What is 3ivX codec ? Relationship between DivX, XviD, AVI, MPEG4 and FFDSHOW. What I am getting if I install 3ivx? Is it worth to me? What is the relationship between avi mp4 mpeg4 divx. Is this 3ivx codec used in both avi and mp4 files? How is it related to MPEG-4 and DivX? Where does "ffdshow" come into play in this schema? 3ivx decoder is a free MPEG4 playback solution. It plays a variety of different MPEG4 implemantations. It can play back footage encoded with 3ivx D4, DivX 3, 4 and 5, Apple MPEG-4, Philips MPEG-4, XviD, Sorenson MPEG-4, Dicas MPEG-4, MPEGSolutions MPEG-4 and others. So it can be used as good all-in-one MPEG4 decompressor. Once installed, you do not need to download DivX, XviD and other MPEG4 decoders to watch video. But it has limitation: with 3ivX you can't create DivX or XviD files. 3ivx is capable only of playing of DivX/XviD files (not encoding). So, if you decided to use some video conversion tools you still need Adware/Shareware DivX Pro codec and Freeware XviD codec. 3ivX codec is a commercial software. It isn't completely free. You need to install this codec only if you decided to create your own 3ivX format file. If you want to have similar but completely free MPEG4 playback solution with many outstanding video processing advantages then you should try FFDSHOW decoder. FFDSHOW decoder also can be used only for playing (not encoding). It can play XviD, DivX3/4/5, MP4 and H.263+. Also, it includes: postprocessing, blur, sharpen, noise, gamma/hue correction etc. FFDSHOW is an alternative implementation of MPEG-4 decoder. Many users apparently love it, because it allows you to playback a lot of videostreams without the need to search for the right codec (it's decoder only), it offers a bunch of useful postprocessing options, it normally doesn't cause problems like some codecpacks do. AVI and MP4 are containers. They store audio and video information in a single file. Video information may be encoded with any codec and placed within a container. DivX, XviD and 3ivx are different implementations of a video codec/format called MPEG-4 Video. These formats can be put into either the AVI or MP4 containers. Unfortunately, many Windows users and developers (in this case, DivX, Inc.) have been slow to adopt real MP4 support. SUMMARY: For DivX, XviD, 3ivX playback use: freeware FFDSHOW For XviD encoding use: Free XviD Codec For DivX encoding use: Commercial DivX Pro Codec or free tool: S.U.P.E.R. For 3ivX encoding use: Commercial 3ivX Pro Codec You absolutely do not need to pay for 3ivx to use the video encoder/decoder for testing purposes, but, due to licensing limitations imposed by the MPEG-4 audio license holders you do need to pay for the audio component should you choose to use it (Or, if you don't, just unregister audio 3ivX component). If you don't want to pay but still want to use AAC audio, use CoreAAC Parser and Decoder.  See Also:  The best video codec ? Microsoft WMV9, DivX, XviD comparison.