SlideShare une entreprise Scribd logo
1  sur  10
White paper




h.264 video compression standard.
New possibilities within video surveillance.
table of contents
1. introduction                     3

2. Development of h.264             3

3. how video compression works      4

4. h.264 profiles and levels        5

5. Understanding frames             5

6. Basic methods of reducing data   6

 7. efficiency of h.264             7

8. Conclusion                       9
1.   introduction
     The latest video compression standard, H.264 (also known as MPEG-4 Part 10/AVC for Advanced Video
     Coding), is expected to become the video standard of choice in the coming years.

     H.264 is an open, licensed standard that supports the most efficient video compression techniques available
     today. Without compromising image quality, an H.264 encoder can reduce the size of a digital video file by
     more than 80% compared with the Motion JPEG format and as much as 50% more than with the MPEG-4
     Part 2 standard. This means that much less network bandwidth and storage space are required for a video
     file. Or seen another way, much higher video quality can be achieved for a given bit rate.

     Jointly defined by standardization organizations in the telecommunications and IT industries, H.264 is
     expected to be more widely adopted than previous standards.

     H.264 has already been introduced in new electronic gadgets such as mobile phones and digital video
     players, and has gained fast acceptance by end users. Service providers such as online video storage and
     telecommunications companies are also beginning to adopt H.264.

     In the video surveillance industry, H.264 will most likely find the quickest traction in applications where
     there are demands for high frame rates and high resolution, such as in the surveillance of highways,
     airports and casinos, where the use of 30/25 (NTSC/PAL) frames per second is the norm. This is where
     the economies of reduced bandwidth and storage needs will deliver the biggest savings.

     H.264 is also expected to accelerate the adoption of megapixel cameras since the highly efficient
     compression technology can reduce the large file sizes and bit rates generated without compromising
     image quality. There are tradeoffs, however. While H.264 provides savings in network bandwidth and
     storage costs, it will require higher performance network cameras and monitoring stations.


2.   Development of h.264
     H.264 is the result of a joint project between the ITU-T’s Video Coding Experts Group and the ISO/IEC
     Moving Picture Experts Group (MPEG). ITU-T is the sector that coordinates telecommunications standards
     on behalf of the International Telecommunication Union. ISO stands for International Organization for
     Standardization and IEC stands for International Electrotechnical Commission, which oversees standards
     for all electrical, electronic and related technologies. H.264 is the name used by ITU-T, while ISO/IEC has
     named it MPEG-4 Part 10/AVC since it is presented as a new part in its MPEG-4 suite. The MPEG-4 suite
     includes, for example, MPEG-4 Part 2, which is a standard that has been used by IP-based video encoders
     and network cameras.

     Designed to address several weaknesses in previous video compression standards, H.264 delivers on its
     goals of supporting:

     > Implementations that deliver an average bit rate reduction of 50%, given a fixed video quality
       compared with any other video standard
     > Error robustness so that transmission errors over various networks are tolerated
     > Low latency capabilities and better quality for higher latency
     > Straightforward syntax specification that simplifies implementations
     > Exact match decoding, which defines exactly how numerical calculations are to be made by an
       encoder and a decoder to avoid errors from accumulating

     H.264 also has the flexibility to support a wide variety of applications with very different bit rate
     requirements. For example, in entertainment video applications—which include broadcast, satellite, cable
     and DVD—H.264 will be able to deliver a performance of between 1 to 10 Mbit/s with high latency, while
     for telecom services, H.264 can deliver bit rates of below 1 Mbit/s with low latency.




                                                                                                              3
3.     how video compression works
             Video compression is about reducing and removing redundant video data so that a digital video file can
             be effectively sent and stored. The process involves applying an algorithm to the source video to create
             a compressed file that is ready for transmission or storage. To play the compressed file, an inverse
             algorithm is applied to produce a video that shows virtually the same content as the original source
             video. The time it takes to compress, send, decompress and display a file is called latency. The more
             advanced the compression algorithm, the higher the latency, given the same processing power.

             A pair of algorithms that works together is called a video codec (encoder/decoder). Video codecs that
             implement different standards are normally not compatible with each other; that is, video content that is
             compressed using one standard cannot be decompressed with a different standard. For instance, an
             MPEG-4 Part 2 decoder will not work with an H.264 encoder. This is simply because one algorithm cannot
             correctly decode the output from another algorithm but it is possible to implement many different
             algorithms in the same software or hardware, which would then enable multiple formats to be
             compressed.

             Different video compression standards utilize different methods of reducing data, and hence, results
             differ in bit rate, quality and latency.

             Results from encoders that use the same compression standard may also vary because the designer of
             an encoder can choose to implement different sets of tools defined by a standard. As long as the output
             of an encoder conforms to a standard’s format and decoder, it is possible to make different implementations.
             This is advantageous because different implementations have different goals and budget. Professional
             non-real-time software encoders for mastering optical media should have the option of being able to
             deliver better encoded video than a real-time hardware encoder for video conferencing that is integrated
             in a hand-held device. A given standard, therefore, cannot guarantee a given bit rate or quality.
             Furthermore, the performance of a standard cannot be properly compared with other standards, or even
             other implementations of the same standard, without first defining how it is implemented.

             A decoder, unlike an encoder, must implement all the required parts of a standard in order to decode a
             compliant bit stream. This is because a standard specifies exactly how a decompression algorithm should
             restore every bit of a compressed video.

             The graph below provides a bit rate comparison, given the same level of image quality, among the
             following video standards: Motion JPEG, MPEG-4 Part 2 (no motion compensation), MPEG-4 Part 2 (with
             motion compensation) and H.264 (baseline profile).
                                        Doorway scene
                                        H.264 (Baseline profile)
                                        MPEG-4 Part 2 (No motion compensation)
                                        MPEG-4 Part 2 (With motion compensation)
                                        Motion JPEG
                                7,000


                                6,000


                                5,000
            Bit rate (kbit/s)




                                4,000



                                3,000


                                2,000


                                1,000


                                   0
                                                                      50                100
                                                                             Time (s)


Figure 1.    An H.264 encoder generated up to 50% fewer bits per second for a sample video sequence than an MPEG-4 encoder with motion
             compensation. The H.264 encoder was at least three times more efficient than an MPEG-4 encoder with no motion compensation
             and at least six times more efficient than Motion JPEG.



                                                                                                                                     4
4.    h.264 profiles and levels
            The joint group involved in defining H.264 focused on creating a simple and clean solution, limiting
            options and features to a minimum. An important aspect of the standard, as with other video standards,
            is providing the capabilities in profiles (sets of algorithmic features) and levels (performance classes)
            that optimally support popular productions and common formats.

            H.264 has seven profiles, each targeting a specific class of applications. Each profile defines what
            feature set the encoder may use and limits the decoder implementation complexity.

            Network cameras and video encoders will most likely use a profile called the baseline profile, which is
            intended primarily for applications with limited computing resources. The baseline profile is the most
            suitable given the available performance in a real-time encoder that is embedded in a network video
            product. The profile also enables low latency, which is an important requirement of surveillance video and
            also particularly important in enabling real-time, pan/tilt/zoom (PTZ) control in PTZ network cameras.

            H.264 has 11 levels or degree of capability to limit performance, bandwidth and memory requirements.
            Each level defines the bit rate and the encoding rate in macroblock per second for resolutions ranging
            from QCIF to HDTV and beyond. The higher the resolution, the higher the level required.


      5.    Understanding frames
            Depending on the H.264 profile, different types of frames such as I-frames, P-frames and B-frames, may
            be used by an encoder.

            An I-frame, or intra frame, is a self-contained frame that can be independently decoded without any
            reference to other images. The first image in a video sequence is always an I-frame. I-frames are needed
            as starting points for new viewers or resynchronization points if the transmitted bit stream is damaged.
            I-frames can be used to implement fast-forward, rewind and other random access functions. An encoder
            will automatically insert I-frames at regular intervals or on demand if new clients are expected to join in
            viewing a stream. The drawback of I-frames is that they consume much more bits, but on the other hand,
            they do not generate many artifacts.

            A P-frame, which stands for predictive inter frame, makes references to parts of earlier I and/or P
            frame(s) to code the frame. P-frames usually require fewer bits than I-frames, but a drawback is that
            they are very sensitive to transmission errors because of the complex dependency on earlier P and I
            reference frames.

            A B-frame, or bi-predictive inter frame, is a frame that makes references to both an earlier reference
            frame and a future frame.




             I     B     B      P     B      B      P     B      B      I     B      B     P




Figure 2.   A typical sequence with I-, B- and P-frames. A P-frame may only reference preceding I- or P-frames, while a B-frame may
            reference both preceding and succeeding I- or P-frames.




                                                                                                                                 5
When a video decoder restores a video by decoding the bit stream frame by frame, decoding must always
            start with an I-frame. P-frames and B-frames, if used, must be decoded together with the reference
            frame(s).

            In the H.264 baseline profile, only I- and P-frames are used. This profile is ideal for network cameras and
            video encoders since low latency is achieved because B-frames are not used.


      6.    Basic methods of reducing data
            A variety of methods can be used to reduce video data, both within an image frame and between a series
            of frames.

            Within an image frame, data can be reduced simply by removing unnecessary information, which will
            have an impact on the image resolution.

            In a series of frames, video data can be reduced by such methods as difference coding, which is used by
            most video compression standards including H.264. In difference coding, a frame is compared with a
            reference frame (i.e. earlier I- or P-frame) and only pixels that have changed with respect to the reference
            frame are coded. In this way, the number of pixel values that are coded and sent is reduced.




Figure 3.   With Motion JPEG format, the three images in the above sequence are coded and sent as separate unique images (I-frames) with
            no dependencies on each other.




Figure 4.   With difference coding (used in most video compression standards including H.264), only the first image (I-frame) is coded in its
            entirety. In the two following images (P-frames), references are made to the first picture for the static elements, i.e. the house, and
            only the moving parts, i.e. the running man, is coded using motion vectors, thus reducing the amount of information that is sent
            and stored.


            The amount of encoding can be further reduced if detection and encoding of differences is based on
            blocks of pixels (macroblocks) rather than individual pixels; therefore, bigger areas are compared and
            only blocks that are significantly different are coded. The overhead associated with indicating the
            location of areas to be changed is also reduced.




                                                                                                                                                 6
Difference coding, however, would not significantly reduce data if there was a lot of motion in a video.
            Here, techniques such as block-based motion compensation can be used. Block-based motion
            compensation takes into account that much of what makes up a new frame in a video sequence can be
            found in an earlier frame, but perhaps in a different location. This technique divides a frame into a series
            of macroblocks. Block by block, a new frame—for instance, a P-frame—can be composed or ‘predicted’
            by looking for a matching block in a reference frame. If a match is found, the encoder simply codes the
            position where the matching block is to be found in the reference frame. Coding the motion vector, as it
            is called, takes up fewer bits than if the actual content of a block were to be coded.
                          Search window
                                                   Matching block




                         Motion vector                            Target block




                Earlier reference frame                  P-frame

Figure 5.   Illustration of block-based motion compensation



      7.    efficiency of h.264
            H.264 takes video compression technology to a new level. With H.264, a new and advanced intra
            prediction scheme is introduced for encoding I-frames. This scheme can greatly reduce the bit size of an
            I-frame and maintain a high quality by enabling the successive prediction of smaller blocks of pixels
            within each macroblock in a frame. This is done by trying to find matching pixels among the earlier-
            encoded pixels that border a new 4x4 pixel block to be intra-coded. By reusing pixel values that have
            already been encoded, the bit size can be drastically reduced. The new intraprediction is a key part of the
            H.264 technology that has proven to be very efficient. For comparison, if only I-frames were used in an
            H.264 stream, it would have a much smaller file size than a Motion JPEG stream, which uses only
            I-frames.

             In this mode, four bottom pixels from      In this mode, four right-most pixels       In this mode, eight bottom pixels from
             the block above are copied vertically      from the block to the left are copied      the blocks above are copied diagonally
             into part of an intra-coded macro-         horizontally into part of an intra-coded   into part of an intra-coded macro-
             block.                                     macroblock.                                block.




Figure 6.   Illustrations of some of the modes that intra prediction can take in coding 4x4 pixels within one of the 16 blocks that make up a
            macroblock. Each of the 16 blocks in a macroblock may be coded using different modes.




                                                                                                                                            7
Original source image                                              intra predicted image




            residual image                                                     Output image


Figure 7.   The above images illustrate the efficiency of H.264’s intra prediction scheme, whereby the intra predicted image is sent for “free”.
            Only the residual content and the intra prediction modes need to be coded to produce the output image.


            Block-based motion compensation—used in encoding P- and B-frames—has also been improved in H.264.
            An H.264 encoder can choose to search for matching blocks—down to sub-pixel accuracy—in a few or
            many areas of one or several reference frames. The block size and shape can also be adjusted to improve
            a match. In areas where no matching blocks can be found in a reference frame, intra-coded macroblocks
            are used. The high degree of flexibility in H.264’s block-based motion compensation pays off in crowded
            surveillance scenes where the quality can be maintained for demanding applications. Motion compensation
            is the most demanding aspect of a video encoder and the different ways and degrees with which it can
            be implemented by an H.264 encoder can have an impact on how efficiently video is compressed.




                                                                                                                                              8
With H.264, typical blocky artifacts—seen in highly compressed video using Motion JPEG and MPEG
            standards other than H.264—can be reduced using an in-loop deblocking filter. This filter smoothes block
            edges using an adaptive strength to deliver an almost perfect decompressed video.




Figure 8.   Blocky artifacts in the highly compressed image at left are reduced when a deblocking filter is applied, as seen in the image at
            right.



      8.    Conclusion
            H.264 presents a huge step forward in video compression technology. It offers techniques that enable
            better compression efficiencies due to more accurate prediction capabilities, as well as improved
            resilience to errors. It provides new possibilities for creating better video encoders that enable higher
            quality video streams, higher frame rates and higher resolutions at maintained bit rates (compared with
            previous standards), or, conversely, the same quality video at lower bit rates.

            H.264 represents the first time that the ITU, ISO and IEC have come together on a common, international
            standard for video compression. Due to its flexibility, H.264 has been applied in diverse areas such as
            high-definition DVD (e.g. Blu-ray), digital video broadcasting including high-definition TV, online video
            storage (e.g. YouTube), third-generation mobile telephony, in software such as QuickTime, Flash and
            Apple Computer’s MacOS X operating system, and in home video game consoles such PlayStation 3.
            With support from many industries and applications for consumer and professional needs, H.264 is
            expected to replace other compression standards and methods in use today.

            As the H.264 format becomes more broadly available in network cameras, video encoders and video
            management software, system designers and integrators will need to make sure that the products and
            vendors they choose support this new open standard. And for the time being, network video products that
            support both H.264 and Motion JPEG are ideal for maximum flexibility and integration possibilities.




                                                                                                                                          9
www.axis.com




                                                                                                                                                             31669/EN/R1/0803
about axis Communications
Axis is an IT company offering network video solutions
for professional installations. The company is the global
market leader in network video, driving the ongoing
shift from analog to digital video surveillance. Axis
products and solutions focus on security surveillance
and remote monitoring, and are based on innovative,
open technology platforms.
Axis is a Swedish-based company, operating worldwide
with offices in 18 countries and cooperating with part-
ners in more than 70 countries. Founded in 1984, Axis is
listed on the OMX Nordic Exchange, Large Cap and Infor-
mation Technology. For more information about Axis,
please visit our website at www.axis.com.




©2008 Axis Communications AB. AXIS COMMUNICATIONS, AXIS, ETRAX, ARTPEC and VAPIX are registered trademarks or trademark applications of Axis AB
in various jurisdictions. All other company names and products are trademarks or registered trademarks of their respective companies. We reserve the right
to introduce modifications without notice.

Contenu connexe

Tendances

Introduction to H.264 Advanced Video Compression
Introduction to H.264 Advanced Video CompressionIntroduction to H.264 Advanced Video Compression
Introduction to H.264 Advanced Video CompressionIain Richardson
 
Video Compression Standards - History & Introduction
Video Compression Standards - History & IntroductionVideo Compression Standards - History & Introduction
Video Compression Standards - History & IntroductionChamp Yen
 
HEVC VIDEO CODEC By Vinayagam Mariappan
HEVC VIDEO CODEC By Vinayagam MariappanHEVC VIDEO CODEC By Vinayagam Mariappan
HEVC VIDEO CODEC By Vinayagam MariappanVinayagam Mariappan
 
h.264 video compression standard.
h.264 video compression standard.h.264 video compression standard.
h.264 video compression standard.Videoguy
 
Subjective quality evaluation of the upcoming HEVC video compression standard
Subjective quality evaluation of the upcoming HEVC video compression standard Subjective quality evaluation of the upcoming HEVC video compression standard
Subjective quality evaluation of the upcoming HEVC video compression standard Touradj Ebrahimi
 
Getting the most out of H.264
Getting the most out of H.264Getting the most out of H.264
Getting the most out of H.264Iain Richardson
 
Introduction to HEVC
Introduction to HEVCIntroduction to HEVC
Introduction to HEVCYoss Cohen
 
H.264 nal and RTP
H.264 nal and RTPH.264 nal and RTP
H.264 nal and RTPYoss Cohen
 
Video Coding Standard
Video Coding StandardVideo Coding Standard
Video Coding StandardVideoguy
 
The H.265/MPEG-HEVC Standard
The H.265/MPEG-HEVC StandardThe H.265/MPEG-HEVC Standard
The H.265/MPEG-HEVC StandardIMTC
 
H.265ImprovedCE_over_H.264-HarmonicMay2014Final
H.265ImprovedCE_over_H.264-HarmonicMay2014FinalH.265ImprovedCE_over_H.264-HarmonicMay2014Final
H.265ImprovedCE_over_H.264-HarmonicMay2014FinalDonald Pian
 
Compressed Video Quality
Compressed Video QualityCompressed Video Quality
Compressed Video QualityIain Richardson
 

Tendances (17)

H263.ppt
H263.pptH263.ppt
H263.ppt
 
Introduction to H.264 Advanced Video Compression
Introduction to H.264 Advanced Video CompressionIntroduction to H.264 Advanced Video Compression
Introduction to H.264 Advanced Video Compression
 
Video Compression Standards - History & Introduction
Video Compression Standards - History & IntroductionVideo Compression Standards - History & Introduction
Video Compression Standards - History & Introduction
 
H261
H261H261
H261
 
mpeg4
mpeg4mpeg4
mpeg4
 
HEVC VIDEO CODEC By Vinayagam Mariappan
HEVC VIDEO CODEC By Vinayagam MariappanHEVC VIDEO CODEC By Vinayagam Mariappan
HEVC VIDEO CODEC By Vinayagam Mariappan
 
h.264 video compression standard.
h.264 video compression standard.h.264 video compression standard.
h.264 video compression standard.
 
Subjective quality evaluation of the upcoming HEVC video compression standard
Subjective quality evaluation of the upcoming HEVC video compression standard Subjective quality evaluation of the upcoming HEVC video compression standard
Subjective quality evaluation of the upcoming HEVC video compression standard
 
Getting the most out of H.264
Getting the most out of H.264Getting the most out of H.264
Getting the most out of H.264
 
Introduction to HEVC
Introduction to HEVCIntroduction to HEVC
Introduction to HEVC
 
H.264 nal and RTP
H.264 nal and RTPH.264 nal and RTP
H.264 nal and RTP
 
Video Coding Standard
Video Coding StandardVideo Coding Standard
Video Coding Standard
 
The H.265/MPEG-HEVC Standard
The H.265/MPEG-HEVC StandardThe H.265/MPEG-HEVC Standard
The H.265/MPEG-HEVC Standard
 
Deblocking_Filter_v2
Deblocking_Filter_v2Deblocking_Filter_v2
Deblocking_Filter_v2
 
H.265ImprovedCE_over_H.264-HarmonicMay2014Final
H.265ImprovedCE_over_H.264-HarmonicMay2014FinalH.265ImprovedCE_over_H.264-HarmonicMay2014Final
H.265ImprovedCE_over_H.264-HarmonicMay2014Final
 
Compressed Video Quality
Compressed Video QualityCompressed Video Quality
Compressed Video Quality
 
Feature hevc
Feature hevcFeature hevc
Feature hevc
 

En vedette

Cac chuan nen va ung dung truyen video tren mang internet
Cac chuan nen va ung dung truyen video tren mang internetCac chuan nen va ung dung truyen video tren mang internet
Cac chuan nen va ung dung truyen video tren mang internetNo Name
 
video compression techique
video compression techiquevideo compression techique
video compression techiqueAshish Kumar
 
Video Compression Basics
Video Compression BasicsVideo Compression Basics
Video Compression BasicsSanjiv Malik
 
H.264 video compression standard.
H.264 video compression standard.H.264 video compression standard.
H.264 video compression standard.Axis Communications
 
Video Codecs and the Future by Vince Puglia
Video Codecs and the Future by Vince PugliaVideo Codecs and the Future by Vince Puglia
Video Codecs and the Future by Vince PugliaDialogic Inc.
 
Cac chuan nen ITU
Cac chuan nen ITUCac chuan nen ITU
Cac chuan nen ITUTrung Vi
 
The motion estimation
The motion estimationThe motion estimation
The motion estimationsakshij91
 
Images compression using huffman algorithm matlab
Images compression using huffman algorithm matlabImages compression using huffman algorithm matlab
Images compression using huffman algorithm matlabTan Hoang Luu
 
Introduction To Video Compression
Introduction To Video CompressionIntroduction To Video Compression
Introduction To Video Compressionguestdd7ccca
 
Compression: Video Compression (MPEG and others)
Compression: Video Compression (MPEG and others)Compression: Video Compression (MPEG and others)
Compression: Video Compression (MPEG and others)danishrafiq
 
multimedia technologies Introduction
multimedia technologies Introductionmultimedia technologies Introduction
multimedia technologies IntroductionMohammed Fareed
 
Introduction To Multimedia
Introduction To MultimediaIntroduction To Multimedia
Introduction To MultimediaJomel Penalba
 
Digital Image Processing
Digital Image ProcessingDigital Image Processing
Digital Image ProcessingSahil Biswas
 

En vedette (18)

Chương iii
Chương iiiChương iii
Chương iii
 
Cac chuan nen va ung dung truyen video tren mang internet
Cac chuan nen va ung dung truyen video tren mang internetCac chuan nen va ung dung truyen video tren mang internet
Cac chuan nen va ung dung truyen video tren mang internet
 
video compression techique
video compression techiquevideo compression techique
video compression techique
 
Video Compression Basics
Video Compression BasicsVideo Compression Basics
Video Compression Basics
 
H.264 video compression standard.
H.264 video compression standard.H.264 video compression standard.
H.264 video compression standard.
 
Multimedia Services: Video
Multimedia Services: VideoMultimedia Services: Video
Multimedia Services: Video
 
Codecs
CodecsCodecs
Codecs
 
Video Codecs and the Future by Vince Puglia
Video Codecs and the Future by Vince PugliaVideo Codecs and the Future by Vince Puglia
Video Codecs and the Future by Vince Puglia
 
Cac chuan nen ITU
Cac chuan nen ITUCac chuan nen ITU
Cac chuan nen ITU
 
The motion estimation
The motion estimationThe motion estimation
The motion estimation
 
Images compression using huffman algorithm matlab
Images compression using huffman algorithm matlabImages compression using huffman algorithm matlab
Images compression using huffman algorithm matlab
 
YUV, Y CB CR and Subsampling
YUV, Y CB CR and SubsamplingYUV, Y CB CR and Subsampling
YUV, Y CB CR and Subsampling
 
Introduction To Video Compression
Introduction To Video CompressionIntroduction To Video Compression
Introduction To Video Compression
 
Compression: Video Compression (MPEG and others)
Compression: Video Compression (MPEG and others)Compression: Video Compression (MPEG and others)
Compression: Video Compression (MPEG and others)
 
multimedia technologies Introduction
multimedia technologies Introductionmultimedia technologies Introduction
multimedia technologies Introduction
 
Introduction To Multimedia
Introduction To MultimediaIntroduction To Multimedia
Introduction To Multimedia
 
JPEG Image Compression
JPEG Image CompressionJPEG Image Compression
JPEG Image Compression
 
Digital Image Processing
Digital Image ProcessingDigital Image Processing
Digital Image Processing
 

Similaire à H264 video compression explained

A REAL-TIME H.264/AVC ENCODER&DECODER WITH VERTICAL MODE FOR INTRA FRAME AND ...
A REAL-TIME H.264/AVC ENCODER&DECODER WITH VERTICAL MODE FOR INTRA FRAME AND ...A REAL-TIME H.264/AVC ENCODER&DECODER WITH VERTICAL MODE FOR INTRA FRAME AND ...
A REAL-TIME H.264/AVC ENCODER&DECODER WITH VERTICAL MODE FOR INTRA FRAME AND ...csandit
 
IBM VideoCharger and Digital Library MediaBase.doc
IBM VideoCharger and Digital Library MediaBase.docIBM VideoCharger and Digital Library MediaBase.doc
IBM VideoCharger and Digital Library MediaBase.docVideoguy
 
Spatial Scalable Video Compression Using H.264
Spatial Scalable Video Compression Using H.264Spatial Scalable Video Compression Using H.264
Spatial Scalable Video Compression Using H.264IOSR Journals
 
/conferences/spr2004/presentations/eubanks/eubanks_mpeg4.ppt
/conferences/spr2004/presentations/eubanks/eubanks_mpeg4.ppt/conferences/spr2004/presentations/eubanks/eubanks_mpeg4.ppt
/conferences/spr2004/presentations/eubanks/eubanks_mpeg4.pptVideoguy
 
Paper id 2120148
Paper id 2120148Paper id 2120148
Paper id 2120148IJRAT
 
JPEG2000 Alliance IBC 2009
JPEG2000 Alliance IBC 2009JPEG2000 Alliance IBC 2009
JPEG2000 Alliance IBC 2009Hal J. Reisiger
 
10.1.1.184.6612
10.1.1.184.661210.1.1.184.6612
10.1.1.184.6612NITC
 
Polycom ® Video Communications H.264 and Pro-Motion ™ : The ...
Polycom ® Video Communications H.264 and Pro-Motion ™ : The ...Polycom ® Video Communications H.264 and Pro-Motion ™ : The ...
Polycom ® Video Communications H.264 and Pro-Motion ™ : The ...Videoguy
 
Video Streaming - 4.ppt
Video Streaming - 4.pptVideo Streaming - 4.ppt
Video Streaming - 4.pptVideoguy
 
Polycom Video Communications
Polycom Video CommunicationsPolycom Video Communications
Polycom Video CommunicationsVideoguy
 
mpeg4copy-120428133000-phpapp01.ppt
mpeg4copy-120428133000-phpapp01.pptmpeg4copy-120428133000-phpapp01.ppt
mpeg4copy-120428133000-phpapp01.pptPawachMetharattanara
 
Next generation video compression
Next generation video compressionNext generation video compression
Next generation video compressionEricsson
 
Next generation video compression
Next generation video compressionNext generation video compression
Next generation video compressionEricsson Slides
 
Mpeg4copy 120428133000-phpapp01
Mpeg4copy 120428133000-phpapp01Mpeg4copy 120428133000-phpapp01
Mpeg4copy 120428133000-phpapp01netzwelt12345
 
MPEG Standards. Know What Video Format to Choose MPEG-2 or MPEG-4.pdf
MPEG Standards. Know What Video Format to Choose MPEG-2 or MPEG-4.pdfMPEG Standards. Know What Video Format to Choose MPEG-2 or MPEG-4.pdf
MPEG Standards. Know What Video Format to Choose MPEG-2 or MPEG-4.pdfJohn Peterson
 
The H.264/AVC Advanced Video Coding Standard: Overview and ...
The H.264/AVC Advanced Video Coding Standard: Overview and ...The H.264/AVC Advanced Video Coding Standard: Overview and ...
The H.264/AVC Advanced Video Coding Standard: Overview and ...Videoguy
 

Similaire à H264 video compression explained (20)

A REAL-TIME H.264/AVC ENCODER&DECODER WITH VERTICAL MODE FOR INTRA FRAME AND ...
A REAL-TIME H.264/AVC ENCODER&DECODER WITH VERTICAL MODE FOR INTRA FRAME AND ...A REAL-TIME H.264/AVC ENCODER&DECODER WITH VERTICAL MODE FOR INTRA FRAME AND ...
A REAL-TIME H.264/AVC ENCODER&DECODER WITH VERTICAL MODE FOR INTRA FRAME AND ...
 
Performance Analysis of Various Video Compression Techniques
Performance Analysis of Various Video Compression TechniquesPerformance Analysis of Various Video Compression Techniques
Performance Analysis of Various Video Compression Techniques
 
IBM VideoCharger and Digital Library MediaBase.doc
IBM VideoCharger and Digital Library MediaBase.docIBM VideoCharger and Digital Library MediaBase.doc
IBM VideoCharger and Digital Library MediaBase.doc
 
Spatial Scalable Video Compression Using H.264
Spatial Scalable Video Compression Using H.264Spatial Scalable Video Compression Using H.264
Spatial Scalable Video Compression Using H.264
 
E010132529
E010132529E010132529
E010132529
 
/conferences/spr2004/presentations/eubanks/eubanks_mpeg4.ppt
/conferences/spr2004/presentations/eubanks/eubanks_mpeg4.ppt/conferences/spr2004/presentations/eubanks/eubanks_mpeg4.ppt
/conferences/spr2004/presentations/eubanks/eubanks_mpeg4.ppt
 
Paper id 2120148
Paper id 2120148Paper id 2120148
Paper id 2120148
 
JPEG2000 Alliance IBC 2009
JPEG2000 Alliance IBC 2009JPEG2000 Alliance IBC 2009
JPEG2000 Alliance IBC 2009
 
10.1.1.184.6612
10.1.1.184.661210.1.1.184.6612
10.1.1.184.6612
 
Polycom ® Video Communications H.264 and Pro-Motion ™ : The ...
Polycom ® Video Communications H.264 and Pro-Motion ™ : The ...Polycom ® Video Communications H.264 and Pro-Motion ™ : The ...
Polycom ® Video Communications H.264 and Pro-Motion ™ : The ...
 
Video Streaming - 4.ppt
Video Streaming - 4.pptVideo Streaming - 4.ppt
Video Streaming - 4.ppt
 
Product performance
Product performanceProduct performance
Product performance
 
Polycom Video Communications
Polycom Video CommunicationsPolycom Video Communications
Polycom Video Communications
 
mpeg4copy-120428133000-phpapp01.ppt
mpeg4copy-120428133000-phpapp01.pptmpeg4copy-120428133000-phpapp01.ppt
mpeg4copy-120428133000-phpapp01.ppt
 
[IJET-V1I2P1] Authors :Imran Ullah Khan ,Mohd. Javed Khan ,S.Hasan Saeed ,Nup...
[IJET-V1I2P1] Authors :Imran Ullah Khan ,Mohd. Javed Khan ,S.Hasan Saeed ,Nup...[IJET-V1I2P1] Authors :Imran Ullah Khan ,Mohd. Javed Khan ,S.Hasan Saeed ,Nup...
[IJET-V1I2P1] Authors :Imran Ullah Khan ,Mohd. Javed Khan ,S.Hasan Saeed ,Nup...
 
Next generation video compression
Next generation video compressionNext generation video compression
Next generation video compression
 
Next generation video compression
Next generation video compressionNext generation video compression
Next generation video compression
 
Mpeg4copy 120428133000-phpapp01
Mpeg4copy 120428133000-phpapp01Mpeg4copy 120428133000-phpapp01
Mpeg4copy 120428133000-phpapp01
 
MPEG Standards. Know What Video Format to Choose MPEG-2 or MPEG-4.pdf
MPEG Standards. Know What Video Format to Choose MPEG-2 or MPEG-4.pdfMPEG Standards. Know What Video Format to Choose MPEG-2 or MPEG-4.pdf
MPEG Standards. Know What Video Format to Choose MPEG-2 or MPEG-4.pdf
 
The H.264/AVC Advanced Video Coding Standard: Overview and ...
The H.264/AVC Advanced Video Coding Standard: Overview and ...The H.264/AVC Advanced Video Coding Standard: Overview and ...
The H.264/AVC Advanced Video Coding Standard: Overview and ...
 

Plus de cnssources

The challenges of minimal illumination
The challenges of minimal illuminationThe challenges of minimal illumination
The challenges of minimal illuminationcnssources
 
Which has better zoom?
Which has better zoom?Which has better zoom?
Which has better zoom?cnssources
 
Thermal Surveillance
Thermal SurveillanceThermal Surveillance
Thermal Surveillancecnssources
 
Lighting design guide for network video
Lighting design guide for network videoLighting design guide for network video
Lighting design guide for network videocnssources
 
Axis Intelligent Video
Axis Intelligent VideoAxis Intelligent Video
Axis Intelligent Videocnssources
 
10 reasons why you shouldn't buy an anologue camera
10 reasons why you shouldn't buy an anologue camera10 reasons why you shouldn't buy an anologue camera
10 reasons why you shouldn't buy an anologue cameracnssources
 
Video Compression Techniques
Video Compression TechniquesVideo Compression Techniques
Video Compression Techniquescnssources
 
CNS - An Introduction
CNS - An IntroductionCNS - An Introduction
CNS - An Introductioncnssources
 
CDVI Product Preview
CDVI Product PreviewCDVI Product Preview
CDVI Product Previewcnssources
 
An Introduction to CNS
An Introduction to CNSAn Introduction to CNS
An Introduction to CNScnssources
 

Plus de cnssources (15)

The challenges of minimal illumination
The challenges of minimal illuminationThe challenges of minimal illumination
The challenges of minimal illumination
 
Which has better zoom?
Which has better zoom?Which has better zoom?
Which has better zoom?
 
Thermal Surveillance
Thermal SurveillanceThermal Surveillance
Thermal Surveillance
 
Lighting design guide for network video
Lighting design guide for network videoLighting design guide for network video
Lighting design guide for network video
 
HDTV
HDTVHDTV
HDTV
 
Axis Intelligent Video
Axis Intelligent VideoAxis Intelligent Video
Axis Intelligent Video
 
10 reasons why you shouldn't buy an anologue camera
10 reasons why you shouldn't buy an anologue camera10 reasons why you shouldn't buy an anologue camera
10 reasons why you shouldn't buy an anologue camera
 
Video Compression Techniques
Video Compression TechniquesVideo Compression Techniques
Video Compression Techniques
 
Volkswagen
VolkswagenVolkswagen
Volkswagen
 
Sanral
SanralSanral
Sanral
 
Red Bull
Red BullRed Bull
Red Bull
 
Kia Motors
Kia MotorsKia Motors
Kia Motors
 
CNS - An Introduction
CNS - An IntroductionCNS - An Introduction
CNS - An Introduction
 
CDVI Product Preview
CDVI Product PreviewCDVI Product Preview
CDVI Product Preview
 
An Introduction to CNS
An Introduction to CNSAn Introduction to CNS
An Introduction to CNS
 

Dernier

activity_diagram_combine_v4_20190827.pdfactivity_diagram_combine_v4_20190827.pdf
activity_diagram_combine_v4_20190827.pdfactivity_diagram_combine_v4_20190827.pdfactivity_diagram_combine_v4_20190827.pdfactivity_diagram_combine_v4_20190827.pdf
activity_diagram_combine_v4_20190827.pdfactivity_diagram_combine_v4_20190827.pdfJamie (Taka) Wang
 
Basic Building Blocks of Internet of Things.
Basic Building Blocks of Internet of Things.Basic Building Blocks of Internet of Things.
Basic Building Blocks of Internet of Things.YounusS2
 
UiPath Studio Web workshop series - Day 6
UiPath Studio Web workshop series - Day 6UiPath Studio Web workshop series - Day 6
UiPath Studio Web workshop series - Day 6DianaGray10
 
Machine Learning Model Validation (Aijun Zhang 2024).pdf
Machine Learning Model Validation (Aijun Zhang 2024).pdfMachine Learning Model Validation (Aijun Zhang 2024).pdf
Machine Learning Model Validation (Aijun Zhang 2024).pdfAijun Zhang
 
Comparing Sidecar-less Service Mesh from Cilium and Istio
Comparing Sidecar-less Service Mesh from Cilium and IstioComparing Sidecar-less Service Mesh from Cilium and Istio
Comparing Sidecar-less Service Mesh from Cilium and IstioChristian Posta
 
AI Fame Rush Review – Virtual Influencer Creation In Just Minutes
AI Fame Rush Review – Virtual Influencer Creation In Just MinutesAI Fame Rush Review – Virtual Influencer Creation In Just Minutes
AI Fame Rush Review – Virtual Influencer Creation In Just MinutesMd Hossain Ali
 
Building AI-Driven Apps Using Semantic Kernel.pptx
Building AI-Driven Apps Using Semantic Kernel.pptxBuilding AI-Driven Apps Using Semantic Kernel.pptx
Building AI-Driven Apps Using Semantic Kernel.pptxUdaiappa Ramachandran
 
Crea il tuo assistente AI con lo Stregatto (open source python framework)
Crea il tuo assistente AI con lo Stregatto (open source python framework)Crea il tuo assistente AI con lo Stregatto (open source python framework)
Crea il tuo assistente AI con lo Stregatto (open source python framework)Commit University
 
KubeConEU24-Monitoring Kubernetes and Cloud Spend with OpenCost
KubeConEU24-Monitoring Kubernetes and Cloud Spend with OpenCostKubeConEU24-Monitoring Kubernetes and Cloud Spend with OpenCost
KubeConEU24-Monitoring Kubernetes and Cloud Spend with OpenCostMatt Ray
 
IaC & GitOps in a Nutshell - a FridayInANuthshell Episode.pdf
IaC & GitOps in a Nutshell - a FridayInANuthshell Episode.pdfIaC & GitOps in a Nutshell - a FridayInANuthshell Episode.pdf
IaC & GitOps in a Nutshell - a FridayInANuthshell Episode.pdfDaniel Santiago Silva Capera
 
AI You Can Trust - Ensuring Success with Data Integrity Webinar
AI You Can Trust - Ensuring Success with Data Integrity WebinarAI You Can Trust - Ensuring Success with Data Integrity Webinar
AI You Can Trust - Ensuring Success with Data Integrity WebinarPrecisely
 
UiPath Community: AI for UiPath Automation Developers
UiPath Community: AI for UiPath Automation DevelopersUiPath Community: AI for UiPath Automation Developers
UiPath Community: AI for UiPath Automation DevelopersUiPathCommunity
 
UiPath Platform: The Backend Engine Powering Your Automation - Session 1
UiPath Platform: The Backend Engine Powering Your Automation - Session 1UiPath Platform: The Backend Engine Powering Your Automation - Session 1
UiPath Platform: The Backend Engine Powering Your Automation - Session 1DianaGray10
 
Artificial Intelligence & SEO Trends for 2024
Artificial Intelligence & SEO Trends for 2024Artificial Intelligence & SEO Trends for 2024
Artificial Intelligence & SEO Trends for 2024D Cloud Solutions
 
Nanopower In Semiconductor Industry.pdf
Nanopower  In Semiconductor Industry.pdfNanopower  In Semiconductor Industry.pdf
Nanopower In Semiconductor Industry.pdfPedro Manuel
 
Videogame localization & technology_ how to enhance the power of translation.pdf
Videogame localization & technology_ how to enhance the power of translation.pdfVideogame localization & technology_ how to enhance the power of translation.pdf
Videogame localization & technology_ how to enhance the power of translation.pdfinfogdgmi
 
Meet the new FSP 3000 M-Flex800™
Meet the new FSP 3000 M-Flex800™Meet the new FSP 3000 M-Flex800™
Meet the new FSP 3000 M-Flex800™Adtran
 
Connector Corner: Extending LLM automation use cases with UiPath GenAI connec...
Connector Corner: Extending LLM automation use cases with UiPath GenAI connec...Connector Corner: Extending LLM automation use cases with UiPath GenAI connec...
Connector Corner: Extending LLM automation use cases with UiPath GenAI connec...DianaGray10
 

Dernier (20)

activity_diagram_combine_v4_20190827.pdfactivity_diagram_combine_v4_20190827.pdf
activity_diagram_combine_v4_20190827.pdfactivity_diagram_combine_v4_20190827.pdfactivity_diagram_combine_v4_20190827.pdfactivity_diagram_combine_v4_20190827.pdf
activity_diagram_combine_v4_20190827.pdfactivity_diagram_combine_v4_20190827.pdf
 
Basic Building Blocks of Internet of Things.
Basic Building Blocks of Internet of Things.Basic Building Blocks of Internet of Things.
Basic Building Blocks of Internet of Things.
 
UiPath Studio Web workshop series - Day 6
UiPath Studio Web workshop series - Day 6UiPath Studio Web workshop series - Day 6
UiPath Studio Web workshop series - Day 6
 
Machine Learning Model Validation (Aijun Zhang 2024).pdf
Machine Learning Model Validation (Aijun Zhang 2024).pdfMachine Learning Model Validation (Aijun Zhang 2024).pdf
Machine Learning Model Validation (Aijun Zhang 2024).pdf
 
Comparing Sidecar-less Service Mesh from Cilium and Istio
Comparing Sidecar-less Service Mesh from Cilium and IstioComparing Sidecar-less Service Mesh from Cilium and Istio
Comparing Sidecar-less Service Mesh from Cilium and Istio
 
AI Fame Rush Review – Virtual Influencer Creation In Just Minutes
AI Fame Rush Review – Virtual Influencer Creation In Just MinutesAI Fame Rush Review – Virtual Influencer Creation In Just Minutes
AI Fame Rush Review – Virtual Influencer Creation In Just Minutes
 
Building AI-Driven Apps Using Semantic Kernel.pptx
Building AI-Driven Apps Using Semantic Kernel.pptxBuilding AI-Driven Apps Using Semantic Kernel.pptx
Building AI-Driven Apps Using Semantic Kernel.pptx
 
20150722 - AGV
20150722 - AGV20150722 - AGV
20150722 - AGV
 
Crea il tuo assistente AI con lo Stregatto (open source python framework)
Crea il tuo assistente AI con lo Stregatto (open source python framework)Crea il tuo assistente AI con lo Stregatto (open source python framework)
Crea il tuo assistente AI con lo Stregatto (open source python framework)
 
KubeConEU24-Monitoring Kubernetes and Cloud Spend with OpenCost
KubeConEU24-Monitoring Kubernetes and Cloud Spend with OpenCostKubeConEU24-Monitoring Kubernetes and Cloud Spend with OpenCost
KubeConEU24-Monitoring Kubernetes and Cloud Spend with OpenCost
 
IaC & GitOps in a Nutshell - a FridayInANuthshell Episode.pdf
IaC & GitOps in a Nutshell - a FridayInANuthshell Episode.pdfIaC & GitOps in a Nutshell - a FridayInANuthshell Episode.pdf
IaC & GitOps in a Nutshell - a FridayInANuthshell Episode.pdf
 
20230104 - machine vision
20230104 - machine vision20230104 - machine vision
20230104 - machine vision
 
AI You Can Trust - Ensuring Success with Data Integrity Webinar
AI You Can Trust - Ensuring Success with Data Integrity WebinarAI You Can Trust - Ensuring Success with Data Integrity Webinar
AI You Can Trust - Ensuring Success with Data Integrity Webinar
 
UiPath Community: AI for UiPath Automation Developers
UiPath Community: AI for UiPath Automation DevelopersUiPath Community: AI for UiPath Automation Developers
UiPath Community: AI for UiPath Automation Developers
 
UiPath Platform: The Backend Engine Powering Your Automation - Session 1
UiPath Platform: The Backend Engine Powering Your Automation - Session 1UiPath Platform: The Backend Engine Powering Your Automation - Session 1
UiPath Platform: The Backend Engine Powering Your Automation - Session 1
 
Artificial Intelligence & SEO Trends for 2024
Artificial Intelligence & SEO Trends for 2024Artificial Intelligence & SEO Trends for 2024
Artificial Intelligence & SEO Trends for 2024
 
Nanopower In Semiconductor Industry.pdf
Nanopower  In Semiconductor Industry.pdfNanopower  In Semiconductor Industry.pdf
Nanopower In Semiconductor Industry.pdf
 
Videogame localization & technology_ how to enhance the power of translation.pdf
Videogame localization & technology_ how to enhance the power of translation.pdfVideogame localization & technology_ how to enhance the power of translation.pdf
Videogame localization & technology_ how to enhance the power of translation.pdf
 
Meet the new FSP 3000 M-Flex800™
Meet the new FSP 3000 M-Flex800™Meet the new FSP 3000 M-Flex800™
Meet the new FSP 3000 M-Flex800™
 
Connector Corner: Extending LLM automation use cases with UiPath GenAI connec...
Connector Corner: Extending LLM automation use cases with UiPath GenAI connec...Connector Corner: Extending LLM automation use cases with UiPath GenAI connec...
Connector Corner: Extending LLM automation use cases with UiPath GenAI connec...
 

H264 video compression explained

  • 1. White paper h.264 video compression standard. New possibilities within video surveillance.
  • 2. table of contents 1. introduction 3 2. Development of h.264 3 3. how video compression works 4 4. h.264 profiles and levels 5 5. Understanding frames 5 6. Basic methods of reducing data 6 7. efficiency of h.264 7 8. Conclusion 9
  • 3. 1. introduction The latest video compression standard, H.264 (also known as MPEG-4 Part 10/AVC for Advanced Video Coding), is expected to become the video standard of choice in the coming years. H.264 is an open, licensed standard that supports the most efficient video compression techniques available today. Without compromising image quality, an H.264 encoder can reduce the size of a digital video file by more than 80% compared with the Motion JPEG format and as much as 50% more than with the MPEG-4 Part 2 standard. This means that much less network bandwidth and storage space are required for a video file. Or seen another way, much higher video quality can be achieved for a given bit rate. Jointly defined by standardization organizations in the telecommunications and IT industries, H.264 is expected to be more widely adopted than previous standards. H.264 has already been introduced in new electronic gadgets such as mobile phones and digital video players, and has gained fast acceptance by end users. Service providers such as online video storage and telecommunications companies are also beginning to adopt H.264. In the video surveillance industry, H.264 will most likely find the quickest traction in applications where there are demands for high frame rates and high resolution, such as in the surveillance of highways, airports and casinos, where the use of 30/25 (NTSC/PAL) frames per second is the norm. This is where the economies of reduced bandwidth and storage needs will deliver the biggest savings. H.264 is also expected to accelerate the adoption of megapixel cameras since the highly efficient compression technology can reduce the large file sizes and bit rates generated without compromising image quality. There are tradeoffs, however. While H.264 provides savings in network bandwidth and storage costs, it will require higher performance network cameras and monitoring stations. 2. Development of h.264 H.264 is the result of a joint project between the ITU-T’s Video Coding Experts Group and the ISO/IEC Moving Picture Experts Group (MPEG). ITU-T is the sector that coordinates telecommunications standards on behalf of the International Telecommunication Union. ISO stands for International Organization for Standardization and IEC stands for International Electrotechnical Commission, which oversees standards for all electrical, electronic and related technologies. H.264 is the name used by ITU-T, while ISO/IEC has named it MPEG-4 Part 10/AVC since it is presented as a new part in its MPEG-4 suite. The MPEG-4 suite includes, for example, MPEG-4 Part 2, which is a standard that has been used by IP-based video encoders and network cameras. Designed to address several weaknesses in previous video compression standards, H.264 delivers on its goals of supporting: > Implementations that deliver an average bit rate reduction of 50%, given a fixed video quality compared with any other video standard > Error robustness so that transmission errors over various networks are tolerated > Low latency capabilities and better quality for higher latency > Straightforward syntax specification that simplifies implementations > Exact match decoding, which defines exactly how numerical calculations are to be made by an encoder and a decoder to avoid errors from accumulating H.264 also has the flexibility to support a wide variety of applications with very different bit rate requirements. For example, in entertainment video applications—which include broadcast, satellite, cable and DVD—H.264 will be able to deliver a performance of between 1 to 10 Mbit/s with high latency, while for telecom services, H.264 can deliver bit rates of below 1 Mbit/s with low latency. 3
  • 4. 3. how video compression works Video compression is about reducing and removing redundant video data so that a digital video file can be effectively sent and stored. The process involves applying an algorithm to the source video to create a compressed file that is ready for transmission or storage. To play the compressed file, an inverse algorithm is applied to produce a video that shows virtually the same content as the original source video. The time it takes to compress, send, decompress and display a file is called latency. The more advanced the compression algorithm, the higher the latency, given the same processing power. A pair of algorithms that works together is called a video codec (encoder/decoder). Video codecs that implement different standards are normally not compatible with each other; that is, video content that is compressed using one standard cannot be decompressed with a different standard. For instance, an MPEG-4 Part 2 decoder will not work with an H.264 encoder. This is simply because one algorithm cannot correctly decode the output from another algorithm but it is possible to implement many different algorithms in the same software or hardware, which would then enable multiple formats to be compressed. Different video compression standards utilize different methods of reducing data, and hence, results differ in bit rate, quality and latency. Results from encoders that use the same compression standard may also vary because the designer of an encoder can choose to implement different sets of tools defined by a standard. As long as the output of an encoder conforms to a standard’s format and decoder, it is possible to make different implementations. This is advantageous because different implementations have different goals and budget. Professional non-real-time software encoders for mastering optical media should have the option of being able to deliver better encoded video than a real-time hardware encoder for video conferencing that is integrated in a hand-held device. A given standard, therefore, cannot guarantee a given bit rate or quality. Furthermore, the performance of a standard cannot be properly compared with other standards, or even other implementations of the same standard, without first defining how it is implemented. A decoder, unlike an encoder, must implement all the required parts of a standard in order to decode a compliant bit stream. This is because a standard specifies exactly how a decompression algorithm should restore every bit of a compressed video. The graph below provides a bit rate comparison, given the same level of image quality, among the following video standards: Motion JPEG, MPEG-4 Part 2 (no motion compensation), MPEG-4 Part 2 (with motion compensation) and H.264 (baseline profile). Doorway scene H.264 (Baseline profile) MPEG-4 Part 2 (No motion compensation) MPEG-4 Part 2 (With motion compensation) Motion JPEG 7,000 6,000 5,000 Bit rate (kbit/s) 4,000 3,000 2,000 1,000 0 50 100 Time (s) Figure 1. An H.264 encoder generated up to 50% fewer bits per second for a sample video sequence than an MPEG-4 encoder with motion compensation. The H.264 encoder was at least three times more efficient than an MPEG-4 encoder with no motion compensation and at least six times more efficient than Motion JPEG. 4
  • 5. 4. h.264 profiles and levels The joint group involved in defining H.264 focused on creating a simple and clean solution, limiting options and features to a minimum. An important aspect of the standard, as with other video standards, is providing the capabilities in profiles (sets of algorithmic features) and levels (performance classes) that optimally support popular productions and common formats. H.264 has seven profiles, each targeting a specific class of applications. Each profile defines what feature set the encoder may use and limits the decoder implementation complexity. Network cameras and video encoders will most likely use a profile called the baseline profile, which is intended primarily for applications with limited computing resources. The baseline profile is the most suitable given the available performance in a real-time encoder that is embedded in a network video product. The profile also enables low latency, which is an important requirement of surveillance video and also particularly important in enabling real-time, pan/tilt/zoom (PTZ) control in PTZ network cameras. H.264 has 11 levels or degree of capability to limit performance, bandwidth and memory requirements. Each level defines the bit rate and the encoding rate in macroblock per second for resolutions ranging from QCIF to HDTV and beyond. The higher the resolution, the higher the level required. 5. Understanding frames Depending on the H.264 profile, different types of frames such as I-frames, P-frames and B-frames, may be used by an encoder. An I-frame, or intra frame, is a self-contained frame that can be independently decoded without any reference to other images. The first image in a video sequence is always an I-frame. I-frames are needed as starting points for new viewers or resynchronization points if the transmitted bit stream is damaged. I-frames can be used to implement fast-forward, rewind and other random access functions. An encoder will automatically insert I-frames at regular intervals or on demand if new clients are expected to join in viewing a stream. The drawback of I-frames is that they consume much more bits, but on the other hand, they do not generate many artifacts. A P-frame, which stands for predictive inter frame, makes references to parts of earlier I and/or P frame(s) to code the frame. P-frames usually require fewer bits than I-frames, but a drawback is that they are very sensitive to transmission errors because of the complex dependency on earlier P and I reference frames. A B-frame, or bi-predictive inter frame, is a frame that makes references to both an earlier reference frame and a future frame. I B B P B B P B B I B B P Figure 2. A typical sequence with I-, B- and P-frames. A P-frame may only reference preceding I- or P-frames, while a B-frame may reference both preceding and succeeding I- or P-frames. 5
  • 6. When a video decoder restores a video by decoding the bit stream frame by frame, decoding must always start with an I-frame. P-frames and B-frames, if used, must be decoded together with the reference frame(s). In the H.264 baseline profile, only I- and P-frames are used. This profile is ideal for network cameras and video encoders since low latency is achieved because B-frames are not used. 6. Basic methods of reducing data A variety of methods can be used to reduce video data, both within an image frame and between a series of frames. Within an image frame, data can be reduced simply by removing unnecessary information, which will have an impact on the image resolution. In a series of frames, video data can be reduced by such methods as difference coding, which is used by most video compression standards including H.264. In difference coding, a frame is compared with a reference frame (i.e. earlier I- or P-frame) and only pixels that have changed with respect to the reference frame are coded. In this way, the number of pixel values that are coded and sent is reduced. Figure 3. With Motion JPEG format, the three images in the above sequence are coded and sent as separate unique images (I-frames) with no dependencies on each other. Figure 4. With difference coding (used in most video compression standards including H.264), only the first image (I-frame) is coded in its entirety. In the two following images (P-frames), references are made to the first picture for the static elements, i.e. the house, and only the moving parts, i.e. the running man, is coded using motion vectors, thus reducing the amount of information that is sent and stored. The amount of encoding can be further reduced if detection and encoding of differences is based on blocks of pixels (macroblocks) rather than individual pixels; therefore, bigger areas are compared and only blocks that are significantly different are coded. The overhead associated with indicating the location of areas to be changed is also reduced. 6
  • 7. Difference coding, however, would not significantly reduce data if there was a lot of motion in a video. Here, techniques such as block-based motion compensation can be used. Block-based motion compensation takes into account that much of what makes up a new frame in a video sequence can be found in an earlier frame, but perhaps in a different location. This technique divides a frame into a series of macroblocks. Block by block, a new frame—for instance, a P-frame—can be composed or ‘predicted’ by looking for a matching block in a reference frame. If a match is found, the encoder simply codes the position where the matching block is to be found in the reference frame. Coding the motion vector, as it is called, takes up fewer bits than if the actual content of a block were to be coded. Search window Matching block Motion vector Target block Earlier reference frame P-frame Figure 5. Illustration of block-based motion compensation 7. efficiency of h.264 H.264 takes video compression technology to a new level. With H.264, a new and advanced intra prediction scheme is introduced for encoding I-frames. This scheme can greatly reduce the bit size of an I-frame and maintain a high quality by enabling the successive prediction of smaller blocks of pixels within each macroblock in a frame. This is done by trying to find matching pixels among the earlier- encoded pixels that border a new 4x4 pixel block to be intra-coded. By reusing pixel values that have already been encoded, the bit size can be drastically reduced. The new intraprediction is a key part of the H.264 technology that has proven to be very efficient. For comparison, if only I-frames were used in an H.264 stream, it would have a much smaller file size than a Motion JPEG stream, which uses only I-frames. In this mode, four bottom pixels from In this mode, four right-most pixels In this mode, eight bottom pixels from the block above are copied vertically from the block to the left are copied the blocks above are copied diagonally into part of an intra-coded macro- horizontally into part of an intra-coded into part of an intra-coded macro- block. macroblock. block. Figure 6. Illustrations of some of the modes that intra prediction can take in coding 4x4 pixels within one of the 16 blocks that make up a macroblock. Each of the 16 blocks in a macroblock may be coded using different modes. 7
  • 8. Original source image intra predicted image residual image Output image Figure 7. The above images illustrate the efficiency of H.264’s intra prediction scheme, whereby the intra predicted image is sent for “free”. Only the residual content and the intra prediction modes need to be coded to produce the output image. Block-based motion compensation—used in encoding P- and B-frames—has also been improved in H.264. An H.264 encoder can choose to search for matching blocks—down to sub-pixel accuracy—in a few or many areas of one or several reference frames. The block size and shape can also be adjusted to improve a match. In areas where no matching blocks can be found in a reference frame, intra-coded macroblocks are used. The high degree of flexibility in H.264’s block-based motion compensation pays off in crowded surveillance scenes where the quality can be maintained for demanding applications. Motion compensation is the most demanding aspect of a video encoder and the different ways and degrees with which it can be implemented by an H.264 encoder can have an impact on how efficiently video is compressed. 8
  • 9. With H.264, typical blocky artifacts—seen in highly compressed video using Motion JPEG and MPEG standards other than H.264—can be reduced using an in-loop deblocking filter. This filter smoothes block edges using an adaptive strength to deliver an almost perfect decompressed video. Figure 8. Blocky artifacts in the highly compressed image at left are reduced when a deblocking filter is applied, as seen in the image at right. 8. Conclusion H.264 presents a huge step forward in video compression technology. It offers techniques that enable better compression efficiencies due to more accurate prediction capabilities, as well as improved resilience to errors. It provides new possibilities for creating better video encoders that enable higher quality video streams, higher frame rates and higher resolutions at maintained bit rates (compared with previous standards), or, conversely, the same quality video at lower bit rates. H.264 represents the first time that the ITU, ISO and IEC have come together on a common, international standard for video compression. Due to its flexibility, H.264 has been applied in diverse areas such as high-definition DVD (e.g. Blu-ray), digital video broadcasting including high-definition TV, online video storage (e.g. YouTube), third-generation mobile telephony, in software such as QuickTime, Flash and Apple Computer’s MacOS X operating system, and in home video game consoles such PlayStation 3. With support from many industries and applications for consumer and professional needs, H.264 is expected to replace other compression standards and methods in use today. As the H.264 format becomes more broadly available in network cameras, video encoders and video management software, system designers and integrators will need to make sure that the products and vendors they choose support this new open standard. And for the time being, network video products that support both H.264 and Motion JPEG are ideal for maximum flexibility and integration possibilities. 9
  • 10. www.axis.com 31669/EN/R1/0803 about axis Communications Axis is an IT company offering network video solutions for professional installations. The company is the global market leader in network video, driving the ongoing shift from analog to digital video surveillance. Axis products and solutions focus on security surveillance and remote monitoring, and are based on innovative, open technology platforms. Axis is a Swedish-based company, operating worldwide with offices in 18 countries and cooperating with part- ners in more than 70 countries. Founded in 1984, Axis is listed on the OMX Nordic Exchange, Large Cap and Infor- mation Technology. For more information about Axis, please visit our website at www.axis.com. ©2008 Axis Communications AB. AXIS COMMUNICATIONS, AXIS, ETRAX, ARTPEC and VAPIX are registered trademarks or trademark applications of Axis AB in various jurisdictions. All other company names and products are trademarks or registered trademarks of their respective companies. We reserve the right to introduce modifications without notice.