_patches = (image_size // patch_size) ** 2
patch_dim = channels * patch_size ** 2
assert pool in {'cls', 'mean'}, 'pool type must be either cls (cls token) or mean (mean pooling)'
self.to_patch_embedding = nn.Sequential(
Rearrange('b c (h p1) (w p2) -> b (h w) (p1 p2 c)', p1 = patch_size, p2 = patch_size),
nn.Linear(patch_dim, dim),
)
self.pos_embedding = nn.Parameter(torch.randn(1, num_patches + 1, dim))
self.cls_token = nn.Parameter(torch.randn(1, 1, dim))
self.dropout = nn.Dropout(emb_dropout)
self.transformer = Transformer(dim, depth, heads, dim_head, mlp_dim, dropout)
self.pool = pool
self.to_latent = nn.Identity()
self.mlp_head = nn.Sequential(
nn.LayerNorm(dim),
nn.Linear(dim, num_classes)
)
def forward(self, img, mask = None):
x = self.to_patch_embedding(img)
b, n, _ = x.shape #batch,num_patches,channels #
cls_tokens = repeat(self.cls_token, '() n d -> b n d', b = b)
x = torch.cat((cls_tokens, x), dim=1)
x += self.pos_embedding[:, :(n + 1)]
x = self.dropout(x)
x = self.transformer(x, mask)
x = x.mean(dim = 1) if self.pool == 'mean' else x[:, 0]
x = self.to_latent(x)
return self.mlp_head(x)
def valid_idx(idx, h):
i = idx // h
j = idx % h
pad = h // 7
if j < pad or i >= h - pad or j >= h - pad:
return False
else:
return True
import random
from math import sqrt
class RandomSelect(nn.Module):
def __init__(self):
super().__init__()
def forward(self, x):
# batch,7x7
size=x.shape[1]
h=int(sqrt(size))
candidates = list(range(size))
candidates = [idx for idx in candidates if valid_idx(idx, h)]
max_k = len(candidates)
if self.training:
k = 8
if k==-1:
k=max_k
else:
k = max_k
candidates = random.sample(candidates, k)
x = x[:,candidates]
return x
class VideoiT(nn.Module):
def __init__(self, *, image_size, patch_size, num_patches, num_classes, dim, depth, heads, mlp_dim, pool = 'cls', channels = 3, dim_head = 64, dropout = 0., emb_dropout = 0.):
super().__init__()
assert image_size % patch_size == 0, 'Image dimensions must be divisible by the patch size.'
patch_dim = channels * patch_size ** 2
assert pool in {'cls', 'mean'}, 'pool type must be either cls (cls token) or mean (mean pooling)'
self.to_patch = Rearrange('b c t (h p1) (w p2) -> b (h w) t (p1 p2 c)', p1 = patch_size, p2 = patch_size)
self.patch_to_embedding=nn.Linear(patch_dim, dim)
self.num_patches=num_patches
self.pos_embedding = nn.Parameter(torch.randn(1, num_patches + 1, dim))
self.cls_token = nn.Parameter(torch.randn(1, 1, dim))
self.dropout = nn.Dropout(emb_dropout)
self.transformer = Transformer(dim, depth, heads, dim_head, mlp_dim, dropout)
self.pool = pool
self.random_select=RandomSelect()
self.to_latent = nn.Identity()
self.mlp_head = nn.Sequential(
nn.LayerNorm(dim),
nn.Linear(dim, num_classes)
)
def forward(self, img, mask = None):
real_b=img.shape[0]
x = self.to_patch(img)
x = self.random_select(x)
n=x.shape[1]
x=x.reshape(real_b*n,self.num_patches,-1)
x = self.patch_to_embedding(x)
b, n, _ = x.shape #batch,num_patches,channels #
cls_tokens = repeat(self.cls_token, '() n d -> b n d', b = b)
x = torch.cat((cls_tokens, x), dim=1)
x += self.pos_embedding[:, :(n + 1)]
x = self.dropout(x)
x = self.transformer(x, mask)
x = x.mean(dim = 1) if self.pool == 'mean' else x[:, 0]
x = self.to_latent(x)
x = self.mlp_head(x)
x = x.reshape(real_b,-1)
return x
class TimeTransformer(nn.Module):
def __init__(self,num_patches, num_classes, dim, depth, heads, mlp_dim, pool = 'cls', dim_head = 64, dropout = 0., emb_dropout = 0.):
super().__init__()
assert pool in {'cls', 'mean'}, 'pool type must be either cls (cls token) or mean (mean pooling)'
self.num_patches=num_patches
self.pos_embedding = nn.Parameter(torch.randn(1, num_patches + 1, dim))
self.cls_token = nn.Parameter(torch.randn(1, 1, dim))
self.dropout = nn.Dropout(emb_dropout)
self.transformer = Transformer(dim, depth, heads, dim_head, mlp_dim, dropout)
self.pool = pool
self.to_latent = nn.Identity()
self.mlp_head = nn.Sequential(
nn.LayerNorm(dim),
nn.Linear(dim, num_classes)
)
def forward(self, x):
b, n, _ = x.shape #batch,num_patches,channels #
cls_tokens = repeat(self.cls_token, '() n d -> b n d', b = b)
x = torch.cat((cls_tokens, x), dim=1)
x += self.pos_embedding[:, :(n + 1)]
x = self.dropout(x)
x = self.transformer(x, mask=None)
x = x.mean(dim = 1) if self.pool == 'mean' else x[:, 0]
x = self.to_latent(x)
return self.mlp_head(x)
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