1. Mathieu Spénard 1 School of Computing Science Simon Fraser University Power Consumption of Google Android’s Video Decoder Mathieu Spénard

2. Outline  Goal  How the experiment was conducted  Experiment results  Challenges and Difficulties  Conclusion 2

3. 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 3

4. 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 4

5. 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 5

6. Mathieu Spénard Results 6

7. Results 7

8. Results 8

9. 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 9

10. 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) 10

11. 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 11

12. 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/lind aandny-lindamanager-jpBj.aspx 12