Flash is an absolute resource drain you've probably noticed how it completely hogs resources when you watch a video. Ever wonder how much more power is consumed watching flash over a regular video file? Is it a significant number? For those too lazy to read the rest, the simple answer is yes. And now to the details.
Recently I was watching a hulu video on a 1080P monitor and I noticed it was a little choppy. I decided to conduct an experiment and actually measure the difference in resource, power utilization between flash and h.264 (in mplayer). Not having the desire to make a video and encode it for flash and h.264 I randomly chose a trailer which was sufficiently long and was widely available in multiple formats. Tron Legacy, conveniently available through youtube and The Pirate Bay in 1080P, excellent.
In a more or less idle state my laptop draws around 1500mA of current (according to ACPI), CPU utilization is around 3% and clock averaged both cores is somewhere around 1.5Ghz (1Ghz min 2Ghz max .25Ghz step size utilizing the on-demand CPU frequency governor). Firing up the video through youtube in windowed mode (which scales the video to around 800pixels) The CPU utilization jumps up to around 85% and current draw to around 44000mA clock is continually kept at 2Ghz on both cores. Setting the movie to full screen (1080 pixels wide) decreases CPU usage to 70% and current draw to 3500mA, this might sound counter intuitive but it makes perfect sense as at 1920 wide the video is in native resolution and does not need to be scaled (This actually demonstrates that Flash does not make good use of the hardware scaling AKA Xv). Viewing the same 1080p trailer in mplayer, does reduce CPU load and current draw. Size of the video window does not matter much scaling it to about 800pixels or viewing in native 1920 pixels wide results in same numbers, thanks to mplayers Xv support. CPU utilization is around 40% and CPU does quite frequently clock down to reduce power consumption, current draw is around 3000mA.
So what does all of this mean. Assuming the voltage at the built in ACPI ammeter is equal to battery voltage (11.1V) that means the difference in power consumption between playing a video in flash vs Mplayer h.264 is about equivalent to medium strength CFL light bulb (1.5A*11.1V=15watts). Now this experiment is completely unscientific and has many flaws, primarily perhaps that I use Linux 64 bit flash player (10,0,42,34) the vast majority of flash users are obviously on windows and its possible that it runs better on windows platforms but I wouldn't bet money on that.
It makes me wonder if google is supposedly so concerned about being green maybe they should think about switching the default video format for youtube. We can do some interesting estimations. Lets assume that the average user of youtube watches 10 minutes worth of content in the default flash format, that means they consume about ( 10hours * 15watts / 60 minutes in an hour * 52 weeks in a year / 1000 watt hours in megawatt hours) .13 kilowatt hours per year more than using other formats. This does not sound like all that much but, assuming that 5% of the world population fits into this category it equals to about 40 000 000 kilowatts of power that could be saved. What does this number really mean? I invite you to go to the EPA Greenhouse calculator and plug it in. You'll see its equivalent to annual emission of 5500 cars. Again the numbers are completely unscientific but even if they are off by a factor of 3, it is still a significant number. It would be nice for someone to conduct a more thorough investigation.
While conducting this experiment I noticed something interesting. Playing the 1080p video in youtube would work fine for the first 1.5 min but then it would get choppy. The full trailer was fully downloaded so it didn't make much sense. Firing up KDE System monitor I was able to quite quickly to figure out the problem. As the video got choppy the CPU clock would drop while usage remained high, clearly the problem must be with cooling. System monitor was reporting CPU temperature of about 100C and power consumption of almost 6000mA. It had been a while since I cleaned the inside of my laptop, so I stripped it apart and took out a nice chunk of dust that was between the radiator and the fan. After this CPU temperature never went above 85C and current draw was at a much more reasonable 4400 while playing the flash video. Hopefully this will resolve my choppy hulu problem.
The graphs of this experiment are available. The flash graph, at first the scale trailer was played following by full screen. For the mplayer graph the inverse was done, first full screen then scaled .. but it doesn't matter much for mplayer.LILUG WWTS software 2010-04-07T22:42:19