MPEG is a format rather than a codec. MPEG actually means the Moving Picture Experts Group which is a group of people who meet to discuss audio and video standards. This group has been meeting since 1988.
MPEG-1
The first format released was MPEG-1 in 1992. MPEG-1 became the standard format for audio and video on computers and became the heart of the VCD standard. Most music traded on theinternet today is in MP3 format which is a part of the MPEG-1 standard.
MPEG-1 was very low quality and low resolution in comparison to the video standards of today and it is rare to see MPEG-1 used these days for downloading movies and tv shows.
MPEG-2
MPEG-2 was created to overcome the weaknesses of the MPEG-1 format. MPEG-2 is now the most widly used audio and video standard in the world today . MPEG-2 is used in SVCD, DVD’s, standard and high definition digital tv, satalite and pay tv applications around the world.
MPEG-2 is a high quality format but one of its main drawbacks as it relates to the internetis its size. The SVCD format uses a low bitrate MPEG-2 but still needed at least 1.4gb for a movie. Since Divx and Xvid codecs can produce a better quality movie for half of the size they quickly took over as the standard.
The only time you normally see MPEG-2 videos when downloading movies from the internet is with dvd-r images. A full dvd-r is over 4gb in size yet offers only a marginally better experience. Until internet speeds increas it is unlikely that these downloads will be commonplace.
MPEG-4
MPEG-4 was released in 1998 and since then the codecs that are based on this format have been the most popular method of video compression on the internet.
MPEG-4 was released with many different parts and this allowed the creation of many different codes based on MPEG-4. Each codec is known better by their individual names rather than MPEG-4. Codecs like Divx, Xvid are based on different parts than x264.
VCD and SVCD
Up until recently many Cam, telesync, screener and telecine releases were in the VCD and SVCD format. Technically speaking VCD and SVCD are not the codecs involved. That is actually MPEG1 and MPEG2 respectively.
The video resolution was slightly better for SVCD but overall the file size was too high, the video quality and resolution were too low and both of these formats are very rarely seen any more for movies or tv shows.
If you somehow come across a VCD or SVCD release the files you download are actually cd image files so the easiest way to handle it is burn it to a CD and pop it into a dvd players. DVD’s are actually high bitrate MPEG2 video so they are able to play the VCD and SVCD videos.
DVD-R
Sometimes you will see complete dvd images available for download. DVD utilises MPEG2 and whilst the quality is superior to most other options you can download the size is quite large with a single move requiring nearly 5gb. This is just not practical on most broadband connections in Australia.
Many commercial DVD’s are dual layers which represents nearly 10gb but the dvd extras and multiple languages are often stripped out so it can fit on a single layer DVD.