A bit of everything. Obviously the software vs hardware decoding of video is a major factor, but you'll also sometimes find ads/animation causing a huge CPU spi

A bit of everything. Obviously the software vs hardware decoding of video is a major factor, but you'll also sometimes find ads/animation causing a huge CPU spike. This is almost solely due to a Flash Designer/Animator creating the flash movie, they tend to just bump the frame rate up to something ridiculous like 60-90 fps to get smooth animation, and also overuse onFrameEnter event handlers which can be attached using the timeline.