Using RegEx (Regular Expressions) to strip out unwanted html from bbcode?

[GrimeForum]

Along with alot of other forums, we use the youtube embed bbcode (and have done for the past 4-5 years).
A common bug which annoys everyone, is when someone posts a complete youtube link within the bbcode tags.
This causes the page to immediately re-direct to youtube's homepage.
Ive looked at one particular plugin that auto-embeds youtube videos from links, which uses RegEx to strip out the unwanted parts in the url leaving just the video ID.

What Im looking for is the same thing but to work for the BBCode, so that if someone was to post the full youtube link, it will remove the "http://www.youtube.com/watch?v=" and "&featured=fejof&.." leaving just the video ID so that it will properly embed no matter what.

Can anyone help me please?

I have no idea how to implement this but have posted the RegEx used from the autoembed plugin below.

/<a href=\"https?:\/\/((.+\.youtube\.com\/watch\?v=)|(youtu\.be\/))([a-zA-Z0-9-_]+)(.*)?\"( target=\"_blank\")?>.*<\/a>/

Obviously somewhere in there would be the {PARAM} however it would work.