I probably can’t answer but I can get some information to help someone who can!
So the first question – how do you send this to FB? Are you using our Share This plugin?

Yes.

Actually share this plugin works perfectly if there is an image attached somewhere in the topic.  It picks out the first image and uses that.  If there’s no image, it pulls the featured image that is set for the forum.  This is working as one would expect.

However if the user pastes in a link from vimeo or something, video is automatically embeded as per WP oembed (I think), but no image is pulled by share this.

My workaround is to manually create an image from the video and edit the users post and attach the image to his/her post.  Share this then grabs that attached image.

At the moment – without advice – I am just speculating, but could this be because a WP embedded video is actually sourced in an iFrame and targets like Facebook are, in all probability, going to deny creating an iFrame simply because of the potential security risk?

Well, my understanding of the way Facebook et al. work is that they go to the provided link and “scrape” the meta data from the page.  In that meta data are a bunch of tags.  Tags are things like og:title=”My web page” where og stands for “open graph” (facebook’s defined standard set of tags).

So we want the tags to be right before facebook scrapes the page and I think simplepress SEO or maybe the Sharethis plugin are the things that set those tags up.

The tag we are mainly concerned with is “og:image”  (open graph image). I can see the og:image tag being set to the first attached image in the topic if one exsists, and failing that it is set to the feature image for the forum – this is working.  But if I put in a vimeo video link as the first post, the og:image tag isn’t affected.  Essentially it is only grabbing attached images, and not doing anything with embedded video.

What I’d like is for the software to set the og:image tag to the video thumbnail. 

This may be more of a feature request than a bug, but I think it would REALLY improve the ability to share posts on social media.

yes, you have the general idea of how open graph tags works… and how we have implemented what you speak of…

not familiar at all with vimeo other than having heard of it, how would one get a video thumbnail given an embedded url to the video?

and definitely a feature request… which we could always add to our list if we understand the concept…  how would it work with non vimeo videos?  vimeo is far from the most common video and would be best to support the masses vice a single one…

Let me do the research on this.  I will post back here with a method that I think will work.

I think the two most popular video hosts would be youtube and vimeo.  I’ll work on methods for both.

Youtube:

There are a predictable set of urls outlined in the refence link below but generally go something like this:

http://img.youtube.com/vi/<insert-youtube-video-id-here>/0.jpg

Reference:

http://stackoverflow.com/questions/2068344/how-do-i-get-a-youtube-video-thumbnail-from-the-youtube-api

Vimeo:

Similarly, a predictable url:

“http://vimeo.com/api/v2/video/.php”

But you have to either parse the file or just deserialize as outlined in the reference below like this:

Reference:

https://arjunphp.com/how-to-get-thumbnail-of-vimeo-video-using-the-video-id/

Emmet Brown said
Vimeo:

Similarly, a predictable url:

“http://vimeo.com/api/v2/video/<video id>.php”

But you have to either parse the file or just deserialize as outlined in the reference below like this:

Reference:

https://arjunphp.com/how-to-get-thumbnail-of-vimeo-video-using-the-video-id/

that’s two of the many 🙂  but we can add it to the list…  if we do it, might be better for a plugin than core since its not used by the majority but still desired by some…

I would say specifically it’d be desired by the people who install the “Share This” plugin.  Its not really fully complete without being able to share posts with videos to facebook and twitter properly.

Anyways, thanks for thinking about it.

as mentioned, the problem is the sheer number that could be supported… wp oembed is constantly tweaking, adding and removing supported video sites… support nightmare…  but we will consider perhaps some of the prime players..

So apparently you can piggyback on the work of oembed.  The oembed protocol returns a thumbnail in the meta-data if it’s available.  I’ll look into it and see if I can find the exact method.

only question would be if the oembed stuff was done before forum content 🙂  but we are all ears… can add what you find to the consideration ticket we have…