TBag: Three Recipes for Building up a Lightweight Hybrid Network for Real-Time SISR

The prevalent convolution neural network (CNN) and Transformer have revolutionized the area of single-image super-resolution (SISR). Though these models have significantly improved performance, they often struggle with real-time applications or on resource-constrained platforms due to their complexity. In this paper, we propose TBag, a lightweight hybrid network that combines the strengths of CNN and Transformer to address these challenges. Our method simplifies the Transformer block with three key optimizations: 1) No projection layer is applied to the value in the original self-attention operation; 2) The number of tokens is rescaled before the self-attention operation and then rescaled back for easing of computation; 3) The expansion factor of the original feed-forward network (FFN) is adjusted. These optimizations enable the development of an efficient hybrid network tailored for real-time SISR. Notably, the hybrid design of CNN and Transformer further enhances both local detail recovery and global feature modeling. Extensive experiments show that TBag achieves a competitive trade-off between effectiveness and efficiency compared to previous lightweight SISR methods (e.g., +0.42 dB PSNR with an 86.7% reduction in latency). Moreover, TBag's real-time capabilities make it highly suitable for practical applications, with the TBag-Tiny version achieving up to 59 FPS on hardware devices. Future work will explore the potential of this hybrid approach in other image restoration tasks, such as denoising and deblurring.