Mathieu Spénard 1

School of Computing ScienceSimon Fraser University

Power Consumption of Google Android’s Video Decoder

Mathieu Spénard

Mathieu Spénard

Outline

Goal

How the experiment was conducted

Experiment results

Challenges and Difficulties

Conclusion

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Mathieu Spénard

Goal

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

Experiment done on a real phone, not a chip

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

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Mathieu Spénard

Tools Used

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

Ffmpeg [2] to encode videos

City, Crew and Foreman video sequences [3]

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

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Mathieu Spénard

Experiment

Encoded City, Crew and Foreman using ffmpeg- 30fps- CIF- Bitrates from 100kbps to 3000kpbs- Noted the mean Y-PSNR

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

Repeat for all encoded videos

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Mathieu Spénard

Results

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Mathieu Spénard

Results

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Mathieu Spénard

Results

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Mathieu Spénard

Results

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

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

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Mathieu Spénard

Challenges and Difficulties

Was not parsing the right data at the beginning

PowerTutor is slow

PowerTutor has a too coarse granularity

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

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Mathieu Spénard

Conclusion

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

System overhead consumes more power than decoding

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

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

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Mathieu Spénard

References

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

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

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

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

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