How to Convert a Flash Video File (.flv) to MP4 with FFMpeg

1. Download Flash Video using something like Video DownloadHelper (plugin for FireFox) or KeepVid.
2. Now you have the file you want; it's time to convert the .flv file to something a little easier to work with. 
3. FFMpeg is very easy to use and can be downloaded here.
4. Open a command prompt.
• Note: It may be easiest to place the .flv file in the same folder as ffmpeg.exe.
5. In the command line enter "ffmpeg -i FILE_NAME.flv -ar 22050 NEW_FILE_NAME.mp4".
• This basically says "Using ffmpeg, take the file FILE_NAME.flv, change the sample rate (this is the -ar 22050 part, and it makes a world of difference to the audio quality), and output a file called NEW_FILE_NAME in the mp4 format."

Instead of mp4, you could output an avi, wmv, mpg, or almost any other video file, or eve audio file like mp3.

That's it. Now you have your converted video file.

Download ffmpeg.exe for Windows (direct link) (8.5MB)

Tips

• Save the line of code (ffmpeg -i FILE_NAME.flv -ar 22050 NEW_FILE_NAME.mp4) in a text document or text file for easy access.
• You can then Extract Audio from MP4 Files with AOA Audio Extractor and Remove Unnecessary Audio with Audacity if you want.

More:

• Use Google to find FREE music on the web
• Download mp3 (music) files with wget
• Converting Audio/Videos using FFMPEG
• Download the latest FFmpeg Windows Builds (ffmpeg.exe compiled for Windows).