2.  What is a codec ?

To fully understand the VideoLAN solution, you must understand the difference between a codec and a container format

To decode a stream, VLC first demuxes it. This means that it reads the container format and separates audio, video, and subtitles, if any. Then, each of these are passed decoders that do the mathematical processing to decompress the streams .

There is a particular thing about MPEG: