Many streaming videos are in the wrong aspect ratio. Almost all discussion of this I ever find deals with how to download and correct the videos, or how to make sure your videos are correct if you're uploading them. I'm specifically asking for a way to control the aspect ratio of streaming videos.
For YouTube, I have a Greasemonkey script installed that does exactly this. But... that's only for YouTube. I want something that works on (hopefully) any Flash-based streaming video, including in fullscreen mode.
Linux Mint 12 KDE, Firefox 12.0, Flash 126.96.36.199.