MPEG, moving pictures expert group.. designed a way of compressing video data using compression based on DCT. Each frame in an MPEG video is compressed as a JPEG. The data that stays the same in successive frames is then removed. Not all frames are stored, just a few, called ‘i-frames’.. The next set of frames does not store images, just the data that has changed since the last i-frame.
AVI, audio video interleave files are a type of RIFF. Can store files in a variety of formats as defined by information at the start of the file. Uncompressed files are so large that they are never normally used, so AVI files are generally used to store videos in more compact formats than uncompressed data. When saving files the ratio can be set so that embedded audio data will be every 3 frames of the video data. This means the audio and video data will be mixed up in the data file.