网上有相关介绍，使用videoHeight&videoWidth

但是 我测试总是获取不到

然后在stackoverflow上搜索到类似问题http://stackoverflow.com/questions/4129102/html5-video-dimensions

其中有个大牛说

It should be noted that this solution doesn't actually work in modern browsers since the videoWidth and videoHeight properties aren't set until after the "loadedmetadata" event has fired.

If you happen to query for those properties far enough after the VIDEO element is rendered it may sometimes work, but in most cases this will return values of 0 for both properties.

都开始渲染了再获取到尺寸是不是有点晚？还有什么其他办法吗？