WinFF is a GUI for the command line video converter, FFMPEG. It will convert most any video file that FFmpeg will convert. WinFF does multiple files in multiple formats at one time. You can for example convert mpeg’s, flv’s, and mov’s, all into avi’s all at once. WinFF is available for Windows 95, 98 , ME, NT, XP, VISTA, and Debian, Ubuntu, Redhat based GNU/Linux distributions. WinFF is available in Brazillian Portuguese, Bulgarian, Chinese Tradditional, Danish, English, French, German, Italian, Polish, Portuguese, Spanish, and Turkish.
* Easy to use interface.
* Fast (Winff does not hinder FFmpeg in anyway).
* High quality output.
* Converts multiple different files all to the same format at once.
* Convert video to audio.
* Convert between audio formats.
* No external codecs needed.
* Includes a variety of preset conversion settings for common formats and devices.
* Preset conversions can be created to encode to any format FFmpeg supports.
* Easy access to common conversion options such as bitrate, frame size, frame rate.
* Specify additional command line parameters for advanced users (options button).
* Easily change FFmpeg versions.
* Supports FFmpeg’s multi threading for dual core processors
* Multilingual, available in over 10 languages
Install winff
Option 1:
First,add the GPG key by this command in terminal(Applications/Accessories/Terminal):

wget --quiet --output-document=- "" | sudo apt-key add -

add the repository:

echo "deb jaunty universe" | sudo tee /etc/apt/sources.list.d/winff.list

Of course you need to change “jaunty” to “hardy” or “intrepid” if you have that.
Now, install WinFF directly by running:

sudo apt-get update
sudo apt-get install winff

interpid users also want to run:

sudo apt-get install libavcodec-unstripped-51

jaunty users also want to run:

sudo apt-get install libavcodec-unstripped-52

Option 2:
Ubuntu packages are available at here provided by Launchpad.

Option 3:

For other OS,download winff from this page.

Using Winff
Launch winff from Applications->Sound&Video->WinFF.
And in this window,click on Add and navigate to select an audio or video file you want to convert to other format.
This file will list in the box,input output details and click on Convert.