H.264/MPEG-4 AVC

Anonymous_2

http://en.wikipedia.org/wiki/H.264

H.264/MPEG-4 AVC
From Wikipedia, the free encyclopedia.
(Redirected from H.264)

H.264, or MPEG-4 Part 10, is a high compression digital video codec standard written by the ITU-T Video Coding Experts Group (VCEG) together with the ISO/IEC Moving Picture Experts Group (MPEG) as the product of a collective partnership effort known as the Joint Video Team (JVT). The ITU-T H.264 standard and the ISO/IEC MPEG-4 Part 10 standard (formally, ISO/IEC 14496-10) are technically identical, and the technology is also known as AVC, for Advanced Video Coding. The final drafting work on the first version of the standard was completed in May of 2003.

H.264 is a name related to the ITU-T line of H.26x video standards, while AVC relates to the ISO/IEC MPEG side of the partnership project that completed the work on the standard, after earlier development done in the ITU-T as a project called H.26L. It is usual to call the standard as H.264/AVC (or AVC/H.264 or H.264/MPEG-4 AVC or MPEG-4/H.264 AVC) to emphasize the common heritage. The name H.26L, harkening back to its ITU-T history, is far less common, but still used. Occasionally, it has also been referred to as "the JVT codec", in reference to the JVT organization that developed it. (Such partnership and multiple naming is not unprecedented, as the video codec standard known as MPEG-2 also arose from a partnership between MPEG and the ITU-T, and MPEG-2 video is also known in the ITU-T community as H.262.)

The intent of H.264/AVC project has been to create a standard that would be capable of providing good video quality at bit rates that are substantially lower (e.g., half or less) than what previous standards would need (e.g., relative to MPEG-2, H.263, or MPEG-4 Part 2), and to do so without so much of an increase in complexity as to make the design impractical (excessively expensive) to implement. An additional goal was to do this in a flexible way that would allow the standard to be applied to a very wide variety of applications (e.g., for both low and high bit rates, and low and high resolution video) and to work well on a very wide variety of networks and systems (e.g., for broadcast, DVD storage, RTP/IP packet networks, and ITU-T multimedia telephony systems).

The JVT recently completed the development of some extensions to the original standard that are known as the Fidelity Range Extensions (FRExt). These extensions support higher-fidelity video coding by supporting increased sample accuracy (including 10-bit and 12-bit coding) and higher-resolution color information (including sampling structures known as YUV 4:2:2 and YUV 4:4:4). Several other features are also included in the Fidelity Range Extensions project (such as adaptive switching between 4×4 and 8×8 integer transforms, encoder-specified perceptual-based quantization weighting matrices, efficient inter-picture lossless coding, support of additional color spaces, and a residual color transform). The design work on the Fidelity Range Extensions was completed in July of 2004, and the drafting was finished in September of 2004.

Since the completion of the original version of the standard in May of 2003, the JVT has also done one round of "corrigendum" errata corrections, and an additional round of such corrigendum work was recently completed and approved in the ITU-T and ISO/IEC.
Contents
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    * 1 Features
    * 2 Patent licensing
    * 3 Applications
    * 4 Products and Implementations
          o 4.1 Software implementations
          o 4.2 Hardware implementations
    * 5 External links

[edit]

Features

H.264/AVC contains a number of new features that allow it to compress video much more effectively than older codecs and to provide more flexibility for application to a wide variety of network environments. In particular, some such key features include:

    * Multi-picture motion compensation using previously-encoded pictures as references in a much more flexible way than in past standards, thus allowing up to 32 reference pictures to be used in some cases (unlike in prior standards, where the limit was typically one or, in the case of conventional "B pictures", two). This particular feature usually allows modest improvements in bit rate and quality in most scenes. But in certain types of scenes, for example scenes with rapid repetitive flashing or back-and-forth scene cuts or uncovered background areas, it allows a very significant reduction in bit rate.
    * Variable block-size motion compensation (VBSMC) with block sizes as large as 16×16 and as small as 4×4, enabling very precise segmentation of moving regions.
    * Six-tap filtering for derivation of half-pel luma sample predictions, in order to lessen the aliasing and eventually provide sharper image.
    * Macroblock pair structure, allowing 16x16 macroblocks in field mode (vs. 16x8 in MPEG-2).
    * Quarter-pixel precision for motion compensation, enabling very precise description of the displacements of moving areas. For chroma the resolution is typically halved (see 4:2:0) therefore the motion compensation precision is down to one-eighth pixel.
    * 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.
    * An in-loop deblocking filter which helps prevent the blocking artifacts common to other DCT-based image compression techniques.
    * An exact-match integer 4×4 spatial block transform (similar to the well-known DCT design), and in the case of the new FRExt "High" profiles, the ability for the encoder to adaptively select between a 4×4 and 8×8 transform block size for the integer transform operation.
    * A secondary Hadamard transform performed on "DC" coefficients of the primary spatial transform (for chroma DC coefficients and also luma in one special case) to obtain even more compression in smooth regions.
    * 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.263+ and MPEG-4 Part 2).
    * Context-adaptive binary arithmetic coding (CABAC), which is a clever technique to losslessly compress syntax elements in the video stream knowing the probabilities of syntax elements in a given context.
    * 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 (Exp-Golomb) coding.
    * A network abstraction layer (NAL) definition allowing the same video syntax to be used in many network environments, including features such as sequence parameter sets (SPSs) and picture parameter sets (PPSs) that provide more robustness and flexibility than provided in prior designs.
    * Switching slices (called SP and SI slices), features that allow an encoder to direct a decoder to jump into an ongoing video stream for such purposes as video streaming bit rate switching and "trick mode" operation. When a decoder jumps into the middle of a video stream using the SP/SI feature, it can get an exact match to the decoded pictures at that location in the video stream despite using different pictures (or no pictures at all) as references prior to the switch.
    * Flexible macroblock ordering (FMO, also known as slice groups) and arbitrary slice ordering (ASO), which are techniques for restructuring the ordering of the representation of the fundamental regions (called macroblocks) in pictures. Typically considered an error/loss robustness feature, FMO and ASO can also be used for other purposes.
    * Data partitioning (DP), a feature providing the ability to separate more important and less important syntax elements into different packets of data, enabling the application of unequal error protection (UEP) and other types of improvement of error/loss robustness.
    * Redundant slices (RS), an error/loss robustness feature allowing an encoder to send an extra representation of a picture region (typically at lower fidelity) that can be used if the primary representation is corrupted or lost.
    * A simple automatic process for preventing the accidental emulation of start codes, which are special sequences of bits in the coded data that allow random access into the bitstream and recovery of byte alignment in systems that can lose byte synchronization.
    * Supplemental enhancement information (SEI) and video usability information (VUI), which are extra information that can be inserted into the bitstream to enhance the use of the video for a wide variety of purposes.
    * Auxiliary pictures, which can be used for such purposes as alpha compositing.
    * Frame numbering, a feature that allows the creation of "sub-sequences" (enabling temporal scalability by optional inclusion of extra pictures between other pictures), and the detection and concealment of losses of entire pictures (which can occur due to network packet losses or channel errors).
    * Picture order count, a feature that serves to keep the ordering of the pictures and the values of samples in the decoded pictures isolated from timing information (allowing timing information to be carried and controlled/changed separately by a system without affecting decoded picture content).

These techniques, along with several others, help H.264 to perform significantly better than any prior standard can, under a wide variety of circumstances in a wide variety of application environments. H.264 can often perform radically better than MPEG-2 video—typically obtaining the same quality at half of the bit rate or less.

Like other ISO/IEC MPEG video standards, H.264/AVC has a reference software implementation that can be freely downloaded. Its main purpose is to give examples of H.264/AVC features, rather than being a useful application per se. (See the links section for a pointer to that software.) Some reference hardware design work is also under way in MPEG.
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Patent licensing

As with MPEG-2 Parts 1 and 2 and MPEG-4 Part 2 amongst others, the vendors of H.264/AVC products and services are expected to pay patent licensing royalties for the patented technology that their products use. The primary source of licenses for patents applying to this standard is a private organization known as MPEG-LA, LLC (which is not affiliated in any way with the MPEG standardization organization, but which also administers patent pools for MPEG-2 Part 1 Systems, MPEG-2 Part 2 Video, MPEG-4 Part 2 Video, and other technologies). Via Licensing also operates an H.264 patent pool.
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Applications

Both of the major candidate next-generation DVD rival formats planned for product deployment in late 2005 include the H.264/AVC High Profile as a mandatory player feature — specifically:

    * The HD-DVD format of the DVD Forum
    * The Blu-ray Disc format of the Blu-Ray Disc Association (BDA)

The Digital Video Broadcast (DVB) standards body in Europe approved the use of H.264/AVC for broadcast television in Europe in late 2004.

The prime minister of France, Jean-Pierre Raffarin, announced the selection of H.264/AVC as a requirement for receivers of HDTV and pay TV channels for digital terrestrial broadcast television services (referred to as "TNT") in France in late 2004.

The Advanced Television Systems Committee (ATSC) standards body in the United States is in final consideration work on potential use of H.264/AVC for U.S. broadcast television.

The Digital Multimedia Broadcast (DMB) service in the Republic of Korea will use H.264/AVC.

Mobile-segment terrestrial broadcast services of ISDB-T in Japan will use the H.264/AVC codec, including major broadcasters:

    * NHK
    * Tokyo Broadcasting System (TBS)
    * Nippon Television (NTV)
    * TV Asahi
    * Fuji TV
    * TV Tokyo

Direct broadcast satellite TV services will use the new standard, including:

    * DirecTV (in the United States)
    * Dish Network (in the United States)
    * Euro1080 (in Europe)
    * Premiere (in Germany)
    * ProSieben HD & Sat1 HD(in Germany, ProSiebenSat.1 Media AG)
    * BSkyB (in the United Kingdom and Ireland)

The 3rd Generation Partnership Project (3GPP) has approved the inclusion of H.264/AVC as an optional feature in release 6 of its mobile multimedia telephony services specifications.

The Motion Imagery Standards Board (MISB) of the United States Department of Defense (DoD) has adopted H.264/AVC as its preferred video codec for essentially all applications.

The North Atlantic Treaty Organisation (NATO) similarly adopted H.264/AVC for its international military use.

The Internet Engineering Task Force (IETF) has completed a payload packetization format (RFC 3984) for carrying H.264/AVC video using its Real-time Transport Protocol (RTP).

The Internet Streaming Media Alliance (ISMA) has adopted H.264/AVC for its new ISMA 2.0 specifications.

The Moving Picture Experts Group (MPEG) has fully integrated support of H.264/AVC into its system standards (e.g., MPEG-2 and MPEG-4 systems) and its ISO media file format specification.

The International Telecommunications Union-Telecom. Standardization Sector (ITU-T) has adopted H.264/AVC in its H.32x suite of multimedia telephony systems specifications. Based on the ITU-T standards, H.264/AVC is already widely used for videoconferencing, including its support in products of the two main companies in that market (Polycom and Tandberg). Essentially all new videoconferencing products now include support for H.264/AVC.

H.264 will probably be used by various video-on-demand services on the Internet to provide films and television shows directly to computers.
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Products and Implementations
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Software implementations

The Nero Recode 2 DVD backup program, developed by Nero AG, includes an H.264 encoder (as of September 2005, corresponding to Main Profile, except interlaced video support) developed by Ateme. An upcoming version expected to be released in late 2005 will support High Profile and also interlaced video.

x264 is a GPL-licensed H.264 encoder that is used in the free VideoLAN and MPlayer multimedia players and, as of September 2005, remains the only reasonably complete open source implementation of the standard, with support for most of the Main Profile features except interlaced video and preliminary support for High Profile features. [1] A Video for Windows frontend is also available. x264 is not likely to be incorporated into commercial products because of its license and patent issues surrounding the standard itself.

Apple Computer has integrated H.264 (Main Profile) into Mac OS X version 10.4 (Tiger), as well as QuickTime version 7, which was released on April 29, 2005 with Tiger. QuickTime 7 is also now available for Microsoft's Windows operating system. Apple uses H.264 in the system for video playback and use in iChat video conferences. In April 2005, Apple Computer updated its version of DVD Studio Pro to support authoring HD content. DVD Studio Pro allows for the burning of HD-DVD content to both standard DVDs and HD-DVD media (even though no burners are available). For playing back HD-DVDs burnt onto a standard DVD, Apple requires a PowerPC G5, Apple DVD Player v4.6, and Mac OS X v10.4 or later. On October 12, 2005, Apple added H.264 video playback to their iPod lineup - known simply as " the iPod" - will use this format, as well as standard MPEG-4, for video playback. It will use H.264 video with quality levels up to 768 kbps, 320 x 240, 30 frames per second.

Sorenson offers an implementation of H.264. The Sorenson AVC Pro codec is available in Sorenson Squeeze 4.1 for MPEG-4.

Main Concept offers an H.264 encoder.
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Hardware implementations

Several companies are producing custom chips capable of decoding H.264/AVC video. Chips capable of real-time decoding at high-definition picture resolutions include these:

    * Broadcom BCM7411
    * Conexant CX2418X
    * Sigma Designs SMP8630, EM8622L, and EM8624L
    * STMicroelectronics STB7100, NOMADIK (STn 8800/8810/8815 series)

Such chips will allow widespread deployment of low-cost devices capable of playing H.264/AVC video at standard-definition and high-definition television resolutions.

ASTRI IC Designs Group is producing programmable media processor core, capable of real-time encoding and decoding video with H.264/AVC and China standards in CIF resolution concurrently, for low-power portable multimedia and mobile applications.

NeoMagic also has a chip product called the MiMagic 6, which is targeted for low-power applications (and is thus not HD-capable).

ATI Technologies has announced that its next-generation graphics processing unit (GPU), codenamed R520, would feature hardware acceleration of H.264. [2] [3]

NVIDIA has released a beta driver for hardware H.264 decoding on its 7800 GPUs. [4]

The PlayStation Portable console features hardware decoding of video files in the H.264 format.

Apple's video iPod can play H.264 videos.

Envivio, Inc. is shipping broadcast H.264 encoders for standard definition live encoding and off-line encoders for High Definition (720p, 1080i, 1080p). Envivio also supplies H.264 decoders for Windows, Linux and Macintosh as well as H.264 Video Servers and Authoring tools.

Modulus Video is shipping broadcast-quality H.264 standard definition real-time encoders to broadcasters (including telephone companies) and has announced its high definition real-time encoder (the ME6000) for shipment in mid 2005. The Modulus Video HD encoder technology was demonstrated at NAB in April 2004, where it won a "Pick Hit" award. The Modulus design uses technology from LSI Logic.

Hantro is shipping a multiple format video codec targeted for mobile system on chip designs, the implementation supports MPEG-4 simple profile, H.263 baseline and H.264/AVC baseline formats as well as JPEG still image.

Optibase is shipping integrated carrier grade TV streaming platform based on H.264. [5]

Tandberg television has announced a real-time high-definition encoder product (the EN5990). DirecTV and BSkyB have selected that product for their DBS deployments.

Harmonic has announced a real-time encoder product (the DiviCom MV 100). TF1 (the French broadcaster) and the Video Networks Limited (VNL) Homechoice video on demand service in London have announced the use of that product.

The Premiere DBS deployment will use set-top boxes from Pace Micro.
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External links

    * H.264/AVC overview paper including new FRExt enhancements (Sullivan, Topiwala, and Luthra)
    * Various papers on H.264/AVC and related topics (Wiegand)
    * More papers on H.264/AVC and related topics (Marpe)
    * H.264/AVC Software Coordination (Suehring)
    * List of H.264/AVC resources and codecs
    * H.264/MPEG-4 Part 10 Tutorials (Richardson)
    * Book: H.264 and MPEG-4 Video Compression (Richardson)
    * H.264/AVC Textbook (in Japanese: Okubo, Kadono, Kikuchi, and Suzuki)
    * JVT Experts Group document archive
    * MPEG LA Terms of H.264/MPEG-4 AVC Patent License
    * MPEG Industry Forum
    * AVC Alliance
    * ITU-T official publication page
    * ISO official publication page
    * W&W Communications H.264 Overview and IEEE Paper
    * HD Trailers Using H.264 (may require Quicktime 7 or Quicktime Alternative)
    * MPEG-4 AVC/H.264 video codecs comparison

Anonymous_2

http://www.mainconcept.com/h264_encoder.shtml

Discover a new degree of excellence with the H.264 Encoder v2 for Microsoft® Windows®, based on a completely rewritten engine! The current version offers encoding and decoding in the highest quality. Moreover, the MainConcept H.264 Encoder v2 features extraordinary quality improvement. H.264/AVC (Advanced Video Coding), also known as MPEG-4 Part 10, is poised to be a major video standard because it can replace several popular formats while offering significant advantages over them. Our encoder possesses a simple interface, which resembles that of the acclaimed MainConcept MPEG Encoder. This makes it easier for you to discover the unprecidented efficiency of the new format.

H.264 AVC (Advanced Video Coding) - also known as MPEG-4 Part 10 - is poised to be a major video standard because it can replace several popular formats while offering significant advantages over them.

Major features include:
        A straightforward encoding method
       
        Advanced compression - a high rate-distortion efficiency which can result in significant bitrate savings over MPEG-2
       
        The illustration below shows the dramatic savings in bitrate and file size that H.264 can achieve while providing comparable quality to other formats.
       
       
       
        Network friendliness - a network abstraction layer designed for highly efficient transmission of header data
       
        Profiles for a wide variety of applications ranging from video telephony to high-end broadcasting and storage
       
        Includes AAC (Advanced Audio Coding) encoding and decoding.
       
        Configurable GOP structure.
       
        Entropy Coding: CAVLC and CABAC
       
        Bitrate Modes: Constant Bitrate (CBR) and Variable Bitrate (VBR)
In summary, H.264 is a powerful, efficient, robust format that is ideal for the video applications of the future. MainConcept's H.264 solution is entirely our own codebase, optimized throughout for the best possible quality.
Our H.264 Encoder also includes our H.264 Decoder, enabling you to play H.264 files in Windows Media Player and other DirectShow compatible programs.
NOTE: This demo version places a watermark on encoded material and has a five minute capture time restriction.
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Current version: 2.0.12
Price: $499 (Download version)
Download Demo


The H.264 Encoder v2 includes the following new features and improvements:

- Completely rewritten engine
- 2-pass encoding
- Multiple slices per pictures
- B-slices as reference
- Full-pel, Half-pel and even Quarter-pel motion-estimation
- In-Loop Deblocking Filter
- Automatic Scene Cange Detection
- User-defined chapter points
- And many more enhancements and optimizations

High-Resolution Manuals:

In order to keep the file size reasonable, the H.264 Encoder v2 includes a user guide with low-resolution graphics now. However, we are making high-resolution manuals available for free downloading separately below, in zipped Adobe® Acrobat® format:

English manual for H.264 Encoder v2 (2.00 MB)

Anonymous_2

H.264 Stunning Video Quality from 3G to HD

http://www.apple.com/quicktime/technologies/h264/

QuickTime 7 features a state-of-the-art video codec called H.264, which delivers stunning quality at remarkably low data rates. Ratified as part of the MPEG-4 standard (MPEG-4 Part 10), this ultra-efficient technology gives you excellent results across a broad range of bandwidths, from 3G for mobile devices to iChat AV for video conferencing to HD for broadcast and DVD.
Pixar
Massive Quality, Minimal Files

H.264 uses the latest innovations in video compression technology to provide incredible video quality from the smallest amount of video data. This means you see crisp, clear video in much smaller files, saving you bandwidth and storage costs over previous generations of video codecs. H.264 delivers the same quality as MPEG-2 at a third to half the data rate and up to four times the frame size of MPEG-4 Part 2 at the same data rate. H.264 is truly a sight to behold.
Scalable from 3G to HD and Beyond

H.264 achieves the best-ever compression efficiency for a broad range of applications, such as broadcast, DVD, video conferencing, video-on-demand, streaming and multimedia messaging. And true to its advanced design, H.264 delivers excellent quality across a wide operating range, from 3G to HD and everything in between. Whether you need high-quality video for your mobile phone, iChat, Internet, broadcast or satellite delivery, H.264 provides exceptional performance at impressively low data rates.
Use Scenario         Resolution & Frame Rate         Example Data Rates
Mobile Content         176x144, 10-15 fps         50-60 Kbps
Internet/Standard Definition         640x480, 24 fps         1-2 Mbps
High Definition         1280x720, 24p         5-6 Mbps
Full High Definition         1920x1080, 24p         7-8 Mbps
No Wait for HD

The impressive efficiency of H.264 makes state-of-the-art video more accessible to more people, enabling you to experience the full quality of HD video on today’s computers. With H.264, an Apple Cinema HD Display and a dual Power Mac G5, you can turn your home office into a home theater, complete with gorgeous HD playback.
The New Industry Standard

Already ratified as part of the MPEG-4 standard — MPEG-4 Part 10 — and the ITU-T’s latest video-conferencing standard, H.264 is now mandatory for the HD-DVD and Blu-ray specifications (the two formats for high-definition DVDs) and ratified in the latest versions of the DVB (Digital Video Broadcasters) and 3GPP (3rd Generation Partnership Project) standards. Numerous broadcast, cable, videoconferencing and consumer electronics companies consider H.264 the video codec of choice for their new products and services. This adoption by a wide variety of open standards means that any company in the world can create devices — mobile phones, set-top boxes, DVD players and more — that will work seamlessly with QuickTime 7.
QuickTime
Built into QuickTime 7

Because H.264 is now an integral part of the QuickTime 7 architecture in Tiger, QuickTime-based applications — including iChat AV, Final Cut Pro HD and a litany of third-party applications — can take full advantage of this incredible new video codec.

Get ready for QuickTime 7 with H.264 to change the digital video universe. Experience this powerful addition to QuickTime 7 in Tiger.
H.264 in QuickTime 7: Under the Hood

H.264 in QuickTime 7 for Tiger implements a set of advanced technologies and patent-pending techniques to create pristine video at low data rates. The H.264 encoder features:

    * Intelligent multi-pass encoding for the best possible results at the desired bit rate with the optimal number of compression passes.
    * Time-saving single-pass encoding for creating draft encodes, meeting impending deadlines and live encoding with QuickTime Broadcaster.
    * Peak-constrained VBR options for limited data-rate scenarios such as streaming and CD/DVD playback.
    * Advanced frame reordering (B-frame) support to more efficiently represent movie data.
    * 4x4 integer transform for reducing traditional blocking and ringing artifacts, especially in areas of fine detail.
    * Improved intraframe prediction for more efficient compression of details and gradients in high-motion video.
    * Increased precision in motion estimation for crisp reconstruction of objects in motion.
    * Flexible block sizes in motion estimation for more efficient encoding of complicated motion in areas of fine detail.
    * Adaptively tuned in-loop deblocking filter for eliminating blocking artifacts, resulting in a smooth, clean image.

Anonymous_2

H.264 Freqently Asked Question

http://www.apple.com/quicktime/technologies/h264/faq.html

What is H.264?

H.264 is the next-generation video compression technology in the MPEG-4 standard, also known as MPEG-4 Part 10. H.264 can match the best possible MPEG-2 quality at up to half the data rate. H.264 also delivers excellent video quality across the entire bandwidth spectrum — from 3G to HD and everything in between (from 40 Kbps to upwards of 10 Mbps).

What are H.26L, AVC and JVT?

These names are sometimes also used to refer to the H.264 video codec. H.264 is the result of the combined efforts of two standards bodies — the ITU (International Telecommunication Union) and ISO MPEG (International Organization for Standardization’s Moving Picture Experts Group) — that together formed a body called the Joint Video Team (JVT). ITU originally referred to this new technology as H.26L, while MPEG originally referred to this technology as AVC. During the development of the standard, some also referred to the codec as JVT. H.264, however, is emerging as the most commonly-used name.

Why is H.264 being included in QuickTime 7?

A few years ago, the International Organization for Standardization selected the QuickTime file format as the basis for MPEG-4. QuickTime in turn embraced open standards and now leads the market in MPEG-4, 3GPP and 3GPP2 content creation and playback. Apple continues to build on this commitment to open standards by incorporating H.264 — the latest MPEG-4 video codec — directly into QuickTime. And since H.264 is an open standard, companies around the world can create products that will interoperate with one another. In addition to the enormous benefits of H.264 being a worldwide standard, Apple is very excited about the incredible video quality that H.264 can provide. Not only does it deliver excellent video; it does so at data rates much lower than MPEG-2 and plays back seamlessly on today’s shipping hardware.

Will application developers be able to access H.264 via QuickTime APIs?

Yes, H.264 is built into the QuickTime media architecture just like other QuickTime video codecs. So application developers can use QuickTime APIs to add H.264 encoding and decoding capabilities to their software products. For example, iChat AV in Tiger as well as hundreds of other applications that use the QuickTime architecture can take advantage of the new H.264 support in QuickTime 7.

Does H.264 require special hardware?

While H.264 is a computationally advanced codec, it runs on today’s shipping computers with no additional hardware required. For example, a full HD movie (1920x1080, 8 Mbps, 24 fps) encoded with H.264 plays back beautifully on a dual Power Mac G5. Internet-sized content (40kbps - 300kbps) will run on the most basic of processors, like those in mobile phones and consumer-level computers.

In which industries does H.264 play a role?

H.264 is an extremely scalable codec. From 3G to HD and beyond, H.264 provides excellent quality to the broadest range of bandwidths and user scenarios. Best of all, H.264 is a standard — so companies across the telecommunications, consumer electronics and broadcast industries can create products that will interoperate with one another. H.264 has been broadly adopted by organizations representing everything from mobile phones to HDTV, and you will find a broad spectrum of interoperating products — consumer and professional, hardware and software — supporting this standard. Visit mpegif.org for news and product announcements about H.264.

How does H.264 compare with MPEG-2?

HD MPEG-2 content at 1920x1080 traditionally runs at 12-20 Mbps, while H.264 can deliver 1920x1080 content at 7-8 Mbps at the same or better quality. H.264 provides DVD quality at about half the data rate of MPEG-2. Because of this efficiency, H.264, an ISO standard, stands to be the likely successor to MPEG-2 in the professional media industry.

How does H.264 compare with Windows Media 9?

Windows Media 9 is proprietary, developed by a single company; H.264 has been through intense peer review by worldwide experts from a large number of industry segments and is ratified as a worldwide standard. And while video quality tests are subjective, we believe H.264 delivers superior video quality when compared with Windows Media 9.

How does H.264 compare with MPEG-4 in QuickTime 6?

The MPEG-4 video in QuickTime 6, referred to as MPEG-4 Part 2, plays an important role in the evolution of standards for the Internet and wireless multimedia industries, where it has been widely adopted. H.264, also known as MPEG-4 Part 10, is a newer technology than MPEG-4 Part 2, providing up to four times the frame size of video encoded with the MPEG-4 Part 2 video codec at a given data rate. H.264 will undoubtedly build upon the success of MPEG-4 Part 2.

Is there still a use for MPEG-4 Part 2 after MPEG-4 Part 10 is available?

Absolutely. Just as MPEG-1 and MPEG-2 are still used in the industry today, MPEG-4 Part 2 will continue to be used. You will use MPEG-4 Part 2 anywhere you want to be compatible with MPEG-4 Part 2 devices or players, such as the millions of 3G mobile phones and digital still cameras that capture and play back MPEG-4 Part 2 video.

How does H.264 compare with H.263?

H.263, created by the ITU, is primarily known as a video codec designed for low-latency video conferencing applications. H.264 has been adopted by the ITU as the successor to H.263 for these same low-latency video conferencing scenarios. H.264 provides much higher quality than H.263 across the entire bandwidth spectrum, thanks to advancements in technology since the introduction of H.263 more than a decade ago. H.264 is already being adopted in video conferencing solutions such as Apple’s iChat AV in Tiger and products from Tandberg and Polycom, the two main suppliers of professional video conferencing systems.

How does H.264 compare with Pixlet?

H.264 and Pixlet are designed for different uses.

Pixlet is focused on workflow, designed for digital filmmakers, animators and effects artists to easily review high-resolution image sequences on a standard PowerMac or PowerBook. Pixlet plays every frame of a sequence without frame-to-frame dependencies so that a media professional can scrutinize every detail of a sequence. Pixlet enables high-end digital film frames at 960x540 (at about 20 Mbps) to play in real time with a 1GHz G4 or faster Macintosh, while 1920x1080 frames (at about 40 Mbps) will play in real time on a dual 2GHz G5 or faster. This capability eliminates the need to invest in costly, proprietary hardware for the professional review process.

H.264 is a delivery codec, optimized for high quality and efficiency. It leverages data that does not change between frames for more efficient compression. While Pixlet may require about 40 Mbps for 1920x1080 content, H.264 delivers 1920x1080 content at about 8 Mbps. This efficiency in H.264 enables delivery to and playback on a wide range of devices, from mobile phones to computers to HDTV and beyond.

What is the relationship between H.264 and the new standards for High Definition DVDs?

H.264 has been ratified as mandatory in both the HD-DVD and Blu-ray specifications for High Definition DVD.

Has H.264 been adopted by other standards bodies?

Yes. In terms of broadcast, H.264 has already been adopted by Europe’s DVB, the top 6 Japanese broadcasters, and is under final consideration in the US’s ATSC. The ITU-T has chosen H.264 for its H.241 videoconferencing specification. And in the mobile arena, H.264 has been adopted by the 3GPP (for GSM) organization and is under final consideration with the 3GPP2 (for CDMA2000) organization.

What are H.264’s licensing terms?

Licensing terms for H.264 are available at www.mpegla.com and www.vialicensing.com

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XViD完蛋！X264电影压缩率画质全对比
PCPOP.COM 2005年05月12日 作者：速龙
       

1：你满足下载电影的清晰度吗？
    随着宽带的普及，在网上下载电影成了很多用户的选择。比如ADSL用户免费下载一个几百MB的电影只需2小时左右，所以很多人乐此不疲。而如果追究这些电影，尤其是高清晰的好莱坞大片的来源，其实它们绝大多数都来自DVD。

电影下载最新格式评测


    经过破解小组的压缩处理，一张容量在4.7～8.5GB之间的DVD就被压缩到0.7～1.4GB左右的AVI文件（通常称之为DVDRip）。然后如果再进行压缩的话，还可以将其制作成RMVB文件，容量能够再降低一半左右。


    由此看来，从DVD到DVDRip压缩过程的质量就直接决定了我们下载观看电影的清晰度。近年来国际上普遍使用的压缩编码是XViD，它属于MPEG4的一种。也许大家觉得这种编码已经足够优秀了，它在画质损失很少的情况下把电影容量压缩到了原来的几分之一。但别忘了技术是永远在发展的，现在又有一种更加优秀的编码格式渐渐进入了这个领域，它就是H.264。

2：不怕压缩 文件越小优势越大

    H.264是ITU-T的VCEG（视频编码专家组）和ISO/IEC的MPEG（活动图像编码专家组）的联合视频组（JVT：joint video team）开发的一个新的数字视频编码标准，它既是ITU-T的H.264，又是ISO/IEC的MPEG-4的第10 部分。

    H.264编码最大的优势在于它能够以更低的码率得到更高的画质，例如一部2小时1080p格式的HDTV电影，如果使用与DVD相同的MPEG2编码，需要15GB左右的空间来保存；而如果使用H.264编码的话只需一半左右的容量，并且画质与MPEG2的不相上下。


    随着高清时代的来临，HDTV用何种编码也是眼下的热门话题。MPEG2虽然目前比较流行，但其码率较高的缺点限制了应用范围。在掌上设备日益普及的今天，MPEG2这种容量很大的格式显然不适合移动影音需求。


    因此目前比较看好的未来高清视频编码格式有微软的WMV9、MPEG2与H.264，其中后两者是目前网络下载电影的主流编码格式。接下来我们就来比较一下用XViD（同样隶属于MPEG4）和X264（一种开发源代码的H.264）压缩的DVDRip电影到底谁更强。

3：画质对比 实战好莱坞动作大片

    这次我们选择从网上下载的《血溅13号警署》作为测试项目，用XViD和X264两种编码的版本做画质和CPU占用率对比，播放软件为暴风影音v6.4.8.4：

  
(见下图)

    下面的截图非常明显的展示出了X264编码的优势，它表现栏杆的图案、人物面部的缺陷与警徽上面的文字的细节都比XViD版本要清晰。看过了画质对比，下面让我们再来测试一下另一个重要的方面：播放时的CPU占用率。

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细节：注意警徽上的文字

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4：对比CPU占用率&怎样下载X264？

    除了画质之外，大家最关心的恐怕就是播放X264影片时候的CPU占用率了。因此我们使用比较低端的赛扬1.7GHz加上512MB内存的平台进行测试，X264在解码过程中需要更多的CPU资源，不过既然赛扬1.7GHz的CPU应付起来都非常轻松，那么目前的主流平台就根本不必把CPU占用率的问题放在眼里了。

    最后也许有人要问，我怎么才能知道自己下载的电影是X264还是XViD编码的呢？其实很简单，对于命名正规的下载网站来说，我们只要观察文件夹名称就可以清楚的分辨两种视频格式。

    其实H.264并不是什么新的概念，它很早已被制定为手机视频以及下一代高清数字电视等领域的候选编码格式。但将H.264编码中的一个分支：X264应用到下载版电影的制作上面，还是最近的事情。X264编码可以用相同的容量得到比XViD更好的画质，随着其源代码的不断完善，很可能会在不久的将来大行其道。