Audio file format

An audio file format is a file format for storing digital audio data on a computer system. The bit layout of the audio data (excluding metadata) is called the audio coding format and can be uncompressed, or compressed to reduce the file size, often using lossy compression. The data can be a raw bitstream in an audio coding format, but it is usually embedded in a container format or an audio data format with defined storage layer.

Format types

It is important to distinguish between the audio coding format, the container containing the raw audio data, and an audio codec. A codec performs the encoding and decoding of the raw audio data while this encoded data is (usually) stored in a container file. Although most audio file formats support only one type of audio coding data (created with an audio coder), a multimedia container format (as Matroska or AVI) may support multiple types of audio and video data.

There are three major groups of audio file formats:

Uncompressed audio format

One major uncompressed audio format, LPCM, is the same variety of PCM as used in Compact Disc Digital Audio and is the format most commonly accepted by low level audio APIs and D/A converter hardware. Although LPCM can be stored on a computer as a raw audio format, it is usually stored in a .wav file on Windows or in a .aiff file on macOS. The AIFF format is based on the Interchange File Format (IFF), and the WAV format is based on the similar Resource Interchange File Format (RIFF). WAV and AIFF are designed to store a wide variety of audio formats, lossless and lossy; they just add a small, metadata-containing header before the audio data to declare the format of the audio data, such as LPCM with a particular sample rate, bit depth, endianness and number of channels. Since WAV and AIFF are widely supported and can store LPCM, they are suitable file formats for storing and archiving an original recording.

BWF (Broadcast Wave Format) is a standard audio format created by the European Broadcasting Union as a successor to WAV. Among other enhancements, BWF allows more robust 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 AETA,[1] Sound Devices,[2] Zaxcom,[3] HHB Communications Ltd,[4] Fostex, Nagra, Aaton,[5] and TASCAM all use BWF as their preferred format.

Lossless compressed audio format

A lossless compressed format stores data in less space without losing any information. The original, uncompressed data can be recreated from the compressed version.

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 music. In a lossless compressed format, however, the music would occupy a smaller file than an uncompressed format and the silence would take up almost no space at all.

Lossless compression formats include the common[6] FLAC, WavPack, Monkey's Audio, ALAC (Apple Lossless). They provide a compression ratio of about 2:1 (i.e. their files take up half the space of PCM). Development in lossless compression formats aims to reduce processing time while maintaining a good compression ratio.

Lossy compressed audio format

Lossy compression enables even greater reductions in file size by removing some of the audio information and simplifying the data. This, of course, results in a reduction in audio quality, but a variety of techniques are used, mainly by exploiting psychoacoustics, to remove the parts of the sound that have the least effect on perceived quality, and to minimize the amount of audible noise added during the process. The popular MP3 format is probably the best-known example, but the AAC format found on the iTunes Music Store is also common. Most formats offer a range of degrees of compression, generally measured in bit rate. The lower the rate, the smaller the file and the more significant the quality loss.

List of formats

File Extension Creation Company Description
.3gp Multimedia container format can contain proprietary formats as AMR, AMR-WB or AMR-WB+, but also some open formats
.aa Audible.com (Amazon.com) A low-bitrate audiobook container format with DRM, containing audio encoded as either MP3 or the ACELP speech codec.
.aac The Advanced Audio Coding format is based on the MPEG-2 and MPEG-4 standards. AAC files are usually ADTS or ADIF containers.
.aax Audible.com (Amazon.com) An Audiobook format, which is a variable-bitrate (allowing high quality) M4B file encrypted with DRM. MPB contains AAC or ALAC encoded audio in an MPEG-4 container. (More details below.)
.act ACT is a lossy ADPCM 8 kbit/s compressed audio format recorded by most Chinese MP3 and MP4 players with a recording function, and voice recorders
.aiff Apple A standard audio file format used by Apple. It could be considered the Apple equivalent of wav.
.amr AMR-NB audio, used primarily for speech.
.ape Matthew T. Ashland Monkey's Audio lossless audio compression format.
.au Sun Microsystems The standard audio file format used by Sun, Unix and Java. The audio in au files can be PCM or compressed with the μ-law, a-law or G729 codecs.
.awb AMR-WB audio, used primarily for speech, same as the ITU-T's G.722.2 specification.
.dct NCH Software A variable codec format designed for dictation. It has dictation header information and can be encrypted (as may be required by medical confidentiality laws). A proprietary format of NCH Software.
.dss Olympus DSS files are an Olympus proprietary format. It is a fairly old and poor codec. GSM or MP3 are generally preferred where the recorder allows. It allows additional data to be held in the file header.
.dvf Sony A Sony proprietary format for compressed voice files; commonly used by Sony dictation recorders.
.flac A file format for the Free Lossless Audio Codec, a lossless compression codec.
.gsm Designed for telephony use in Europe, gsm is a very practical format for telephone quality voice. It makes a good compromise between file size and quality. Note that wav files can also be encoded with the gsm codec.
.iklax iKlax An iKlax Media proprietary format, the iKlax format is a multi-track digital audio format allowing various actions on musical data, for instance on mixing and volumes arrangements.
.ivs 3D Solar UK Ltd A proprietary version with Digital Rights Management developed by 3D Solar UK Ltd for use in music downloaded from their Tronme Music Store and interactive music and video player.
.m4a An audio-only MPEG-4 file, used by Apple for unprotected music downloaded from their iTunes Music Store. Audio within the m4a file is typically encoded with AAC, although lossless ALAC may also be used.
.m4b An Audiobook / podcast extension with AAC or ALAC encoded audio in an MPEG-4 container. Both M4A and M4B formats can contain metadata including chapter markers, images, and hyperlinks, but M4B allows "bookmarks" (remembering the last listening spot), whereas M4A does not.[7]
.m4p Apple A version of AAC with proprietary Digital Rights Management developed by Apple for use in music downloaded from their iTunes Music Store.
.mmf Yamaha, Samsung A Samsung audio format that is used in ringtones. Developed by Yamaha (SMAF stands for "Synthetic music Mobile Application Format", and is a multimedia data format invented by the Yamaha Corporation, .mmf file format).
.mp3 MPEG Layer III Audio. It is the most common sound file format used today.
.mpc Musepack or MPC (formerly known as MPEGplus, MPEG+ or MP+) is an open source lossy audio codec, specifically optimized for transparent compression of stereo audio at bitrates of 160–180 kbit/s.
.msv Sony A Sony proprietary format for Memory Stick compressed voice files.
.nmf NICE NICE Media Player audio file
.nsf Nintendo The NES Sound Format (.nsf) is used for storing and playing music from the NES and related systems.[8]
.ogg, .oga, .mogg Xiph.Org Foundation A free, open source container format supporting a variety of formats, the most popular of which is the audio format Vorbis. Vorbis offers compression similar to MP3 but is less popular. Mogg, the "Multi-Track-Single-Logical-Stream Ogg-Vorbis", is the multi-channel or multi-track Ogg file format.
.opus Internet Engineering Task Force A lossy audio compression format developed by the Internet Engineering Task Force (IETF) and made especially suitable for interactive real-time applications over the Internet. As an open format standardised through RFC 6716, a reference implementation is provided under the 3-clause BSD license.
.ra, .rm RealNetworks A RealAudio format designed for streaming audio over the Internet. The .ra format allows files to be stored in a self-contained fashion on a computer, with all of the audio data contained inside the file itself.
.raw A raw file can contain audio in any format but is usually used with PCM audio data. It is rarely used except for technical tests.
.sln Signed Linear PCM format used by Asterisk. Prior to v.10 the standard formats were 16-bit Signed Linear PCM sampled at 8 kHz and at 16 kHz. With v.10 many more sampling rates were added.[9]
.tta The True Audio, real-time lossless audio codec.
.vox The vox format most commonly uses the Dialogic ADPCM (Adaptive Differential Pulse Code Modulation) codec. Similar to other ADPCM formats, it compresses to 4-bits. Vox format files are similar to wave files except that the vox files contain no information about the file itself so the codec sample rate and number of channels must first be specified in order to play a vox file.
.wav Standard audio file container format used mainly in Windows PCs. Commonly used for storing uncompressed (PCM), CD-quality sound files, which means that they can be large in size—around 10 MB per minute. Wave files can also contain data encoded with a variety of (lossy) codecs to reduce the file size (for example the GSM or MP3 formats). Wav files use a RIFF structure.
.wma Microsoft Windows Media Audio format, created by Microsoft. Designed with Digital Rights Management (DRM) abilities for copy protection.
.wv Format for wavpack files.
.webm Royalty-free format created for HTML5 video.
.8svx Electronic Arts The IFF-8SVX format for 8-bit sound samples, created by Electronic Arts in 1984 at the birth of the Amiga.

See also

References

  1. ^ "AETA AUDIO SYSTEMS: home". 2016-01-29. Archived from the original on January 29, 2016.
  2. ^ "Sound Devices - Home". www.sounddevices.com.
  3. ^ "Zaxcom". zaxcom.com.
  4. ^ "- HHB". www.hhb.co.uk.
  5. ^ "Aaton Digital". aaton.com.
  6. ^ 2008 ripping/encoding general poll - Hydrogenaudio Forums
  7. ^ expertise, Mark Harris Brings music; Producer, Including a Background as a Music; composer; Articles, To Digital Music. "What is the M4b Format?". Lifewire.
  8. ^ "NSF - Nesdev wiki". wiki.nesdev.com.
  9. ^ "Asterisk 10 Codecs and Audio Formats - Asterisk Project - Asterisk Project Wiki". wiki.asterisk.org.
8SVX

8-Bit Sampled Voice (8SVX) is an audio file format standard developed by Electronic Arts for the Commodore-Amiga computer series. It is a data subtype of the IFF file container format. It typically contains linear pulse-code modulation (LPCM) digital audio.

Au file format

The Au file format is a simple audio file format introduced by Sun Microsystems. The format was common on NeXT systems and on early Web pages. Originally it was headerless, being simply 8-bit µ-law-encoded data at an 8000 Hz sample rate. Hardware from other vendors often used sample rates as high as 8192 Hz, often integer factors of video clock signals. Newer files have a header that consists of six unsigned 32-bit words, an optional information chunk and then the data (in big endian format).

Although the format now supports many audio encoding formats, it remains associated with the µ-law logarithmic encoding. This encoding was native to the SPARCstation 1 hardware, where SunOS exposed the encoding to application programs through the /dev/audio interface. This encoding and interface became a de facto standard for Unix sound.

Audio Interchange File Format

Audio Interchange File Format (AIFF) is an audio file format standard used for storing sound data for personal computers and other electronic audio devices. The format was developed by Apple Inc. in 1988 based on Electronic Arts' Interchange File Format (IFF, widely used on Amiga systems) and is most commonly used on Apple Macintosh computer systems.

The audio data in most AIFF files is uncompressed pulse-code modulation (PCM). This type of AIFF file uses much more disk space than lossy formats like MP3—about 10 MB for one minute of stereo audio at a sample rate of 44.1 kHz and a bit depth of 16 bits. There is also a compressed variant of AIFF known as AIFF-C or AIFC, with various defined compression codecs.

In addition to audio data, AIFF can include loop point data and the musical note of a sample, for use by hardware samplers and musical applications.

The file extension for the standard AIFF format is .aiff or .aif. For the compressed variants it is supposed to be .aifc, but .aiff or .aif are accepted as well by audio applications supporting the format.

Call-recording software

Call recording software records telephone conversations over PSTN or VoIP in a digital audio file format. Call recording is distinct from call logging and tracking, which record details about the call but not the conversation; however, software may include both recording and logging functionality.

Digital Speech Standard

Digital Speech Standard (DSS) is a proprietary compressed digital audio file format defined by the International Voice Association, a co-operative venture by Olympus, Philips and Grundig Business Systems.

DSS was originally developed in 1994 by Grundig with the University of Nuremberg. In 1997, the digital speech standard was released, which was based on the previous codec. It is commonly used on digital dictation recorders. Modern phycoacoustical codecs that perform nearly as well at only slightly higher bitrates have led to this speech coding standard being less used in modern voice recording equipment.

IMF (file format)

IMF is an audio file format created by id Software for the AdLib sound card for use in their video games. The default filename extension is also "imf". The abbreviation stands for "id music file" or "id's music format".

The format is similar to MIDI, in that it defines musical notes, and does not support sampled digital audio for sound effects. IMF files store the actual bytes sent to the AdLib's OPL2 chip, which uses FM synthesis to produce audio output. The format is based on the AdLib command syntax, with a few modifications. Due to the limited features and relatively low sound quality, modern games no longer use IMF music.

Once extracted from a game, IMF files can be played with special sound libraries which emulate AdLib cards. One of the most popular ones is AdPlug, which can be used, for instance, through its Winamp plugin.

Interchange File Format

Interchange File Format (IFF), is a generic container file format originally introduced by the Electronic Arts company in 1985 (in cooperation with Commodore/Amiga) in order to facilitate transfer of data between software produced by different companies.

IFF files do not have any standard extension. On many systems that generate IFF files, file extensions are not important (the OS stores file format metadata separately from the file name). An .iff extension is commonly used for ILBM format files, which use the IFF container format.

Resource Interchange File Format is a format developed by Microsoft and IBM in 1991 that is based on IFF, except the byte order has been changed to little-endian to match the x86 processor architecture. Apple's AIFF is a big-endian audio file format developed from IFF. The TIFF image file format is unrelated.

List of audio conversion software

An audio conversion app (also known as an audio converter) transcodes one audio file format into another; for example, from FLAC into MP3. It may allow selection of encoding parameters for each of the output file to optimize its quality and size. An audio converter uses at least two sets of audio codecs to decode the source file format and to encode the destination file.

Audio converters include:

AIMP

Audacity

Brasero

CDex

Exact Audio Copy

FFmpeg

FL Studio

foobar2000

FormatFactory

Freemake Audio Converter

Free Studio

fre:ac

iTunes

k3b

MediaCoder

MediaHuman Audio Converter

MediaMonkey

SoX

VLC Media Player

Winamp

WMA Convert

XMedia Recode

MT9

MT9 is a digital audio file format developed by Korea's Electronics and Telecommunications Research Institute (ETRI). The format is currently being promoted by Audizen under the commercial name of Music 2.0.MT9 allows listeners to adjust the volume for each channel – such as guitar, drums, bass and vocals - muting or amplifying their favourite parts. This feature would also likely be used by artists, who could more easily create remixes from existing songs, and this could possibly create intellectual property conflicts.

The format was supposedly presented to the Moving Picture Experts Group (MPEG) in its 84th meeting in Archamps, France, in April 2008, and voted as a candidate for a new international standard for digital audio, being scheduled to be further discussed by the MPEG during its 85th meeting in Hanover, Germany, in July 2008.

However, the press releases of both meetings make no mention of this.

Samsung and LG both showed interest in equipping their mobile phones with an MT9 player and their first commercial products are likely to debut early 2009, according to Audizen's CEO Ham Seung-chul.

Original Sound Quality

Original Sound Quality (OSQ) is an audio file format developed in 2002 by Steinberg Media Technologies GmbH and implemented e.g. in their audio editing software Wavelab 4 (and following releases) for lossless audio data compression.

In combination with good source material this format allows compression rates up to 50%. Because of that it is not comparable to other audio formats like MP3, which reach compression rates up to 90% because of their lossy compression algorithms. Therefore OSQ is used rather for archiving then for daily use.

When using this format it is important to know that OSQ is a proprietary format developed by Steinberg that is generally speaking not supported by other audio software tools. A possible alternative to OSQ might be the free codec FLAC.

Portable Sound Format

The Portable Sound Format (PSF) is an audio file format ripped directly from video games from a variety of video game consoles. The format was originally used for PlayStation video games, but has since been adapted to support other systems.

The PSF format was created by Neill Corlett in 2003, who also wrote the Winamp plug-in Highly Experimental that plays PSF1 and PSF2 files.

Generally, PSF files contain a number of samples and a Music sequencer player program. This takes far less space than an equivalent streamed format of the same music (WAV, MP3) while still sounding exactly like the original track. Background music stored in PSF files can usually be looped forever, as the sequencer handles its own loop points.

Several PSF sub-formats also have a miniPSF/PSFlib capability, wherein data used by multiple tracks is stored only once in an accompanying PSFlib file. Further differences are stored in a miniPSF file, which can be zlib compressed to further increasing storage efficiency.

A PSF2 file is the PlayStation 2 equivalent of a PSF. PSF2 is internally structured as a file system, rather than PSF, which is a single PS executable. PSF's native sample rate is 44,100 Hz, while PSF2's is 48,000 Hz. Rates may vary from 8,000 Hz to 96,000 Hz.

Both PSF and PSF2 files contain a header which specifies the type of video game system the file contains data for, and an optional set of tags at the end which can give detailed information such as game name, artist and length.

RF64

RF64 is a BWF-compatible multichannel audio file format enabling file sizes to exceed 4 GB. It has been specified by the European Broadcasting Union.

The file format is designed to meet the requirements for multichannel sound in broadcasting and audio

archiving. It is based on the Microsoft RIFF/WAVE format and Wave Format Extensible for multichannel

parameters. Additions are made to the basic specification to allow for more than 4 GB file sizes when

needed (the new maximum filesize is now approximately 16 exabytes). The format is transparent to the BWF and all its supplements and chunks.

A maximum of 18 surround channels, stereo down mix channel and bit stream signals with non-PCM coded data

can also be stored in the file format. RF64 can be used in the entire programme chain from capture to editing

and play out and for short or long term archiving of multichannel files.

Due to the inconsistent usage of CUE data definition, the additional requirement that CUE chunk names be stored in an additional LABL chunk, along with the inherent 32-bit limitation of the CUE chunk pointer index, the RF64 format also defines a new R64M marker chunk.

The RF64 file format should fulfill the longer-term need for multichannel sound in broadcasting and archiving.

The required effort for software implementers is very small. The changes that will be needed to update

existing systems will be reasonable in cost.

In its basic form, the 32-bit chunk size field at offset 4 in the file is set to -1 (0xFFFFFFFF), and immediately following that a new 'DS64' chunk is inserted (before the FMT chunk). This new DS64 chunk will contain the 64-bit sizes of the DATA chunk(s), using a simple sequential table mechanism to point to additional DATA chunks. The first 4 bytes of the file are then changed from 'RIFF' to 'RF64'.

Some existing software (notably Adobe Audition 2.0 and 3.0) already use a variation of this scheme for filesizes larger than 4 GB. Audition uses a simple 'daisy-chaining' mechanism, where data chunks of 4 GB are simply appended to the file (with a size field set to -1) until a data chunk of less than 4 GB is encountered.

An RF64 file with a bext chunk becomes an MBWF-file. The terms ‘RF64’ and ‘MBWF’ can then be considered synonymous.

Raw audio format

RAW Audio format or just RAW Audio is an audio file format for storing uncompressed audio in raw form. Comparable to WAV or AIFF in size, RAW Audio file does not include any header information (sampling rate, bit depth, endian, or number of channels). Data can be written in PCM, IEEE 754 or ASCII.

SND

SND may refer to:

SND (file), a digital audio file format

Au file format, a digital audio file format which sometimes uses the file extension ".snd"

SND (band), a Sheffield-based electronic music duo

Society for News Design

Scottish National Dictionary

Serbian National Defense Council, a Serbian diaspora activist organization

Sinus node dysfunction

Slovak National Theatre (Slovenské národné divadlo)

Sindhi language's ISO 639 code

SND, post-nominal letters of a Sister of Notre Dame de Namur

SND Experiment (particle physics)

SND Films, film distributor

SND (file)

A SND (SouND) file is a digital sound file format. There is more than one in existence [disambiguation page needed].

Most commonly a .snd file contains a NeXT sound file. This is essentially the same as the au file format used by Sun Microsystems. The first four bytes of a .snd file contain the hex number 0x2e736e64 which displays as ".snd" when interpreted as ASCII text.

Another .snd file format is attributed to Apple Inc. Data stored in such files are commands for the Macintosh Sound Manager including 'wavetable' sample-based instruments and sound samples. Thus it is some kind of improved midi format. As well it can serve as a pure audio file format if only one command and one sound sample is stored in it. In this format, the first two bytes specify a 16-bit integer contain the number 1 or 2.

Programs supporting audio files with the .snd extension generally assume (and check) that it is NeXT/SUN (AU) format.

The manufacturer of electronic music instruments AKAI had an audio file format with the extension .snd. The first byte contains the number 1 and the second the number 4.The manufacturer of the HOM-BOT Robot Vacuum Cleaner LG Group is using audio files with the extension .snd. The sounds are encoded in PCM (single channel, 16 kHz, 16 bits signed).

The Unity Game Engine uses a compressed format called .snd for sound packages.

Timeline of audio formats

An audio format is a medium for sound recording and reproduction. The term is applied to both the physical recording media and the recording formats of the audio content—in computer science it is often limited to the audio file format, but its wider use usually refers to the physical method used to store the data.

Music is recorded and distributed using a variety of audio formats, some of which store additional information.

VGM (file format)

VGM (Video Game Music) is an audio file format for multiple video game platforms, such as Sega Master System, Game Gear, Mega Drive/Genesis, MSX, Neo Geo, IBM PC AT (Adlib/SoundBlaster), and has expanded to a variety of arcade system boards since its release.

The standard filename extension is .vgm, but files can also be Gzip compressed into .vgz files. Technically, .vgz files should be named .vgm.gz, but because some popular operating systems' file managers cannot handle file name suffixes that themselves contain a period, .vgz is used in order to launch a VGM player, not a file archiver program such as WinZip or WinRAR.

The VGM format is different from formats like NSF or SID, which contain the game's music code. Instead, the instructions sent to the sound chip are logged.

On November 20, 2005, VGM 1.50 was officially announced, and a new version of the input plug-in released. The new version of the format supported PCM optimization for the Yamaha YM2612 sound chip, which significantly reduces the size of VGM files by avoiding redundancy. The first YM2612 VGM archive, Project 2612, optimized all of its packages soon after.

WAV

Waveform Audio File Format (WAVE, or more commonly known as WAV due to its filename extension; pronounced "wave" or WAV) (rarely, Audio for Windows) is a Microsoft and IBM audio file format standard for storing an audio bitstream on PCs. It is an application of the Resource Interchange File Format (RIFF) bitstream format method for storing data in "chunks", and thus is also close to the 8SVX and the AIFF format used on Amiga and Macintosh computers, respectively. It is the main format used on Microsoft Windows systems for raw and typically uncompressed audio. The usual bitstream encoding is the linear pulse-code modulation (LPCM) format.

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