About Audio Format : Description About Audio Files.

An audio file format is a file format for storing audio data on a computer system. It can be a raw bitstream, but it is usually a container format or an audio data format with defined storage layer.

The general approach towards storing digital audio is to sample the audio voltage which, on playback, would correspond to a certain level of signal in an individual channel with a certain resolution—the number of bits per sample—in regular intervals (forming the sample rate). This data can then be stored uncompressed, or compressed to reduce the file size.

It is important to distinguish between a file format and a codec. A codec performs the encoding and decoding of the raw audio data while the data itself is stored in a file with a specific audio file format. Most of the publicly documented audio file formats can be created with one of two or more encoders or codecs. Although most audio file formats support only one type of audio data (created with an audio coder), a multimedia container format (as MKV or AVI) may support multiple types of audio and video data.

There are three major groups of audio file formats:

Uncompressed audio formats, such as WAV, AIFF, AU or raw header-less PCM;
formats with lossless compression, such as FLAC, Monkey's Audio (filename extension APE), WavPack (filename extension WV), Shorten, TTA, ATRAC Advanced Lossless, Apple Lossless, MPEG-4 SLS, MPEG-4 ALS, MPEG-4 DST, Windows Media Audio Lossless (WMA Lossless).
formats with lossy compression, such as MP3, Vorbis, Musepack, AAC, ATRAC and lossy Windows Media Audio (WMA).

There is one major uncompressed audio format, PCM, which is usually stored as a .wav on Windows or as .aiff on Mac OS. WAV and AIFF are flexible file formats designed to store more or less any combination of sampling rates or bitrates. This makes them suitable file formats for storing and archiving an original recording.

The AIFF format is based on the IFF format. The WAV format is based on the RIFF file format, which is similar to the IFF format.

BWF (Broadcast Wave Format) is a standard audio format created by the European Broadcasting Union as a successor to WAV. BWF allows metadata to be stored in the file. See European Broadcasting Union: Specification of the Broadcast Wave Format (EBU Technical document 3285, July 1997). This is the primary recording format used in many professional audio workstations in the television and film industry. BWF files include a standardized Timestamp reference which allows for easy synchronization with a separate picture element. Stand-alone, file based, multi-track recorders from Sound Devices, Zaxcom, HHB USA, Fostex, and Aaton all use BWF as their preferred format.

A lossless compressed format requires more processing time than an uncompressed format but is more efficient in space usage.

Uncompressed audio formats encode both sound and silence with the same number of bits per unit of time. Encoding an uncompressed minute of absolute silence produces a file of the same size as encoding an uncompressed minute of symphonic orchestra music. In a lossless compressed format, however, the music would occupy a marginally smaller file and the silence take up almost no space at all.

Lossless compression formats (such as the most widespread FLAC, WavPack, Monkey's Audio, ALAC/Apple Lossless) provide a compression ratio of about 2:1. Development in lossless compression formats aims to reduce processing time while maintaining a good compression ratio.