Howto convert Mpeg or Mp4 to FLV Video file format
This is a very simple console conversion method I came across, in order to create this format it does depend to a large extent on the source file being converted from. In other words if you have a crap source file your resultant file will or may look worse, so always choose the best quality and best resolution file you can lay your hands on before converting.
If not already done so install ffmpeg using synaptic or some other package manager suitable with your system. You can if you have apt-get install from the command line also, thus.
#> sudo apt-get update && sudo apt-get upgrade && sudo apt-get install ffmpeg
#> ffmpeg -i source_file_mpg_or_mp4.ext destination_file.flv