# Video codec

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Video_codec
> Markdown URL: https://mediated.wiki/source/Video_codec.md
> Source: https://en.wikipedia.org/wiki/Video_codec
> Source revision: 1354433816
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Digital video coder/decoder

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Video codec" – news · newspapers · books · scholar · JSTOR (May 2023) (Learn how and when to remove this message)

A short video explaining the concept of video codecs.

A **video codec** is [software](/source/Software) or [hardware](/source/Computer_hardware) that [compresses](/source/Data_compression) and [decompresses](/source/Uncompressed_video) [digital video](/source/Digital_video). In the context of video compression, *[codec](/source/Codec)* is a [portmanteau](/source/Portmanteau) of *encoder* and *decoder*, while a device that only compresses is typically called an *[encoder](/source/Encoder_(digital))*, and one that only decompresses is a *decoder*.

The compressed data format usually conforms to a standard [video coding format](/source/Video_coding_format). The compression is typically [lossy](/source/Lossy), meaning that the compressed video lacks some information present in the original video. A consequence of this is that decompressed video has lower quality than the original, uncompressed video because there is insufficient information to accurately reconstruct the original video.

There are complex relationships between the [video quality](/source/Video_quality), the amount of data used to represent the video (determined by the [bit rate](/source/Bit_rate)), the complexity of the encoding and decoding algorithms, sensitivity to data losses and errors, ease of editing, random access, and end-to-end delay ([latency](/source/Latency_(engineering))).

## History

Further information: [Video coding format § History](/source/Video_coding_format#History)

Historically, video was stored as an analog signal on [magnetic tape](/source/Magnetic_tape). Around the time when the [compact disc](/source/Compact_disc) entered the market as a digital-format replacement for analog audio, it became feasible to also store and convey video in digital form. Because of the large amount of storage and bandwidth needed to record and convey raw video, a method was needed to reduce the amount of data used to represent the raw video. Since then, [engineers](/source/Engineers) and [mathematicians](/source/Mathematicians) have developed a number of solutions for achieving this goal that involve compressing the digital video data.

In 1974, [discrete cosine transform](/source/Discrete_cosine_transform) (DCT) compression was introduced by [Nasir Ahmed](/source/N._Ahmed), T. Natarajan and [K. R. Rao](/source/K._R._Rao).[1][2][3] During the late 1980s, a number of companies began experimenting with DCT [lossy compression](/source/Lossy_compression) for video coding, leading to the development of the [H.261](/source/H.261) standard.[4] H.261 was the first practical video coding standard,[5] and was developed by a number of companies, including [Hitachi](/source/Hitachi), [PictureTel](/source/PictureTel), [NTT](/source/Nippon_Telegraph_and_Telephone), [BT](/source/BT_plc), and [Toshiba](/source/Toshiba), among others.[6] Since H.261, DCT compression has been adopted by all the major video coding standards that followed.[4]

The most popular [video coding standards](/source/Video_coding_standard) used for codecs have been the [MPEG](/source/MPEG) standards. [MPEG-1](/source/MPEG-1) was developed by the [Motion Picture Experts Group](/source/Motion_Picture_Experts_Group) (MPEG) in 1991, and it was designed to compress [VHS](/source/VHS)-quality video. It was succeeded in 1994 by [MPEG-2](/source/MPEG-2)/[H.262](/source/H.262),[5] which was developed by a number of companies, primarily [Sony](/source/Sony), [Thomson](/source/Technicolor_SA) and [Mitsubishi Electric](/source/Mitsubishi_Electric).[7] MPEG-2 became the standard video format for [DVD](/source/DVD) and [SD digital television](/source/SD_digital_television).[5] In 1999, it was followed by [MPEG-4](/source/MPEG-4_Visual)/[H.263](/source/H.263), which was a major leap forward for video compression technology.[5] It was developed by a number of companies, primarily Mitsubishi Electric, Hitachi and [Panasonic](/source/Panasonic).[8]

The most widely used video coding format, as of 2016, is [H.264/MPEG-4 AVC](/source/H.264%2FMPEG-4_AVC). It was developed in 2003 by a number of organizations, primarily Panasonic, [Godo Kaisha IP Bridge](/source/Godo_kaisha) and [LG Electronics](/source/LG_Electronics).[9] H.264 is the main video encoding standard for [Blu-ray Discs](/source/Blu-ray_Disc), and is widely used by streaming internet services such as [YouTube](/source/YouTube), [Netflix](/source/Netflix), [Vimeo](/source/Vimeo), and [iTunes Store](/source/ITunes_Store), web software such as [Adobe Flash Player](/source/Adobe_Flash_Player) and [Microsoft Silverlight](/source/Microsoft_Silverlight), and various [HDTV](/source/HDTV) broadcasts over terrestrial and satellite television.

AVC has been succeeded by [HEVC](/source/HEVC) (H.265), developed in 2013. It is heavily patented, with the majority of patents belonging to [Samsung Electronics](/source/Samsung_Electronics), [GE](/source/GE), NTT and [JVC Kenwood](/source/JVC_Kenwood).[10][11] The adoption of HEVC has been hampered by its complex licensing structure. HEVC is, in turn, succeeded by [Versatile Video Coding](/source/Versatile_Video_Coding) (VVC).

There are also the open and free [VP8](/source/VP8), [VP9](/source/VP9) and [AV1](/source/AV1) video coding formats, used by YouTube, all of which were developed with involvement from [Google](/source/Google).

## Applications

Video codecs are used in DVD players, [Internet video](/source/Internet_video), [video on demand](/source/Video_on_demand), [digital cable](/source/Digital_cable), [digital terrestrial television](/source/Digital_terrestrial_television), [videotelephony](/source/Videotelephony) and a variety of other applications. In particular, they are widely used in applications that record or transmit video, which may not be feasible with the high data volumes and bandwidths of uncompressed video. For example, they are used in [operating theaters](/source/Operating_theater) to record surgical operations, in [IP cameras](/source/IP_camera) in security systems, and in [remotely operated underwater vehicles](/source/Remotely_operated_underwater_vehicle) and [unmanned aerial vehicles](/source/Unmanned_aerial_vehicle). Any video stream or file can be encoded using a wide variety of live video format options.[12]

## Video codec design

Further information: [Video coding format](/source/Video_coding_format)

Video codecs seek to represent a fundamentally analog data set in a digital format. Because of the design of analog video signals, which represent [luminance](/source/Luminance_(video)) (luma) and [color information](/source/Chrominance) (chrominance, chroma) separately, a common first step in image compression in codec design is to represent and store the image in a [YCbCr](/source/YCbCr) 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 using [chroma subsampling](/source/Chroma_subsampling) to achieve more efficient data compression. It is common to represent the ratios of information stored in these different channels in the following way YCbCr. Different codecs use different chroma subsampling ratios as appropriate to their compression needs. Video compression schemes for Web and DVD make use of a 4:2:1 color sampling pattern, and the [DV](/source/DV_(video_format)) 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 4:2:2 and 4:4:4 ratios. Examples of these codecs include Panasonic's DVCPRO50 and DVCPROHD codecs (4:2:2), Sony's HDCAM-SR (4:4:4), Panasonic's HDD5 (4:2:2), [Apple](/source/Apple_Inc.)'s Prores HQ 422 (4:2:2).[13]

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](/source/Downsampling) may also be used to reduce the raw data rate before the basic encoding process. The most popular encoding transform is the 8x8 DCT. Codecs that make use of a [wavelet](/source/Wavelet) transform are also entering the market, especially in camera workflows that involve dealing with [RAW](/source/Raw_image_format) image formatting in motion sequences. This process involves representing the video image as a set of [macroblocks](/source/Macroblocks). For more information about this critical facet of video codec design, see [B-frames](/source/B-frames).[14]

The output of the transform is first [quantized](/source/Quantization_(image_processing)), then [entropy encoding](/source/Entropy_encoding) is applied to the quantized values. When a DCT has been used, the coefficients are typically scanned using a [zig-zag scan](https://en.wikipedia.org/w/index.php?title=Zig-zag_scan&action=edit&redlink=1) 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](/source/Variable-length_code). Some encoders compress the video in a multiple-step process called *n-pass* encoding (e.g. 2-pass), which performs a slower but potentially higher quality compression.

The decoding process consists of performing, to the extent possible, an inversion of each stage of the encoding process.[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] 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.

Video codec designs are usually standardized or eventually become standardized—i.e., specified precisely in a published document. However, only the decoding process need 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

Main article: [List of codecs § Video compression formats](/source/List_of_codecs#Video_compression_formats)

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, reducing the need to choose a single dominant video compression format to achieve [interoperability](/source/Interoperability).

Standard [video compression formats](/source/Video_compression_format) can be supported by multiple encoder and decoder implementations from multiple sources. For example, video encoded with a standard [MPEG-4 Part 2](/source/MPEG-4_Part_2) codec such as [Xvid](/source/Xvid) can be decoded using any other standard [MPEG-4 Part 2](/source/MPEG-4_Part_2) codec such as [FFmpeg MPEG-4](https://en.wikipedia.org/w/index.php?title=FFmpeg_MPEG-4&action=edit&redlink=1) or [DivX Pro Codec](https://en.wikipedia.org/w/index.php?title=DivX_Pro_Codec&action=edit&redlink=1), because they all use the same video format.

Codecs have their qualities and drawbacks. [Comparisons](/source/Comparison_of_video_codecs) are frequently published. The trade-off between compression power, speed, and fidelity (including [artifacts](/source/Compression_artifact)) is usually considered the most important figure of technical merit.

## Codec packs

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](/source/K-Lite_Codec_Pack), [Perian](/source/Perian) and [Combined Community Codec Pack](/source/Combined_Community_Codec_Pack).

## See also

- [Bit rate](/source/Bit_rate)

- [Comparison of video codecs](/source/Comparison_of_video_codecs)

- [Data compression § Video](/source/Data_compression#Video)

- [Display resolution](/source/Display_resolution)

- [Frame rate](/source/Frame_rate)

- [List of open-source codecs](/source/List_of_open-source_codecs)

- [Multiplexing](/source/Multiplexing)

- [Sampling rate](/source/Sampling_rate)

- [Subjective video quality](/source/Subjective_video_quality)

- [Transcoding](/source/Transcoding)

- [Video quality](/source/Video_quality)

## References

1. **[^](#cite_ref-pubDCT_1-0)** [Ahmed, Nasir](/source/N._Ahmed); Natarajan, T.; Rao, K. R. (January 1974), "Discrete Cosine Transform", *IEEE Transactions on Computers*, **C-23** (1): 90–93, [doi](/source/Doi_(identifier)):[10.1109/T-C.1974.223784](https://doi.org/10.1109%2FT-C.1974.223784)

1. **[^](#cite_ref-pubRaoYip_2-0)** [Rao, K. R.](/source/K._R._Rao); Yip, P. (1990), *Discrete Cosine Transform: Algorithms, Advantages, Applications*, Boston: Academic Press, [ISBN](/source/ISBN_(identifier)) [978-0-12-580203-1](https://en.wikipedia.org/wiki/Special:BookSources/978-0-12-580203-1)

1. **[^](#cite_ref-t81_3-0)** ["T.81 – DIGITAL COMPRESSION AND CODING OF CONTINUOUS-TONE STILL IMAGES – REQUIREMENTS AND GUIDELINES"](https://www.w3.org/Graphics/JPEG/itu-t81.pdf) (PDF). CCITT. September 1992. Retrieved 12 July 2019.

1. ^ [***a***](#cite_ref-Ghanbari_4-0) [***b***](#cite_ref-Ghanbari_4-1) Ghanbari, Mohammed (2003). [*Standard Codecs: Image Compression to Advanced Video Coding*](https://books.google.com/books?id=7XuU8T3ooOAC&pg=PA1). [Institution of Engineering and Technology](/source/Institution_of_Engineering_and_Technology). pp. 1–2. [ISBN](/source/ISBN_(identifier)) [9780852967102](https://en.wikipedia.org/wiki/Special:BookSources/9780852967102).

1. ^ [***a***](#cite_ref-history_5-0) [***b***](#cite_ref-history_5-1) [***c***](#cite_ref-history_5-2) [***d***](#cite_ref-history_5-3) ["The History of Video File Formats Infographic — RealPlayer"](http://www.real.com/resources/digital-video-file-formats/). 22 April 2012.

1. **[^](#cite_ref-h261-patents_6-0)** ["ITU-T Recommendation declared patent(s)"](https://www.itu.int/ITU-T/recommendations/related_ps.aspx?id_prod=1088). *ITU*. Retrieved 12 July 2019.

1. **[^](#cite_ref-mp2-patents_7-0)** ["MPEG-2 Patent List"](https://web.archive.org/web/20190529164140/https://www.mpegla.com/wp-content/uploads/m2-att1.pdf) (PDF). *[MPEG LA](/source/MPEG_LA)*. Archived from [the original](https://www.mpegla.com/wp-content/uploads/m2-att1.pdf) (PDF) on 29 May 2019. Retrieved 7 July 2019.

1. **[^](#cite_ref-mp4-patents_8-0)** ["MPEG-4 Visual - Patent List"](https://web.archive.org/web/20190706184814/https://www.mpegla.com/wp-content/uploads/m4v-att1.pdf) (PDF). *[MPEG LA](/source/MPEG_LA)*. Archived from [the original](https://www.mpegla.com/wp-content/uploads/m4v-att1.pdf) (PDF) on 6 July 2019. Retrieved 6 July 2019.

1. **[^](#cite_ref-avc-patents_9-0)** ["AVC/H.264 – Patent List"](https://web.archive.org/web/20230125102953/https://www.mpegla.com/wp-content/uploads/avc-att1.pdf) (PDF). *MPEG LA*. Archived from [the original](https://www.mpegla.com/wp-content/uploads/avc-att1.pdf) (PDF) on 25 January 2023. Retrieved 6 July 2019.

1. **[^](#cite_ref-hevc-patents_10-0)** ["HEVC Patent List"](https://web.archive.org/web/20210410171930/https://www.mpegla.com/wp-content/uploads/hevc-att1.pdf) (PDF). *[MPEG LA](/source/MPEG_LA)*. Archived from [the original](https://www.mpegla.com/wp-content/uploads/hevc-att1.pdf) (PDF) on 10 April 2021. Retrieved 6 July 2019.

1. **[^](#cite_ref-hevcadvance_11-0)** ["HEVC Advance Patent List"](https://web.archive.org/web/20200824174620/https://www.hevcadvance.com/licensors/). *[HEVC Advance](https://en.wikipedia.org/w/index.php?title=HEVC_Advance&action=edit&redlink=1)*. Archived from [the original](https://www.hevcadvance.com/licensors/) on 24 August 2020. Retrieved 6 July 2019.

1. **[^](#cite_ref-12)** ["What is the Best Video Codec for Web Streaming? (2021 Update)"](https://www.dacast.com/blog/best-video-codec/). *Dacast*. 2021-06-18. Retrieved 2022-02-11.

1. **[^](#cite_ref-13)** Hoffman, P. (June 2011). *Requirements for Internet-Draft Tracking by the IETF Community in the Datatracker*. [doi](/source/Doi_(identifier)):[10.17487/rfc6293](https://doi.org/10.17487%2Frfc6293).

1. **[^](#cite_ref-14)** Richardson, Iain E. G. (2002). *Video Codec Design*. [doi](/source/Doi_(identifier)):[10.1002/0470847832](https://doi.org/10.1002%2F0470847832). [ISBN](/source/ISBN_(identifier)) [978-0-471-48553-7](https://en.wikipedia.org/wiki/Special:BookSources/978-0-471-48553-7).[*[page needed](https://en.wikipedia.org/wiki/Wikipedia:Citing_sources)*]

## External links

- [Wyner-Ziv Coding of Video](http://ivms.stanford.edu/~dsc/wzcodingvideo) [Archived](https://web.archive.org/web/20110930024946/http://ivms.stanford.edu/~dsc/wzcodingvideo) 2011-09-30 at the [Wayback Machine](/source/Wayback_Machine) describes another algorithm for video compression that performs close to the [Slepian–Wolf bound](/source/Slepian%E2%80%93Wolf_bound) (with links to source code).

- [AMD Media Codecs](https://web.archive.org/web/20120828085725/http://support.amd.com/us/gpudownload/windows/Pages/eyespeed_downloads.aspx)—optional download (formerly called [ATI Avivo](/source/ATI_Avivo))

v t e Multimedia compression and container formats Video compression ISO, IEC, MPEG DV MJPEG Motion JPEG 2000 MPEG-1 MPEG-2 Part 2 MPEG-4 Part 2 / ASP Part 10 / AVC Part 33 / IVC MPEG-H Part 2 / HEVC MPEG-I Part 3 / VVC MPEG-5 Part 1 / EVC Part 2 / LCEVC ITU-T, VCEG H.120 H.261 H.262 H.263 H.264 / AVC H.265 / HEVC H.266 / VVC H.267 / Enhanced Compression Model SMPTE VC-1 VC-2 VC-3 VC-5 VC-6 TrueMotion and AOMedia TrueMotion S VP3 VP6 VP7 VP8 VP9 AV1 AV2 Chinese Standard AVS1 P2/AVS+ (GB/T 20090.2/16) AVS2 P2 (GB/T 33475.2,GY/T 299.1) HDR Vivid (GY/T 358) AVS3 P2 (GY/T 368) Others Apple Video AVS Bink Cinepak Daala DVI FFV1 Huffyuv Indeo Lagarith Microsoft Video 1 MSU Lossless OMS Video Pixlet ProRes 422 4444 QuickTime Animation Graphics RealVideo RTVideo SheerVideo Smacker Sorenson Video/Spark Theora Thor Ut WMV XEB YULS Audio compression ISO, IEC, MPEG MPEG-1 Layer II Multichannel MPEG-1 Layer I MPEG-1 Layer III (MP3) AAC HE-AAC AAC-LD MPEG Surround MPEG-4 ALS MPEG-4 SLS MPEG-4 DST MPEG-4 HVXC MPEG-4 CELP MPEG-D USAC MPEG-H 3D Audio ITU-T G.711 A-law µ-law G.718 G.719 G.722 G.722.1 G.722.2 G.723 G.723.1 G.726 G.728 G.729 G.729.1 IETF Opus iLBC Speex Vorbis FLAC 3GPP AMR AMR-WB AMR-WB+ EVRC EVRC-B EVS GSM-HR GSM-FR GSM-EFR ETSI AC-3 AC-4 DTS Bluetooth SIG SBC LC3 Chinese Standard AVS1 P10 (GB/T 20090.10) AVS2 P3 (GB/T 33475.3) Audio Vivid (GY/T 363) DRA (GB/T 22726) ExAC (SJ/T 11299.4) Others ACELP ALAC Asao ATRAC CELT Codec 2 iSAC Lyra MELP Monkey's Audio MT9 Musepack OptimFROG OSQ QCELP RCELP RealAudio SD2 SHN SILK Siren SMV SVOPC TTA True Audio TwinVQ VMR-WB VSELP WavPack WMA MQA aptX aptX HD aptX Low Latency aptX Adaptive LDAC LHDC LLAC TrueHD Image compression IEC, ISO, IETF, W3C, ITU-T, JPEG CCITT Group 4 GIF HEIC / HEIF HEVC JBIG JBIG2 JPEG JPEG 2000 JPEG-LS JPEG XL JPEG XR JPEG XS JPEG XT PNG APNG TIFF TIFF/EP TIFF/IT Others AV1 AVIF BPG DjVu EXR FLIF ICER MNG PGF QOI QTVR WBMP WebP Containers ISO, IEC MPEG-ES MPEG-PES MPEG-PS MPEG-TS ISO/IEC base media file format MPEG-4 Part 14 (MP4) Motion JPEG 2000 MPEG-21 Part 9 MPEG media transport ITU-T H.222.0 T.802 IETF RTP Ogg Matroska SMPTE GXF MXF Others 3GP and 3G2 AMV ASF AIFF AVI AU BPG Bink Smacker BMP DivX Media Format EVO Flash Video HEIF IFF M2TS Matroska WebM QuickTime File Format RatDVD RealMedia RIFF WAV MOD and TOD VOB, IFO and BUP Collaborations NETVC MPEG LA Alliance for Open Media Methods Entropy Arithmetic Huffman Modified LPC ACELP CELP LSP WLPC Lossless Lossy LZ DEFLATE LZW PCM A-law µ-law ADPCM DPCM Transforms DCT FFT MDCT Wavelet Daubechies DWT Lists Comparison of audio coding formats Comparison of video codecs List of codecs See Compression methods for techniques and Compression software for codecs

v t e Data compression methods Lossless type Entropy Adaptive coding Arithmetic Asymmetric numeral systems Golomb Huffman Adaptive Canonical Modified Range Shannon Shannon–Fano Shannon–Fano–Elias Tunstall Unary Universal Exp-Golomb Fibonacci Gamma Levenshtein Dictionary Byte-pair encoding Lempel–Ziv 842 LZ4 LZJB LZO LZRW LZSS LZW LZWL Snappy Other BWT CTW CM Delta Incremental DMC DPCM Grammar Re-Pair Sequitur LDCT MTF PAQ PPM RLE Hybrid LZ77 + Huffman Deflate LZX LZS LZ77 + ANS LZFSE LZ77 + Huffman + ANS Zstandard LZ77 + Huffman + context Brotli LZSS + Huffman LHA/LZH LZ77 + Range LZMA LZHAM RLE + BWT + MTF + Huffman bzip2 Lossy type Transform Discrete cosine transform DCT MDCT DST FFT Wavelet Daubechies DWT SPIHT Predictive DPCM ADPCM LPC ACELP CELP LAR LSP WLPC Motion Compensation Estimation Vector Psychoacoustic Audio Concepts Bit rate ABR CBR VBR Companding Convolution Dynamic range Latency Nyquist–Shannon theorem Sampling Silence compression Sound quality Speech coding Sub-band coding Codec parts A-law μ-law DPCM ADPCM DM FT FFT LPC ACELP CELP LAR LSP WLPC MDCT Psychoacoustic model Image Concepts Chroma subsampling Coding tree unit Color space Compression artifact Image resolution Macroblock Pixel PSNR Quantization Standard test image Texture compression Methods Chain code DCT Deflate Fractal KLT LP RLE Wavelet Daubechies DWT EZW SPIHT Video Concepts Bit rate ABR CBR VBR Display resolution Frame Frame rate Frame types Interlace Video characteristics Video quality Codec parts DCT DPCM Deblocking filter Lapped transform Motion Compensation Estimation Vector Wavelet Daubechies DWT Theory Compressed data structures Compressed suffix array FM-index Entropy Information theory Timeline Kolmogorov complexity Prefix code Quantization Rate–distortion Redundancy Symmetry Smallest grammar problem Community Hutter Prize People Mark Adler David A. Huffman Phil Katz

Authority control databases: National Poland

---
Adapted from the Wikipedia article [Video codec](https://en.wikipedia.org/wiki/Video_codec) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Video_codec?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.