Video understanding

(system) #1

JPEG is the well known standard for compressing a single image, and MJPEG is simply a sequence of JPEG. MPEG-4 is one of the ‘motion codec’s’ (along with MPEG2, MPEG1, H.261, H.263) which look for matches between frames in order to just encode the differences, then match blocks that have moved their position from one frame to the next.
By exploiting the fact that in 25/30 fps video 90% of the scene remains the same, or has only moved its position slightly from the previous frame, MPEG-4 delivers much better compression than MJPEG (see table below).
The MPEG and H.26x standards, defined respectively by the ISO and the ITU organisations, have long followed ‘parallel paths’ but are coming together in the H.264 standard, which is also known as MPEG-4 Part 10.

Below is a table showing examples to enable you to compare compression technology.
Recording Comparison :
Compression Standards glossary (minimised)
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:
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 Video-CD, the most popular video distribution format throughout much of Asia.
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.
Standard for multimedia and Web compression. MPEG-4 is based on object-based compression, similar in nature to the Virtual Reality Modelling 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.
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.
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.

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 compression technique used for full-colour or grey-scale images, by exploiting the fact that the human eye will not notice small colour changes.
JPEG 2000
An initiative that will provide an image coding system using compression techniques based on the use of wavelet technology.
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 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.
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.
Based on H.261 with enhancements that improve video quality over modems. It supports CIF, QCIF, SQCIF, 4CIF and 16CIF resolutions.
H.264 (see our DVR range)
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 less than 1 Mbps, and is optional for full-motion video over wireless, satellite, and ADSL Internet connections.