Why does the video’s poster image look pixelated on mobile devices?
This is the default start-screen of youtube’s video. On desktop browsers (non-mobile) the poster image is sharp because the plugin overlaying a sharp image that it downloads. For mobile browsers it cannot do this, since the video needs to be clickable to start playing. I cannot make the video start by clicking an image above the video. They (the mobile browser developers, Apple or Google in this case) have added this measure to ensure video’s cannot start playing by themselves when you open a page as it would eat up your bandwidth. Unfortunately there is no solution to this problem.