Activation and Weight Distribution Balancing for Optimal Post-Training Quantization in Learned Image Compression

Recently, Learned Image Compression (LIC) models have garnered significant attention due to their superior performance in comparison to traditional image codecs. However, the growing complexity of these deep learning-based models results in high memory consumption and computational load, which limits their practical deployment. Quantization has emerged as a promising technique to reduce both the storage requirements and computational overhead. Despite its success in high-level vision tasks like image recognition and object detection, quantization techniques applied to LIC models remain underexplored. In this work, we identify the unique challenges of quantizing LIC models, specifically focusing on the impact of latent distribution ranges in high-bitrate. We observe that the activation layers of high-bitrate models exhibit a wider distribution range, which causes significant performance degradation after quantization. Furthermore, we explore the limitations of existing LIC quantization schemes, such as per-channel quantization for activation layers, which result in poor hardware acceleration performance and increased data storage overhead. To address these challenges, we propose the activation and weight distribution balancing post-training quantization (AWDB-PTQ) method for LIC models, which uses a coarse-to-fine strategy to optimize balancing coefficients. In addition, we employ per-tensor activation quantization and symmetric uniform quantization to better facilitate hardware acceleration. Experimental results demonstrate that our proposed method outperforms existing methods in terms of both compression performance and computational efficiency. Our code and data are available at: https://github.com/jie-yu16/AWDB-PTQ.