I'd like to find out how Tumblr retrieves video thumbnails.
Normal video posts (not using API) when viewed from the dashboard or /tagged/ filters, some sites's video shows thumbnails, some doesn't show up.
Works for http://www.youtube.com and http://www.vimeo.com.
However, http://www.ted.com and http://www.slideshare.net thumbnails doesn't show up.
I was wondering if any of the Tumblr devs can enlighten me on the process how and where they get the thumbnail data from. Is there a general method for retrieval that by that I can conform a document structure to?
It would also be great if the API allows you to set thumbnail url too, sort of like facebook's opengraph image meta data.