Mobile handheld devices have stringent constraints on power consumption because they run on batteries that have a limited lifetime. Conserving power to prolong battery life is of primary importance for these devices. Several factors such as backlight intensity, the hard disk, the CPU, the network interface and the nature of the application contribute significantly towards power consumption for a mobile device. While significant research effort has been made to optimize power consumption at the application, network and processor levels, comparatively little work has been done to reduce or adapt to the power consumed by the backlight. In this paper, we propose an adaptive middleware based approach to optimize backlight power consumption for mobile handheld devices when playing streaming MPEG-1 video, without significantly compromising on video quality. Our performance results indicate that up to 60% of the power consumed by the backlight can be saved by using the proposed approach.