Power use measurement: h264vb vs h265crf

Droid4 backlight was set to level 5/7 - good for normal room brightness.

echo 5 > /sys/class/backlight/backlight/brightness

The same beginning time as above excerpts were used from the movie, but running for 10 minutes (600 seconds) to get a better power estimate. Mplayer was used since it's fastest player currently in repository.

mplayer -vo x11 -fs -ss 01:36:00 -endpos 600

Power use was tracked once/min for 10 minutes with Droid4 powermanagement script from repo:

/etc/init.d/droid4-powermanagement status > poweruse_h265.txt

CPU use was tracked once/10sec for 10 minutes with pidstat:

pidstat -C mplayer -u 10 60|grep -v PID > cpuuse_h265.txt

The output files are attached in a .tgz

Zigeunerweisen results

CPU H264vb: 41.2%
CPU H265crf: 58.9%

Discarding the first power reading (it hasn't yet registered a full minute of video playback) we take the mean of 9 readings:

Power H264vb: 1427 mW
Power H265crf: 1760 mW

Note this movie was low-motion, 720x540 and quite easy on the CPU at 58.9%. More action-oriented 960x540 movies tend to push h265 CPU use into the 75-95% range.

The EB41 battery is rated at 6.6 watt-hours, but even my best replacement batteries deliver only approx. 5.5 watt-hours. This means watching these encodes for 2 hours would use approximately:

h264vb 53% of battery
h265crv 64% of battery

For the whole movie, the tested h265crf encode would require a bit less than 20% more total energy than the h264vb, since the high power peak included is a larger percentage of the sample than the whole movie.

The high-motion tree blossom scene in h265 at around 1500kbit/s pushes CPU to 93.4% and power drain to 2076mW, versus 46% and 1472mW on the bitrate-limited h264. Based on that peak we can infer that a high-bitrate two hour movie using 90+% of one CPU core would consume around 4.1 watt-hours, or 75% of a typical old EB41 battery.

Notice that power use does not scale linearly with CPU use since we have fixed costs like backlight. This is why the 43% higher CPU use of HEVC in this test only costs half as much additional energy.