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Adaptive Display Power Management for Mobile Games Adaptive Display Power Management for Mobile Games

Adaptive Display Power Management for Mobile Games - PowerPoint Presentation

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Uploaded On 2015-12-09

Adaptive Display Power Management for Mobile Games - PPT Presentation

Bhojan Anand Karthik Thirugnanam Jeena Sebastian Pravein G Kannan Akhihebbal L Ananda Mun Choon Chan and Rajesh Krishna Balan ID: 219731

gamma power quality user power gamma user quality image backlight display evaluation brightness conservative significant challenge key loss lcd

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Slide1

Adaptive Display Power Management for Mobile Games

Bhojan Anand‡, Karthik Thirugnanam†, Jeena Sebastian‡, Pravein G. Kannan‡, Akhihebbal L. Ananda‡, Mun Choon Chan‡ and Rajesh Krishna Balan†‡ National University of Singapore (NUS) and † Singapore Management University (SMU)

1Slide2

Problem: Display draws significant phone power

Key Challenge: No loss in end user experienceKey problem and Solution2Display45-50%

Network

35-40%

CPU

4-15%

Measured on HTC Magic while streaming a Youtube VideoSlide3

Dynamically adjust image brightness and LCD display backlight levels

50-70% display power savings with no significant user experience impactKey problem and Solution3Slide4

Key problem and Solution

BackgroundSystem DesignEvaluationDiscussion/Future Work 4Talk OutlineSlide5

LCD displays have two components:

Power consumed mostly by the BacklightThus brightening the image, and darkening the backlight saves power. 5Background - LCD DisplaysBacklight - Provides light, and consumes powerLCD Panel - Filters light based on image to be displayedSlide6

Method 1: Naively dim the display

Creates visible artifacts (flicker, brightness loss, etc)Especially noticeable in high frame rate applications6Background: Saving Display PowerSlide7

Method 2: Compensate with increased brightness

Linearly apply same transform to entire imageLeads to saturated images7Background: Saving Display PowerSlide8

Method 2: Compensate with increased brightness

Non linear approaches prevent saturation but cause contrast lossOur solution uses this approach intelligently8

Background: Saving Display PowerSlide9

Gamma Correction, or gamma, is a tone mapping function used to brighten scenesVery Low Saturation relative to linear

Low computational overhead 9Non Linear Gamma CorrectionBefore After: Gamma 2Slide10

10

Effect of Gamma on Image QualityOriginal

Image after Gamma Increase

(gamma=2)

Image after Gamma 

Increase

and

backlight

reductionSlide11

Games are popular and resource intensive

Extremely high frame ratesFlicker and brightness changes very noticeable to users We use two representative gamesQuake III – Commercial First Person Shooting (FPS) game Planeshift – Massively Multiplayer Role Playing Game (MMORPG)    

11

Test ApplicationsSlide12

Key problem and Solution

BackgroundSystem DesignEvaluationDiscussion/Future Work 12Talk OutlineSlide13

Ultimate goal: Save significant power with no loss in end user experience

Challenge 1: Understanding the relationship between the backlight intensity, gamma, image brightness, and the power consumedChallenge 2: Identifying human thresholds for brightness compensationChallenge 3: Dynamically applying the solution 13System Design: Key ChallengesSlide14

Relationship found to be linear. No other major contributing factors

14Challenge 1: Backlight vs PowerHTC HeroLaptop (W500)HTC MagicSlide15

Perceived brightness kept constantNon linear compensation necessaryUseful gamma range is 1 to 4

15Challenge 1: Backlight vs GammaSlide16

Obtained via small user study5 postgraduate students

Each user shown a range of imagesCovered a full range of brightnessFor each image, users had to boost gamma to obtain two quality thresholds Described in next slideTool provided boosted gamma at .1 intervals with automatic backlight compensation16Challenge 2: Human ThresholdsSlide17

Conservative: Image quality comparable to originalAggressive: Image quality is affected but acceptable

17Challenge 2: Two ThresholdsSlide18

18

Challenge 3: Runtime AlgorithmStartCalculate Average Brightness of last X Samples. Is there a change?

Mode + Brightness -> Gamma & Backlight

Leave Settings as it is

Sleep Thread for Y ms

Yes

NoSlide19

Test platformMost of the evaluation on LaptopPrototype Mobile implementation available (demo)

Objective Analytical Experiments Power measurements Measured power saved in different modesPerceived User ImpactLarge scale user study (60 users) with Quake IIIMeasured perceived quality loss in different modes19Evaluation MethodologySlide20

20

Evaluation: Three Test ModesUnmodified

Conservative

Aggressive

Two bounding modes tested but omitted for simplicity Slide21

A recorded trace used to measure powerEvaluation: Power Savings

21Slide22

Large Scale User study60 Singapore Management University undergrads.34 Male and 26 Female students with differing background and game experiences

Participants trained on an unmodified version of the gameThey then played the 3 different versions of the gamePlay order randomized with recalibration at every step22User Study MethodologySlide23

Users rated each version by 6 criteriaCovered different quality dimensions

Evaluation: User Study Results23

Bad

Good

Strongly Agree =

Strongly Disagree =

Neutral =Slide24

Difference between Aggressive and Conservative significant

24Evaluation: Aggressive vs ConservativeSlide25

Difference

betw. Conservative and DefaultEvaluation: Power vs Perception25Slide26

Conservative (Dynamic Conservative)High QualityPerceived quality comparable to default.

Significant Savings – 49% Aggressive (Dynamic Aggressive)High Power Saving – 68%Acceptable Quality26Evaluation: ConclusionsSlide27

OLED DisplaysDo not use BacklightPower consumption depends on displayed content

Algorithm needs to be rethoughtOther Limitations & Future WorkInitial User studies were small scale, and in a controlled environmentPower Measurements could be more accurate, esp for mobile phoneEvaluation of mobile implementation27DiscussionSlide28

General systematic approach to save power on LCD screens

Identified key parameters determining the quality vs power savings tradeoffImplemented and tested with 60 end usersSystem achieves significant power savings with minimal overhead and quality loss28ContributionsSlide29

Thank you

Any Questions 29