My audio and video are not in sync in many streams but some are OK. I do not have any extensions, add-ons and I am using the default theme. I have disabled hardware acceleration. I am now running in Safe Mode and the problem persists. The video and audio sync for the first few minutes and then they work their way futhter and further apart, usually several seconds out of sync. I don't think this particular situation has been covered in the other posts.