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MPEG-4 and the New, 'Flat' World
9/29/2004
Interestingly, from a purely technical perspective, MPEG-4 has been compared to and considered an upgrade of MPEG-2. And in truth, MPEG-4 can offer the same image and sound quality as MPEG-2. But here’s the difference: with MPEG-4, the needed bandwidth can be reduced by as much 50 percent, for the same quality. In other words, by replacing MPEG-2 with MPEG-4, the sender can double the number of channels being sent over the same bandwidth.
In fact, with the new MPEG-4.10 AVC (Advanced Video Coding) standard being readied for prime time, manufacturers are now creating open and standards-based codecs that will ultimately simplify the encoding and the decoding of streams of multimedia information at varying baud rates. The form factor for this new capability may be hardware or software within a PC, or may be a stand-alone appliance. Like most technology today, cost, functionality, and ease of use will become the deciding factors in determining which system is used and in which environments.
But let’s talk more about this new standard....
Looking at the Standard
In 2003, the ISO standard designation MPEG-4 Part 10/AVC (Advanced Video Coding) was developed and approved for the broadcast television industry. MPEG-4 (also known as ITU-T H.264) was seen to be the next step beyond the high-definition (HD) TV MPEG-2 standard. But high-definition TV requires 19 Mbps, while a standard-definition (SDTV) picture requires only 4 Mbps. Furthermore, some information channels, such as HTML images, need only a few thousand bits per second. So, just where will MPEG-4 find its home? MPEG-4 has the capability to effectively utilize whatever bandwidth is available between the sender and the receiver. And as bandwidth is clearly a constraining factor—and more and more we are moving to an all-digital system—MPEG-4 augments and may well replace MPEG-2 in the future. Multimedia images will be enabled not only in the living room but anywhere a cell phone or computer can be used, wired or wirelessly.
Where’s the Magic?
The magic lies in the “scheme” of things: Unlike MPEG-2, which follows the old scheme of sending static images of the entire scene one after another, MPEG-4 is an object-based encoding scheme. With MPEG-4, individual objects that make up the image or sound are created and sent with location and timing information for the display. At the decoder, these objects are then reassembled and presented, based on the requirements of the display system. That means that if the display system has the capacity for many colors, levels of brightness, depth of rendition, and motion handling at XGA resolution, then a higher baud rate signal will be required. However, if the display device is a browser on a dial-up connected computer, then the baud rate requirements would be considerably less.
You may be asking: Hasn’t all this capability been possible before MPEG-4? The answer is yes, though with the systems prior to MPEG-4, this would have required one encoder or translator for each delivered baud rate transmitted. The cost and complexity of using and managing such a system have been barriers to the success now expected with MPEG-4.
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