The Semantic-Level Feature Coupling-and-Recoupling (C.R.) module enables knowledge sharing and feature reusability across disparate datasets at the Bird-Eye-View (BEV) feature level.
Let fbevi,fbevj∈RC×H×W denote BEV feature maps extracted from the 2D backbone for samples from dataset i and dataset j, where C is the channel dimension and H,W are spatial height and width.
Feature Coupling: Features from N datasets are concatenated along the channel dimension:
fcatbev=[fbev1,fbev2,…,fbevN]∈RNC×H×W
A shared BEV representation fsharedbev is extracted by combining foreground-aware spatial attention and dataset-level attention masks:
fsharedbev=[Mshared⊙Φd(Conv(fcatbev))]fcatbev
where ⊙ denotes element-wise multiplication. The foreground-aware spatial attention map Mshared∈R1×H×W is computed via channel-wise maximum pooling: Mshared=ϕp(fcatbev). The dataset-level attention mask Φd(⋅) applies a Multi-Layer Perceptron (MLP) followed by an N-class channel-wise softmax to re-scale the concatenated features into dataset-agnostic representations.
Feature Recoupling: The shared representation fsharedbev is fused back into dataset-specific feature streams via residual Squeeze-and-Excitation (SE) blocks:
f^bevk=SEk(fsharedbev)+fbevkfor k∈{1,…,N}
where SEk recalibrates channel-wise dependencies specifically for the k-th dataset before feeding into the detection head.