Converting FLVs to MPEGs on Ubuntu
The first thing you need to do is to install the ffmpeg program.
sudo apt-get install ffmpeg
Next, you might want to install on your system all the necessary video and audio codecs.
sudo apt-get install ubuntu-restricted-extras
Assuming I have an input FLV file with filename video.flv and I want to convert it to a MPEG video:
ffmpeg -i video.flv video.mpg
Where -i is the flag that tells the program the name of the input file. After the input file directly follows the name of the output file. In this example, video.mpg.
According to the official manual page of ffmpeg, it automatically converts the video losslessly as possible. This means, output parameters for the conversion will be based on the input parameters.
For more information about ffmpeg, you can read on their official documentation here.