I’m using Full-Text RSS to extract content of articles, and obviously, those articles contains videos from YouTube, Vimeo… With iFrames. What I’ve found is that when you extract the content of those articles, the src of the iFrame looks like this:
Are you sure this is as a result of Full-Text RSS? It’s quite common to have URLs appear in that format (without the protocol appearing). It simply means that the site on which that iframe is displayed will determine whether the final URL will be ‘http://’ or ‘https://’. If the site is served through SSL (‘https://’) then the iframe will also be served through SSL (‘https://www.youtube.com…’). More information here: http://www.paulirish.com/2010/the-protocol-relative-url/
I know that we do not rewrite URLs like this ourselves yet, so my guess is that that’s how it appeared on the original site. If you’d like us to check, please provide a URL and we’ll have a look.