School of Computing Science Simon Fraser University Power Consumption of Google Android’s Video Decoder Mathieu Spénard

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Outline

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Goal

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How the experiment was conducted

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Experiment results

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Challenges and Difficulties

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Conclusion Mathieu Spénard 2

Goal

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Understand how a video decoder consumes power within a cell phone, when renderin H.264/AVC encoded videos

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Experiment done on a real phone, not a chip

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Understand how various processes involved in a phone impacts the overall power consumption of rendering a video Mathieu Spénard 3

Tools Used

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Power Tutor [1], which allows measuring power on the phone using a software with a 5% accuracy for the HTC G1, HTC G2 and Nexus One

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Ffmpeg [2] to encode videos

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City, Crew and Foreman video sequences [3]

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Linda File Manager [4], a free file management system that allows for quickly navigating files within an Android phone Mathieu Spénard 4

Experiment

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Encoded City, Crew and Foreman using ffmpeg

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30fps

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CIF

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Bitrates from 100kbps to 3000kpbs

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Noted the mean Y-PSNR

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Transfer the files to a Google Nexus One phone Set it to plane mode (no 3G antenna/WiFi) Start PowerTutor Using Linda Manager, navigate and start an encoded video When it is over, stop PowerTutor, save the log and rename it so it is easy to retrieve

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Repeat for all encoded videos Mathieu Spénard 5

Results

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Results

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Results

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Results

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Video decoder couldn’t play videos encoded at 2000, 2250 and 2500 kbps, and also from 4000 to 5000 kbps

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Couldn’t stop the Compass process. Consumes very little power, but could add to the operating system overhead Mathieu Spénard 9

Challenges and Difficulties

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Was not parsing the right data at the beginning

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PowerTutor is slow

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PowerTutor has a too coarse granularity

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Not a lot of precision for the OLED screen power consumption because of an unrooted phone (brightness only) Mathieu Spénard 10

Conclusion

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Bitrate and mean Y-PSNR do have an impact on the power consumption of a H.264/AVC video decoder

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System overhead consumes more power than decoding

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Screen consumes most of power; does not leave a lot of room for improvement

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A study using a 3D video decoder could give a different decoder/screen power consumption Mathieu Spénard 11

References

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[1] “PowerTutor,” http://ziyang.eecs.umich.edu/projects/powertutor/

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[2] “FFmpeg.” [Online]. Available: http://www.ffmpeg.org/

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[3] “Video Library and Tools - NSL.” [Online]. Available: http://nsl.cs.sfu.ca/wiki/index.php/Video_Library_and_ Tools

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[4] “Linda File Manager.” [Online].Available: http://www.androlib.com/android.application.com/lind aandny-lindamanager-jpBj.aspx

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