There are many ways to download an embedded streaming video, in youtube and apple movie trailer.
Using unplug plugins for firefox browser is just one of those, is easy to use. If you are not using firefox browser, may be you can consider install one in your system.
After installed unplug, you should see a fish icon with green color at the right side of url input box of the browser. You access to youtube website, click on the fish icon, it will extract out the video link.
Just click on the link should download the streaming video. You can use VLC player to view you video on desktop.