Arista Transcoder.
As its website says, it is the easiest way to convert your media. Arista comes with a whole lot of features.
Video formats it supports are : H.264, MPEG2, MPEG4/DivX, VP8, Theora, Flash Video.
And some of the audio formats are : AA3, Vorbis, OGG, FLAC, Speex and WAV.
If you're not sure of the format you want to convert it to, you can just right away select the device to which you're converting the file to. Just select any of the following device from the list: Android, Computer, DVD Player, iPhone/iPod/iPad, Nokia N Series or Web.
In addition to all this, you can create a video using your webcam directly and store it in any of the formats as said above. You can also create presets and store them and share them with others. You can visit the preset page of arista transcoder for more information.
If you're not sure of the format you want to convert it to, you can just right away select the device to which you're converting the file to. Just select any of the following device from the list: Android, Computer, DVD Player, iPhone/iPod/iPad, Nokia N Series or Web.
In addition to all this, you can create a video using your webcam directly and store it in any of the formats as said above. You can also create presets and store them and share them with others. You can visit the preset page of arista transcoder for more information.
Screenshots: http://www.transcoder.org/screenshots/
Installation Instruction
Arista Transcoder being Open-source, you can download the code from their website and compile it.
Or you can straight away download it from your Ubuntu Software Center.
Or in your terminal, you can just type in
sudo apt-get install arista
Hope that saves a lot of time for you.