  Conventional planar video streaming is the most popular application in mobile
systems and the rapid growth of 360 video content and virtual reality (VR)
devices are accelerating the adoption of VR video streaming. Unfortunately,
video streaming consumes significant system energy due to the high power
consumption of the system components (e.g., DRAM, display interfaces, and
display panel) involved in this process.
  We propose BurstLink, a novel system-level technique that improves the energy
efficiency of planar and VR video streaming. BurstLink is based on two key
ideas. First, BurstLink directly transfers a decoded video frame from the host
system to the display panel, bypassing the host DRAM. To this end, we extend
the display panel with a double remote frame buffer (DRFB), instead of the
DRAM's double frame buffer, so that the system can directly update the DRFB
with a new frame while updating the panel's pixels with the current frame
stored in the DRFB. Second, BurstLink transfers a complete decoded frame to the
display panel in a single burst, using the maximum bandwidth of modern display
interfaces. Unlike conventional systems where the frame transfer rate is
limited by the pixel-update throughput of the display panel, BurstLink can
always take full advantage of the high bandwidth of modern display interfaces
by decoupling the frame transfer from the pixel update as enabled by the DRFB.
This direct and burst frame transfer of BurstLink significantly reduces energy
consumption in video display by reducing access to the host DRAM and increasing
the system's residency at idle power states.
  We evaluate BurstLink using an analytical power model that we rigorously
validate on a real modern mobile system. Our evaluation shows that BurstLink
reduces system energy consumption for 4K planar and VR video streaming by 41%
and 33%, respectively.
