Testing Android battery drain at different native resolutions

CNET Labs runs native-resolution video battery-drain tests on Android phones.

The only phones brave enough to endure the rigors of native-resolution battery testing! Or the only phones we had available at press time...

A few weeks ago I posted detailing the performance scores of several smartphones .

Of particular interest were the video battery results for the Android phones. Some commenters took issue with the fact that I used 720p video to drain the battery life of the Android phones, while the iPhone 4 was tested with video running at that device's native resolution.

Some thought this was an unfair battery drain, as the 720p video would have to be resized to fit a phone's native resolution, possibly taking away processing cycles, draining the battery more quickly. Commenters suggested that the video run at each phone's native resolution.

This idea piqued my curiosity, so I went back and re-encoded the original 720p video to run at each Android phone's particular resolution.

I only had access to the three phones listed in the chart below when I conducted the retests, so this list may seem limited in scope; however, I think the following chart paints a pretty clear picture.

Phone name 720p video battery life
(in hours)
Native-resolution video battery life
(in hours)
HTC Evo 4G 6.8
5.6
Motorola Atrix 4G 7
6.5
Samsung Epic 4G 6.9
5.9

Analysis

From the evidence provided here, running a 720p movie on an Android phone draws less power from the battery than running a movie at the phone's native resolution. Each drains anywhere from 30 minutes to over an hour faster when running a native-resolution movie.

The full specification of 720p is 1280x720-pixel resolution. The Atrix 4G's native resolution, for example, is 960x540 pixels. Honestly, we were surprised by the results. The video we used is exactly the same (same bit rate and so on), save for the difference in resolution.

We're not fully sure why running at full resolution draws more power, but it could be that the phones are optimized to play movies at that resolution more than at native res, since 720p is a movie standard and 960x540 pixels isn't so much.

The mVideoPlayer app we used could also have something to do with it, but we've yet to have a chance to test with an alternate app. As time allows, I may run more tests, but for now we'll be sticking with 720p as our Android phone battery-life draining standard.

How we tested

We evaluated battery life by continually running a movie file on each smartphone until its battery died.

We set each smartphone to Airplane mode and adjusted its respective brightness to 140 candelas per square meter (cd/M2) or as close to that number as possible.

"Toy Story 3" was the movie of choice used to drain the battery.

We used the movie player app mVideoPlayer as it provides a much-needed repeat video function that not all native Android movie players include.

 

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