Moving Picture Experts Group (MPEG) is a digital video standard for compression of full-motion images. The compression ratios achieved with MPEG encoding make it an ideal standard for the delivery of digital video data. MPEG-1 deals with mono and stereo sound coding, at sampling frequencies commonly used for high-quality audio. MPEG-2 contains an extension to lower sampling frequencies, providing better sound quality at the low bit rates, and an extension for multichannel sound. MPEG-3 and MPEG-4, with further improvements, are under development. Both MPEG-1 and MPEG-2 have a three-layer structure. Each layer represents a family of coding algorithms. Layer 3 deals with sound encoding, and can’t be used by itself to encode audio files. In this form, it is known as MP3.