HAMP-LIC: Hessian-Aware Mixed-Precision Post-Training Quantization for Learned Image Compression
This work addresses the significant degradation in reconstruction quality and cross-platform codec inconsistency observed in existing neural image compression models when deployed at low bitrates, primarily due to the neglect of inter-layer quantization sensitivity variations. To overcome these limitations, the authors propose a four-stage mixed-precision post-training quantization (PTQ) framework that introduces Hessian trace-based block-level sensitivity estimation for the first time. This approach integrates task-aware fine-tuning, global constraint-guided bit-width allocation, and block-level reconstruction, thereby completely eliminating cross-platform discrepancies. Evaluated on the Minnen2018 and Cheng2020 models, the method achieves up to a 4.85× compression ratio with only a 0.59% BD-rate loss, substantially outperforming current fixed- and mixed-precision PTQ baselines.