  While the evolution of mobile computing is experiencing a considerable
growth, it is at the same time seriously threatened by the limitations of the
battery technology, which does not keep pace with the evergrowing increase in
energy requirements of mobile applications. A novel approach for reducing the
energy appetite of mobile apps comes from the approximate computing field,
which proposes techniques that in a controlled manner sacrifice computation
accuracy for higher energy savings. Building on this philosophy we propose a
context-aware mobile video quality adaptation that reduces the energy needed
for video playback, while ensuring that a user's quality expectations with
respect to the mobile video are met. We confirm that the decoding resolution
can play a significant role in reducing the overall power consumption of a
mobile device and conduct two user studies to investigate how the context in
which a video is played, its content, and the user's personality, modulate a
user's quality expectations. We discover that a user's physical activity, the
spatial/temporal properties of the video, and the user's personality traits
interact and jointly influence the minimal acceptable playback resolution,
paving the way for context-adaptable approximate mobile computing.
