H264.indd 1 and because theydonotexploit thetemporal redundancy. optimal encodingscheme interms of compression efficiency digital photocameras andvideoeditingsystems areasub- dundancy. Hence, the“motionJPEG” movies usedinsome and ITU-T Rec. T.800 (JPEG2000) onlyexploitthespatialre- Still-image coding algorithmssuchasITU-T Rec. T.81 (JPEG) and spatial(how thepixelschangewithin thesameframe). in thesignal:temporal (changesfromone frametothenext) sion algorithmssuchasH.264 exploittwotypesofredundancy evancy (byquantization)from theinputsignal.Videocompres- transformation; andbyentropy coding)andreducingirrel- spatial/temporal prediction; by spatial/temporaldecorrelating Signal compressionconsists ofreducingredundancy(by Multimedia servicesoverpacketnetworks(MSPN),suchas • MultimediaMessaging Services(MMS)overISDN, DSL, • ormultimediastreamingservices, Video-on-demand • Real-time conversationalservices(RTC), suchas • Interactive orserialstoragemultimedia(ISMSSM)on • plication areasincludingbutnotlimitedtothefollowing: The newRecommendation isdestinedtoinfluencefurtherap- Mobile(3GPPand3GPP2)forstreaming. by Third-Generation bled incomparisontothecodingschemespreviouslyspecified important rolebecausethecompressionefficiencywillbe dou- Also, inthefieldofmobilecommunication,H.264 willplayan bled incomparisontocurrentsystemsusingH.262 (MPEG-2). H.264, thenumberofprogrammespersatellitecanbedou- business areaisTVtransmissionoversatellite.Bychoosing enables streamingoverxDSLconnections.Anotherinteresting video signalsatabout1Mbit/swithTV(PAL) quality, which benefit fromthenewstandard.Itisnowpossibletotransmit ing overcable,satellite,cablemodem,terrestrial,etc., will new applicationareasandbusinessopportunities.Broadcast- AdvancedVideoCoding(AVC) standardwillleadto MPEG-4 The increasedcompressionefficiencyofthenewITU-T H.264/ Application

www.itu.int/ITU-T multimedia mailing(MMM),etc. Ethernet, LAN, wirelessand mobile networks,etc. LAN,, DSL, wireless networks,etc. such asremotevideosurveillance(RVS),overISDN, cable mixtures ofthese. LAN, wirelessandmobile networks,modemsor DSL, videoconferencing andvideophone,overISDN, Ethernet, optical andmagneticdevices,DVD, etc. Still-Image Coding Highlights Coding ITU-T needed forthe MainProfile. nificant amount ofimplementationcomplexity beyondwhatis Profile addsmore compressionefficiencywithout addingasig- term industryimplementation interest.Thisis becausetheHigh rapidly overtake theMainProfile interms of dominantnear- embrace itaswell.Indeed, appears thattheHighProfile may as majordirect-broadcast satelliteserviceproviders maysoon ropean broadcasttelevision. Several otherenvironmentssuch Forum andtheDVB (digitalvideo broadcast)standardsforEu- specificationoftheDVDBlu-ray DiscAssociation,the HD-DVD Videospecificationofthe specifications, includingtheBD-ROM be incorporatedintoseveral importantnear-term application particularly theHighProfile. The HighProfile appearscertainto Industry hasbeenquicktoembrace thenewcapabilities,and TheHigh 4:4:4Profile (H444P) TheHigh 4:2:2Profile (H422P) • TheHigh 10Profile (Hi10P) • TheHigh Profile (HP) • • This projectproducedasuiteoffournewprofiles: rangeextensions” (FRExt). extensions arenamedthe“fidelity sions ofthetoolset.Thisefforttookaboutoneyearandthese and post-processing, itwasnecessarytodevelopsomeexten- video, content-contribution, content-distribution, studioediting For applicationssuchashigh-resolutionentertainment-quality TheMainProfile (MP) TheExtendedProfile (XP) • TheBaselineProfile (BP) • • of 2003: in theoriginalH.264 specificationthatwascompletedinMay of theapplication.Thefollowingthreeprofilesweredefined implement anynumberofprofiles,dependingontheneeds tools (calledprofiles)aredefined.Adecodermaychoose to them arerequiredforeveryapplication,sosubsetsofcoding H.264 containsarichsetofvideocodingtools,butnotall media, Internetstreaming, wirelesscommunication,etc. ing televisionbroadcasting, videoconferencing, digitalstorage higher compressionofvideoforvariousapplicationsinclud- part10AVC) inresponsetothegrowingneedfor as MPEG-4 was developedtogetherwithISO/IEC(whereitisstandardized flexible mannerforawidevarietyofnetworkenvironments. It ommendation designedtoenabletheuseofcodedvideo ina H.264 AdvancedVideoCoding(AVC) isthelatestITU-T Rec- H.264: membership: www.itu/ITU-T/membership/ and news: www.itu.int/ITU-T/news/e-flash workshops: www.itu.int/ITU-T/worksem/ A FlexibleToolkit

03.2005 [email protected] ITU-T International TelecommunicationUnion communication for video opportunities New Video Coding The Advanced 21.03.2005, 11:55:01 www.itu.int/ITU-T

ITU-T Video Coding Performance of H.264 Rate-Distortion Performance Curves Standards and the and Comparison with Prior Coding Standards In the following chart, Peak Signal-to-Noise Ratio (PSNR) vs. H.264 / MPEG-4 AVC bit-rate curves for the four is shown for the test se- Project quence “Tempete”. For this sequence (chosen as an example) To illustrate performance gains that can be achieved when us- coding for various applications has evolved over and for all other sequences from the test set, H.264 signifi- ing the H.264 standard, the results of a comparison with some cantly outperforms the other codecs. the last decade and a half, as demonstrated by the develop- successful prior coding standards are reported below. The four ment of the ITU-T H.261, H.262 and H.263 standards. H.261, codecs compared produce bit streams conforming to the fol- standardized in 1990, was the first successful such standard, lowing standards: enabling interoperable videoconferencing over dial-up digital • H.262, Main Profile (MP) telecommunication networks. H.262 (a standard jointly devel- • H.263, High Latency Profile (HLP) oped with ISO/IEC and more commonly known as MPEG-2 • H.264, Main Profile (MP) Video), developed a few years later, was the enabling technol- ogy for digital systems worldwide. It allowed digital The input video for this comparison consists of a set of well- transmission of TV video over satellite, cable, and terrestrial known lower-rate Quarter Common Intermediate Format platforms. And H.263 provided enhanced compression and ro- (QCIF) (10 Hz and 15 Hz) and higher-rate Common Interme- bustness for various applications including Internet and wire- diate Format (CIF) (15 Hz and 30 Hz) sequences with different less video. However, more continued to be learned to further amounts of motion and spatial detail. improve video technology and to diversify the range of digital All video encoders were optimized with regards to their video applications. rate-distortion efficiency using Lagrangian techniques. These In early 1998, the ITU-T Video Coding Experts Group (VCEG) techniques have gained importance due to their effectiveness, issued a call for proposals on a project it called H.26L, with the conceptual simplicity, and ability to evaluate a large number target of doubling the coding efficiency (which means halving of possible coding choices in an optimized fashion. In addi- the necessary for a given level of video quality) in com- tion to performance gains, the use of a specific and efficient On the following chart, the bit-rate savings relative to the parison to any existing video coding standard. Then, in De- coder control for all video encoders allowed a fair comparison H.262 (MPEG-2) video coding standard are plotted against cember of 2001, VCEG and the Moving Picture Experts Group between them in terms of coding efficiency. the PSNR objective quality of the luminance* component for (MPEG) of ISO/IEC formed a Joint Video Team (JVT), with the H.263 HLP and H.264 MP. H.264 MP significantly outperforms charter to finalize the draft new (AVC) the other standards. standard which would become ITU-T Recommendation H.264. MPEG approved identical technical content in its correspond- ing standard called MPEG-4 part 10 (ISO/IEC 14496-10). H.264/MPEG-4 AVC represents a major step forward in the development of video coding standards. It typically outper- forms prior standards by roughly a factor of two or more, particularly in comparison to H.262/MPEG-2. This improve- ment enables new applications and business opportunities to be developed. Additional computational resources are needed for implementing H.264, but have been supplied by The above table presents the average bit-rate savings provided the phenomenon known as Moore’s Law. Furthermore, H.264 by each encoder relative to the other tested encoders, aver- is a collaboratively designed allowing all manu- aged over this set of test sequences and bit rates. It can be facturers to produce encoders and decoders based on it. This seen that H.264 significantly outperforms all other ITU-T video will help to create a competitive market, keeping prices down coding standards. and ensuring that products made by a wide variety of different (Quality study reference: T. Wiegand et al., “Rate-Constrained manufacturers will be fully compatible with each other. Coder Control and Comparison of Video Coding Standards”, *The luminance component of the video signal represents the in IEEE Trans CSVT Special Issue on H.264/AVC Video Coding gray-shade brightness component of the image, and is the most Standard, July 2003.) perceptually important part of a colour image.

For more information: www.itu.int/ITU-T/studygroups/com16 www.itu.int/ITU-T

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