One of my ongoing tasks is modernizing and fixing up issues with TimedMediaHandler, the MediaWiki extension we use to handle audio and video files on Wikipedia and Wikimedia Commons.
One of many “little cuts” has been that the thumbnail frame of a video file defaults to the halfway point in the file, which is sometimes great and sometimes useless (such as a blank transition frame). You can override the thumbnail to use for a given invocation in a wiki page, but can’t set a default to be used in places where no parameter is added… such as when a WebM or Ogg video got selected as the default poster image via the PageImages extension.
To resolve this, we’re reviving an old request to make it possible to set the default thumbnail frame time for a video.
I’ve got a patch partially working, using a parser function so you can put something like {{#thumbtime:90}} on the file page to set the default to 90 seconds in, or {{#thumbtime:35:17}} for 35 minutes and 17 seconds in, etc. The expanded time in seconds is saved as a page property on the File: page, then extracted and copied into the extended file metadata by a hook in TimedMediaHandler. The metadata gets queried when we the generate HTML harness for the video/thumbnail, and we pass the time down in the URL of the thumb just as we would if you had specifically requested that time.
Currently however it’s incompatible with CommonsMetadata extension, which we kind of need. ;) So I’ve got to figure that out and either get them to play nice, or store the data in a different way.
(Just using the page props locally isn’t enough because we have to export the data from Wikimedia Commons to other sites.)