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team jvt with the charter to finalize the video coding standard 9 formal approval of the specification came in march 2003 the jvt was is chaired by gary sullivan thomas wiegand and ajay luthra motorola u s later arris u s in july 2004 the fidelity range extensions frext project was finalized from january 2005 to november 2007 the jvt was working on an extension of h 264 avc towards scalability by an annex g called scalable video coding svc the jvt management team was extended by jens rainer ohm rwth aachen university germany from july 2006 to november 2009 the jvt worked on multiview video coding mvc an extension of h 264 avc towards 3d television and limited range free viewpoint television that work included the development of two new profiles of the standard the multiview high profile and the stereo high profile throughout the development of the standard additional messages for containing supplemental enhancement information sei have been developed sei messages can contain various types of data that indicate the timing of the video pictures or describe various properties of the coded video or how it can be used or enhanced sei messages are also defined that can contain arbitrary user defined data sei messages do not affect the core decoding process but can indicate how the video is recommended to be post processed or displayed some other high level properties of the video content are conveyed in video usability information vui such as the indication of the color space for interpretation of the video content as new color spaces have been developed such as for high dynamic range and wide color gamut video additional vui identifiers have been added to indicate them fidelity range extensions and professional profiles edit the standardization of the first version of h 264 avc was completed in may 2003 in the first project to extend the original standard the jvt then developed what was called the fidelity range extensions frext these extensions enabled higher quality video coding by supporting increased sample bit depth precision and higher resolution color information including the sampling structures known as y c b c r 4 2 2 a k a yuv 4 2 2 and 4 4 4 several other features were also included in the frext project such as adding an 8 8 integer discrete cosine transform integer dct with adaptive switching between the 4 4 and 8 8 transforms encoder specified perceptual based quantization weighting matrices efficient inter picture lossless coding and support of additional color spaces the design work on the frext project was completed in july 2004 and the drafting work on them was completed in september 2004 five other new profiles see version 7 below intended primarily for professional applications were then developed adding extended gamut color space support defining additional aspect ratio indicators defining two additional types of supplemental enhancement information post filter hint and tone mapping and deprecating one of the prior frext profiles the high 4 4 4 profile that industry feedback by whom indicated should have been designed differently scalable video coding edit the next major feature added to the standard was scalable video coding svc specified in annex g of h 264 avc svc allows the construction of bitstreams that contain layers of sub bitstreams that also conform to the standard including one such bitstream known as the base layer that can be decoded by a h 264 avc codec that does not support svc for temporal bitstream scalability i e the presence of a sub bitstream with a smaller temporal sampling rate than the main bitstream complete access units are removed from the bitstream when deriving the sub bitstream in this case high level syntax and inter prediction reference pictures in the bitstream are constructed accordingly on the other hand for spatial and quality bitstream scalability i e the presence of a sub bitstream with lower spatial resolution quality than the main bitstream the nal network abstraction layer is removed from the bitstream when deriving the sub bitstream in this case inter layer prediction i e the prediction of the higher spatial resolution quality signal from the data of the lower spatial resolution quality signal is typically used for efficient coding the scalable video coding extensions were completed in november 2007 multiview video coding edit the next major feature added to the standard was multiview video coding mvc specified in annex h of h 264 avc mvc enables the construction of bitstreams that represent more than one view of a video scene an important example of this functionality is stereoscopic 3d video coding two profiles were developed in the mvc work multiview high profile supports an arbitrary number of views and stereo high profile is designed specifically for two view stereoscopic video the multiview video coding extensions were completed in november 2009 3d avc and mfc stereoscopic coding edit additional extensions were later developed that included 3d video coding with joint coding of depth maps and texture termed 3d avc multi resolution frame compatible mfc stereoscopic and 3d mfc coding various additional combinations of features and higher frame sizes and frame rates versions edit versions of the h 264 avc standard include 29 completed revisions corrigenda and amendments 10 applications edit further information list of video services using h 264 mpeg 4 avc the h 264 video format has a very broad application range that covers all forms of digital compressed video from low bit rate internet streaming applications to hdtv broadcast and digital cinema applications with nearly lossless coding with the use of h 264 bit rate savings of 50 or more compared to mpeg 2 part 2 are reported for example h 264 has been reported to give the same digital satellite tv quality as current mpeg 2 implementations with less than half the bitrate with current mpeg 2 implementations working at around 3 5 mbit s and h 264 at only 1 5 mbit s 11 sony claims that 9 mbit s avc recording mode is equivalent to the image quality of the hdv format which uses approximately 18 25 mbit s 12 to ensure compatibility and problem free adoption of h 264 avc many standards bodies have amended or added to their video related standards so that users of these standards can employ h 264 avc both the blu ray disc format and the now discontinued hd dvd format include the h 264 avc high profile as one of three mandatory video compression formats the digital video broadcast project dvb approved the use of h 264 avc for broadcast television in late 2004 the advanced television systems committee atsc standards body in the united states approved the use of h 264 avc for broadcast television in july 2008 13 14 it has also been approved for use with the more recent atsc m h mobile handheld standard using the avc and svc portions of h 264 15 the closed circuit television and video surveillance markets have included the technology in many products many common dslrs use h 264 video wrapped in quicktime mov containers as the native recording format derived formats edit avchd is a high definition recording format designed by sony and panasonic that uses h 264 conforming to h 264 while adding additional application specific features and constraints avc intra is an intraframe only compression format developed by panasonic xavc is a recording format designed by sony that uses level 5 2 of h 264 mpeg 4 avc which is the highest level supported by that video standard 16 17 xavc can support 4k resolution 4096 2160 and 3840 2160 at up to 60 frames per second fps 16 17 sony has announced that cameras that support xavc include two cinealta cameras the sony pmw f55 and sony pmw f5 18 the sony pmw f55 can record xavc with 4k resolution at 30 fps at 300 mbit s and 2k resolution at 30 fps at 100 mbit s 19 xavc can record 4k resolution at 60 fps with 4 2 2 chroma sampling at 600 mbit s 20 21 design edit features edit h 264 avc mpeg 4 part 10 contains a number of new features that allow it to compress video much more efficiently than older standards and to provide more flexibility for application to a wide variety of network environments in particular some such key features include multi picture inter picture prediction including the following features using previously encoded pictures as references in a much more flexible way than in past standards allowing up to 16 reference frames or 32 reference fields in the case of interlaced encoding to be used in some cases in profiles that support non idr frames most levels specify that sufficient buffering should be available to allow for at least 4 or 5 reference frames at maximum resolution this is in contrast to prior standards where the limit was typically one or in the case of conventional b pictures b frames two variable block size motion compensation vbsmc with block sizes as large as 16 16 and as small as 4 4 enabling precise segmentation of moving regions the supported luma prediction block sizes include 16 16 16 8 8 16 8 8 8 4 4 8 and 4 4 many of which can be used together in a single macroblock chroma prediction block sizes are correspondingly smaller when chroma subsampling is used the ability to use multiple motion vectors per macroblock one or two per partition with a maximum of 32 in the case of a b macroblock constructed of 16 4 4 partitions the motion vectors for each 8 8 or larger partition region can point to different reference pictures the ability to use any macroblock type in b frames including i macroblocks resulting in much more efficient encoding when using b frames this feature was notably left out from mpeg 4 asp six tap filtering for derivation of half pel luma sample predictions for sharper subpixel motion compensation quarter pixel motion is derived by linear interpolation of the halfpixel values to save processing power quarter pixel precision for motion compensation enabling precise description of the displacements of moving areas for chroma the resolution is typically halved both vertically and horizontally see 4 2 0 therefore the motion compensation of chroma uses one eighth chroma pixel grid units weighted prediction allowing an encoder to specify the use of a scaling and offset when performing motion compensation and providing a significant benefit in performance in special cases such as fade to black fade in and cross fade transitions this includes implicit weighted prediction for b frames and explicit weighted prediction for p frames spatial prediction from the edges of neighboring blocks for intra coding rather than the dc only prediction found in mpeg 2 part 2 and the transform coefficient prediction found in h 263v2 and mpeg 4 part 2 this includes luma prediction block sizes of 16 16 8 8 and 4 4 of which only one type can be used within each macroblock integer discrete cosine transform integer dct 5 22 23 a type of discrete cosine transform dct 22 where the transform is an integer approximation of the standard dct 24 it has selectable block sizes 25 and exact match integer computation to reduce complexity including an exact match integer 4 4 spatial block transform allowing precise placement of residual signals with little of the ringing often found with prior codec designs it is similar to the standard dct used in previous standards but uses a smaller block size and simple integer processing unlike the cosine based formulas and tolerances expressed in earlier standards such as h 261 and mpeg 2 integer processing provides an exactly specified decoded result an exact match integer 8 8 spatial block transform allowing highly correlated regions to be compressed more efficiently than with the 4 4 transform this design is based on the standard dct but simplified and made to provide exactly specified decoding adaptive encoder selection between the 4 4 and 8 8 transform block sizes for the integer transform operation a secondary hadamard transform performed on dc coefficients of the primary spatial transform applied to chroma dc coefficients and also luma in one special case to obtain even more compression in smooth regions lossless macroblock coding features including a lossless pcm macroblock representation mode in which video data samples are represented directly 26 allowing perfect representation of specific regions and allowing a strict limit to be placed on the quantity of coded data for each macroblock an enhanced lossless macroblock representation mode allowing perfect representation of specific regions while ordinarily using substantially fewer bits than the pcm mode flexible interlaced scan video coding features including macroblock adaptive frame field mbaff coding using a macroblock pair structure for pictures coded as frames allowing 16 16 macroblocks in field mode compared with mpeg 2 where field mode processing in a picture that is coded as a frame results in the processing of 16 8 half macroblocks picture adaptive frame field coding paff or picaff allowing a freely selected mixture of pictures coded either as complete frames where both fields are combined for encoding or as individual single fields a quantization design including logarithmic step size control for easier bit rate management by encoders and simplified inverse quantization scaling frequency customized quantization scaling matrices selected by the encoder for perceptual based quantization optimization an in loop deblocking filter that helps prevent the blocking artifacts common to other dct based image compression techniques resulting in better visual appearance and compression efficiency an entropy coding design including context adaptive binary arithmetic coding cabac an algorithm to losslessly compress syntax elements in the video stream knowing the probabilities of syntax elements in a given context cabac compresses data more efficiently than cavlc but requires considerably more processing to decode context adaptive variable length coding cavlc which is a lower complexity alternative to cabac for the coding of quantized transform coefficient values although lower complexity than cabac cavlc is more elaborate and more efficient than the methods typically used to code coefficients in other prior designs a common simple and highly structured variable length coding vlc technique for many of the syntax elements not coded by cabac or cavlc referred to as exponential golomb coding or exp golomb loss resilience features including a network abstraction layer nal definition allowing the same video syntax to be used in many network environments one very fundamental design concept of h 264 is to generate self contained packets to remove the header duplication as in mpeg 4 s header extension code hec 27 this was achieved by decoupling information relevant to more than one slice from the media stream the combination of the higher level parameters is called a parameter set 27 the h 264 specification includes two types of parameter sets sequence parameter set sps and picture parameter ...
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