Thumbnail preview is a feature that allows you to get a preview thumbnail image of your video stream. Thumbnails are delivered via a webhook POST request to your server so that you can save the image and distribute with your infrastructure.
If thumbnail functionality is enabled for the stream, it will extract an intra frame from the incoming feed to create a thumbnail. While the stream has an active publisher, a Thumbnail webhook is sent at most every 30 seconds.
Reference Documents- https://docs.dolby.io/streaming-apis/docs/thumbnail-webhooks
We have some sample code to demonstrate receiving a thumbnail hook and saving it to disk: Webhook Code Example (download and save)