A codec is a device or computer program capable of encoding or decoding a digital data stream or signal.

In software, an " audio codec " is a computer program implementing an algorithm that compresses and decompresses digital audio data according to a given audio file format or streaming media audio format.

On November 25, 2004 he released a proof of concept program that allows Linux users ( via VLC ) to play video encoded with Microsoft's proprietary WMV9 codec, by porting the reference version of the software.

Xvid is not a video format – it is a program ( codec ) for compressing and decompressing to the MPEG-4 ASP format.

The most notable parts of FFmpeg are libavcodec, an audio / video codec library used by several other projects, libavformat, an audio / video container mux and demux library, and the ffmpeg command line program for transcoding multimedia files.

* PSP codec, a program capable of encoding and / or decoding a digital data stream for the H. 264 standard for video compression

::* MPEG-2 codec based format, which records MPEG-2 program stream or MPEG-2 transport stream to various kinds of tapeless media ( hard disks, solid-state memory, etc ).

Both systems use the MPEG transport stream and H. 262 / MPEG-2 Part 2 video codec specified in MPEG-2 ; they differ significantly in how related services ( such as multichannel audio, captions, and program guides ) are encoded.

Professional video over IP systems use some existing standard video codec to reduce the program material to a bitstream ( e. g., an MPEG transport stream ), and then to use an Internet Protocol ( IP ) network to carry that bitstream encapsulated in a stream of IP packets.

If the next data item is not available when it is needed, the codec has no choice but to produce silence or guess — and if the data is late, it is useless, because the time period when it should have been converted to a signal has already passed.

Music or tones such as DTMF or fax tones cannot be transported reliably with this codec, and thus some other method such as G. 711 or out-of-band methods should be used to transport these signals.

The format does not specify how ( i. e. with which codec ) the video or audio should be encoded ; it just specifies the structure of the video / audio stream.

The viewpoint held by Christopher Montgomery, creator of the Ogg format, is that the units of muxed codec data should be a separate abstraction layer from the units of data used by the codec in order to limit the amount of buffering necessary when decoding the contained data.

The Microsoft Windows implementation of the Indeo codec contains several security vulnerabilities and one should not play Indeo videos from untrusted sources.

Note that wav files can also be encoded with the gsm codec.

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.

Not all audio codecs can be used for streaming applications, and for such applications a codec designed to stream data effectively will usually be chosen.

The codec was first designed to be utilized in H. 324 based systems ( PSTN and other circuit-switched network videoconferencing and videotelephony ), but has since also found use in H. 323 ( RTP / IP-based videoconferencing ), H. 320 ( ISDN-based videoconferencing ), RTSP ( streaming media ) and SIP ( Internet conferencing ) solutions.

In conjunction with an appropriate codec using MPEG or various manufacturers proprietary algorithms, an ISDN BRI can be used to send stereo bi-directional audio coded at 128 kbit / s with 20 Hz – 20 kHz audio bandwidth, although commonly the G. 722 algorithm is used with a single 64 kbit / s B channel to send much lower latency mono audio at the expense of audio quality.

The addition of MDLP ( MiniDisc LongPlay ) codec allowed up to 4 times the amount of music to be stored on one MiniDisc, at the sacrifice of some sound quality.

Their main downfall would be Sony's stubborn resistance to supporting the ubiquitous MP3 codec in their early players and many users found it frustrating to convert their MP3 music collection to ATRAC3 for use on the Network Walkman, while Apple's iPod supported MP3 out of the box and came with the iTunes software.

This transition away from the ATRAC codec was to allow the Walkman line to be adopted by more potential customers and their specific and unique preferences on online music services.

Any ACM codec can be used to compress a WAV file.

The rockbox project further extended this codec to be suitable for embedded cores, allowing playback on portable MP3 players and cell phones running open source software.

By way of the RIFF format, the audio-visual data contained in the " movi " chunk can be encoded or decoded by software called a codec, which is an abbreviation for ( en ) coder / decoder.

In addition, a TA may contain an interface and codec for one or more analog telephone lines ( aka a / b line ), allowing an existing POTS installation to be upgraded to ISDN without changing phones.

Support for any media codec and container format can be added using specific DirectShow filters or Media Foundation codecs ( Media Foundation codecs only in Windows Vista and later ).

Like most other audio compression codecs, some signals will " trip " the codec and cause artifacts, though these are not usually severe enough to be obvious.

Video codec designs are often standardized or will be in the future-i. e., specified precisely in a published document.

For example, video created with a standard MPEG-4 Part 2 codec such as Xvid can be decoded ( played back ) using any other standard MPEG-4 Part 2 codec such as FFmpeg MPEG-4 or DivX Pro Codec, because they all use the same video format.

Speex is a patent-free audio compression format designed for speech and also a free software speech codec that may be used on VoIP applications and podcasts.

The design goals have been to make a codec that would be optimized for high quality speech and low bit rate.

Since Speex was designed for Voice over IP ( VoIP ) instead of cell phone use, the codec must be robust to lost packets, but not to corrupted ones.

If the media were in the appropriate codec on the server, they only need to be transferred, but if they were recorded using a different codec, they also have to be transcoded during the transfer ( by appropriate software ).

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.

* Electronic encoding transforms a signal into a code optimized for transmission or storage, generally done with a codec.

When a user with a low bitrate codec talks to a user with another codec, additional distortion is introduced by each transcoding.

The next enhanced codec developed by ITU-T VCEG ( in partnership with MPEG ) after H. 263 is the H. 264 standard, also known as AVC and MPEG-4 part 10.

* A codec builder to implement only the subset of the standard needed, while maintaining interworking with other MPEG-4 devices that implement the same combination.

In contrast to Nortel's DMS-100 which uses individual line cards with a codec, most lines are on two-stage analog space-division concentrators or Line Units, which connect as many as 512 lines, as needed, to the 8 Channel cards that each contain 8 codecs, and to high-level service circuits for ringing and testing.

In November of the following year, Video for Windows was introduced with the ability to play digital video files in an AVI container format, with codec support for RLE and Video1, and support for playing uncompressed files.

On Windows XP and above with WMP 9 Series and later, the Windows Media Audio Professional codec is included which supports multichannel audio at up to 24-bit 192 kHz resolution.

* Ogg Vorbis, the Vorbis free software / open source audio codec, commonly used with the Ogg container

Online video material is encoded by a variety of codecs, and this has led to the availability of codec packs-a pre-assembled set of commonly used codecs combined with an installer available as a software package for PCs, such as K-Lite Codec Pack.

* Sorenson 3: A video compression format and codec that is popularly used by Apple's QuickTime, sharing many features with H. 264.

* Sorenson Spark: A codec and compression format that was licensed to Macromedia for use in its Flash Video starting with Flash Player 6.