Thumbnailing

Overview
This update allows builders to easily retrieve thumbnails for ongoing livestreams, as well as on-demand assets. Thumbnails are frequently used as poster images when displaying livestreams or assets within an application, and can also enable timeline hover previews (i.e., hovering over the player's timeline bar and seeing a preview image for a portion of the video).
Details
For livestreams, we provide a single updating thumbnail URL - it will return the first frame of the most recent segment of video. 
For on-demand assets we provide a way to retrieve a list of thumbnails for your video assets. Thumbnails will be generated as part of the asset processing step, with each “segment” (roughly 2-3 seconds) of video resulting in one image. These images are stored in a WebVTT file that is suitable for use in timeline hover previews in addition to retrieval of single images.
Thumbnail URLs for both Live and VOD assets will be accessible through the existing playback info API endpoint.
For more information, please refer to the guides linked below. 
Resources
Livestream Thumbnails
Asset Thumbnails
Known Limitations
The Livepeer Player supports thumbnails through the posterImage
 prop. However, you will need to supply the imageURL; it will not retrieve it automatically. 
While the thumbnailing feature enables timeline hover previews, the Livepeer Player does not yet have this capability. It will be added in a future release.