  This paper derives optimal spatial scaling and rate control parameters for
power-efficient wireless video streaming on portable devices. A video streaming
application is studied, which receives a high-resolution and high-quality video
stream from a remote server and displays the content to the end-user.We show
that the resolution of the input video can be adjusted such that the
quality-power trade-off is optimized. Making use of a power model from the
literature and subjective quality evaluation using a perceptual metric, we
derive optimal combinations of the scaling factor and the rate-control
parameter for encoding. For HD sequences, up to 10% of power can be saved at
negligible quality losses and up to 15% of power can be saved at tolerable
distortions. To show general validity, the method was tested for Wi-Fi and a
mobile network as well as for two different smartphones.
