Audio converter

For example, an audio transcoder converts from one compressed audio format to another (e.g., MP3 to AAC) by means of two audio codecs: One for decoding (uncompressing) the source and one for encoding (compressing) the destination file or stream. Audio file format. Comparison of audio coding formats. List of audio conversion software.

MPEG-1

MPG.mpgMPEG-1 Part 2
Layer I audio files typically use the extension .mp1 or sometimes .m1a MPEG-1 Layer II (MP2—often incorrectly called MUSICAM) is a lossy audio format designed to provide high quality at about 192 kbit/s for stereo sound. Decoding MP2 audio is computationally simple, relative to MP3, AAC, etc.

FLAC

.flacFree Lossless Audio CodecFLAC
FLAC (Free Lossless Audio Codec) is an audio coding format for lossless compression of digital audio, and is also the name of the free software project producing the FLAC tools, the reference software package that includes a codec implementation. Digital audio compressed by FLAC's algorithm can typically be reduced to between 50 and 70 percent of its original size and decompress to an identical copy of the original audio data. FLAC is an open format with royalty-free licensing and a reference implementation which is free software. FLAC has support for metadata tagging, album cover art, and fast seeking. Development was started in 2000 by Josh Coalson.

RealNetworks

Film.comRealRealNetworks, Inc.
RealNetworks are pioneers in the streaming media markets and broadcast one of the earlier audio events over the Internet — a baseball game between the New York Yankees and Seattle Mariners — on September 5, 1995. They announced streaming video technology in 1997. According to some accounts, by 2000, more than 85% of streaming content on the Internet was in the Real format. Despite this success, problems arose because Real's primary business model depended upon the sale of streaming media server software, and Microsoft and Apple were giving those products away. As servers from Microsoft and Apple became more capable, Real's server sales inevitably eroded.

MPEG-4 SLS

HD-AACScalable Lossless CodingMPEG-4 Scalable To Lossless (SLS)
MPEG-4 SLS, or MPEG-4 Scalable to Lossless as per ISO/IEC 14496-3:2005/Amd 3:2006 (Scalable Lossless Coding), is an extension to the MPEG-4 Part 3 (MPEG-4 Audio) standard to allow lossless audio compression scalable to lossy MPEG-4 General Audio coding methods (e.g., variations of AAC). It was developed jointly by the Institute for Infocomm Research (I 2 R) and Fraunhofer, which commercializes its implementation of a limited subset of the standard under the name of HD-AAC. Standardization of the HD-AAC profile for MPEG-4 Audio is under development (as of September 2009).

Variable bitrate

VBRvariable bit ratevariable
MP3, WMA and AAC audio files can optionally be encoded in VBR, while Opus, Vorbis are always in VBR. Variable bit rate encoding is also commonly used on MPEG-2 video, MPEG-4 Part 2 video (Xvid, DivX, etc.), MPEG-4 Part 10/H.264 video, Theora, Dirac and other video compression formats. Additionally, variable rate encoding is inherent in lossless compression schemes such as FLAC and Apple Lossless. The advantages of VBR are that it produces a better quality-to-space ratio compared to a CBR file of the same data.

Compact Disc Digital Audio

Audio CDCDRed Book
Common audio file formats for this purpose include WAV and AIFF, which simply preface the LPCM data with a short header; FLAC, ALAC, and Windows Media Audio Lossless, which compress the LPCM data in ways that conserve space yet allow it to be restored without any changes; and various lossy, perceptual coding formats like MP3 and AAC, which modify and compress the audio data in ways that irreversibly change the audio, but that exploit features of human hearing to make the changes difficult to discern. Recording publishers have created CDs that violate the Red Book standard. Some do so for the purpose of copy prevention, using systems like Copy Control.

MPEG-4 Part 3

AACAAC+ISO/IEC 14496-3
TwinVQ – one of the object types defined in MPEG-4 Audio version 1. MPEG-4 Part 2. MPEG-4 Part 14 container format (MP4). Digital rights management. Advanced Audio Coding (AAC). ISO/IEC JTC 1/SC 29. Apple: MPEG-4: AAC. "HE-AAC" (VideoLAN WIKI). EBU subjective listening tests on low-bitrate audio codecs. AAC radio stations – Online radio stations in AAC format. Tuner2 – Directory of radio stations in AAC+ format at various bitrates. RadioFeeds UK & Ireland – Page containing plenty of terrestrial stations webcasting in AAC+ format. A page comparing codecs including He-AAC @64 kbit/s by listening tests. (Page is offline). Official MPEG web site.

Internet

onlinethe Internetweb
Podcasting is a variation on this theme, where – usually audio – material is downloaded and played back on a computer or shifted to a portable media player to be listened to on the move. These techniques using simple equipment allow anybody, with little censorship or licensing control, to broadcast audio-visual material worldwide. Digital media streaming increases the demand for network bandwidth. For example, standard image quality needs 1 Mbit/s link speed for SD 480p, HD 720p quality requires 2.5 Mbit/s, and the top-of-the-line HDX quality needs 4.5 Mbit/s for 1080p. Webcams are a low-cost extension of this phenomenon.

Apple Inc.

AppleApple ComputerApple Computer, Inc.
On October 23 of the same year, Apple debuted the iPod portable digital audio player. The product, which was first sold on November 10, 2001, was phenomenally successful with over 100million units sold within six years. In 2003, Apple's iTunes Store was introduced. The service offered online music downloads for $0.99 a song and integration with the iPod. The iTunes Store quickly became the market leader in online music services, with over five billion downloads by June 19, 2008. Two years later, the iTunes Store was the world's largest music retailer.

Sampling (signal processing)

sampling ratesamplingsample rate
When it is necessary to capture audio covering the entire 20–20,000 Hz range of human hearing, such as when recording music or many types of acoustic events, audio waveforms are typically sampled at 44.1 kHz (CD), 48 kHz, 88.2 kHz, or 96 kHz. The approximately double-rate requirement is a consequence of the Nyquist theorem. Sampling rates higher than about 50 kHz to 60 kHz cannot supply more usable information for human listeners. Early professional audio equipment manufacturers chose sampling rates in the region of 50 kHz for this reason.

Lossless compression

losslesslossless data compressioncompression
Apple Lossless (ALAC – Apple Lossless Audio Codec). Adaptive Transform Acoustic Coding (ATRAC). Audio Lossless Coding (also known as MPEG-4 ALS). Direct Stream Transfer (DST). Dolby TrueHD. DTS-HD Master Audio. Free Lossless Audio Codec (FLAC). Meridian Lossless Packing (MLP). Monkey's Audio (Monkey's Audio APE). MPEG-4 SLS (also known as HD-AAC). OptimFROG. Original Sound Quality (OSQ). RealPlayer (RealAudio Lossless). Shorten (SHN). TTA (True Audio Lossless). WavPack (WavPack lossless). WMA Lossless (Windows Media Lossless). PNG – Portable Network Graphics. TIFF – Tagged Image File Format. WebP – (high-density lossless or lossy compression of RGB and RGBA images).

Peer-to-peer

P2Ppeer to peerpeer-to-peer network
Some proprietary multimedia applications, such as Spotify, use a peer-to-peer network along with streaming servers to stream audio and video to their clients. Peercasting for multicasting streams. Pennsylvania State University, MIT and Simon Fraser University are carrying on a project called LionShare designed for facilitating file sharing among educational institutions globally. Osiris is a program that allows its users to create anonymous and autonomous web portals distributed via P2P network. Bitcoin and alternatives such as Ether, Nxt and Peercoin are peer-to-peer-based digital cryptocurrencies. Dalesa, a peer-to-peer web cache for LANs (based on IP multicasting).

YouTube

youtube.comYouTube channelYouTuber
The default video stream is encoded in the VP9 format with stereo Opus audio; if VP9/WebM is not supported in the browser/device or the browser's user agent reports Windows XP, then H.264/MPEG-4 AVC video with stereo AAC audio is used instead. From 2008 to 2017, users could add "annotations" to their videos—such as pop-up text messages and hyperlinks. These functions were notably used as the basis for interactive videos, which used hyperlinks to other videos to achieve branching elements.

MP3 player

digital audio playerMP3 playersmusic player
An MP3 player or Digital Audio Player is an electronic device that can play digital audio files. It is a type of Portable Media Player. The term 'MP3 player' is a misnomer, as most players play more than the MP3 file format. Since the MP3 format is widely used, almost all players can play that format. In addition, there are many other digital audio formats. Some formats are proprietary, such as Windows Media Audio (WMA), and Advanced Audio Coding (AAC). Some of these formats also may incorporate digital rights management (DRM), such as WMA DRM, which are often part of paid download sites.

ITunes

iTunes IndiaApple iTunesGenius playlist
The software supports importing digital audio tracks that can then be transferred to iOS devices, as well as supporting ripping content from CDs. iTunes supports WAV, AIFF, Apple Lossless, AAC, and MP3 audio formats. It uses the Gracenote music database to provide track name listings for audio CDs. When users rip content from a CD, iTunes attempts to match songs to the Gracenote service. For self-published CDs, or those from obscure record labels, iTunes will normally only list tracks as numbered entries ("Track 1", "Track 2") on an unnamed album by an unknown artist, requiring manual input of data.

WAV

.wavWAVEwave file
The RIFF format acts as a "wrapper" for various audio coding formats. Though a WAV file can contain compressed audio, the most common WAV audio format is uncompressed audio in the linear pulse code modulation (LPCM) format. LPCM is also the standard audio coding format for audio CDs, which store two-channel LPCM audio sampled at 44,100 Hz with 16 bits per sample. Since LPCM is uncompressed and retains all of the samples of an audio track, professional users or audio experts may use the WAV format with LPCM audio for maximum audio quality. WAV files can also be edited and manipulated with relative ease using software.

International Organization for Standardization

ISOInternational Organization for Standardization (ISO)ISO standard
The first document that is produced for example for audio and video coding standards is called a verification model (VM) (previously also called a "simulation and test model"). When a sufficient confidence in the stability of the standard under development is reached, a working draft (WD) is produced. This is in the form of a standard but is kept internal to working group for revision. When a working draft is sufficiently solid and the working group is satisfied that it has developed the best technical solution to the problem being addressed, it becomes committee draft (CD). If it is required, it is then sent to the P-members of the TC/SC (national bodies) for ballot.

International Electrotechnical Commission

IECInternational Electrotechnical Commission (IEC)(IEC)
The International Electrotechnical Commission (IEC; in French: Commission électrotechnique internationale) is an international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology". IEC standards cover a vast range of technologies from power generation, transmission and distribution to home appliances and office equipment, semiconductors, fibre optics, batteries, solar energy, nanotechnology and marine energy as well as many others.

Filename extension

file extensionextensionextensions
In many Internet protocols, such as HTTP and MIME email, the type of a bitstream is stated as the media type, or MIME type, of the stream, rather than a filename extension. This is given in a line of text preceding the stream, such as Content-type: text/plain. There is no standard mapping between filename extensions and media types, resulting in possible mismatches in interpretation between authors, web servers, and client software when transferring files over the Internet.

Pulse-code modulation

PCMlinear PCMLPCM
It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amplitude of the analog signal is sampled regularly at uniform intervals, and each sample is quantized to the nearest value within a range of digital steps. Linear pulse-code modulation (LPCM) is a specific type of PCM where the quantization levels are linearly uniform. This is in contrast to PCM encodings where quantization levels vary as a function of amplitude (as with the A-law algorithm or the μ-law algorithm). Though PCM is a more general term, it is often used to describe data encoded as LPCM.

Bandwidth (computing)

bandwidthnetwork bandwidthbandwidths
A bit stream's bandwidth is proportional to the average consumed signal bandwidth in hertz (the average spectral bandwidth of the analog signal representing the bit stream) during a studied time interval. Channel bandwidth may be confused with useful data throughput (or goodput). For example, a channel with x bps may not necessarily transmit data at x rate, since protocols, encryption, and other factors can add appreciable overhead. For instance, much internet traffic uses the transmission control protocol (TCP), which requires a three-way handshake for each transaction.

Wii Menu

News ChannelMii ChannelNintendo Channel
The update replaced MP3 support with support for MPEG-4 encoded audio files encoded with AAC in the .m4a extension. Wii owners who updated to version 1.1 can revert to version 1.0 by deleting it from the channels menu in the data management setup. Consoles released after December 10, 2007 will come with the version 1.1 update pre-installed, and cannot be downgraded to version 1.0. Owners of Japanese systems can download a "Revert to Photo Channel 1.0" Channel from the Wii Shop Channel if they wish to do so.