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| import numpy as np | |
| import torch | |
| import torch.nn as nn | |
| import torch.nn.functional as F | |
| from raft_core_update import BasicUpdateBlock, SmallUpdateBlock | |
| from raft_core_extractor import BasicEncoder, SmallEncoder | |
| from raft_core_corr import CorrBlock, AlternateCorrBlock | |
| from raft_core_utils_utils import bilinear_sampler, coords_grid, upflow8 | |
| try: | |
| autocast = torch.cuda.amp.autocast | |
| except: | |
| # dummy autocast for PyTorch < 1.6 | |
| class autocast: | |
| def __init__(self, enabled): | |
| pass | |
| def __enter__(self): | |
| pass | |
| def __exit__(self, *args): | |
| pass | |
| class RAFT(nn.Module): | |
| def __init__(self, args): | |
| super(RAFT, self).__init__() | |
| self.args = args | |
| if args.small: | |
| self.hidden_dim = hdim = 96 | |
| self.context_dim = cdim = 64 | |
| args.corr_levels = 4 | |
| args.corr_radius = 3 | |
| else: | |
| self.hidden_dim = hdim = 128 | |
| self.context_dim = cdim = 128 | |
| args.corr_levels = 4 | |
| args.corr_radius = 4 | |
| if 'dropout' not in self.args: | |
| self.args.dropout = 0 | |
| if 'alternate_corr' not in self.args: | |
| self.args.alternate_corr = False | |
| # feature network, context network, and update block | |
| if args.small: | |
| self.fnet = SmallEncoder(output_dim=128, norm_fn='instance', dropout=args.dropout) | |
| self.cnet = SmallEncoder(output_dim=hdim+cdim, norm_fn='none', dropout=args.dropout) | |
| self.update_block = SmallUpdateBlock(self.args, hidden_dim=hdim) | |
| else: | |
| self.fnet = BasicEncoder(output_dim=256, norm_fn='instance', dropout=args.dropout) | |
| self.cnet = BasicEncoder(output_dim=hdim+cdim, norm_fn='batch', dropout=args.dropout) | |
| self.update_block = BasicUpdateBlock(self.args, hidden_dim=hdim) | |
| def freeze_bn(self): | |
| for m in self.modules(): | |
| if isinstance(m, nn.BatchNorm2d): | |
| m.eval() | |
| def initialize_flow(self, img): | |
| """ Flow is represented as difference between two coordinate grids flow = coords1 - coords0""" | |
| N, C, H, W = img.shape | |
| coords0 = coords_grid(N, H//8, W//8, device=img.device) | |
| coords1 = coords_grid(N, H//8, W//8, device=img.device) | |
| # optical flow computed as difference: flow = coords1 - coords0 | |
| return coords0, coords1 | |
| def upsample_flow(self, flow, mask): | |
| """ Upsample flow field [H/8, W/8, 2] -> [H, W, 2] using convex combination """ | |
| N, _, H, W = flow.shape | |
| mask = mask.view(N, 1, 9, 8, 8, H, W) | |
| mask = torch.softmax(mask, dim=2) | |
| up_flow = F.unfold(8 * flow, [3,3], padding=1) | |
| up_flow = up_flow.view(N, 2, 9, 1, 1, H, W) | |
| up_flow = torch.sum(mask * up_flow, dim=2) | |
| up_flow = up_flow.permute(0, 1, 4, 2, 5, 3) | |
| return up_flow.reshape(N, 2, 8*H, 8*W) | |
| def forward(self, image1, image2, iters=12, flow_init=None, upsample=True, test_mode=False): | |
| """ Estimate optical flow between pair of frames """ | |
| image1 = 2 * (image1 / 255.0) - 1.0 | |
| image2 = 2 * (image2 / 255.0) - 1.0 | |
| image1 = image1.contiguous() | |
| image2 = image2.contiguous() | |
| hdim = self.hidden_dim | |
| cdim = self.context_dim | |
| # run the feature network | |
| with autocast(enabled=self.args.mixed_precision): | |
| fmap1, fmap2 = self.fnet([image1, image2]) | |
| fmap1 = fmap1.float() | |
| fmap2 = fmap2.float() | |
| if self.args.alternate_corr: | |
| corr_fn = AlternateCorrBlock(fmap1, fmap2, radius=self.args.corr_radius) | |
| else: | |
| corr_fn = CorrBlock(fmap1, fmap2, radius=self.args.corr_radius) | |
| # run the context network | |
| with autocast(enabled=self.args.mixed_precision): | |
| cnet = self.cnet(image1) | |
| net, inp = torch.split(cnet, [hdim, cdim], dim=1) | |
| net = torch.tanh(net) | |
| inp = torch.relu(inp) | |
| coords0, coords1 = self.initialize_flow(image1) | |
| if flow_init is not None: | |
| coords1 = coords1 + flow_init | |
| flow_predictions = [] | |
| for itr in range(iters): | |
| coords1 = coords1.detach() | |
| corr = corr_fn(coords1) # index correlation volume | |
| flow = coords1 - coords0 | |
| with autocast(enabled=self.args.mixed_precision): | |
| net, up_mask, delta_flow = self.update_block(net, inp, corr, flow) | |
| # F(t+1) = F(t) + \Delta(t) | |
| coords1 = coords1 + delta_flow | |
| # upsample predictions | |
| if up_mask is None: | |
| flow_up = upflow8(coords1 - coords0) | |
| else: | |
| flow_up = self.upsample_flow(coords1 - coords0, up_mask) | |
| flow_predictions.append(flow_up) | |
| if test_mode: | |
| return coords1 - coords0, flow_up | |
| return flow_predictions | |