Is Xvid a Video Format?

Xvid (formerly "XviD") is a video codec library following the MPEG-4 standard, specifically MPEG-4 Part 2 Advanced Simple Profile (ASP). It uses ASP features such as b-frames, global and quarter pixel motion compensation, lumi masking, trellis quantization, and H.263, MPEG and custom quantization matrices.

Xvid is a primary competitor of the DivX Pro Codec. In contrast with the DivX codec, which is proprietary software developed by DivX, Inc., Xvid is free software distributed under the terms of the GNU General Public License. This also means that unlike the DivX codec, which is only available for a limited number of platforms, Xvid can be used on all platforms and operating systems for which the source code can be compiled. (from wikipedia)

From the above information according to wikipedia, XviD is not a video format. Since XviD uses MPEG-4 Advanced Simple Profile (ASP) compression, any video that is encoded with it is termed “MPEG-4 ASP video” – not “XviD video” – and can therefore be decoded with all MPEG-4 ASP compliant decoders. This includes a large number of media players and decoders, in particular all the ones based on the free/open source libavcodec library from FFmpeg.