Video Compression Technology

We're familiar with the more common video compression technologies used for DVR Applications in the market today like MPEG-4 and H.264. We know that H.264 is a higher compression standard over MPEG-4; but do we know why and how is that so? We need not to go deeply into the compression rates comparisons and very technical stuffs. Here's a layman presentation of the Basic Image Compression Standards - what they offer and where they are more commonly used for.



Video Compression Technology

At its most basic level, compression is performed when an input video stream is analyzed and information that is indiscernible to the viewer is discarded. Each event is then assigned a code - commonly occurring events are assigned few bits and rare events will have codes more bits. These steps are commonly called signal analysis, quantization and variable length encoding respectively.

Compression Standards

MPEG stands for the Moving Picture Experts Group. MPEG is an ISO/IEC working group, established in 1988 to develop standards for digital audio and video formats. There are five MPEG standards being used or in development. Each compression standard was designed with a specific application and bit rate in mind, although MPEG compression scales well with increased bit rates. They include:

MPEG-1
Designed for up to 1.5 Mbit/sec
Standard for the compression of moving pictures and audio. This was based on CD-ROM video applications, and is a popular standard for video on the Internet, transmitted as .mpg files. In addition, level 3 of MPEG-1 is the most popular standard for digital compression of audio--known as MP3. MPEG-1 is the standard of compression for VideoCD, the most popular video distribution format throughout much of Asia.

MPEG-2
Designed for between 1.5 and 15 Mbit/sec
Standard on which Digital Television set top boxes and DVD compression is based. It is based on MPEG-1, but designed for the compression and transmission of digital broadcast television. The most significant enhancement from MPEG-1 is its ability to efficiently compress interlaced video. MPEG-2 scales well to HDTV resolution and bit rates, obviating the need for an MPEG-3.

MPEG-4
Standard for multimedia and Web compression. MPEG-4 is based on object-based compression, similar in nature to the Virtual Reality Modeling Language. Individual objects within a scene are tracked separately and compressed together to create an MPEG4 file. This results in very efficient compression that is very scalable, from low bit rates to very high. It also allows developers to control objects independently in a scene, and therefore introduce interactivity.

MPEG-7 - this standard, currently under development, is also called the Multimedia Content Description Interface. When released, the group hopes the standard will provide a framework for multimedia content that will include information on content manipulation, filtering and personalization, as well as the integrity and security of the content. Contrary to the previous MPEG standards, which described actual content, MPEG-7 will represent information about the content.

MPEG-21 - work on this standard, also called the Multimedia Framework, has just begun. MPEG-21 will attempt to describe the elements needed to build an infrastructure for the delivery and consumption of multimedia content, and how they will relate to each other.

JPEG stands for Joint Photographic Experts Group. It is also an ISO/IEC working group, but works to build standards for continuous tone image coding. JPEG is a lossy compression technique used for full-color or gray-scale images, by exploiting the fact that the human eye will not notice small color changes.

JPEG 2000 is an initiative that will provide an image coding system using compression techniques based on the use of wavelet technology.

DV (Digital Video) is a high-resolution digital video format used with video cameras and camcorders. The standard uses DCT to compress the pixel data and is a form of lossy compression. The resulting video stream is transferred from the recording device via FireWire (IEEE 1394), a high-speed serial bus capable of transferring data up to 50 MB/sec.

H.261 is an ITU standard designed for two-way communication over ISDN lines (video conferencing) and supports data rates which are multiples of 64Kbit/s. The algorithm is based on DCT and can be implemented in hardware or software and uses intraframe and interframe compression. H.261 supports CIF and QCIF resolutions.

H.263 is based on H.261 with enhancements that improve video quality over modems. It supports CIF, QCIF, SQCIF, 4CIF and 16CIF resolutions.

H.264, also known as MPEG-4 AVC (Advanced Video Coding), is a video compression standard that offers significantly greater compression than its predecessors. The standard offers up to twice the compression of the current MPEG-4 ASP (Advanced Simple Profile), in addition to improvements in perceptual quality. The H.264 standard can provide DVD-quality video at under 1 Mbps, and is optional for full-motion video over wireless, satellite, and ADSL Internet connections.

DivX Compression

DivX is a software application that uses the MPEG-4 standard to compress digital video, so it can be downloaded over a DSL/cable modem connection in a relatively short time with no reduced visual quality. The latest version of the codec, DivX 4.0, is being developed jointly by DivXNetworks and the open source community. DivX works on Windows 98, ME, 2000, CE, Mac and Linux.

Terms

ISO/IEC

International Organization for Standardization - a non-governmental organization that works to promote the development of standardization to facilitate the international exchange of goods and services and spur worldwide intellectual, scientific, technological and economic activity.

International Electrotechnical Commission - international standards and assessment body for the fields of electrotechnology

Codec - A video codec is software that can compress a video source (encoding) as well as play compressed video (decompress).

CIF - Common Intermediate Format - a set of standard video formats used in video conferencing, defined by their resolution. The original CIF is also known as Full CIF (FCIF).

QCIF - Quarter CIF (resolution 176x144)
SQCIF - Sub quarter CIF (resolution 128x96)
4CIF - 4 x CIF (resolution 704x576)
16CIF - 16 x CIF (resolution 1408x1152

Reference:
http://www.wave-report.com/tutorials/VC.htm

MPEG-4 vs H.264 Video Compression Technology

Despite its pristine technology, why is it that a lot of CCTV Installers still prefer MPEG-4 DVRs over the more advanced H.264 DVRs? Would there be anything (functions or processes) that you can do better with MPEG-4 Videos that you cannot seem to execute falwlessly with H.264 Videos? Do you believe that the MPEG-4 Video Compression Technology will soon be obsolete and casted off the CCTV market thru the advancement of the H.264 Video Compression Technology? Your comments, opinions, relevant knowledge and information are mostly welcome.


Stated below is a General Comparison of the MPEG-4 and H.264 Video Compression Technologies:

Overview of MPEG-4 Encoding Format:

• MPEG-4 is a standard used to compress audio and visual data. The MPEG-4 standard is generally used for streaming media and CD distribution, video conversation, and broadcast television. MPEG-4 incorporates many features of MPEG-1, MPEG-2 and other related standards.

• MPEG-4 is still a developing standard and is divided into several parts. The standard includes the concept of “profiles” and “levels,” allowing a specific set of capabilities to be defined in a manner appropriate for a subset of applications.

• MPEG-4 is able to crunch massive video files into pieces small enough to send over mobile networks. While these blurry pictures are unlikely to persuade millions of people to upgrade immediately their mobile phones but holds enough promise for future.

• Perhaps more important are the interactive features that MPEG-4 offers. The video functions almost like a Web page, but allowing people to interact with the picture on the screen or to manipulate individual elements in real time.

• MPEG-4 also allows other types of content to be bundled into a file, such as video or images. These files require special software to play.

• MPEG-4 would allow the interactivity of the video which may open potential to do far more than just point and click at links on the screen. Individual elements of the video like a character, a ball in a sporting event, a rocket ship in a science-fiction epic can exist in a separate layer from the rest of the video. This could allow viewers to interact with these elements somehow, even changing the direction of the story.

Overview of H.264 Encoding Format:

• Also known as MPEG-4 Part 10 or AVC (for Advanced Video Coding).

• Poised to become the next standard for format of convergence in the digital video industry regardless of the video playback platform . Big Internet players like Google/YouTube, Adobe, and Apple iTunes are all backing this cross-platform format.

• H.264 standard is jointly maintained with MPEG so that they have identical technical content.

• The intention behind H.264/AVC project was to provide good video quality at substantially lower bit rates than previous standards. An additional goal was to provide enough flexibility to allow the standard to be applied to a wide variety of applications on a wide variety of networks and systems.

• H.264/AVC/MPEG-4 Part 10 contains Multi-picture inter-picture prediction including the features like using previously-encoded pictures as references in a more flexible way than in past standards, allowing up to 32 reference pictures to be used sometimes.

• H.264 provides quarter-pixel precision for motion compensation enables very precise description of the displacements of moving areas. For chroma the resolution is typically halved both vertically and horizontally, therefore the motion compensation of chroma uses one-eighth chroma pixel grid units.

• H.264 provides six-tap filtering for derivation of half-pel luma sample predictions, to lessen the aliasing and eventually provide sharper images.

• H.264 provides flexible interlaced-scan video coding features, includes Macro block-adaptive frame-field (MBAFF) coding, using a macroblock pair structure for pictures coded as frames, allowing 16×16 macroblocks in field mode compared with 16×8 half-macroblocks in MPEG-2. An enhanced lossless macroblock representation mode allowing perfect representation of specific regions while ordinarily using substantially fewer bits than the PCM mode. Picture-adaptive frame-field coding, allowing a freely-selected mixture of pictures coded as MBAFF frames with pictures coded as individual single fields (half frames) of interlaced video.

• H.264 is more attractive for video network delivery and for delivery of HD, high definition video.

• H.264 or AVC is an open format with published specification and is available for anyone to implement.

Reference: http://www.reelseo.com/encoding-formats-mpeg4-vs-h264/