封面图
https://developer.qiniu.com/dora/1313/video-frame-thumbnails-vframe
http://xxxx.com/xx91.mp4?vframe/jpg/offset/10/w/480/h/360
视频信息,时长等
https://developer.qiniu.com/dora/1247/audio-and-video-metadata-information-avinfo
http://78re52.com1.z0.glb.clouddn.com/resource%2Fthinking-in-go.mp4?avinfo