File size: 8,009 Bytes
a220803
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
import torch
import torch.nn as nn
import torch.nn.functional as F
from networks.blocks.raft import (
    coords_grid,
    BasicUpdateBlock, BidirCorrBlock
)
from networks.blocks.feat_enc import (
    LargeEncoder
)
from networks.blocks.ifrnet import (
    resize,
    Encoder,
    InitDecoder,
    IntermediateDecoder
)
from networks.blocks.multi_flow import (
    multi_flow_combine,
    MultiFlowDecoder
)


class Model(nn.Module):
    def __init__(self, 
                 corr_radius=3, 
                 corr_lvls=4, 
                 num_flows=5, 
                 channels=[84, 96, 112, 128], 
                 skip_channels=84):
        super(Model, self).__init__()
        self.radius = corr_radius
        self.corr_levels = corr_lvls
        self.num_flows = num_flows

        self.feat_encoder = LargeEncoder(output_dim=128, norm_fn='instance', dropout=0.)
        self.encoder = Encoder(channels, large=True)
        self.decoder4 = InitDecoder(channels[3], channels[2], skip_channels)
        self.decoder3 = IntermediateDecoder(channels[2], channels[1], skip_channels)
        self.decoder2 = IntermediateDecoder(channels[1], channels[0], skip_channels)
        self.decoder1 = MultiFlowDecoder(channels[0], skip_channels, num_flows)

        self.update4 = self._get_updateblock(112, None)
        self.update3_low = self._get_updateblock(96, 2.0)
        self.update2_low = self._get_updateblock(84, 4.0)
        
        self.update3_high = self._get_updateblock(96, None)
        self.update2_high = self._get_updateblock(84, None)
        
        self.comb_block = nn.Sequential(
            nn.Conv2d(3*self.num_flows, 6*self.num_flows, 7, 1, 3),
            nn.PReLU(6*self.num_flows),
            nn.Conv2d(6*self.num_flows, 3, 7, 1, 3),
        )

    def _get_updateblock(self, cdim, scale_factor=None):
        return BasicUpdateBlock(cdim=cdim, hidden_dim=192, flow_dim=64, 
                                corr_dim=256, corr_dim2=192, fc_dim=188, 
                                scale_factor=scale_factor, corr_levels=self.corr_levels, 
                                radius=self.radius)

    def _corr_scale_lookup(self, corr_fn, coord, flow0, flow1, embt, downsample=1):
        # convert t -> 0 to 0 -> 1 | convert t -> 1 to 1 -> 0
        # based on linear assumption
        t1_scale = 1. / embt
        t0_scale = 1. / (1. - embt)
        if downsample != 1:
            inv = 1 / downsample
            flow0 = inv * resize(flow0, scale_factor=inv)
            flow1 = inv * resize(flow1, scale_factor=inv)
            
        corr0, corr1 = corr_fn(coord + flow1 * t1_scale, coord + flow0 * t0_scale) 
        corr = torch.cat([corr0, corr1], dim=1)
        flow = torch.cat([flow0, flow1], dim=1)
        return corr, flow
    
    def forward(self, img0, img1, embt, scale_factor=1.0, eval=False, **kwargs):
        mean_ = torch.cat([img0, img1], 2).mean(1, keepdim=True).mean(2, keepdim=True).mean(3, keepdim=True)
        img0 = img0 - mean_
        img1 = img1 - mean_
        img0_ = resize(img0, scale_factor) if scale_factor != 1.0 else img0
        img1_ = resize(img1, scale_factor) if scale_factor != 1.0 else img1
        b, _, h, w = img0_.shape
        coord = coords_grid(b, h // 8, w // 8, img0.device)
        
        fmap0, fmap1 = self.feat_encoder([img0_, img1_]) # [1, 128, H//8, W//8]
        corr_fn = BidirCorrBlock(fmap0, fmap1, radius=self.radius, num_levels=self.corr_levels)

        # f0_1: [1, c0, H//2, W//2] | f0_2: [1, c1, H//4, W//4]
        # f0_3: [1, c2, H//8, W//8] | f0_4: [1, c3, H//16, W//16]
        f0_1, f0_2, f0_3, f0_4 = self.encoder(img0_)
        f1_1, f1_2, f1_3, f1_4 = self.encoder(img1_)

        ######################################### the 4th decoder #########################################
        up_flow0_4, up_flow1_4, ft_3_ = self.decoder4(f0_4, f1_4, embt)
        corr_4, flow_4 = self._corr_scale_lookup(corr_fn, coord, 
                                                 up_flow0_4, up_flow1_4, 
                                                 embt, downsample=1)

        # residue update with lookup corr
        delta_ft_3_, delta_flow_4 = self.update4(ft_3_, flow_4, corr_4)
        delta_flow0_4, delta_flow1_4 = torch.chunk(delta_flow_4, 2, 1)
        up_flow0_4 = up_flow0_4 + delta_flow0_4
        up_flow1_4 = up_flow1_4 + delta_flow1_4
        ft_3_ = ft_3_ + delta_ft_3_

        ######################################### the 3rd decoder #########################################
        up_flow0_3, up_flow1_3, ft_2_ = self.decoder3(ft_3_, f0_3, f1_3, up_flow0_4, up_flow1_4)
        corr_3, flow_3 = self._corr_scale_lookup(corr_fn, 
                                                 coord, up_flow0_3, up_flow1_3, 
                                                 embt, downsample=2)

        # residue update with lookup corr
        delta_ft_2_, delta_flow_3 = self.update3_low(ft_2_, flow_3, corr_3)
        delta_flow0_3, delta_flow1_3 = torch.chunk(delta_flow_3, 2, 1)
        up_flow0_3 = up_flow0_3 + delta_flow0_3
        up_flow1_3 = up_flow1_3 + delta_flow1_3
        ft_2_ = ft_2_ + delta_ft_2_
        
        # residue update with lookup corr (hr)
        corr_3 = resize(corr_3, scale_factor=2.0)
        up_flow_3 = torch.cat([up_flow0_3, up_flow1_3], dim=1)
        delta_ft_2_, delta_up_flow_3 = self.update3_high(ft_2_, up_flow_3, corr_3)
        ft_2_ += delta_ft_2_
        up_flow0_3 += delta_up_flow_3[:, 0:2]
        up_flow1_3 += delta_up_flow_3[:, 2:4]
        
        ######################################### the 2nd decoder #########################################
        up_flow0_2, up_flow1_2, ft_1_  = self.decoder2(ft_2_, f0_2, f1_2, up_flow0_3, up_flow1_3)
        corr_2, flow_2 = self._corr_scale_lookup(corr_fn, 
                                                 coord, up_flow0_2, up_flow1_2, 
                                                 embt, downsample=4)
        
        # residue update with lookup corr
        delta_ft_1_, delta_flow_2 = self.update2_low(ft_1_, flow_2, corr_2)
        delta_flow0_2, delta_flow1_2 = torch.chunk(delta_flow_2, 2, 1)
        up_flow0_2 = up_flow0_2 + delta_flow0_2
        up_flow1_2 = up_flow1_2 + delta_flow1_2
        ft_1_ = ft_1_ + delta_ft_1_
        
        # residue update with lookup corr (hr)
        corr_2 = resize(corr_2, scale_factor=4.0)
        up_flow_2 = torch.cat([up_flow0_2, up_flow1_2], dim=1)
        delta_ft_1_, delta_up_flow_2 = self.update2_high(ft_1_, up_flow_2, corr_2)
        ft_1_ += delta_ft_1_
        up_flow0_2 += delta_up_flow_2[:, 0:2]
        up_flow1_2 += delta_up_flow_2[:, 2:4]
        
        ######################################### the 1st decoder #########################################
        up_flow0_1, up_flow1_1, mask, img_res = self.decoder1(ft_1_, f0_1, f1_1, up_flow0_2, up_flow1_2)
        
        if scale_factor != 1.0: 
            up_flow0_1 = resize(up_flow0_1, scale_factor=(1.0/scale_factor)) * (1.0/scale_factor)
            up_flow1_1 = resize(up_flow1_1, scale_factor=(1.0/scale_factor)) * (1.0/scale_factor)
            mask = resize(mask, scale_factor=(1.0/scale_factor))
            img_res = resize(img_res, scale_factor=(1.0/scale_factor))

        # Merge multiple predictions 
        imgt_pred = multi_flow_combine(self.comb_block, img0, img1, up_flow0_1, up_flow1_1, 
                                                                        mask, img_res, mean_)
        imgt_pred = torch.clamp(imgt_pred, 0, 1)

        if eval:
            return  { 'imgt_pred': imgt_pred, }
        else:
            up_flow0_1 = up_flow0_1.reshape(b, self.num_flows, 2, h, w)
            up_flow1_1 = up_flow1_1.reshape(b, self.num_flows, 2, h, w)
            return {
                'imgt_pred': imgt_pred,
                'flow0_pred': [up_flow0_1, up_flow0_2, up_flow0_3, up_flow0_4],
                'flow1_pred': [up_flow1_1, up_flow1_2, up_flow1_3, up_flow1_4],
                'ft_pred': [ft_1_, ft_2_, ft_3_],
            }