topical media & game development
research directions -- digital video formats
In the online version you will find a brief
overview of
digital video technology, written by Andy Tanenbaum,
as well as some examples of videos of our university,
encoded at various bitrates for different
viewers.
What is the situation?
For traditional television, there are three standards.
The american (US) standard, NTSC,
is adopted in North-America, South-America and Japan.
The european standard, PAL, whuch seems to be
technically superior, is adopted by the rest of
the world, except France and the eastern-european countries,
which have adopted the other european standard, SECAM.
An overview of the technical properties of these
standards, with permission taken from Tanenbaum's account,
is given below.
| system |
spatial resolution |
frame rate |
mbps |
| NTSC | 704 x 480 |
30 |
243 mbps |
| PAL/SECAM |
720 x 576 |
25 |
249 mbps |
Obviously real-time distribution of a more than
200 mbps signal is not possible, using the nowadays available
internet connections.
Even with compression on the fly, the signal would require
25 mbps, or 36 mbps with audio.
Storing the signal on disk is hardly an alternative,
considering that one hour would require 12 gigabytes.
When looking at the differences between streaming
video (that is transmitted real-time) and
storing video on disk, we may
observe the following tradeoffs:
| item |
streaming |
downloaded |
| bandwidth |
equal to the display rate |
may be arbitrarily small |
| disk storage |
none |
the entire file must be stored |
| startup delay |
almost none |
equal to the download time |
| resolution |
depends on available bandwidth |
depends on available disk storage |
So, what are our options?
Apart from the quite successful MPEG encodings,
which have found their way in the DVD,
there are a number of proprietary formats
used for transmitting video over the internet:
formats
Quicktime, introduced by Apple, early 1990s, for local viewing;
RealVideo, streaming video from RealNetworks; and
Windows Media, a proprietary encoding scheme fromMicrosoft.
Examples of these formats, encoded for various bitrates
are available at Video at VU.
Apparently, there is some need for digital video
on the internet,
for example as propaganda for attracting students,
for looking at news items at a time that suits you,
and (now that digital video cameras become affordable)
for sharing details of your family life.
Is digital video all there is?
Certainly not!
In the next section, we will deal with standards
that allow for incorporating (streaming) digital video
as an element in a compound multimedia presentation,
possibly synchronized with other items, including
synthetic graphics.
Online, you will find some examples
of digital video that are used as texture maps
in 3D space.
These examples are based on the technology presented
in section [7-3], and use the streaming
video codec from Real Networks that is integrated
as a rich media extension in the
blaxxun
Contact 3D VRML plugin.
comparison of codecs
A review of codecs,
including Envivio MPEG-4, QuickTime 6, RealNetworks
9 en Windows Media 9 was published januari 2005 by
the European Broadcast Union.
It appeared that The Real Networks codecs came out best,
closely followed by the Windows Media 9 result.
Ckeck it out!
(C) Æliens
04/09/2009
You may not copy or print any of this material without explicit permission of the author or the publisher.
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