How to save any Flash Video to disk from Firefox in Linux

I've used youtube-dl to download videos from YouTube, but it can't handle, say, about.com videos. Or any of the other random video sites popping up all around the net. Turns out there is a very simple way to save any FLV file to disk in Firefox (as a friend showed me):

1. Type about:cache in the Location bar.
2. Click "Disk Cache Device", loading this page might take some time.
   
3. Search for the FLV file (Ctrl+F). You may have to look around a bit.
   
4. Once found, click the link, which will open up a "Cache entry information" page.
   
5. On that page, the "file on disk" parameter shows you where Firefox has stored that FLV file in its cache on disk. Now just cp that file to wherever you want it:
   
   cp /path/from/file/on/disk /path/to/where/I/want/FLV/file.flv
   

Incredibly simple and easy! (Tested on Ubuntu Feisty)

Flash 9.0 on 64-bit Ubuntu with Firefox 2.0

I'm watching the Mac vs. PC ads on Youtube, in the 64-bit Firefox 2.0 browser. This shouldn't be working, Adobe does not have an official 64-bit Flash player for any operating system, let alone Linux. You ask how? Here's the trick:

1. Get nspluginwrapper sources from the Debian website.
2. Compile and install.
3. Get the Flash 9.0 player from Adobe.
4. Untar, and copy libflashplayer.so and flashplayer.xpt to ~/.mozilla/plugins/
5. Run nspluginwrapper -i ~/.mozilla/plugins/libflashplayer.so
6. Enjoy!

I've done this before, with an older version of nspluginwrapper, but could never get sound working. Maybe the fact that I used RPMs (converted by alien) messed things up. Even now, however, nspluginwrapper segfaults. Thankfully it works for nspluginwrapper -i, which is all I that's required.

As an aside, swfdec is a free software Flash viewer that plays Flash videos, and so is gnash.

Furthermore, youtube-dl allows you to download the flash videos to your hard disk, where mplayer or ffplay (better) can play them.