poster frame

A  poster frame  is a static image taken from one frame of video to represent a video (like a video post) visually in various contexts such as a thumbnail or before the video is played.

Why
You should include an explicit poster frame on your video posts to provide an image that is representative of what the video is about, since the first frame might not show much, or is blank.

How
Use the HTML5  attribute on the   tag with a URL to the poster frame image like a JPEG.

Shane Becker
supports explicit poster frames in his video posts since 2013-07-07(private GitHub repo commit). Example:
 * http://veganstraightedge.com/videos/2013/5/31/1/backyard-squirrel-buddy (updated 2015-12-13 with fallback  tag)
 * markup:
 * tag with  intending to communicate the   attribute
 * tag with  tag for   video file and   tag with   as a fallback for cases when native video isn't supported.

Tantek
undefined supports explicit poster frames in his video posts since 2015-360 using an upgrade to the CASSIS  function that implements: Video with poster and Video with poster and hyperlink auto-linking syntaxes. Example:
 * 2015-360: http://tantek.com/2015/360/t2/best-starwars-speak-droid
 * manual POSSE tweet video: https://twitter.com/t/status/680897393814994944

Silo Examples
Silos that support video posts with explicit poster frame selection:
 * Instagram

In particular the following silos that support video posts DO NOT support poster frames:
 * Twitter