Video codec
Encyclopedia
A video codec
is a device or software that enables video compression and/or decompression for digital video. The compression usually employs lossy data compression
. Historically, video was stored as an analog signal on magnetic tape
. Around the time when the compact disc
entered the market as a digital-format replacement for analog audio, it became feasible to also begin storing and using video in digital form, and a variety of such technologies began to emerge.
Audio and video call for customized methods of compression. Engineers and mathematicians have tried a number of solutions for tackling this problem.
There is a complex balance between the video quality
, the quantity of the data needed to represent it (also known as the bit rate
), the complexity of the encoding and decoding algorithms, robustness to data losses and errors, ease of editing, random access, the state of the art of compression algorithm design, end-to-end delay, and a number of other factors.
systems (players, recorders), Video CD
systems, in emerging satellite and digital terrestrial broadcast systems, various digital devices and software products with video recording and/or playing capability. 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.
Encoding media by the public has seen an upsurge with the availability of CD and DVD-writers.
color space. The conversion to YCbCr
provides two benefits: first, it improves compressibility by providing decorrelation of the color signals; and second, it separates the luma signal, which is perceptually much more important, from the chroma
signal, which is less perceptually important and which can be represented at lower resolution to achieve more efficient data compression. It is common to represent the ratios of information stored in these different channels in the following way Y:Cb:Cr. Refer to the following article for more information about Chroma subsampling
.
Different codecs will use different chroma subsampling
ratios as appropriate to their compression needs. Video compression schemes for Web and DVD make use of a 4:2:0 color sampling pattern, and the DV
standard uses 4:1:1 sampling ratios. Professional video codecs designed to function at much higher bitrates and to record a greater amount of color information for post-production manipulation sample in 3:1:1 (uncommon), 4:2:2 and 4:4:4 ratios. Examples of these codecs include Panasonic
's DVCPRO50 and DVCPROHD codecs (4:2:2), and then Sony
's HDCAM-SR (4:4:4) or Panasonic's HDD5 (4:2:2). Apple's new Prores HQ 422 codec also samples in 4:2:2 color space. More codecs that sample in 4:4:4 patterns exist as well, but are less common, and tend to be used internally in post-production houses. It is also worth noting that video codecs can operate in RGB space as well. These codecs tend not to sample the red, green, and blue channels in different ratios, since there is less perceptual motivation for doing so—just the blue channel could be undersampled.
Some amount of spatial and temporal downsampling
may also be used to reduce the raw data rate before the basic encoding process.
The most popular such transform is the 8x8 discrete cosine transform
(DCT). Codecs which make use of a wavelet
transform are also entering the market, especially in camera workflows which involve dealing with RAW
image formatting in motion sequences. The output of the transform is first quantized
, then entropy encoding
is applied to the quantized values. When a DCT has been used, the coefficients are typically scanned using a zig-zag scan order, and the entropy coding typically combines a number of consecutive zero-valued quantized coefficients with the value of the next non-zero quantized coefficient into a single symbol, and also has special ways of indicating when all of the remaining quantized coefficient values are equal to zero. The entropy coding method typically uses variable-length coding tables
. Some encoders can compress the video in a multiple step process called n-pass encoding (e.g. 2-pass), which performs a slower but potentially better quality compression.
The decoding process consists of performing, to the extent possible, an inversion of each stage of the encoding process. The one stage that cannot be exactly inverted is the quantization
stage. There, a best-effort approximation of inversion is performed. This part of the process is often called "inverse quantization" or "dequantization", although quantization is an inherently non-invertible process.
This process involves representing the video image as a set of macroblocks. For more information about this critical facet of video codec design, see B-frames.
Video codec designs are often standardized or will be in the future- i.e., specified precisely in a published document. However, only the decoding process needs to be standardized to enable interoperability. The encoding process is typically not specified at all in a standard, and implementers are free to design their encoder however they want, as long as the video can be decoded in the specified manner. For this reason, the quality of the video produced by decoding the results of different encoders that use the same video codec standard can vary dramatically from one encoder implementation to another.
Video in most of the publicly documented or standardized video compression formats can be created with multiple encoders made by different people. Many video codecs use common, standard video compression formats, which makes them compatible. 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.
Some widely-used software codecs are listed below.
All of the codecs above have their qualities and drawbacks. Comparisons are frequently published. The trade-off between compression power, speed, and fidelity (including artifacts
) is usually considered the most important figure of technical merit.
MPlayer
or VLC media player
contain many popular codecs in a portable standalone library, available for many operating systems, including Windows, Linux, and Mac OS X. This also resolves many issues within Windows in conflicting and poorly installed codecs.
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...
is a device or software that enables video compression and/or decompression for digital video. The compression usually employs lossy data compression
Lossy data compression
In information technology, "lossy" compression is a data encoding method that compresses data by discarding some of it. The procedure aims to minimize the amount of data that need to be held, handled, and/or transmitted by a computer...
. Historically, video was stored as an analog signal on magnetic tape
Magnetic tape
Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders...
. Around the time when the compact disc
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...
entered the market as a digital-format replacement for analog audio, it became feasible to also begin storing and using video in digital form, and a variety of such technologies began to emerge.
Audio and video call for customized methods of compression. Engineers and mathematicians have tried a number of solutions for tackling this problem.
There is a complex balance between the video quality
Video quality
Video quality is a characteristic of a video passed through a video transmission/processing system, a formal or informal measure of perceived video degradation...
, the quantity of the data needed to represent it (also known as the bit rate
Bit rate
In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
), the complexity of the encoding and decoding algorithms, robustness to data losses and errors, ease of editing, random access, the state of the art of compression algorithm design, end-to-end delay, and a number of other factors.
Applications
Digital video codecs are found in DVDDVD
A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....
systems (players, recorders), Video CD
Video CD
Before the advent of DVD and Blu-ray, the Video CD became the first format for distributing films on standard 120 mm optical discs. The format is a standard digital format for storing video on a Compact Disc...
systems, in emerging satellite and digital terrestrial broadcast systems, various digital devices and software products with video recording and/or playing capability. 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.
Encoding media by the public has seen an upsurge with the availability of CD and DVD-writers.
Video codec design
Video codecs seek to represent a fundamentally analog data set in a digital format. Because of the design of analog video signals, which represent luma and color information separately, a common first step in image compression in codec design is to represent and store the image in a YCbCrYCbCr
YCbCr or Y′CbCr, sometimes written or , is a family of color spaces used as a part of the color image pipeline in video and digital photography systems. Y′ is the luma component and CB and CR are the blue-difference and red-difference chroma components...
color space. The conversion to YCbCr
YCbCr
YCbCr or Y′CbCr, sometimes written or , is a family of color spaces used as a part of the color image pipeline in video and digital photography systems. Y′ is the luma component and CB and CR are the blue-difference and red-difference chroma components...
provides two benefits: first, it improves compressibility by providing decorrelation of the color signals; and second, it separates the luma signal, which is perceptually much more important, from the chroma
Chrominance
Chrominance is the signal used in video systems to convey the color information of the picture, separately from the accompanying luma signal . Chrominance is usually represented as two color-difference components: U = B' − Y' and V = R' − Y'...
signal, which is less perceptually important and which can be represented at lower resolution to achieve more efficient data compression. It is common to represent the ratios of information stored in these different channels in the following way Y:Cb:Cr. Refer to the following article for more information about Chroma subsampling
Chroma subsampling
Chroma subsampling is the practice of encoding images by implementing less resolution for chroma information than for luma information, taking advantage of the human visual system's lower acuity for color differences than for luminance....
.
Different codecs will use different chroma subsampling
Chroma subsampling
Chroma subsampling is the practice of encoding images by implementing less resolution for chroma information than for luma information, taking advantage of the human visual system's lower acuity for color differences than for luminance....
ratios as appropriate to their compression needs. Video compression schemes for Web and DVD make use of a 4:2:0 color sampling pattern, and the DV
DV
DV is a format for the digital recording and playing back of digital video. The DV codec was launched in 1995 with joint efforts of leading producers of video camcorders....
standard uses 4:1:1 sampling ratios. Professional video codecs designed to function at much higher bitrates and to record a greater amount of color information for post-production manipulation sample in 3:1:1 (uncommon), 4:2:2 and 4:4:4 ratios. Examples of these codecs include Panasonic
Panasonic
Panasonic is an international brand name for Japanese electric products manufacturer Panasonic Corporation, which was formerly known as Matsushita Electric Industrial Co., Ltd...
's DVCPRO50 and DVCPROHD codecs (4:2:2), and then Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
's HDCAM-SR (4:4:4) or Panasonic's HDD5 (4:2:2). Apple's new Prores HQ 422 codec also samples in 4:2:2 color space. More codecs that sample in 4:4:4 patterns exist as well, but are less common, and tend to be used internally in post-production houses. It is also worth noting that video codecs can operate in RGB space as well. These codecs tend not to sample the red, green, and blue channels in different ratios, since there is less perceptual motivation for doing so—just the blue channel could be undersampled.
Some amount of spatial and temporal downsampling
Downsampling
In signal processing, downsampling is the process of reducing the sampling rate of a signal. This is usually done to reduce the data rate or the size of the data....
may also be used to reduce the raw data rate before the basic encoding process.
The most popular such transform is the 8x8 discrete cosine transform
Discrete cosine transform
A discrete cosine transform expresses a sequence of finitely many data points in terms of a sum of cosine functions oscillating at different frequencies. DCTs are important to numerous applications in science and engineering, from lossy compression of audio and images A discrete cosine transform...
(DCT). Codecs which make use of a wavelet
Wavelet
A wavelet is a wave-like oscillation with an amplitude that starts out at zero, increases, and then decreases back to zero. It can typically be visualized as a "brief oscillation" like one might see recorded by a seismograph or heart monitor. Generally, wavelets are purposefully crafted to have...
transform are also entering the market, especially in camera workflows which involve dealing with RAW
RAW image format
A camera raw image file contains minimally processed data from the image sensor of either a digital camera, image scanner, or motion picture film scanner. Raw files are so named because they are not yet processed and therefore are not ready to be printed or edited with a bitmap graphics editor...
image formatting in motion sequences. The output of the transform is first quantized
Quantization (image processing)
Quantization, involved in image processing, is a lossy compression technique achieved by compressing a range of values to a single quantum value. When the number of discrete symbols in a given stream is reduced, the stream becomes more compressible. For example, reducing the number of colors...
, then entropy encoding
Entropy encoding
In information theory an entropy encoding is a lossless data compression scheme that is independent of the specific characteristics of the medium....
is applied to the quantized values. When a DCT has been used, the coefficients are typically scanned using a zig-zag scan order, and the entropy coding typically combines a number of consecutive zero-valued quantized coefficients with the value of the next non-zero quantized coefficient into a single symbol, and also has special ways of indicating when all of the remaining quantized coefficient values are equal to zero. The entropy coding method typically uses variable-length coding tables
Huffman coding
In computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression. The term refers to the use of a variable-length code table for encoding a source symbol where the variable-length code table has been derived in a particular way based on...
. Some encoders can compress the video in a multiple step process called n-pass encoding (e.g. 2-pass), which performs a slower but potentially better quality compression.
The decoding process consists of performing, to the extent possible, an inversion of each stage of the encoding process. The one stage that cannot be exactly inverted is the quantization
Quantization (image processing)
Quantization, involved in image processing, is a lossy compression technique achieved by compressing a range of values to a single quantum value. When the number of discrete symbols in a given stream is reduced, the stream becomes more compressible. For example, reducing the number of colors...
stage. There, a best-effort approximation of inversion is performed. This part of the process is often called "inverse quantization" or "dequantization", although quantization is an inherently non-invertible process.
This process involves representing the video image as a set of macroblocks. For more information about this critical facet of video codec design, see B-frames.
Video codec designs are often standardized or will be in the future- i.e., specified precisely in a published document. However, only the decoding process needs to be standardized to enable interoperability. The encoding process is typically not specified at all in a standard, and implementers are free to design their encoder however they want, as long as the video can be decoded in the specified manner. For this reason, the quality of the video produced by decoding the results of different encoders that use the same video codec standard can vary dramatically from one encoder implementation to another.
Commonly used video codecs
A variety of video compression formats can be implemented on PCs and in consumer electronics equipment. It is therefore possible for multiple codecs to be available in the same product, avoiding the need to choose a single dominant video compression format for compatibility reasons.Video in most of the publicly documented or standardized video compression formats can be created with multiple encoders made by different people. Many video codecs use common, standard video compression formats, which makes them compatible. 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.
Some widely-used software codecs are listed below.
Lossless codecs
- FFv1FFV1FFV1, which stands for "FF video codec 1", is a lossless intra-frame video codec. It can use either variable length coding or arithmetic coding for entropy coding...
: FFv1's compression factor is comparable to Motion JPEG 2000, but based on quicker algorithms (allows real-time capture). Written by Michael Niedermayer and published as part of FFmpegFFmpegFFmpeg is a free software project that produces libraries and programs for handling multimedia data. 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...
under to GNU GPL. - HuffyuvHuffyuvHuffyuv is a lossless video codec created by Ben Rudiak-Gould which is meant to replace uncompressed YCbCr as a video capture format.Despite the "YUV" in the name, it does not compress the YUV color space, but YCbCr...
: Huffyuv (or HuffYUV) is a very fast, lossless Win32 video codec written by Ben Rudiak-Gould and published under the terms of the GNU GPL as free software, meant to replace uncompressed YCbCr as a video capture format. - LagarithLagarithLagarith is an open source lossless video codec written by Ben Greenwood. It was designed and written with a few aims in mind:Speed: while not as fast as Huffyuv, it still outperforms most other lossless video codecs when it comes to encoding times, although decoding speed may be slower...
: A more up-to-date fork of Huffyuv is available as Lagarith. - YULSYULSYULS or YUVsoft's Lossless Video Codec is a lossless video codec developed by YUVsoft. It was designed to produce highly compressed lossless video. Compared to many lossless video codecs, YULS has the best compression ratio.- Releases :...
- x264X264x264 is a free software library for encoding video streams into the H.264/MPEG-4 AVC format. It is released under the terms of the GNU General Public License.-History:...
has a lossless mode.
MPEG-4 Part 2 codecs
- DivX Pro CodecDivXDivX is a brand name of products created by DivX, Inc. , including the DivX Codec which has become popular due to its ability to compress lengthy video segments into small sizes while maintaining relatively high visual quality.There are two DivX codecs; the regular MPEG-4 Part 2 DivX codec and the...
: A proprietaryProprietary softwareProprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering.Complementary...
MPEG-4 ASP codec made by DivX, Inc.DivX, Inc.DivX, Inc. , based in San Diego, California, now part of Sonic Solutions, a division of Rovi, was the corporation behind the MPEG-4 Part 2-based codec, DivX. The company's codec has been downloaded over 240 million times since January 2003... - XvidXviDXvid is a video codec library following the MPEG-4 standard, specifically MPEG-4 Part 2 Advanced Simple Profile . It uses ASP features such as b-frames, global and quarter pixel motion compensation, lumi masking, trellis quantization, and H.263, MPEG and custom quantization matrices.Xvid is a...
: FreeFree softwareFree software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
/open-source implementation of MPEG-4 ASP, originally based on the OpenDivX project. - FFmpegFFmpegFFmpeg is a free software project that produces libraries and programs for handling multimedia data. 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...
MPEG-4: Included in the open-source libavcodecLibavcodeclibavcodec is a free software/open source LGPL-licensed library of codecs for encoding and decoding video and audio data. Same name but incompatible libraries are provided from both FFmpeg project and Libav project....
codec library, which is used by default for decoding and/or encoding in many open-source video players, frameworks, editors and encoding tools such as MPlayerMPlayerMPlayer is a free and open source media player. The program is available for all major operating systems, including Linux and other Unix-like systems, Microsoft Windows and Mac OS X. Versions for OS/2, Syllable, AmigaOS and MorphOS are also available. The Windows version works, with some minor...
, VLCVLC media playerVLC media player is a free and open source media player and multimedia framework written by the VideoLAN project.VLC is a portable multimedia player, encoder, and streamer supporting many audio and video codecs and file formats as well as DVDs, VCDs, and various streaming protocols. It is able to...
, ffdshowFfdshowffdshow is a media decoder and encoder mainly used for the fast and high-quality decoding of video in the MPEG-4 ASP and AVC formats, but it supports numerous other video and audio formats as well...
or GStreamerGStreamerGStreamer is a pipeline-based multimedia framework written in the C programming language with the type system based on GObject.GStreamer allows a programmer to create a variety of media-handling components, including simple audio playback, audio and video playback, recording, streaming and editing...
. Compatible with other standard MPEG-4 codecs like Xvid or DivX Pro Codec. - 3ivx3ivx3ivx is a video codec suite, created by 3ivx Technologies, based in Sydney, Australia, that allows the creation of MPEG-4 compliant data streams. It has been designed around a need for decreased processing power for use mainly in embedded systems. First versions were published in 2001...
: A commercial MPEG-4 codec created by 3ivx Technologies.
H.264/MPEG-4 AVC codecs
- x264X264x264 is a free software library for encoding video streams into the H.264/MPEG-4 AVC format. It is released under the terms of the GNU General Public License.-History:...
: A GPL-licensed implementation of the H.264 video standard. x264 is only an encoder. - Nero DigitalNero DigitalNero Digital is a brand name applied to a suite of MPEG-4-compatible video and audio compression codecs developed by Nero AG of Germany and Ateme of France...
: Commercial MPEG-4 ASP and AVC codecs developed by Nero AGNero AGNero is a global computer software company headquartered in Karlsbad, Germany. It is perhaps most well-known for its burning software, Nero Burning ROM.-History:The company was founded as Ahead Software GmbH in 1995 by Richard Lesser....
. - QuickTimeQuickTimeQuickTime is an extensible proprietary multimedia framework developed by Apple Inc., capable of handling various formats of digital video, picture, sound, panoramic images, and interactivity. The classic version of QuickTime is available for Windows XP and later, as well as Mac OS X Leopard and...
H.264: H.264 implementation released by Apple. - DivX Pro Codec: An H.264 decoder and encoder was added in version 7.
Microsoft codecs
- WMV (Windows Media Video): Microsoft's family of proprietary video codec designs including WMV 7, WMV 8, and WMV 9. The latest generation of WMV is standardized by SMPTE as the VC-1VC-1VC-1 is the informal name of the SMPTE 421M video codec standard, which was initially developed as a proprietary video format by Microsoft before it was released as a formal SMPTE standard video format on April 3, 2006...
standard. - MS MPEG-4v3: A proprietary and not MPEG-4MPEG-4MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
compliant video codec created by Microsoft. Released as a part of Windows Media Tools 4. A hacked version of Microsoft's MPEG-4v3 codec became known as DivX ;-).
On2 codecs
- VP6VP6On2 TrueMotion VP6 is a proprietary lossy video compression format and video codec. It is an incarnation of the TrueMotion video codec, a series of video codecs developed by On2 Technologies. This codec is commonly used by Adobe Flash, Flash Video, and JavaFX media files.- Overview :The VP6 codec...
, VP6-E, VP6-S, VP7VP7TrueMotion VP7 is a video codec developed by On2 Technologies as a successor to earlier efforts such as VP3, VP5 and TrueMotion VP6. It is a codec with both VFW and DirectShow support that On2 Technologies claims has better compression than leading competitive codecs such as MPEG-4 AVC and VC-1.-...
, VP8VP8VP8 is an open video compression format released by Google, originally created by On2 Technologies.After purchasing On2 Technologies in early 2010, Google has provided an irrevocable patent promise for underlying patents for the VP8 format, and released a bitstream format specification under a...
: Proprietary high definition video compression formats and codecs developed by On2 Technologies used in platforms such as Adobe Flash Player 8 and above, Adobe Flash Lite, Java FX and other mobile and desktop video platforms. Supports resolution up to 720p and 1080p. VP8VP8VP8 is an open video compression format released by Google, originally created by On2 Technologies.After purchasing On2 Technologies in early 2010, Google has provided an irrevocable patent promise for underlying patents for the VP8 format, and released a bitstream format specification under a...
has been made open source by Google under the name libvpx or VP8 codec library. - libtheora: A reference implementation of the TheoraTheoraTheora is a free lossy video compression format. It is developed by the Xiph.Org Foundation and distributed without licensing fees alongside their other free and open media projects, including the Vorbis audio format and the Ogg container....
video compression format developed by the Xiph.org FoundationXiph.Org FoundationXiph.Org Foundation is a non-profit organizationthat produces free multimedia formats and software tools. It focuses on the Ogg family of formats, the most successful of which has been Vorbis, an open and freely licensed audio format and codec designed to compete with the patented MP3 and AAC...
, based upon On2 Technologies' VP3VP3On2 TrueMotion VP3 is a lossy video compression format and video codec. It is an incarnation of the TrueMotion video codec, a series of video codecs developed by On2 Technologies....
codec, and christened by On2 as the successor in VP3's lineage. Theora is targeted at competing with MPEG-4MPEG-4MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
video and similar lower-bitrate video compression schemes.
Other codecs
- Schrödinger and dirac-research: implementations of the DiracDirac (codec)Dirac is an open and royalty-free video compression format, specification and system developed by BBC Research at the BBC. Schrödinger and dirac-research are open and royalty-free software implementations of Dirac...
compression format developed by BBC Research at the BBC. Dirac provides video compression from web video up to ultra HD and beyond. - DNxHD codecDNxHD codecAvid DNxHD, which stands for "Digital Nonlinear Extensible High Definition", is a lossy high-definition video post-production codec engineered for multi-generation compositing with reduced storage and bandwidth requirements. It is an implementation of SMPTE VC-3 standard...
: a lossy high-definition video production codec developed by Avid Technology. It is an implementation of VC-3. - Sorenson 3Sorenson codecSorenson codec may refer to either of three proprietary video codecs: Sorenson Video, Sorenson Video 3 or Sorenson Spark. Sorenson Video is also known as Sorenson Video Codec, Sorenson Video Quantizer or SVQ...
: A video compression format and codec that is popularly used by Apple's QuickTimeQuickTimeQuickTime is an extensible proprietary multimedia framework developed by Apple Inc., capable of handling various formats of digital video, picture, sound, panoramic images, and interactivity. The classic version of QuickTime is available for Windows XP and later, as well as Mac OS X Leopard and...
, sharing many features with H.264. Many movie trailers found on the web use this compression format. - Sorenson SparkSorenson codecSorenson codec may refer to either of three proprietary video codecs: Sorenson Video, Sorenson Video 3 or Sorenson Spark. Sorenson Video is also known as Sorenson Video Codec, Sorenson Video Quantizer or SVQ...
: A codec and compression format that was licensed to Macromedia for use in its Flash Video starting with Flash Player 6. It is considered as an incomplete implementation of the H.263H.263H.263 is a video compression standard originally designed as a low-bitrate compressed format for videoconferencing. It was developed by the ITU-T Video Coding Experts Group in a project ending in 1995/1996 as one member of the H.26x family of video coding standards in the domain of the ITU-T.H.263...
standard. - RealVideoRealVideoRealVideo is a suite of proprietary video compression formats developed by RealNetworks – the specific format changes with the version. It was first released in 1997 and is at version 10. RealVideo is supported on many platforms, including Windows, Mac, Linux, Solaris, and several mobile...
: Developed by RealNetworksRealNetworksRealNetworks, Inc. is a provider of Internet media delivery software and services based in Downtown Seattle, Washington, United States. The company is the creator of RealAudio, a compressed audio format; RealVideo, a compressed video format; RealPlayer, a media player; RealDownloader, a download...
. A popular compression format and codec technology a few years ago, now fading in importance for a variety of reasons. - CinepakCinepakCinepak is a video codec developed by Peter Barrett at SuperMac Technologies, and released in 1991 with the Video Spigot, and then in 1992 as part of Apple Computer's QuickTime video suite. It was designed to encode 320x240 resolution video at 1x CD-ROM transfer rates. The codec was ported to the...
: A very early codec used by Apple's QuickTime. - IndeoIndeoIndeo Video is a video codec developed by Intel in 1992. It was sold to Ligos Corporation in 2000. While its original version was related to Intel's DVI video stream format, a hardware-only codec for the compression of television-quality video onto compact disks, Indeo was distinguished by being...
, an older video compression format and codec initially developed by Intel.
All of the codecs above have their qualities and drawbacks. Comparisons are frequently published. The trade-off between compression power, speed, and fidelity (including artifacts
Compression artifact
A compression artifact is a noticeable distortion of media caused by the application of lossy data compression....
) is usually considered the most important figure of technical merit.
Missing codecs and video-file issues
A common problem, when an end user wants to watch a video stream encoded with a specific codec, is that if the exact codec is not present and properly installed on the user's machine, the video won't play (or won't play optimally).MPlayer
MPlayer
MPlayer is a free and open source media player. The program is available for all major operating systems, including Linux and other Unix-like systems, Microsoft Windows and Mac OS X. Versions for OS/2, Syllable, AmigaOS and MorphOS are also available. The Windows version works, with some minor...
or VLC media player
VLC media player
VLC media player is a free and open source media player and multimedia framework written by the VideoLAN project.VLC is a portable multimedia player, encoder, and streamer supporting many audio and video codecs and file formats as well as DVDs, VCDs, and various streaming protocols. It is able to...
contain many popular codecs in a portable standalone library, available for many operating systems, including Windows, Linux, and Mac OS X. This also resolves many issues within Windows in conflicting and poorly installed codecs.
See also
- Comparison of video codecsComparison of video codecsA video codec is software or a device that provides encoding and decoding which may or may not include the use of video compression and/or decompression for digital video....
- List of codecs
- BitrateBitrateIn telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
- MultiplexingMultiplexingThe multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...
- Frame rateFrame rateFrame rate is the frequency at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems...
- Subjective video qualitySubjective video qualitySubjective video quality is a subjective characteristic of video quality. It is concerned with how video is perceived by a viewer and designates his or her opinion on a particular video sequence...
- List of open source codecs
- Sampling rateSampling rateThe sampling rate, sample rate, or sampling frequency defines the number of samples per unit of time taken from a continuous signal to make a discrete signal. For time-domain signals, the unit for sampling rate is hertz , sometimes noted as Sa/s...
- Transcoding
- Video compression
- Display resolutionDisplay resolutionThe display resolution of a digital television or display device is the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by all different factors in cathode ray tube , flat panel or projection...
- Video qualityVideo qualityVideo quality is a characteristic of a video passed through a video transmission/processing system, a formal or informal measure of perceived video degradation...
External links
- Wyner-Ziv Coding of Video describes another algorithm for video compression that performs close to the Slepian-Wolf bound (with links to source code).
- Video codecs standards PDF files with some codec standards description
- History of main codecs Evolution of digital video compression