Towards Syn-to-Real IQA: A Novel Perspective on Reshaping Synthetic Data Distributions

TL;DR

This paper introduces SynDR-IQA, a novel framework that reshapes synthetic data distributions to improve the generalization of blind image quality assessment models trained on synthetic datasets, addressing clustering issues in feature representations.

Contribution

The paper presents a new distribution reshaping framework for synthetic data in BIQA, including content upsampling and cluster downsampling strategies, to enhance model generalization.

Findings

Improved cross-dataset BIQA performance

Effective distribution reshaping strategies

Enhanced generalization from synthetic to real data

Abstract

Blind Image Quality Assessment (BIQA) has advanced significantly through deep learning, but the scarcity of large-scale labeled datasets remains a challenge. While synthetic data offers a promising solution, models trained on existing synthetic datasets often show limited generalization ability. In this work, we make a key observation that representations learned from synthetic datasets often exhibit a discrete and clustered pattern that hinders regression performance: features of high-quality images cluster around reference images, while those of low-quality images cluster based on distortion types. Our analysis reveals that this issue stems from the distribution of synthetic data rather than model architecture. Consequently, we introduce a novel framework SynDR-IQA, which reshapes synthetic data distribution to enhance BIQA generalization. Based on theoretical derivations of sample diversity and redundancy's impact on generalization error, SynDR-IQA employs two strategies: distribution-aware diverse content upsampling, which enhances visual diversity while preserving content distribution, and density-aware redundant cluster downsampling, which balances samples by reducing the density of densely clustered areas. Extensive experiments across three cross-dataset settings (synthetic-to-authentic, synthetic-to-algorithmic, and synthetic-to-synthetic) demonstrate the effectiveness of our method. The code is available at https://github.com/Li-aobo/SynDR-IQA.