Cassic: Towards Content-Adaptive State-Space Models for Learned Image Compression

Learned image compression (LIC) demonstrates superior rate-distortion (RD) performance compared to traditional methods. Recent method MambaVC attempts to introduce Mamba, a variant of state space models, into this field aim to establish a new paradigm beyond convolutional neural networks and transformers. However, this approach relies on predefined four-directional scanning, which prioritizes spatial proximity over content and semantic relationships, resulting in suboptimal redundancy elimination. Additionally, it focuses solely on nonlinear transformations, neglecting entropy model improvements crucial for accurate probability estimation in entropy coding. To address these limitations, we propose a novel framework based on content-adaptive visual state space model, Cassic, through dual innovation. First, we design a content-adaptive selective scan based on weighted activation maps and bit allocation maps, subsequently developing a content-adaptive visual state space block. Second, we present a mamba-based channel-wise auto-regressive entropy model to fully leverage inter-slice bit allocation consistency for enhanced probability estimation. Extensive experimental results demonstrate that our method achieves state-of-the-art performance across three datasets while maintaining faster processing speeds than existing MambaVC approach.