High Efficiency Video Coding: Difference between revisions - Wikipedia

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{{Infobox technology standard

| title = HEVC / H.265 / MPEG-H Part 2

| long_name = High ~~efficiency~~Efficiency ~~video~~Video ~~coding~~Coding

| image =

| caption =

| status = In force

| ~~first_published~~ year_started = {{Start date|2013|06|07|df=y}}

| ~~version_date~~ first_published = {{Start date|~~2021~~2013|0807|2207}}▼

| version = 89.0

▲| version_date = {{Start date|2021|08|22}}

| version_date = {{Start date|2023|09|13}}

| organization = [[ITU-T]], [[ISO]], [[International Electrotechnical Commission|IEC]]

~~| committee = [[ITU-T Study Group 16|SG16]] (Secretary: [[Simao Campos]]) ([[VCEG]]), [[MPEG]]~~

| ~~base_standards~~committee = [[ITU-T Study =Group ~~[[H.261~~16|SG16]], (Secretary: [[~~H.262]],~~Simao ~~[[H.263~~Campos]],) ([[~~H.264~~VCEG]]), [[MPEG-1]]

| ~~related_standards~~base_standards = [[H.~~266~~261]], [[~~Essential~~H.262]], ~~Video~~[[H.263]], ~~Coding|MPEG~~[[ISO/IEC 14496-52]], [[H.264]]

| related_standards = [[H.266]], [[Essential Video Coding|MPEG-5]], [[MPEG-H]]

| abbreviation =

| domain = [[Video compression]]

| license = [[MPEG LA]]<ref>{{cite tech report |publisher=Library of Congress |location=Washington, D.C. |series=Sustainability of Digital Formats |type=Preliminary draft |title=High Efficiency Video Coding (HEVC) Family, H.265, MPEG-H Part 2 |date=19 November 2020 |url=https://www.loc.gov/preservation/digital/formats/fdd/fdd000530.shtml |access-date=1 December 2021}}</ref>

| website = {{URL|https://www.itu.int/rec/T-REC-H.265}}

}}

'''High Efficiency Video Coding''' ('''HEVC'''), also known as '''H.265''' and '''MPEG-H Part 2''', is a [[video coding format|video compression standard]] designed as part of the [[MPEG-H]] project as a successor to the widely used [[Advanced Video Coding]] (AVC, H.264, or [[MPEG-4]] Part 10). In comparison to AVC, HEVC offers from 25% to 50% better [[data compression]] at the same level of [[video quality]], or substantially improved video quality at the same [[bit rate]]. It supports resolutions up to 8192×4320, including [[Ultra-high-definition television|8K UHD]], and unlike the primarily 8-bit AVC, HEVC's higher fidelity Main 10 profile has been incorporated into nearly all supporting hardware.

While AVC uses the integer [[discrete cosine transform]] (DCT) with 4×4 and 8×8 block sizes, HEVC uses both integer DCT and [[discrete sine transform]] (DST) with varied block sizes between 4×4 and 32×32. The [[High Efficiency Image File Format|High Efficiency Image Format]] (HEIF) is based on HEVC.<ref name="apple">{{cite web |last1=Thomson |first1=Gavin |last2=Shah |first2=Athar |title=Introducing HEIF and HEVC |url=https://devstreaming-cdn.apple.com/videos/wwdc/2017/503i6plfvfi7o3222/503/503_introducing_heif_and_hevc.pdf |publisher=[[Apple Inc.]] |year=2017 |access-date=5 August 2019}}</ref>

== Concept ==

In most ways, HEVC is an extension of the concepts in H.264/MPEG-4 AVC. Both work by comparing different parts of a frame of video to find areas that are redundant, both within a single frame and between consecutive frames. These redundant areas are then replaced with a short description instead of the original pixels. The primary changes for HEVC include the expansion of the pattern comparison and difference-coding areas from 16×16 pixel to sizes up to 64×64, improved [[quadtree|variable-block-size segmentation]], improved "intra" prediction within the same picture, improved [[motion vector]] prediction and motion region merging, improved [[motion compensation]] filtering, and an additional filtering step called sample-adaptive offset filtering. Effective use of these improvements requires much more signal processing capability for compressing the video, but has less impact on the amount of computation needed for decompression.

HEVC was standardized by the Joint Collaborative Team on Video Coding (JCT-VC), a collaboration between the [[International Organization for Standardization|ISO]]/[[International Electrotechnical Commission|IEC]] [[Moving Picture Experts Group|MPEG]] and [[ITU-T Study Group 16]] [[Video Coding Experts Group|VCEG]]. The ISO/IEC group refers to it as MPEG-H Part 2 and the ITU-T as H.265. The first version of the HEVC standard was ratified in January 2013 and published in June 2013. The second version, with multiview extensions (MV-HEVC), range extensions (RExt), and scalability extensions (SHVC), was completed and approved in 2014 and published in early 2015. Extensions for [[3D video]] (3D-HEVC) were completed in early 2015, and extensions for screen content coding (SCC) were completed in early 2016 and published in early 2017, covering video containing rendered graphics, text, or animation as well as (or instead of) camera-captured video scenes. In October 2017, the standard was recognized by a [[Primetime Emmy Engineering Award]]

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|title=ITU, ISO and IEC receive another Primetime Emmy for video compression

|website=[[International Telecommunication Union]]

|date=October 26, 2017
|access-date=November 13, 2017

|archive-date=April 19, 2019

|archive-url=https://web.archive.org/web/20190419174859/https://news.itu.int/itu-iso-iec-receive-another-primetime-emmy-for-video-compression-video/

|url-status=dead

}}</ref><ref name=Aachen>{{cite web

|url=http://www.rwth-aachen.de/cms/root/Die-RWTH/Aktuell/Pressemitteilungen/November-2017/~ovhi/Engineering-Emmy-Award-fuer-HEVC-Standar/?lidx=1

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HEVC contains technologies covered by [[patent]]s owned by the organizations that participated in the JCT-VC. Implementing a device or software application that uses HEVC may require a license from HEVC patent holders. The ISO/IEC and ITU require companies that belong to their organizations to offer their patents on [[reasonable and non-discriminatory licensing]] (RAND) terms. Patent licenses can be obtained directly from each patent holder, or through patent licensing bodies, such as [[MPEG LA]], [[Access Advance]], and Velos Media.

The combined licensing fees currently offered by all of the patent licensing bodies are higher than for AVC. The licensing fees are one of the main reasons HEVC adoption has been low on the web and is why some of the largest tech companies ([[Amazon (company)|Amazon]], [[~~Advanced Micro Devices|~~AMD]], [[Apple Inc.|Apple]], [[Arm ~~(company)~~Holdings|ARM]], [[Cisco]], [[Google]], [[Intel]], [[Microsoft]], [[Mozilla]], [[Netflix]], [[Nvidia]], and more) have joined the [[Alliance for Open Media]],<ref>{{cite web |url=https://www.streamingmedia.com/Articles/Editorial/Featured-Articles/A-Progress-Report-The-Alliance-for-Open-Media-and-the-AV1-Codec-110383.aspx |title=A Progress Report: The Alliance for Open Media and the AV1 Codec |website=Streaming Media Magazine |last=Ozer |first=Jan |date=April 12, 2016 }}</ref> which finalized royalty-free alternative video coding format [[AV1]] on March 28, 2018.<ref name="AV1 Finalized"/>

==History==

The HEVC format was jointly developed by more than a dozen organisations across the world. The majority of active patent contributions towards the development of the HEVC format came from five organizations: [[Samsung Electronics]] (4,249 patents), [[General Electric]] (1,127 patents),<ref name="hevcadvance"/> M&K Holdings (907 patents), [[Nippon Telegraph and Telephone|NTT]] ({{#expr:16+862}} patents), and [[JVC Kenwood]] (628 patents).<ref name="mpegla"/> Other patent holders include [[Fujitsu]], [[Apple Inc.|Apple]], [[Canon Inc.|Canon]], [[Columbia University]], [[KAIST]], [[Kwangwoon University]], [[Massachusetts Institute of Technology|MIT]], [[Sungkyunkwan University]], [[Funai]], [[Hikvision]], [[Korean Broadcasting System|KBS]], [[KT Corporation|KT]] and [[NEC]].<ref>{{cite web|title=Licensors Included in the HEVC Patent Portfolio License|url=https://www.mpegla.com/programs/hevc/licensors/ |website=[[MPEG LA]] |access-date=18 June 2019|archive-date=April 13, 2021|archive-url=https://web.archive.org/web/20210413125606/https://www.mpegla.com/programs/hevc/licensors/|url-status=dead}}</ref>

===Previous work===

In 2004, the ITU-T [[Video Coding Experts Group]] (VCEG) began a major study of technology advances that could enable the creation of a new video compression standard (or substantial compression-oriented enhancements of the [[H.264/MPEG-4 AVC]] standard).{{sfn|Sullivan|2012}} In October 2004, various techniques for potential enhancement of the H.264/MPEG-4 AVC standard were surveyed. In January 2005, at the next meeting of VCEG, VCEG began designating certain topics as "Key Technical Areas" (KTA) for further investigation. A software codebase called the KTA codebase was established for evaluating such proposals.<ref>T. Wedi and T. K. Tan, [http://wftp3.itu.int/av-arch/video-site/0510_Nic/VCEG-AA06.doc ''AHG report – Coding Efficiency Improvements''], VCEG document VCEG-AA06, 17–18 October 2005.</ref> The KTA software was based on the Joint Model (JM) reference software that was developed by the MPEG & VCEG Joint Video Team for H.264/MPEG-4 AVC. Additional proposed technologies were integrated into the KTA software and tested in experiment evaluations over the next four years.<ref>[http://wftp3.itu.int/av-arch/video-site/0701_Mar/VCEG-AE01r1.doc Meeting Report for 31st VCEG Meeting] VCEG document VCEG-AE01r1, Marrakech, MA, 15–16 January 2007</ref>{{sfn|Sullivan|2012}}<ref name=JCTVCOfficialWebsite>{{cite web|author=ITU TSB|url=http://www.itu.int/ITU-T/studygroups/com16/jct-vc/ |title=Joint Collaborative Team on Video Coding |publisher=[[ITU-T]] |date=2010-05-21 |access-date=2012-08-24}}</ref><ref name=HEVCNovember2013ISOIEC>{{cite news |title=ISO/IEC 23008-2:2013 |publisher=[[International Organization for Standardization]] |url=http://www.iso.org/iso/catalogue_detail.htm?csnumber=35424 |date=2013-11-25 |access-date=2013-11-29}}</ref>

Two approaches for standardizing enhanced compression technology were considered: either creating a new standard or creating extensions of H.264/MPEG-4 AVC. The project had tentative names ''H.265'' and ''H.NGVC'' (Next-generation Video Coding), and was a major part of the work of VCEG until ~~its~~it ~~evolution~~evolved into the HEVC joint project with MPEG in 2010.<ref name=FirstJCTVCMeetingDresden>{{cite web|url=http://www.h265.net/2010/06/the-first-jct-vc-meeting-dresden-de.html |title=The First JCT-VC Meeting, Dresden, DE |author=Jie Dong |publisher=H265.net |date=2010-06-19 |access-date=2012-11-25}}</ref><ref name=StatusH265July2008>{{cite web|url=http://www.h265.net/2008/07/current-status-of-h265.html |title=Current Status of H.265 (as at July 2008) |author=Jie Dong |publisher=H265.net |date=2008-07-01 |access-date=2012-11-25}}</ref><ref name=NGVCRequirements2009>{{cite web|url=http://www.h265.net/2009/04/the-preliminary-requirements-for-ngvc.html |title=The Preliminary Requirements for NGVC |author=Yu Liu |publisher=H265.net |date=2009-04-15 |access-date=2012-11-25}}</ref>

The preliminary requirements for NGVC were the capability to have a [[bit rate]] reduction of 50% at the same subjective image quality compared with the H.264/MPEG-4 AVC High profile, and computational complexity ranging from 1/2 to 3 times that of the High profile.<ref name=NGVCRequirements2009/> NGVC would be able to provide 25% bit rate reduction along with 50% reduction in complexity at the same perceived video quality as the High profile, or to provide greater bit rate reduction with somewhat higher complexity.<ref name=NGVCRequirements2009/><ref name="epvcreqs"/>

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| {{0}}628

| [[Dolby|Dolby Laboratories]]

| {{0}}624

| <ref name="hevcadvance" />

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* Version 6: (June 29, 2019) Sixth approved version of the HEVC/H.265 standard which adds additional SEI messages that include SEI manifest and SEI prefix messages, and corrections to various minor defects in the prior content of the Specification.<ref name=H265DeclaredPatents/><ref name=H265V6>{{cite news |title=ITU-T H.265 (V6) (06/2019) |publisher=ITU |url=https://www.itu.int/ITU-T/recommendations/rec.aspx?rec=13904&lang=en |date=2019-06-29 |access-date=2021-08-05}}</ref>

* Version 7: (November 29, 2019) Seventh approved version of the HEVC/H.265 standard which adds additional SEI messages for fisheye video information and annotated regions, and also includes corrections to various minor defects in the prior content of the Specification.<ref name=H265DeclaredPatents/><ref name=H265V7>{{cite news |title=ITU-T H.265 (V7) (11/2019) |publisher=ITU |url=https://www.itu.int/ITU-T/recommendations/rec.aspx?rec=14107&lang=en |date=2019-11-29 |access-date=2021-08-05}}</ref>

* Version 8: Ason of22 August, 2021 Version 8 iswas ~~in "Additional Review" status while Version 7 is in force~~approved.<ref>{{Cite ~~name~~news |title=~~H265DeclaredPatents~~itu |url=https://www.itu.int/ITU-T/recommendations/rec.aspx?rec=14660}}</ref>

* Version 9: on 13 September, 2023 Version 9 was approved. <ref>{{Cite news |title=itu |url=https://www.itu.int/ITU-T/recommendations/rec.aspx?rec=15647}}</ref>

* Version 10: on 29 July, 2024 Version 10 was approved, it is the latest version.<ref>{{Cite web |title=itu |url=https://www.itu.int/ITU-T/recommendations/rec.aspx?rec=15936&lang=en}}</ref>

==Implementations and products==

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On August 8, 2013, [[Nippon Telegraph and Telephone]] announced the release of their HEVC-1000 SDK software encoder which supports the Main 10 profile, resolutions up to 7680×4320, and frame rates up to 120 fps.<ref name=NTTAugust2013NTT>{{cite news |title=NTT Develops World's Highest-level Compression Software Encoding Engine Fully Compliant with Next-gen "HEVC/H.265" Video Coding Standard, Rolls Out "HEVC-1000 SDK" Codec Development Kit |publisher=[[Nippon Telegraph and Telephone]] |url=http://www.ntt.co.jp/news2013/1308e/130808a.html |date=2013-08-08 |access-date=2013-08-17 |archive-date=February 25, 2021 |archive-url=https://web.archive.org/web/20210225021320/https://www.ntt.co.jp/news2013/1308e/130808a.html |url-status=dead }}</ref>

On November 14, 2013, [[DivX, ~~Inc.~~LLC|DivX]] developers released information on HEVC decoding performance using an Intel i7 CPU at 3.5 GHz with 4 cores and 8 threads.<ref name=DecodingHEVCNovember2013Divx>{{cite news |title=DivX HEVC Encoder and Decoder Performance |publisher=DivX |url=http://labs.divx.com/node/127935 |date=2013-11-14 |access-date=2013-11-14|archive-url=https://web.archive.org/web/20131210144143/http://labs.divx.com/node/127935 |archive-date=2013-12-10 }}</ref> The DivX 10.1 Beta decoder was capable of 210.9 fps at 720p, 101.5 fps at 1080p, and 29.6 fps at 4K.<ref name=DecodingHEVCNovember2013Divx/>

On December 18, 2013, [[ViXS Systems]] announced shipments of their XCode (not to be confused with [[Xcode|Apple's Xcode]] [[Integrated development environment|IDE]] for MacOS) 6400 SoC which was the first SoC to support the Main 10 profile of HEVC.<ref name=VixsHEVCDecember2013Shipments>{{cite news |title=ViXS Begins Shipments of Industry's First SoC to Support Ultra HD 4K and 10-bit HEVC |publisher=Yahoo Finance |url=https://finance.yahoo.com/news/vixs-begins-shipments-industrys-first-220000729.html |date=2013-12-18 |access-date=2014-01-07}}</ref>

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On August 13, 2014, [[Ittiam Systems]] announced availability of its third generation H.265/HEVC codec with 4:2:2 12-bit support.<ref name=IttiamHEVCAugust2014>{{cite news |title=Ittiam Systems announces availability of its third generation H.265/HEVC codec with 422 12-bit support |publisher=[[Ittiam Systems]] |url=http://www.ittiam.com/News/en/press-releases/2014/158-Ittiam-Systems-announces-availability-of-its-third-generation-H265HEVC-codec-with-422-12-bit-support.aspx |date=August 8, 2014 |access-date=November 1, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20141101215501/http://www.ittiam.com/News/en/press-releases/2014/158-Ittiam-Systems-announces-availability-of-its-third-generation-H265HEVC-codec-with-422-12-bit-support.aspx |archive-date=November 1, 2014 |df=mdy-all }}</ref>

On September 5, 2014, the [[Blu-ray Disc Association]] announced that the 4K [[Blu-ray Disc]] specification would support HEVC-encoded 4K video at 60 fps, the [[Rec. 2020]] color space, [[High-dynamic-range imaging|high dynamic range]] ([[Perceptual quantizer|PQ]] and [[Hybrid log–gamma|HLG]]), and 10-bit [[color depth]].<ref name="CNET4KBlu-raySeptember2014">{{cite news |title=4K Blu-ray discs arriving in 2015 to fight streaming media |publisher=[[CNET]] |url=http://www.cnet.com/news/4k-blu-ray-discs-arriving-in-2015-to-fight-streaming-media/ |date=September 5, 2014 |access-date=September 6, 2014}}</ref><ref name="HMM4KBlu-raySeptember2014">{{cite news |title=BDA Updates Blu-ray 4K Timeline |publisher=[[Home Media Magazine]] |url=http://www.homemediamagazine.com/high-def/bda-updates-blu-ray-4k-timeline-34108 |date=September 5, 2014 |access-date=September 6, 2014 |archive-url=https://web.archive.org/web/20140906223337/http://www.homemediamagazine.com/high-def/bda-updates-blu-ray-4k-timeline-34108 |archive-date=September 6, 2014 |url-status=dead |df=mdy-all }}</ref> 4K Blu-ray Discs have a data rate of at least 50  Mbit/s and disc capacity up to 100  GB.<ref name="CNET4KBlu-raySeptember2014"/><ref name="HMM4KBlu-raySeptember2014"/> 4K Blu-ray Discs and players became available for purchase in 2015 or 2016.<ref name="CNET4KBlu-raySeptember2014"/><ref name="HMM4KBlu-raySeptember2014"/>

On September 9, 2014, [[Apple Inc.|Apple]] announced the [[iPhone 6]] and [[iPhone 6 Plus]] which support HEVC/H.265 for FaceTime over cellular.<ref name="AppleIPhone6HEVCSeptember2014">{{cite news |title=Apple's iPhone 6, iPhone 6 Plus use H.265 codec for FaceTime over cellular |publisher=[[AppleInsider]] |author=Mikey Campbell |url=http://appleinsider.com/articles/14/09/12/apples-iphone-6-iphone-6-plus-use-h265-codec-for-facetime-over-cellular |date=September 12, 2014 |access-date=September 13, 2014}}</ref>

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On September 7, 2016 [[Apple Inc.|Apple]] announced the [[Apple A10]] chip, first used in the [[iPhone 7]], which included a hardware HEVC encoder supporting Main 8 and 10. This feature would not be unlocked until the release of [[iOS 11]] in 2017.<ref name="flatpanelshd.com"/>

On October 25, 2016, [[Nvidia]] released the GeForce GTX 1050Ti (GP107) and GeForce GTX 1050 (GP107), which includes full fixed function HEVC Main10/Main12 hardware ~~decoder~~encoder.

===2017===

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===2022===

On October 25, 2022, [[Google Chrome|Chrome]] released version 107, which starts supporting HEVC hardware decoding for all platforms "out of the box", if the hardware is supported.

===Browser support===

HEVC is implemented in these web browsers:

* Android browser (since version 5 from November 2014)<ref name="androidformats">{{cite web|title=Android Core media format and codec support.|url=http://developer.android.com/guide/appendix/media-formats.html|access-date=18 December 2015}}</ref>

* [[Safari (web browser)|Safari]] (since version 11 from September 2017)<ref>{{cite web|url=https://bitmovin.com/wwdc17-hevc-hls-apple-just-announced-feature-support-box/|title=WWDC17 – HEVC with HLS – Apple just announced a feature that we support out of the box |author=Martin Smole |date=6 June 2017 |website=Bitmovin }}</ref>

* [[Microsoft Edge|Edge]] (since version 77 from July 2017, supported on Windows 10 1709+ for devices with supported hardware when HEVC video extensions is installed, since version 107 from October 2022, supported on macOS 11+, Android 5.0+ ~~for all devices~~)<ref>{{cite web|url=https://techcommunity.microsoft.com/t5/discussions/updated-dev-channel-build-77-0-211-3-is-live/m-p/745801#M6548|title=*Updated* Dev channel build 77.0.211.3 is live|date=9 July 2017|website=techcommunity.microsoft.com }}</ref>

* [[Google Chrome|Chrome]] (since version 107 from October 2022, supported on macOS 11+, Android 5.0+ ~~for all devices~~, supported on Windows 87+, ChromeOS, and Linux for devices with supported hardware)<ref>{{cite web|url=https://chromestatus.com/feature/5186511939567616|title=Enable HEVC hardware decoding|date=21 October 2022|website=ChromeStatus }}</ref>

* [[Opera (web browser)|Opera]] (since version 94 from December 2022, supported on the same platforms as Chrome)

In June 2023, an estimated 88.31% of browsers in use on desktop and mobile systems were able to play HEVC videos in HTML5 webpages, based on data from Can I Use.<ref>{{Cite web |title="hevc" {{!}} Can I use... Support tables for HTML5, CSS3, etc |url=https://caniuse.com/?search=hevc |website=Can I use}}</ref>

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! scope="row" | Notes

| - Support introduced in Windows 10 version 1507. <pbr> - Built-in support was removed in Windows 10 version 1709 due to licensing costs. The [https://www.microsoft.com/en-us/p/hevc-video-extensions/9nmzlz57r3t7 HEVC Video Extensions] add-on can be purchased from the Microsoft Store to enable HEVC playback on the default media player app [[Microsoft Movies & TV]].<ref name="microsoft-charging-hevc-extensions" /><pbr> - Since Windows 11 version 22H2, the HEVC Video Extensions is built-in by default installation.<ref>{{cite web | url=https://learn.microsoft.com/en-us/windows/whats-new/whats-new-windows-11-version-22h2 | title=What's new in Windows 11, version 22H2 for IT pros - What's new in Windows | date=August 11, 2023 }}</ref>

| Support introduced in macOS 10.13 High Sierra<ref>{{Cite web|url=https://blog.addpipe.com/heif-hevc-ios-11-quick-overview/|title=HEIF and HEVC in iOS 11: Quick Overview|date=September 22, 2017|website=Deconstruct}}</ref>

| - Support introduced in Android 5.0<ref name="androidformats" /> - Some Android devices may only support 8-bit (Main profile) hardware decoding, but not 10-bit (Main 10 profile).

| - Support introduced in iOS 11.0 - Playback with software decoding is possible on iPhone 5s (at 720p/240 fps, 1080p/60 fps) and iPhone 6 (at 1080p/240 fps). - Hardware decoding is available on [[Apple A9]] (iPhone 6s), while hardware decoding & encoding is available on [[Apple A10]] (iPhone 7).<ref>{{Cite web|url=https://fstoppers.com/gear/which-apple-devices-will-be-able-play-hevc-videos-198152|title=Which Apple Devices Will Be Able to Play HEVC Videos?|first=Stephen|last=Kampff|date=October 2, 2017|website=Fstoppers}}</ref>

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[[File:HEVC Block Diagram.png|thumb|Block diagram of HEVC]]

~~The design of most~~Most video coding standards isare designed primarily ~~aimed at~~to ~~having~~achieve the highest coding efficiency. Coding efficiency is the ability to encode video at the lowest possible bit rate while maintaining a certain level of video quality. There are two standard ways to measure the coding efficiency of a video coding standard, which are to use an objective metric, such as [[peak signal-to-noise ratio]] (PSNR), or to use subjective assessment of video quality. Subjective assessment of video quality is considered to be the most important way to measure a video coding standard since humans perceive video quality subjectively.{{sfn|Ohm|2012}}

HEVC benefits from the use of larger [[coding tree unit]] (CTU) sizes. This has been shown in PSNR tests with a HM-8.0 HEVC encoder where it was forced to use progressively smaller CTU sizes. For all test sequences, when compared with a 64×64 CTU size, it was shown that the HEVC bit rate increased by 2.2% when forced to use a 32×32 CTU size, and increased by 11.0% when forced to use a 16×16 CTU size. In the Class A test sequences, where the resolution of the video was 2560×1600, when compared with a 64×64 CTU size, it was shown that the HEVC bit rate increased by 5.7% when forced to use a 32×32 CTU size, and increased by 28.2% when forced to use a 16×16 CTU size. The tests showed that large CTU sizes increase coding efficiency while also reducing decoding time.{{sfn|Ohm|2012}}

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HEVC MP has also been compared with H.264/MPEG-4 AVC HP for subjective video quality. The video encoding was done for entertainment applications and four different bitrates were made for nine video test sequences with a HM-5.0 HEVC encoder being used. The subjective assessment was done at an earlier date than the PSNR comparison and so it used an earlier version of the HEVC encoder that had slightly lower performance. The bit rate reductions were determined based on subjective assessment using [[mean opinion score]] values. The overall subjective bitrate reduction for HEVC MP compared with H.264/MPEG-4 AVC HP was 49.3%.{{sfn|Ohm|2012}}

[[École Polytechnique Fédérale de Lausanne]] (EPFL) did a study to evaluate the subjective video quality of HEVC at resolutions higher than HDTV. The study was done with three videos with resolutions of 3840×1744 at 24 fps, 3840×2048 at 30 fps, and 3840×2160 at 30 fps. The five second video sequences showed people on a street, traffic, and a scene from the [[Open-source film|open source]] ~~[[computer animation|~~computer animated]] movie ''[[Sintel]]''. The video sequences were encoded at five different bitrates using the HM-6.1.1 HEVC encoder and the JM-18.3 H.264/MPEG-4 AVC encoder. The subjective bit rate reductions were determined based on subjective assessment using mean opinion score values. The study compared HEVC MP with H.264/MPEG-4 AVC HP and showed that, for HEVC MP, the average bitrate reduction based on PSNR was 44.4%, while the average bitrate reduction based on subjective video quality was 66.5%.{{sfn|Hanhart|2012}}{{sfn|Slides|2012}}<ref name=SubjectiveQualityEvaluationHEVCwebsite>{{cite news |title=Subjective quality evaluation of the upcoming HEVC video compression standard |publisher=École Polytechnique Fédérale de Lausanne (EPFL) |url=http://infoscience.epfl.ch/record/180494 |access-date=2012-11-08}}</ref><ref name=CnetHEVCVideoCompression4K>{{cite news |title=HEVC video compression could be the next step for 4K |author=Nic Healey |publisher=cnet |url=http://www.cnet.com.au/hevc-video-compression-could-be-the-next-step-for-4k-339341320.htm |date=2012-08-29 |access-date=2012-11-08}}</ref>

In a HEVC performance comparison released in April 2013, the HEVC MP and Main 10 Profile (M10P) were compared with H.264/MPEG-4 AVC HP and High 10 Profile (H10P) using 3840×2160 video sequences. The video sequences were encoded using the HM-10.0 HEVC encoder and the JM-18.4 H.264/MPEG-4 AVC encoder. The average bit rate reduction based on PSNR was 45% for [[inter frame]] video.

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HEVC was designed with the idea that [[progressive scan]] video would be used and no coding tools were added specifically for [[interlaced video]].{{sfn|Sullivan|2012}} Interlace specific coding tools, such as MBAFF and PAFF, are not supported in HEVC.<ref name=AtemeOverviewHEVCNovember2012>{{cite news |title=HEVC: High-Efficiency Video Coding Next generation video compression |author=Jérôme VIERON |publisher=[[Ateme]] |url=http://www.nabanet.com/wbuarea/library/docs/isog/presentations/2012B/2.4%20Vieron%20ATEME.pdf |date=2012-11-27 |access-date=2013-05-21 |archive-url=https://web.archive.org/web/20130810140359/http://www.nabanet.com/wbuarea/library/docs/isog/presentations/2012B/2.4%20Vieron%20ATEME.pdf |archive-date=2013-08-10 |url-status=dead }}</ref> HEVC instead sends [[metadata]] that tells how the interlaced video was sent.{{sfn|Sullivan|2012}} Interlaced video may be sent either by coding each frame as a separate picture or by coding each field as a separate picture.{{sfn|Sullivan|2012}} For interlaced video HEVC can change between frame coding and field coding using Sequence Adaptive Frame Field (SAFF), which allows the coding mode to be changed for each video sequence.<ref name=AtemeHEVCIntroductionSeptember2013>{{cite news |title=An Introduction to Ultra HDTV and HEVC |author=Gregory Cox |publisher=[[Ateme]] |url=http://ateme.com/IMG/pdf/2013_an_introduction_to_uhdtv_hevc.pdf |date=2013-09-11 |access-date=2014-12-03}}</ref> This allows interlaced video to be sent with HEVC without needing special interlaced decoding processes to be added to HEVC decoders.{{sfn|Sullivan|2012}}

;====Color spaces====

The HEVC standard supports [[color space]]s such as generic film, [[NTSC]], [[PAL]], [[Rec. 601]], [[Rec. 709]], [[Rec. 2020]], [[Rec. 2100]], SMPTE 170M, SMPTE 240M, [[sRGB]], [[sYCC]], [[xvYCC]], [[CIE 1931 color space|XYZ]], and externally specified color spaces.{{sfn|ITU|2015}} HEVC supports color encoding representations such as [[RGB]], [[YCbCr]], and [[YCoCg]].{{sfn|ITU|2015}}

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====Other coding tools====

;=====Entropy coding=====

HEVC uses a [[context-adaptive binary arithmetic coding]] (CABAC) algorithm that is fundamentally similar to CABAC in H.264/MPEG-4 AVC.{{sfn|Sullivan|2012}} CABAC is the only entropy encoder method that is allowed in HEVC while there are two entropy encoder methods allowed by H.264/MPEG-4 AVC.{{sfn|Sullivan|2012}} CABAC and the entropy coding of transform coefficients in HEVC were designed for a higher throughput than H.264/MPEG-4 AVC,<ref name=HEVCCABACIEEE2013>{{cite journal |title=High Throughput CABAC Entropy Coding in HEVC |author=V. Sze|author-link=Vivienne Sze |author2=M. Budagavi |journal=IEEE Transactions on Circuits and Systems for Video Technology |url=https://ieeexplore.ieee.org/document/6317157 |format=PDF |date=2013-01-13 |volume=22 |issue=12 |pages=1778–1791 |access-date=2013-01-13|doi=10.1109/TCSVT.2012.2221526 |s2cid=5295846 }}</ref> while maintaining higher compression efficiency for larger transform block sizes relative to simple extensions.<ref>{{cite journal|last1=Tung|first1=Nguyen|last2=Philipp|first2=Helle|last3=Martin|first3=Winken|last4=Benjamin|first4=Bross|last5=Detlev|first5=Marpe|last6=Heiko|first6=Schwarz|last7=Thomas|first7=Wiegand|title=Transform Coding Techniques in HEVC|journal=Journal of Selected Topics in Signal Processing|date=Dec 2013|volume=7|issue=6|pages=978–989|doi=10.1109/JSTSP.2013.2278071|bibcode=2013ISTSP...7..978N|s2cid=12877203}}</ref> For instance, the number of context coded bins have been reduced by 8× and the CABAC bypass-mode has been improved in terms of its design to increase throughput.{{sfn|Sullivan|2012}}<ref name=HEVCCABACIEEE2013/><ref>{{cite news|last1=Tung|first1=Nguyen|last2=Detlev|first2=Marpe|last3=Heiko|first3=Schwarz|last4=Thomas|first4=Wiegand|title=Reduced-Complexity Entropy Coding of Transform Coefficient Levels Using Truncated Golomb-Rice Codes in Video Compression|url=http://iphome.hhi.de/wiegand/assets/pdfs/2011_09_ICIP_entropy_cod.pdf}}</ref> Another improvement with HEVC is that the dependencies between the coded data has been changed to further increase throughput.{{sfn|Sullivan|2012}}<ref name=HEVCCABACIEEE2013/> Context modeling in HEVC has also been improved so that CABAC can better select a context that increases efficiency when compared with H.264/MPEG-4 AVC.{{sfn|Sullivan|2012}}

;=====Intra prediction=====

[[File:HEVC angular intra prediction modes.png|thumb|upright=1.1|HEVC has 33 intra prediction modes]]

HEVC specifies 33 directional modes for intra prediction compared with the 8 directional modes for intra prediction specified by H.264/MPEG-4 AVC.{{sfn|Sullivan|2012}} HEVC also specifies DC intra prediction and planar prediction modes.{{sfn|Sullivan|2012}} The DC intra prediction mode generates a mean value by averaging reference samples and can be used for flat surfaces.{{sfn|Sullivan|2012}} The planar prediction mode in HEVC supports all block sizes defined in HEVC while the planar prediction mode in H.264/MPEG-4 AVC is limited to a block size of 16×16 pixels.{{sfn|Sullivan|2012}} The intra prediction modes use data from neighboring prediction blocks that have been previously decoded from within the same picture.{{sfn|Sullivan|2012}}

;=====Motion compensation=====

For the interpolation of fractional luma sample positions HEVC uses separable application of one-dimensional half-sample interpolation with an 8-tap filter or quarter-sample interpolation with a 7-tap filter while, in comparison, H.264/MPEG-4 AVC uses a two-stage process that first derives values at half-sample positions using separable one-dimensional 6-tap interpolation followed by integer rounding and then applies [[linear interpolation]] between values at nearby half-sample positions to generate values at quarter-sample positions.{{sfn|Sullivan|2012}} HEVC has improved precision due to the longer interpolation filter and the elimination of the intermediate rounding error.{{sfn|Sullivan|2012}} For 4:2:0 video, the chroma samples are interpolated with separable one-dimensional 4-tap filtering to generate eighth-sample precision, while in comparison H.264/MPEG-4 AVC uses only a 2-tap [[bilinear interpolation|bilinear filter]] (also with eighth-sample precision).{{sfn|Sullivan|2012}}

As in H.264/MPEG-4 AVC, weighted prediction in HEVC can be used either with uni-prediction (in which a single prediction value is used) or bi-prediction (in which the prediction values from two prediction blocks are combined).{{sfn|Sullivan|2012}}

;=====Motion vector prediction=====

HEVC defines a [[Sign (mathematics)|signed]] 16-bit range for both horizontal and vertical motion vectors (MVs).{{sfn|ITU|2015}}<ref name=HEVCJuly2012MeetingNotes>{{cite news |title=Meeting report of the 10th meeting of the Joint Collaborative Team on Video Coding (JCT-VC), Stockholm, SE, 11–20 July 2012 |author=Gary Sullivan |author2=Jens-Rainer Ohm |publisher=JCT-VC |url=http://phenix.it-sudparis.eu/jct/doc_end_user/current_document.php?id=6466 |date=2012-10-13 |access-date=2013-04-28}}</ref><ref name=HEVCJuly2012J0225>{{cite news |title=Restrictions to the maximum motion vector range |author=Alistair Goudie |publisher=JCT-VC |url=http://phenix.it-sudparis.eu/jct/doc_end_user/current_document.php?id=6088 |date=2012-07-02 |access-date=2012-11-26}}</ref><ref name=HEVCJuly2012J0579>{{cite news |title=BoG on miscellaneous limits |author=Keiichi Chono |author2=Minhua Zhou |publisher=JCT-VC |url=http://phenix.it-sudparis.eu/jct/doc_end_user/current_document.php?id=6459 |date=2012-07-19 |access-date=2012-11-26}}</ref> This was added to HEVC at the July 2012 HEVC meeting with the mvLX variables.{{sfn|ITU|2015}}<ref name=HEVCJuly2012MeetingNotes/><ref name=HEVCJuly2012J0225/><ref name=HEVCJuly2012J0579/> HEVC horizontal/vertical MVs have a range of −32768 to 32767 which given the [[Qpel|quarter pixel]] precision used by HEVC allows for a MV range of −8192 to 8191.75 luma samples.{{sfn|ITU|2015}}<ref name=HEVCJuly2012MeetingNotes/><ref name=HEVCJuly2012J0225/><ref name=HEVCJuly2012J0579/> This compares to H.264/MPEG-4 AVC which allows for a horizontal MV range of −2048 to 2047.75 luma samples and a vertical MV range of −512 to 511.75 luma samples.<ref name=HEVCJuly2012J0225/>

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HEVC specifies two loop filters that are applied sequentially, with the [[deblocking filter]] (DBF) applied first and the sample adaptive offset (SAO) filter applied afterwards.{{sfn|Sullivan|2012}} Both loop filters are applied in the inter-picture prediction loop, i.e. the filtered image is stored in the decoded picture buffer (DPB) as a reference for inter-picture prediction.{{sfn|Sullivan|2012}}

;=====Deblocking filter=====

The DBF is similar to the one used by H.264/MPEG-4 AVC but with a simpler design and better support for parallel processing.{{sfn|Sullivan|2012}} In HEVC the DBF only applies to a 8×8 sample grid while with H.264/MPEG-4 AVC the DBF applies to a 4×4 sample grid.{{sfn|Sullivan|2012}} DBF uses a 8×8 sample grid since it causes no noticeable degradation and significantly improves parallel processing because the DBF no longer causes cascading interactions with other operations.{{sfn|Sullivan|2012}} Another change is that HEVC only allows for three DBF strengths of 0 to 2.{{sfn|Sullivan|2012}} HEVC also requires that the DBF first apply horizontal filtering for vertical edges to the picture and only after that does it apply vertical filtering for horizontal edges to the picture.{{sfn|Sullivan|2012}} This allows for multiple parallel threads to be used for the DBF.{{sfn|Sullivan|2012}}

;=====Sample adaptive offset=====

The SAO filter is applied after the DBF and is designed to allow for better reconstruction of the original signal amplitudes by applying offsets stored in a [[lookup table]] in the bitstream.{{sfn|Sullivan|2012}}<ref name=SAOIEEE2012>{{cite news |title=Sample adaptive offset in the HEVC standard |author=Chih-Ming Fu |author2=Elena Alshina |author3=Alexander Alshin |author4=Yu-Wen Huang |author5=Ching-Yeh Chen |author6=Chia-Yang Tsai |author7=Chih-Wei Hsu |author8=Shaw-Min Lei |author9=Jeong-Hoon Park |author10=Woo-Jin Han |publisher=IEEE Transactions on Circuits and Systems for Video Technology |url=https://sites.google.com/site/chihmingfu/paper/SAO%20CSVT.pdf?attredirects=0 |format=PDF |date=2012-12-25 |access-date=2013-01-24}}</ref> Per CTB the SAO filter can be disabled or applied in one of two modes: edge offset mode or band offset mode.{{sfn|Sullivan|2012}}<ref name=SAOIEEE2012/> The edge offset mode operates by comparing the value of a sample to two of its eight neighbors using one of four directional gradient patterns.{{sfn|Sullivan|2012}}<ref name=SAOIEEE2012/> Based on a comparison with these two neighbors, the sample is classified into one of five categories: minimum, maximum, an edge with the sample having the lower value, an edge with the sample having the higher value, or monotonic.{{sfn|Sullivan|2012}}<ref name=SAOIEEE2012/> For each of the first four categories an offset is applied.{{sfn|Sullivan|2012}}<ref name=SAOIEEE2012/> The band offset mode applies an offset based on the amplitude of a single sample.{{sfn|Sullivan|2012}}<ref name=SAOIEEE2012/> A sample is categorized by its amplitude into one of 32 bands ([[histogram]] bins).{{sfn|Sullivan|2012}}<ref name=SAOIEEE2012/> Offsets are specified for four consecutive of the 32 bands, because in flat areas which are prone to banding artifacts, sample amplitudes tend to be clustered in a small range.{{sfn|Sullivan|2012}}<ref name=SAOIEEE2012/> The SAO filter was designed to increase picture quality, reduce banding artifacts, and reduce [[ringing artifacts]].{{sfn|Sullivan|2012}}<ref name=SAOIEEE2012/>

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*Persistent Rice adaptation, a general optimization of entropy coding.

*Higher precision [[H.264/MPEG-4 AVC#Features|weighted prediction]] at high bit depths.<ref name=HEVCMeetingReport15>{{cite news |title=Meeting report of the 15th meeting of the Joint Collaborative Team on Video Coding (JCT-VC), Geneva, CH, 23 Oct. – 1 Nov. 2013 |publisher=ITU-T |url=http://wftp3.itu.int/av-arch/jctvc-site/2013_10_O_Geneva/JCTVC-O_Notes_d9.doc |format=DOC |date=2013-11-03 |access-date=2013-11-09}}</ref>

*Cross-component prediction, allowing the imperfect [[YCbCr]] color decorrelation to let the luma (or G) match set the predicted chroma (or R/B) matches, which results in up to 7% gain for YCbCr 4:4:4 and up to 26% for RGB video. Particularly useful for screen coding.<ref name=HEVCMeetingReport15/><ref>{{cite news|last1=Ali|first1=Khairat|last2=Tung|first2=Nguyen|last3=Mischa|first3=Siekmann|last4=Detlev|first4=Marpe|title=Adaptive Cross-Component Prediction for 4:4:4 High Efficiency Video Coding|url=http://nguyen.ph/wp-content/uploads/2014/12/CCP-ICIP-2014-preprint.pdf|access-date=December 18, 2014|archive-date=December 24, 2018|archive-url=https://web.archive.org/web/20181224215619/http://nguyen.ph/wp-content/uploads/2014/12/CCP-ICIP-2014-preprint.pdf|url-status=dead}}</ref>

*Intra smoothing control, allowing the encoder to turn smoothing on or off per-block, instead of per-frame.

*Modifications of transform skip:

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! [[Color depth|Bit depth]]

| {{Yes|8}} || {{Yes|8 to 10}} || {{Yes|8 to 12}} || {{Yes|8 to 10}} || {{Yes|8 to 12}} || {{Yes|8}} || {{Yes|8 to 10}} || {{Yes|8 to 12}} || {{Yes|8 to 16}}

! [[Chroma subsampling|Chroma sampling]] formats

| {{Yes|4:2:0}} || {{Yes|4:2:0}} || {{Yes|4:2:0}} || {{Yes|4:2:0/ 4:2:2}} || {{Yes|4:2:0/ 4:2:2}} || {{Yes|4:2:0/ 4:2:2/ 4:4:4}} || {{Yes|4:2:0/ 4:2:2/ 4:4:4}} || {{Yes|4:2:0/ 4:2:2/ 4:4:4}} || {{Yes|4:2:0/ 4:2:2/ 4:4:4}}

! 4:0:0 ([[Monochrome]])

| {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}}

! High precision weighted prediction

| {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}}

! Chroma QP offset list

| {{No}} || {{No}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}} || {{Yes}}

! Cross-component prediction