I want to take a thumbnail image of a youtube video, let's say http://www.youtube.com/watch?v=ffaTjpA1scI at 30s or 120s. How can I do that with youtube API?
I do think this is possible, because when I watch a Youtube video, if I move my cursor to the timeline, I can immediately see snapshots at specific time. I just want to retrieve these snapshots programmatically.
I also tried http://img.youtube.com/vi//0.jpg, actually this can get the thumbnail of course, but it cannot get a snapshots at a specific time.
Those specific type thumbnails (used for the timeline snapshots) are not exposed via any sort of official URL scheme or API. I wouldn't recommend trying to reverse-engineer a solution, either.
来源：https://stackoverflow.com/questions/13525507/how-to-get-a-thumbnail-or-snapshot-of-a-youtube-video-at-a-specific-second-wit