Virtual Reality (VR) has the potential of becoming the next ubiquitous computing platform. Continued progress in the burgeoning field of VR depends critically on an efficient computing substrate. In particular, DRAM access energy is known to contribute to a significant portion of system energy. Today's framebuffer compression system alleviates the DRAM traffic by using a numerically lossless compression algorithm. Being numerically lossless, however, is unnecessary to preserve perceptual quality for humans. This paper proposes a perceptually lossless, but numerically lossy, system to compress DRAM traffic. Our idea builds on top of long-established psychophysical studies that show that humans cannot discriminate colors that are close to each other. The discrimination ability becomes even weaker (i.e., more colors are perceptually indistinguishable) in our peripheral vision. Leveraging the color discrimination (in)ability, we propose an algorithm that adjusts pixel colors to minimize the bit encoding cost without introducing visible artifacts. The algorithm is coupled with lightweight architectural support that, in real-time, reduces the DRAM traffic by 66.9\% and outperforms existing framebuffer compression mechanisms by up to 20.4\%. Psychophysical studies on human participants show that our system introduce little to no perceptual fidelity degradation.

翻译：虚拟现实（VR）有潜力成为下一代普适计算平台。这一新兴领域的持续进步关键依赖于高效的计算基础架构。其中，DRAM访问能耗已知占据系统能耗的显著部分。当前帧缓冲压缩系统通过采用数值无损压缩算法来缓解DRAM流量。然而，对于保持人类感知质量而言，数值无损并非必要。本文提出一种感知无损但数值有损的系统，用于压缩DRAM流量。我们的思路基于长期确立的心理物理学研究：人类无法区分彼此相近的颜色。在外围视觉中，这种辨别能力甚至更弱（即更多颜色在感知上难以区分）。利用颜色辨别能力的局限性，我们提出一种算法，通过调整像素颜色来最小化比特编码开销，且不引入可见伪影。该算法结合轻量级硬件架构支持，可实时将DRAM流量减少66.9%，性能优于现有帧缓冲压缩机制高达20.4%。针对人类参与者的心理物理学研究表明，我们的系统几乎不引入感知保真度下降。