1402752 - High CPU usage on YouTube while playing idle, making the rewind bar visible and rewinding the video.

Status: RESOLVED DUPLICATE of bug 1300235

(Firefox :: Untriaged, defect)

Description

[smartfon.reddit]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:56.0) Gecko/20100101 Firefox/56.0
Build ID: 20170918210324

Steps to reproduce:

It uses 2-5 times more CPU than others while playing YouTube videos. I was advised to use a Gecko profiler and post the results here.

Profiler starts. YouTube URL is loaded. The CPU usage spikes to 20% - 40% for a few seconds. Profiler captures: https://perfht.ml/2ynf2p0

Hover the mouse over the video multiple times to make the rewind bar visible. Nothing is clicked. CPU is 15% - 25% : https://perfht.ml/2ymRgJX

Rewind the video multiple times. CPU usage 20% - 30%: https://perfht.ml/2ymUInN

This one shows idle video playback with no interactions. No recent activities that could have caused it to cause a spike. Just plain Firefox decoding and playing the video. CPU usage 8% - 20%. One of the processes that has the higher RAM usage is responsible for most of the CPU usage, but it's usually distributed between multiple firefox.exe processes: https://perfht.ml/2ymLbNq

Dell Inspiron i5577. Intel i7-7700HQ with Intel 630 graphics and latest drivers. GPU has hardware VP9 decoding.   Tested with VP9 and mp4a in "Stats for Nerds". Completely fresh profile with no changes. CPU usage goes below 1% when the video is paused. Tested with and without antivirus. Tested with YouTube's new material and old layouts. Tested with Firefox 55 - 58, with 57 and 58 being slightly better in idle usage. This is not a new problem that has started out of the blue.