Video JS - 海报图片封面/包含

VideoJS 4 uses different CSS behaviour from what I was used to for the poster image from what I can see. I've changed background-size CSS to "cover" instead of "contain", which means that even if the proportions of my image are wrong, the image will fill the poster div. For some reason, however, when you click on the poster to start a video, the poster image seems to go back to "contain" while the video is loading. Is this change being made elsewhere?VideoJS 4 uses different CSS behaviour from wha