  Siamese-based trackers have achieved excellent performance on visual object
tracking. However, the target template is not updated online, and the features
of the target template and search image are computed independently in a Siamese
architecture. In this paper, we propose Deformable Siamese Attention Networks,
referred to as SiamAttn, by introducing a new Siamese attention mechanism that
computes deformable self-attention and cross-attention. The self attention
learns strong context information via spatial attention, and selectively
emphasizes interdependent channel-wise features with channel attention. The
cross-attention is capable of aggregating rich contextual inter-dependencies
between the target template and the search image, providing an implicit manner
to adaptively update the target template. In addition, we design a region
refinement module that computes depth-wise cross correlations between the
attentional features for more accurate tracking. We conduct experiments on six
benchmarks, where our method achieves new state of-the-art results,
outperforming the strong baseline, SiamRPN++ [24], by 0.464->0.537 and
0.415->0.470 EAO on VOT 2016 and 2018. Our code is available at:
https://github.com/msight-tech/research-siamattn.
