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.