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Many Media Standard

Thirty years ago when students at the University of California, Berkeley, devised the first algorithms for making video compression possible, applications were non-existent. But time and circumstances provided an outlet in the form of MPEG.

Simply put, MPEG (pronounced em-peg) stands for Moving Picture Experts Group. And also refers to a family of international standards used for coding audio-visual information as used by movies, video or music in a digital compressed format.

Established in 1988, the MPEG working group of experts (formally known as ISO/IEC JTC1/SC29/WG11) is part of JTC1, the Joint ISO/IEC Technical Committee on Information Technology. The MPEG group's convener is Leonardo Chiariglione aka "The Father of MPEG." ISO/IEC was awarded the 1995-1996 Engineering Emmy for Outstanding Achievement in Technological Development by the National Academy of Television Arts and Sciences.

So far there are several digital compression schemes that use proprietary names. These include QuickTime, AVI, JPEG, MOV, ASF, Video for Windows and Indeo. However, the most prominent and promising remains MPEG. Its major advantage as compared to other coding formats is that MPEG files are much smaller. This has resulted in multimedia files whose integrity and quality takes advantage of sophisticated compression techniques. MPEG files can be decoded by special hardware or by software. All versions of Windows include a built-in Media Player that supports most format. Sometimes you may need to install additional readers or software format processors.

To describe how MPEG work in brief. It achieves a high compression rate by storing only the changes from one frame to another; instead of each entire frame. There are three types of coded frames: I, P and B. Basically you have to search for matching blocks in those frames, and try different things to see which works best for the file.

The video information is then encoded using a technique called DCT (discrete cosine transforms). The basic scheme is to predict motion from frame to frame in the temporal direction, and then DCT to organize the redundancy in the spatial directions. The resultant interaction of the DCT coefficients, the motion vectors, and the quantization parameters is then coded using special Huffman tables. MPEG uses a type of lossy compression, since some data is removed. But the diminishment of data is generally imperceptible to the human senses.

MPEG approaches the growing need for multimedia standards step-by-step. Over the years, the MPEG group has continued to develop formats with higher compression and quality that allow improved playback of digitally stored video and audio over devices like our PCs.

Today, the MPEG family of standards includes three defined "phases": MPEG-1, MPEG-2, MPEG-4, formally known as ISO/IEC-11172, ISO/IEC-13818 and ISO/IEC-14496.

Completed in 1992, MPEG-1 is used for "Coding Moving Pictures and Associated Audio for Digital Storage Media at up to about 1.5 MBit/s". MPEG-1 consists of 4 parts, namely
IS 11172-1 (describes synchronization and multiplexing of video and audio);
IS 11172-2 (describes compression of non-interlaced video signals); IS 11172-3: (compression of audio signals); and CD 11172-4 (procedures for determining the characteristics of coded bit streams and the decoding process and for testing compliance with the requirements stated in the other parts).

The most common MPEG-1 implementations provide a video resolution of 352-by-240 at 30 frames per second (fps). This produces video quality slightly below the quality of conventional VCR videos. Today's popular MP3s are nothing but MPEG-1 Layer 3.

A newer standard, MPEG-2 is used for generic coding of moving pictures and associated audio. And offers resolutions of 720x480 and 1280x720 at 60 fps, with full CD-quality audio. This is sufficient for all the major TV standards, including NTSC, and even HDTV.

DVD-ROMs use MPEG-2. This can compress a 2 hour video into a few gigabytes. While decompressing an MPEG-2 data stream requires only modest computing power, encoding video in MPEG-2 format requires significantly more processing power.

Some derivations of MPEG-1 and MPEG-2 worked quite well. But MPEG-3 no longer exists; its been merged into MPEG-2. A new development is MPEG-4 (also known as DivX).

MPEG-4 is used for very low bit rate audio-visual coding. And is the latest offering from the ISO standards body. This new version is based on the QuickTime file format. But is much more advanced.

Its distinction lies in the fact that it's the first format update designed for the Internet. Application developers finally have the ability to shrink the size of multimedia files so that interactive video services are transmitted more quickly to computers, mobile devices and television set-top boxes. Heretofore, these features have only been available to users of Apple's QuickTime, Microsoft's Media Player or Real Networks' Real Media formats.

Even though you're comfortable using the current MPEG standard, eventually you may decide in favour of MPEG 4. Before you know it, you'll find MPEG 4 on your desktop. It can be either in a software update for your favorite player to run media files using this new standard or an application for editing digital videos. Since media players are free, you won't be charged for the step up, but if you've purchased editing software, then be prepared to receive notification for shelling out more cash in order to get your current tools up to snuff with MPEG 4.

If you're of the opinion that there are too many streaming media formats, top industry players like IDC, Minerva Systems, Gartner, Aztech Labs, Compaq, DAVIC and others would beg to differ. They're backing the support that MPEG 4 is getting from the Internet Streaming Media Alliance (ISMA). This is a technical trade organization attempting to create standards for streamed media software publishers and broadcasters. Recently, Phillips announced its plans to expand cooperation with Sun Microsystems on MPEG-4 data compression technology.

MPEG-4 also uses the same open standards approach that made Linux, Java and other Internet protocols free of proprietary corporate control. This means freedom from the stranglehold that Real Networks, Apple, and Microsoft have exercised over how multimedia works on the Internet, and promotion of the availability of new options in future. But whether MPEG 4 becomes the next big buzz is now dependent completely upon the users.

Amrita Ghosh
[email protected]

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