現今的行動裝置大多配備了高解析度螢幕和高效能運算元件，來顯示高畫質的內容和提升使用者體驗。然而以高解析度和高幀率渲染畫面實際上對於使用者體驗的提升有限，反而會導致裝置的功耗提高。除此之外，行動裝置上的滑動操作也是導致裝置高功耗的一個主要原因。因此本研究提出了一個針對滑動操作進行解析度和幀率調節的省電設計來提高行動裝置的能源使用效率。由於減少執行時運算量是有效降低功耗的方法之一，我們的設計主要透過動態降低滑動時的渲染解析度和顯示幀率來降低滑動所產生的運算量。為了確保降低畫面顯示品質仍保有一定的使用者體驗，本設計主要根據使用者的滑動速度來決定該次滑動所需的最低顯示品質。另外，受限於人眼的動態視力極限，使用者也無法看清楚滑動中顯示的畫面。基於此特性，本設計嘗試在滑動時根據滑動速度來降低渲染解析度和顯示幀率。簡言之，本設計在高速滑動時會進行較大幅度顯示品質調降；低速滑動時則進行小幅度的品質調降來維持使用者體驗。最後我們在一部市面上可見的智慧型手機Google Pixel 4 XL實作我們的設計，以驗證設計的效果和評估省電效能。我們在四個常用的應用程式上進行實驗評估。最終實驗結果顯示我們的設計可以在運行這四個應用程式時達到12到26%的省電效果，同時還維持了一定的使用者體驗。

To improve user experience, super-high-resolution displays and powerful computing units are brought to the latest mobile devices to display detailed content. However, rendering content in high resolution and high frame rate leads to high energy consumption yet improves minimal user experience. Meanwhile, scrolling operation is one of the most frequent interactions, contributing to high energy consumption. This paper presents a resolution and frame rate co-scaling design for scrolling operations to improve the energy efficiency of mobile devices. Since decreasing computation workload is one of the potential ways to reduce energy consumption, the proposed design scales down both the resolution and the frame rate of content when performing a scrolling operation. To reduce graphics workload for scrolling while maintaining user experience at a certain level, the design considers scrolling speed as a factor that can indicate the least requirement of visual quality. Due to the limit of human dynamic visual acuity, a user is not able to view the content in detail when scrolling at high speed. By exploiting this characteristic, the proposed design scales the resolution and the frame rate according to the scrolling speed. In short, the design scales down the quality of content more when scrolling at a high speed; and scales down the quality less when scrolling at a low speed. The proposed design has been implemented on a state-of-art commercial phone, Google Pixel 4 XL, and the effectiveness and the performance are evaluated against four popular applications. The experimental results show that the design works on all four popular applications and can achieve 12 to 26% of power savings without significantly harming the user experience.

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