The simple fact is that for any photograph,
compression throws away pixels, and consequently picture quality
and resolution. There are many different compression
techniques available for still pictures. However, there are basically
only two compression techniques that are broadly supported for pictures, gif
and jpeg, and two video compression standards, MPEG 1 and MPEG 2. It is not much use having a proprietary compression
technique, when nobody can view the picture - a bit like saying
that the English language is not that efficient, so from today we
will use the "Xenfader" language.
Still, frame compression uses different techniques to compress the
picture. The basic approach is to split the picture into regions,
then find out if the same color is represented in a particular region
and share the pixels for that region. Different compression
techniques yield different results:
|Jpeg - Higher
|Jpeg - Lower
|We'll spare you
the download and send just a small section of the picture:
Clearly in the Jpeg - Lower Quality Image example, we have gone
too far with the compression and far too much quality is lost.
Picture size is not the only issue.
DVD video uses highly advanced compression to cut the volume of
data in not only the still frames, but also from frame to frame.
DVD uses MPEG 2 (Moving Picture
Exchange Group 2) compression. MPEG first of all compresses
the individual picture frames, then transmits only the changes in
the picture from frame to frame with an index frame transmitting
the whole picture every now and then. For example, if the camera
was fixed on the tiger example above, the background and much of
the tiger would remain the same, only the mouth of the tiger changes
as it yawns. Only the pixels that change around the mouth
region are transmitted in the next frame. Remember to achieve
smooth motion you need to send 29.7 frames (pictures) for every
second of video.
MPEG 2, the mainstay of video compression, does a great job compressing
video. MPEG 4 is essentially the same, with some interactive
features. Considering that the uncompressed VGA stream at
221 Mbs is compressed down to 6 Mbps to only 3% of it's original
size, MPEG 2 does a great job. However, the
ability to compress a video is largely dependant on the type of
video. If we are shooting steady shots without
much movement from a fixed camera, we can achieve large compression
rates while maintaining reasonable quality. However, if we
are shooting fast moving action from a hand held camera, such as
the generation-X type movies, then the ability to compress the video
stream and maintain quality is eliminated.
6 Mbps Now, What About
Video and movies today are tending towards faster action and shorter
frames, eliminating our ability to maintain quality and high compression.
Ten years ago, the typical movie shot lasted three seconds, today
most generation-X shots are one second.
IT's quite simple, consider if a pixel region on the video changes
from one frame to the next - if the video moves fast and it
does change, then you need to transmit a new pixel color to replace
the old one.
Bandwidth requirements for DVD quality video and up, start at 6
Megabits per second and go higher. Soon we will
probably well exceed the 24 Megabit bandwidth requirement of HDTV,
particularly as we move into the virtual reality world where we
use 32 bit or even 64 bit planes.
The Bottom Line
"The bottom line is that those who claim to deliver quality on-demand
video over regular Internet, need their pixels read."
CLive. IT's simple
math, you need a 6 Mbps pipe just to get into the quality game,
and that's ignoring the enormous I/O (input and output) requirements
and multimedia standards support.
Consider 50 million homes watching DVD quality video on-demand
in the U.S. alone. That's 300,000,000 Megabits per second
bandwidth, or three hundred thousand fiber optic cables all equipped
with the latest technology out of the labs, supporting a Terabit
per second per fiber. And that's not even considering if Dad
wants to watch a different movie to Son or Daughter, let alone Mum's
choice. What about the rest of the world, let's not forget
China and India, why should they too not receive the same quality
InfoTelesys' way is the only way to deliver
on-demand, high quality video, we are building the bandwidth to handle
the enormous I/O. We support the multimedia standards.
InfoTelesys' IT-IT™ can deliver well into the Petabit bandwidth
range, even well into and beyond the Exabit bandwidth range.
This is IT™, InfoTelesys, The Next Internet™.