MPEG-4 and the New, 'Flat' World

With MPEG-4, you can expect to access and display multimedia information from myriad live sources while the information is also accessed remotely—no matter what type of connectivity is in use.

We laugh when we look back at the notion of a “flat” world—the world as it was perceived before Columbus proved it otherwise. But today, even faced with all the wonders of the Internet and other powerful networks, we often find ourselves cursing a world that isn’t flat. Flat, to us, would be a world where all network “receive” locations have the same level of transport speed and the same means of connectivity. In short, flat would be great.

Why Isn’t Our New World ‘Flat’?

As with the Internet, it’s impossible to make a ubiquitous network infrastructure totally flat. That’s because, generally, not all receive locations have the same level of transport speed or the same means of connectivity.

Today, high-definition still images, motion images, and audio are typically sent over separate channels and with different coding schemes. For example, today’s codec may utilize one form of compression for motion video, while another compression algorithm for still images is being interspersed when space is available. The protocols are generally proprietary and fixed in data rate between the sender and all receivers. This means that the user is stuck with proprietary technology at each end.

Yet, the receiving end of the stream must be able to dictate the connection in different ways. That means that if the receiver is a codec providing images to a video projector in a lecture hall, a large amount of bandwidth is required—even while a student taking part at home with a lower-speed connection can see the same image (albeit with fewer pixels). To put it more plainly, the receiving codec makes a connection only at the codec’s desired baud rate. Previously, to make our simultaneous lecture hall/home study scenario possible would have required data-rate conversion and multiple encoding devices, with one device per transmitted data rate/protocol. But that was before MPEG-4.

MPEG-4 to the Rescue

MPEG-4 offers the ability to provide various data rates to match the receiving codec demands, and the ability to display. It allows each receiving device to make use of different speeds based on the size and quality of the image to be presented, and bandwidth available. No additional equipment is required in the transmission path; rather, the decoder utilizes the bandwidth available and needed, based on the receiving device’s capabilities. To illustrate, the difference might be tantamount to seeing images full-screen on a laptop (XGA), versus seeing them on the color screen of a cell phone (sub VGA).

What d'es this advance mean to campus technologists, faculty, and students? What makes MPEG-4 such an important element in multimedia delivery? Simply this: Using this form of streaming, the instructor can access and display multimedia information from servers and other live sources at the room’s control center, while simultaneously, the multimedia information can be made available to persons in remote locations, irrespective of the type of connectivity in use.

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.

When ‘bleeding-edge’ MPEG-4.10 transmission over IP networks turns into standards-based products, the real excitement will begin for AV/multimedia on campus.
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.

Demise of the Scan/Standards Converter

Today, coding and decoding technology has fixed protocols and baud rates as required by the internal transmission systems. Selecting transmission using MPEG-2 or H.323 means the decoder must be matched to the coder with protocol and baud rate. Therefore, viewing an MPEG-2 image on an H.323 codec requires some means of standards conversion. Even if the coder and decoder are compatible and only the baud rate is different, some means of external baud rate conversion is still required. MPEG-4 proposes to remove the need for scan/standards/rate converters by enabling the receiving decoder to use only the bandwidth it has available and is necessary for the display.

Impact on the Smart Classroom

Thus far in our discussion, we’ve been looking at the original intent of MPEG-4 for the broadcast industry. But MPEG-4 will have pronounced impact on the world of education as well—no wonder higher ed and K-12 are also exploring its use! Currently, AV/multimedia trials of MPEG-4.10 transmission over IP networks are being conducted. And it is as these trials of somewhat bleeding-edge technology are turned into standards-based products, that the real excitement will begin. The driver may well be the ability to provide HDTV and SDTV broadcasting via DSL technology and cell phones, but understand this: The residual benefits of these developments will be educational uses. Educators will have achieved the means of delivering instruction without regard for time or place. With MPEG-4, students will be able to see and hear information on a wired PC or wirelessly connected laptop, PDA, or other mobile device (with the appropriate resolution and bandwidth constraints), while the same information is presented with a high-definition image locally. All this while your campus is utilizing available bandwidth more efficiently. Remember: MPEG-4 can send equal picture quality in one-half the bandwidth needed by MPEG-2.

Think, too, about the impact of the replacement of that H.323 codec, the set-top box, or the tuner in the classroom VCR/TV. Replace this “box” with a new MPEG-4 low-bit-rate encoder/decoder to send and receive video and audio to and from remote sites. Add a camera and microphone to a smart classroom system, and the room will be enabled to record what is presented and transmitted to receivers at the receiver’s selected baud rate. No additional equipment required. [For more about MPEG-4, visit www.m4if.com and www.mpeg.org.]

comments powered by Disqus