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The Story Behind: Digital Compression Technology
Media Magic on the Smallest Screens
Video has come a long way from the earliest days of moving pictures when the images from Thomas Alva Edison's and William K.L. Dickson's Kinetoscope first flickered in the 1890s. In just a little over a century, technology has moved from celluloid filmstrips to magnetic tape to digital media capable of being transmitted anywhere in the world - even to mobile phones.
The age of digitised video started with the professionals, with analogue video equipment makers Bosch, RCA and AMPEX each developing a digital video recorder (DVR) in their R&D labs during the late 1970s.
It was Sony that first came up with a commercial product in 1986, introducing the Sony D-1, a format for uncompressed component digital video recording. It was an expensive technology accessible only to the professional television industry. More problematic, uncompressed digital video creates an exceptionally large data file, approximately 270 Mbits per second. Even with the advent of high-bandwidth internet options such as DSL, cable and even Wi-Max, digital video can go nowhere without compression technology to make it storable and transferable.
The basis of digital video compression is Differential Pulse Code Modulation (DPCM), developed in 1980 by Italian engineer and inventor Leonardo Chiariglione and colleagues at Telecom Italia's CSELT laboratory. DPCM breaks-down video information into small packages of data. An analogue signal is sampled and the difference between the actual sample value and its predicted value is quantised and then encoded, forming a digital value. Using algorithms that evaluate the differences between frames, video "codecs" (from "code-decode") evaluate the amount of data that needs to be actually digitised and the amount that can be "predicted" mathematically.
Rapid compression
Two agencies took the lead in pushing for the standardization of digital video compression: the International Telecommunications Union (ITU) and the International Standards Organization (ISO). The ITU developed the H.261 in 1988, addressing mainly the real-time application of video conferencing.
That same year, Chiariglione established the Motion Pictures Experts Group (MPEG) as a working group of the ISO. Their first order of business was to find a standard for digital video storage, and in 1993, the MPEG-1 format was developed, allowing digital video and related audio to be stored on a CD-ROM at the rate of 1.5 Mbit per second.
The next leap forward was in 1994 with the MPEG-2 standard, allowing storage and transfer at rates of 4-9 Mbits per second. MPEG-2 opened up digital video technology to the home user by making High-Definition TV (HDTV) and Digital Versatile Discs (DVDs) possible. With the introduction of MPEG-4 in 1999, digital video became feasible for multimedia streaming over the internet, videophones and advances in HDTV; this format continued to evolve over several years.
Meanwhile, the ITU had continued upgrading its video telephony standards, culminating in the release of H.263 in 1995. Shortly after, the organization's Video Coding Experts Group (VCEG) started looking for a standard designed for low-bitrate visual communications, resulting in the draft standard H.26L, which offered significantly better video compression over previous standards.
VCEG and MPEG joined forces in 2001, creating a Joint Video Team to develop an international standard. The result, introduced in 2003, was two identical standards: ISO MPEG-4 part 10 and ITU H.264, often referred to as MPEG-4 Advanced Video Coding (AVC). With nearly double the compression rate as MPEG-2, the MPEG-4 AVC format has been adopted in a range of industries.
HDTV broadcasters around the world are implementing the standard; Apple Computers has incorporated it since its Tiger operating system in Quicktime, iChat and iPod, among other applications; home entertainment game systems such Sony Playstation and Microsoft Xbox use it; the 3G Partnership Project is advocating it in the development of global multimedia telephony services - the list goes on.
Protecting the future of digital media
In 2003, Chiariglione founded the Digital Media Project (DMP), a non-profit organisation with a mission to "promote the successful development, deployment, and use of digital media, while safeguarding the rights of creators and rights holders to exploit their works, the wishes of end users to enjoy fully the benefits of digital media, and the interests of value-chain players providing products and services".
With members including networks and media corporations from 21 countries, the DMP has developed digital rights management (DRM) interoperability standards and platforms. At its 17th General Assembly in January 2008, DMP announced it is also on a major project called "WIM TV trial at Beijing Olympics" that will stream user-generated video content governed by DRM technologies developed by the DMP.
As the information highway stretches endlessly around the world, digital compression technology will continue to make sure the media files are small enough to share the road.
Read more about the inventor: Leonardo Chiariglione (Italy)