3GP codec The 3gp codec is a computer program that is used to encode or decode a digital data stream or signal. The ‘codec’ term is a portmanteau of 'coder-decoder'. This program is used in the 3gp converters that are available online. The 3gp codec inside the 3gp converters processes the conversion of the different media files into the 3gp media file format. You can convert any of your favorite audio and video files in the 3gp file format with the help of the 3gp converters. The conversion only takes a few minutes and you can either perform the conversion online or by choosing a download version of a converter to convert the files on your computer later when you want in your free time.