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Are All Games Equally Cloud-Gaming-Friendly? An Electromyographic Approach
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Are All Games Equally Cloud-Gaming-Friendly? An Electromyographic Approach

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Cloud gaming makes any computer game playable on a thin client without worrying the hardware requirements as before. It frees players from the need to constantly upgrade their computers as they can ...

Cloud gaming makes any computer game playable on a thin client without worrying the hardware requirements as before. It frees players from the need to constantly upgrade their computers as they can now play games that host on remote servers with a broadband Internet connection and a thin client. However, cloud games are intrinsically more susceptible to latency than online games because game graphics are rendered on server nodes and thin clients do not possess game state information that is required by delay compensation techniques.


In this paper, we investigate how the response latency would affect users' experience when playing games on clouds and how the impact of latency on players' experience varies across different games. We show that not all games are equally friendly to cloud gaming. The same degree of latency may have very different impact on a game's quality of experience depending on the game's real-time strictness. We thus develop a model that can predict a game's real-time strictness based on the rate of players' inputs and game screen dynamics. The model can be used to enhance players' experience in cloud gaming and optimize data center operation cost simultaneously.

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Are All Games Equally Cloud-Gaming-Friendly? An Electromyographic Approach Presentation Transcript

  • 1. Are All GamesEqually Cloud-Gaming-Friendly?NetGames 2012-- An Electromyography ApproachYeng-Ting Lee National Taiwan UniversityKuan-Ta Chen Academia SinicaHan-I Su Academia SinicaChin-Laung Lei National Taiwan University
  • 2. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 2Long-Lasting Problems of GamersGame software becomes more complexThe overhead of setting up a game is significantLocked by a certain computerGames have software and hardware compatibility withcomputersComputer hardware upgradedemands
  • 3. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 3Cloud GamingReal-time game playing via thin clientsCloud game serversInternetStreamingStreamingStreamingPCLaptopMobile
  • 4. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 4Benefits of cloud gamingFrees players from the need of indefinitely upgradingtheir computersNo setting up overhead and compatibility issues fortrying out a game as everything needed will be settledin data centers by game operatorsPeople can play games anywhere, anytime4
  • 5. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 5Cloud Gaming ServicesT5-Labs
  • 6. Unavoidable Delayst0 (Key event sent) t1 (Key event received)t2 (Frame sent)t3 (Frame received)ServerClientGame frameGame screent4 (Frame displayed)Network delay : (t1 – t0)+(t3 – t2)Processing delay : t2 – t1Playout delay : t4 – t3
  • 7. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 7A Comparison with “Traditional”Online GamesUnavoidable extra delaysVideo encoding at the serverVideo decoding and playout buffering at the clientLess effective delay compensationGame states (e.g., game objects’ positions and velocity) sarenot available at the client sideCloud games are intrinsically more susceptibleto latency than online games.
  • 8. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 8Our motivationsQ1: How the response latency in cloud gamingaffects users’ experience?Q2: Are different games equally sensitive tolatency?Searching for opportunities to enhancecloud gaming QoE
  • 9. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 9DefinitionReal-time strictness (RS)How much a game’s QoE degrades when the latency ishigher?Cloud-gaming friendlinessA cloud game’s susceptibility to latency in terms of its QoE
  • 10. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 10Roadmap
  • 11. QOE MEASUREMENT
  • 12. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 12QoE Measurement ApproachesMOS (Mean Opinion Scores)Inaccuracy due to recency effectCostly due to its fewer and coarser (i.e., five-level) responsesSSCQE (Single Stimulus Continuous Quality Evaluation)Requires subjects to continuously reporttheir present gaming experienceMay disturb game play and diminishthe flow experience
  • 13. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 13Facial EMG approach1. Continuous emotion measures (can be at a rate of 1000Hz or even higher)2. Does not disturb game play3. Objective since the emotional indicators are directlymeasured rather than told by subjects(EMG: Electromyography)
  • 14. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 14Facial EMG Measurement SetupThe corrugatorsupercilii muscleNegative emotionsThe amount of annoyancecaused by latency
  • 15. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 15Measurement devicesPowerLab 16/30ElectrodesWires
  • 16. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 16During game play…
  • 17. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 17Latency EmulationReasonsFull control of the latency injected into the input-responseloopFree study of games that are not available on current cloudgaming platformsOur approachUse SetWindowsHookEx API (in Windows) to intercept all the keyboardand mouse inputsEach of the input events is firstly queued in a buffer and later replayedafter a desired time t
  • 18. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 18Selected GamesACTLEGO Batman (Batman)Devil May Cry (DMC)Sangoku Musou 5 (Dynasty Warriors 6) (SM5)FPSCall of Duty: World at War (COD)F.E.A.R 2 (FEAR)Unreal Tournament 3 (Unreal)RPGYs Origin (Ys)Loki: Heroes of Mythology (Loki)Torchlight (Torch)
  • 19. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 19Experiment overview• Latency levels: 0, 50, 100, 200, 400 ms• Each round: 10 minutes with 5-minute breaks• Latency is randomly applied during game play
  • 20. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 20Trace SummarySubjectsTrace
  • 21. QUANTIFYING REAL-TIMESTRICTNESS OF GAMES
  • 22. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 22Overall EMG potentials
  • 23. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 23EMG Potentials for each game1. Diverse baseline EMG potentials for each game2. The increasing rates of EMG potential are game-dependent aswell
  • 24. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 24Deriving real-time strictness (RS)
  • 25. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 25RS of the studied gamesIn general, FPS > RPG > ACT in terms of RSGame pace↑, RS↑, latency-critical↑
  • 26. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 26MODELING THE REAL-TIMESTRICTNESS OF GAMES
  • 27. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 27Real-time strictness modelingMotivationsSubjective measurements are labor-intensiveTo understand the design elements that cause high RSExpected prediction modelOutput: RS estimateInputs User game play inputs User game play video recording
  • 28. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 28Our conjectureHow a game responds to players’ commands isassociated with its real-time strictness.If its commands is “lightweight”Simple, fast, local movesTiming is important  higher RSIf its commands are “heavy”Associated with long and large amounts of animationsTiming is not critical  lower RS
  • 29. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 29Illustrations for command “heaviness”
  • 30. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 30Feature ExtractionScreen dynamicsBased on the motion vectors in H.264 encoded video clipsBasically the variation of motion vectors’ lengths on each game frameUser input rateUsed for normalization(indicates the average complexity of screen changes caused by eachkeyboard/mouse input event)
  • 31. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 31Command heaviness vs. RS
  • 32. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 32RS prediction
  • 33. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 33Application #1: Balance games’ QoEdegradation due to latencyScenarioN users are playing different games at the same timeUsers experience different latencies and games have different RS Each player experiences different levels of QoE degradationUsageUse the model to infer which players are having a worse gamingexperience than othersPrioritize the server’s resources, such as CPU and GPU, to reduce thoseplayers’ latencies and thereby mitigate QoE degradation they wouldotherwise experience
  • 34. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 34Application #2: Co-optimizing data centercost and gaming experienceScenarioN data centers, each has distinct operation cost (electricity and labor)Whenever a user signs in, we need to assign a data center to him forreal-time game playQuestion: Which data center should we assign to the player?UsageUse the model to predict users’ QoE in all the cases and choose the datacenter which provide a “just good enough” gaming experienceData center A:Lower cost, longer delayData center B:Higher cost, shorter delay
  • 35. Are All Games Equally Cloud-Gaming-Friendly? / Kuan-Ta Chen 35SummaryNot all games are equally friendly to cloud gaming dueto different designThe cloud-gaming-friendliness factor could bepredicted by analyzing how a game is playedSuch a prediction model can be used to simultaneouslyoptimize server resource usages and gamingexperience and help achieve a win-win situation forboth the industry and gamers.
  • 36. Thank You!Kuan-Ta ChenAcademia Sinicahttp://www.iis.sinica.edu.tw/~swc