After switching from Release to Nightly (v56), I noticed about a 5-15% higher CPU utilization in the content process while watching YouTube videos. The difference is significant enough that I took note that my battery was draining about 1% per minute of video playback while the CPU fans spun up to high. On Release builds, the content process lingers around 40%. On Nightly, the content process varies between 45% and 55%. macOS Sierra 10.12.2 MacBook Pro (Retina, 15-inch, Late 2013) 2.6 GHz Intel Core i7 16 GB 1600 MHz DDR3 Intel Iris Pro 1536 MB NVIDIA GeForce GT 750M 2048 MB
Also, for some reason, certain videos will cause the content process to climb as high as 70% and stay there which *really* causes the fans to spin up and the battery to drain :-/
Can you compare the two FF versions by doing the following: While watching YouTube, right click on the video player and selects stats for nerds. Copy the text overlay. Are they both webm/vp9 or one is h264 while the other (nightly) is vp9.
(In reply to Jean-Yves Avenard [:jya] from comment #2) > Can you compare the two FF versions by doing the following: > > While watching YouTube, right click on the video player and selects stats > for nerds. > Copy the text overlay. > > Are they both webm/vp9 or one is h264 while the other (nightly) is vp9. I hadn't even considered that. My bad. I just watched a couple videos on one YT channel in Nightly with no problem. When I watched another video from a different YT channel, suddenly my fans started spinning up so I took a look and that's exactly what's happening. Its not a Nightly vs. Release issue, its an h.264 vs. VP9 issue :-( The VP9 videos run at around 50-60% CPU and the 60fps videos hit 80%! When I took the same videos and tested them in Release, I got similar CPU usage, so I'm going to go ahead and close this as INVALID. Thanks for taking a look! Also, out of curiosity, I tested the same video in Chrome and it seemed to have even higher CPU usage there. So, that's a win! :-)