In some sites "class" contains more that BrightcoveExperience
Brightcove videos info is usually found in an <object class="BrightcoveExperience"></object> node, this is passed to a new method of BrightcoveIE that builds a url to extract the video.
It only accepts the urls that are use for embedding the video, it doesn't search in generic webpages to find Brightcove videos
Jaime Marquínez Ferrándiz