MP3 (formally MPEG-1 Audio Layer-3 or MPEG-2 Audio Layer-3) is a digital format for storing audio files and audio streaming. MPEG programmers designed the format. It is one of the most required codecs for digital coding. The format is widely used in various file-sharing sites for evaluation downloading.

Due to lossy compression in this audio format, it is possible to compress CD tracks up to 1/10 of their original size while maintaining high playback quality. Moreover, it can be encoded at higher or lower bit rates to adjust the resulting quality. Overtones, which cannot be perceived by a human ear, are removed. Complex algorithms allow for a smaller size of tracks. As a result, one compact disk can contain several hundred songs. MP3 is compatible with all the most popular operating systems and is supported by most modern DVD-players and music systems.

Before MP3 introduction, MPEG-1 had been widely used. That format contained not only audio data but images as well. MP3 breaks an audio file into parts of the same length. When the processing is over, each part is packed into its frame. It involves the spectral limit technology that requires a continuous input signal to provide the use of two adjacent structures.

When spectral deleting is over, the file is to be compressed with mathematic methods. If necessary, the compression rate can be changed, even inside the same frame. Files of 128 kbit/s have 11-fold compression. Further reduction of the file size will lead to a significant deterioration in sound quality.

AIFF is intended for viewing and processing of audio data, as well as for its storage in digital devices. Apple designers developed it on the base of IFF in late 1980s. Thanks to lossless coding it is very similar to WAV. In Windows OS it is mostly used with .aiff extension.

AIFF files have gained great attention from Mac PC users. They are popular as well among professional musicians who are most particular about sound quality. The fact that the format is widely supported by various multimedia software, and universal players, may also be considered as a notable benefit. To open AIFF files in Windows OS it is required to install Apple iTunes, Windows Media Player, Roxio Creator, and some other programs.

When being coded, the stream is divided in sound segments. A minute of standard stereo sound corresponds with 10 Mb of memory, approximately. Standard non-compressed files use .aif or .aiff. In such files audio data are represented in the form of pulse code modulation. If some data are lost through codecs, .aifc is used.

A standard 16 bit AIFF file has 2 channels for stereo sound, and sampling frequency of 44 100 Hz. Being non-compressed, it differs in size significantly from MP3 and other similar formats. Sometimes it may contain samples and cycle information.