Pre-echo, sometimes called a forward echo, (not to be confused with reverse echo) is a digital audio compression artifact where a sound is heard before it occurs (hence the name). It is most noticeable in impulsive sounds from percussion instruments such as castanets or cymbals. It occurs in transform-based audio compression algorithms – typically based on the modified discrete cosine transform (MDCT) – such as MP3, MPEG-4 AAC, and Vorbis, and is due to quantization noise being spread over the entire transform-window of the codec.


At its core, foobar2000 natively supports a range of audio formats, including MP1, MP2, MP3, MPC, AAC, WMA, Ogg Vorbis, FLAC / Ogg FLAC, ALAC, WavPack, WAV, AIFF, AU, SND, CD, Speex, and Opus. foobar2000 also has a customizable user interface, advanced tagging capabilities and support for ripping Audio CDs, as well as transcoding of all supported audio formats using the Converter component. The player can read inside ZIP, GZIP, and RAR archives. Core functionality has also been tested to work under Wine on Linux.

USB flash drive

flash driveUSB driveflash drives
Fancier devices that function as a digital audio player have a USB host port (type A female typically). Digital audio files can be transported from one computer to another like any other file, and played on a compatible media player (with caveats for DRM-locked files). In addition, many home Hi-Fi and car stereo head units are now equipped with a USB port. This allows a USB flash drive containing media files in a variety of formats to be played directly on devices which support the format. Some LCD monitors for consumer HDTV viewing have a dedicated USB port through which music and video files can also be played without use of a personal computer.


The player supports incoming streams delivered via HTTP (ASF/OGG/MP3/AAC/MPEG PS/MPEG TS, but they only work with internal splitters). The player supports DirectShow playback (AVI, WMV, MKV, MOV, MP4, Ogg Theora, OGM, RMVB, MPEG1, MPEG2, and other audio formats playable via supported decoders). The player features an Async File Source (network) filter for memory caching. Compressed audio album support (zip, rar). Shoutcast (including NSV), Icecast. DTS Wave, AC3, AAC, Ogg, Ape, MPC, FLAC, AMR, ALAC, SHN, WV, Module (MOD, S3M, MTM, UMX, XM and IT), etc. Google Video (GVI), Flash Video (FLV), Nullsoft Streaming Video (NSV), 3GP, PMP, VOB.


Container formats: 3gp, AVI, ASF, FLV, Matroska, MOV (QuickTime), MP4, NUT, Ogg, OGM, RealMedia. Audio formats: AAC, AC3, ALAC, AMR, FLAC, MP3, RealAudio, Shorten, Speex, Vorbis, WMA. Video formats: Cinepak, DV, H.263, H.264/MPEG-4 AVC, HuffYUV, Indeo, MJPEG, MPEG-1, MPEG-2, MPEG-4 ASP, RealVideo, Sorenson, Theora, WMV (partial, including WMV1, WMV2 and WMV3; via FFmpeg). Video devices: V4L, DVB, PVR. Network protocols: HTTP, TCP, UDP, RTP, SMB, MMS, PNM, RTSP. List of codecs. Open source codecs and containers. Comparison of video codecs. Comparison of audio coding formats. Comparison of container formats. Screencast.


The Knife allows ripping Audio CD tracks directly into Musepack files. subband selectable M/S encoding (as in AAC). Huffman coding (as in MP3 and AAC, but more efficient). Since SV8 the bitstream is compressed by highly optimized canonical huffman tables that yields 2% smaller files and faster decoding. noise substitution techniques (as in ATSC A-52 and MPEG-4 AAC V2). pure variable bitrate between 0 and 1300 kbit/s (when needed). Container-independent format. An SV8 MPC is a container file for a Musepack stream. Raw stream encoding is possible. Packetized stream allows muxing into audio and video containers (e.g. MKA/MKV, NUT). Sample-accurate, fast seeking independent of file length.


VMRMicrosoft DirectShowOverlay Mixer Filter
By default, DirectShow includes a number of filters for decoding some common media file formats such as MPEG-1, MP3, Windows Media Audio, Windows Media Video, MIDI, media containers such as AVI, ASF, WAV, some splitters/demultiplexers, multiplexers, source and sink filters and some static image filters. Since the associated patented technologies are licensed in Windows, no license fees are required (e.g., to Fraunhofer, for MP3). Some codecs such as MPEG-4 Advanced Simple Profile, AAC, H.264, Vorbis and containers MOV, MP4 are available from 3rd parties.

Data compression ratio

compression ratiocompression ratios320 kbit/s
Lossless compression of digitized data such as video, digitized film, and audio preserves all the information, but it does not generally achieve compression ratio much better than 2:1 because of the intrinsic entropy of the data. Compression algorithms which provide higher ratios either incur very large overheads or work only for specific data sequences (e.g. compressing a file with mostly zeros). In contrast, lossy compression (e.g. JPEG for images, or MP3 and Opus for audio) can achieve much higher compression ratios at the cost of a decrease in quality, such as Bluetooth audio streaming, as visual or audio compression artifacts from loss of important information are introduced.

Adobe Flash Player

FlashFlash PlayerAdobe Flash
MP3: Support for decoding and playback of streaming MPEG-2 Audio Layer III (MP3) audio was introduced in Flash Player 4. MP3 files can be accessed and played back from a server via HTTP, or embedded inside an SWF file, which is also a streaming format. FLV: Support for decoding and playing back video and audio inside Flash Video (FLV and F4V) files, a format developed by Adobe Systems and Macromedia. Flash Video is only a container format and supports multiple different video codecs, such as Sorenson Spark, VP6 and more recently H.264. Flash Player uses hardware acceleration to display video where present, using technologies such as DirectX Video Acceleration and OpenGL to do so.

Apple TV

AppleApple TV (4th generation)Apple TV (Second Generation)
High or Main Profile level 4.0 or lower, or High or Main Profile level 4.2 or lower (4th generation ), Baseline profile level 3.0 or lower with AAC-LC audio up to 160 kbits/s per channel, 48 kHz, stereo audio in .m4v, .mp4, and .mov file formats. MPEG-4 up to 720×432 (432p) or 640×480 pixels at 30 fps. MPEG-4 video up to 2.5 Mbit/s, 640×480 pixels, 30 frames per second, Simple Profile with AAC-LC audio up to 160 kbit/s, 48 kHz, stereo audio in .m4v, .mp4, and .mov file formats. Motion JPEG up to 720p at 30 fps. Motion JPEG (M-JPEG) up to 35 Mbit/s, 1280×720 pixels, 30 fps, audio in ulaw, PCM stereo audio in .avi file format. JPEG. GIF. TIFF. HEIF (4th generation and later). HE-AAC (V1).


X Multimedia System
AAC support is provided by the FAAD2 library, supporting m4a files. APE Monkey's Audio Codec .ape files — support provided by the mac-port project plugin. Audio CD, including CDDB via FreeDB lookup. FLAC support is provided by a plugin in the FLAC library. Icecast and SHOUTcast streaming supported, and is compatible with Winamp 2 skins. libmikmod supported formats (including .XM, .MOD, .IT) See: MikMod’s Home. JACK plug-in for support of the JACK Audio Connection Kit. ModPlug plug-in for playing .MOD, .S3M, .XM, .IT and other famous tracker formats. mp3PRO support is provided by a third party plugin (which does not support SHOUTcast title streaming).


Zune MarketplaceMicrosoft ZuneZune Video Marketplace
MP3 (used by Zune Marketplace). AAC (unprotected) not AAC (.m4a). WMA Pro (2-channel). WMA Standard (used by Zune Marketplace). WMA lossless. — Redirects to a Q&A for Zune users titled Important changes are coming to Zune Marketplace. Zune Insider – Insider blog & podcast — Dead link. Zune Podcast Support – An interview with Rob Greenlee, Podcast Programming Lead for the Zune about the second generation Zunes' support for podcasts. — Dead link. Zune Podcast Connected Show Interview – An interview with Rob Greenlee. During the Interview we discuss his long career in Podcasting, his work in the Zune Podcast team, how to make podcasts successful and finally the ZuneHD.

Nook Color

color version of the Nook
Supported file formats include EPUB (DRM and non-DRM), PDF, Microsoft Office formats (DOC, DOCX, XLS, PPT, etc.), TXT, JPEG, GIF, PNG, BMP, MP3, AAC, and MP4. A firmware update released 25 April 2011 added an app store, email client, Flash support within the web browser, social networking tools, video and audio embedded within books, and performance improvements. It also has been discovered that the device has hidden Bluetooth connectivity abilities in its wireless chipset, available only after rooting, and/or flashing a device to the CyanogenMod 7 version of Android for this device. When the Nook Color and Tablet were first offered, users could install third-party apps.


liba52mplayer2GNOME MPV
Container formats: 3GP, AVI, ASF, FLV, Matroska, MOV (QuickTime), MP4, NUT, Ogg, OGM, RealMedia, Bink. Video formats: Cinepak, DV, H.263, H.264/MPEG-4 AVC, HuffYUV, Indeo, MJPEG, MPEG-1, MPEG-2, MPEG-4 Part 2, RealVideo, Sorenson, Theora, WMV, Bink. Audio formats: AAC, AC3, ALAC, AMR, DTS, FLAC, Intel Music Coder, Monkey's Audio, MP3, Musepack, RealAudio, Shorten, Speex, Vorbis, WMA, Bink. Subtitle formats: AQTitle, ASS/SSA, CC, JACOsub, MicroDVD, MPsub, OGM, PJS, RT, Sami, SRT, SubViewer, VOBsub, VPlayer. Image formats: BMP, JPEG, MNG, PCX, PTX, TGA, TIFF, SGI, Sun Raster. Protocols: RTP, RTSP, HTTP, FTP, MMS, Netstream (mpst://), SMB, ffmpeg:// (Uses FFmpeg's protocol implementations).

Timeline of audio formats

music formatFormataudio format
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. Audio data compression. Format war. Museum Of Obsolete Media – Audio Formats.


Monkey's Audio (decoding only). MP2. MP3 (native decoder, encoding through LAME). ISO/IEC MPEG audio standards: MP1, MP2, MP3, AAC, HE-AAC and MPEG-4 ALS. Nellymoser Asao Codec in Flash. NTT: TwinVQ. Opus (via libopus). QCELP (decoding only). QDM2 (decoding only). QuickTime related audio codecs: QDesign Music Codec 2 and ALAC. RealAudio 1.0. RealAudio 2.0 (decoding only). RealPlayer related audio codecs: RealAudio 3, 6, 7, 8, 9 and 10 (a.k.a. ralf for RealAudioLosslessFormat). RealPlayer related voice codecs: RealAudio 1, 2 (variant of G.728), 4 and 5. Shorten (decoding only). SMPTE audio standards: SMPTE 302M. Sony: ATRAC1 and ATRAC3. Speex (via libspeex). Truespeech. TTA (decoding only).

Audio signal

audioaudio channelchannel
Audio signals have somewhat standardized levels depending on application. Outputs of professional mixing consoles are most commonly at line level. Consumer audio equipment will also output at a lower line level. Microphones generally output at an even lower level, commonly referred to a mic level. The digital form of an audio signal is used in audio plug-ins and digital audio workstation (DAW) software. The digital information passing through the DAW (i.e. from an audio track through a plug-in and out a hardware output) is an audio signal. A digital audio signal being sent through wire can use several formats including optical (ADAT, TDIF), coaxial (S/PDIF), XLR (AES/EBU), and Ethernet.

Digital-to-analog converter

DACDACsdigital to analog converter
A DAC converts this back into an analog electrical signal, which drives an audio amplifier, which in turn drives a loudspeaker, which finally produces sound. Most modern audio signals are stored in digital form (for example MP3s and CDs) and, in order to be heard through speakers, they must be converted into an analog signal. DACs are therefore found in CD players, digital music players, and PC sound cards. Specialist standalone DACs can also be found in high-end hi-fi systems.

Digital Radio Mondiale

DRMdigitalDigital Radio Mondiale (DRM)
Useful bitrate depends also on other parameters, such as: When DRM was originally designed, it was clear that the most robust modes offered insufficient capacity for the then state-of-the-art audio coding format MPEG-4 HE-AAC (High Efficiency Advanced Audio Coding). Therefore, the standard launched with a choice of three different audio coding systems (source coding) depending on the bitrate: However, with the development of MPEG-4 xHE-AAC, which is an implementation of MPEG Unified Speech and Audio Coding, the DRM standard was updated and the two speech-only coding formats, CELP and HVXC, were replaced.

Digital audio broadcasting

DABDAB+digital radio
The newer DAB+ standard adopted the HE-AAC version 2 audio codec, commonly known as 'AAC+' or 'aacPlus'. AAC+ is approximately three times more efficient than MP2, which means that broadcasters using DAB+ are able to provide far higher audio quality or far more stations than they could with DAB, or a combination of both higher audio quality and more stations. One of the most important decisions regarding the design of a digital radio broadcasting system is the choice of which audio codec to use, because the efficiency of the audio codec determines how many radio stations can be carried on a fixed capacity multiplex at a given level of audio quality.

Digital television

digitaldigital TVDTV
It supports hierarchical transmission of up to three layers and uses MPEG-2 video and Advanced Audio Coding. This standard has been adopted in Japan and the Philippines. ISDB-T International is an adaptation of this standard using H.264/MPEG-4 AVC that been adopted in most of South America and is also being embraced by Portuguese-speaking African countries. Digital Terrestrial Multimedia Broadcasting (DTMB) adopts time-domain synchronous (TDS) OFDM technology with a pseudo-random signal frame to serve as the guard interval (GI) of the OFDM block and the training symbol. The DTMB standard has been adopted in the People's Republic of China, including Hong Kong and Macau.


Twin vector quantizationVQF
Some CD-Ripping/Converter software also support encoding to .vqf format. * Comparison of audio formats MPEG-4 Audio FAQ - ISO (1998). MPEG-4 Natural Audio Coding - scalability in MPEG-4 natural audio, TwinVQ, Audio profiles and levels. What Is VQF? - an article on the historical VQF website (2000). VQF on Hydrogenaudio Knowledgebase (2006). The historical NTT TwinVQ website - by Nippon Telephone and Telegraph (2002), ( 2008). Information about TwinVQ on MP3' Tech (2001). (2002-07-12). Winamp VQF Plugin (2000-07-27).


MIDMIDI fileMusical Instrument Digital Interface
Some MIDI Modules include a Harmonizer and the ability to playback and transpose MP3 audio files. Synthesizers may employ any of a variety of sound generation techniques. They may include an integrated keyboard, or may exist as "sound modules" or "expanders" that generate sounds when triggered by an external controller, such as a MIDI keyboard. Sound modules are typically designed to be mounted in a 19-inch rack. Manufacturers commonly produce a synthesizer in both standalone and rack-mounted versions, and often offer the keyboard version in a variety of sizes. A sampler can record and digitize audio, store it in random-access memory (RAM), and play it back.

Media player (software)

media playeraudio playermedia players
Media Player Classic can play individual audio and video files but many of its features such as color correction, picture sharpening, zooming, set of hotkeys, DVB support and subtitle support are only useful for video material such as films and cartoons. Audio players, on the other hand, specialize in digital audio. For example, AIMP exclusively plays audio formats. MediaMonkey can play both audio and video format but many of its features including media library, lyric discovery, music visualization, online radio, audiobook indexing and tag editing are geared toward consumption of audio material. In addition, watching video files on it can be a trying feat.

List of open-source codecs

freely-licensed data compression technologiesList of open-source audio codecs
Apple Lossless – Lossless compression (MP4). Fraunhofer FDK AAC – Lossy compression (AAC). FFmpeg codecs in the libavcodec library, e.g. AC-3, AAC, ADPCM, PCM, Apple Lossless, FLAC, WMA, Vorbis, MP2, etc. FAAD2 – open-source decoder for Advanced Audio Coding. There is also FAAC, the same project's encoder, but it is proprietary (but still free of charge). libgsm – Lossy compression (GSM 06.10). opencore-amr – Lossy compression (AMR and AMR-WB). liba52 – a free ATSC A/52 stream decoder (AC-3). libdca – a free DTS Coherent Acoustics decoder. Codec2 - Low bitrate compression, primarily voice. List of codecs. Comparison of video codecs. Comparison of audio coding formats.