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.]