Dynamic Backlight Scaling Considering Ambient Luminance for Mobile Videos on LCD Displays

The power consumption of mobile devices is always a concern for users due to the constraints on the size and weight of mobile devices. Up to now, mobile video traffic has accounted for the majority of total traffic, which implies that viewing mobile videos has been the major activity when using mobile devices. Among all the subsystems involving in mobile video playback, the display is the most power consuming subsystem. To reduce the power consumption, dynamic backlight scaling (DBS) technique is developed by adjusting the backlight magnitude when playing the mobile video. However, the convenience of mobile devices makes lots of people watch mobile videos in various luminance environments, which makes the existing DBS methods ineffective since ambient luminance varies greatly. In this paper, we propose a novel DBS strategy to maximally enhance the battery power performance under various ambient luminance conditions through backlight magnitude adjusting, while without negatively impacting users’ quality of experience (QoE). In particular, we conduct a series of subject quality assessment experiments to uncover the quantitative relationship among QoE, ambient luminance, video content luminance, and backlight luminance. We then investigate whether the continuous playback of backlight-scaled videos using the proposed scaling magnitude under various luminance environments would cause flicker effect or not. Motivated by the findings of these studies, we implement a novel DBS strategy for mobile energy saving which is suitable for various ambient luminance conditions. The experimental results demonstrate that the proposed DBS strategy can save more than 40 percent power at most and can save 10 percent power even at a very high ambient luminance condition. We also show that the proposed DBS strategy can be easily adapted to different user preferences and different devices, and can be conveniently integrated into practical applications.