Audio / Video Leads - Composite Video
Chances are, you should probably use composite video interconnect throughout
most of your Home Cinema. All VCRs and DVD players have PHONO composite video
jacks, as do most of today's TVs and receivers. Composite baseband video suffers
from RF interference to a lesser degree than RF video. At baseband video's typical
maximum frequency of about 5 megahertz, only low-frequency radio waves can interfere
with it. Still, this interference can cause problems similar to those you experience
with RF video interconnects, so Philex also double-shields its composite video
interconnects to prevent interference through the interconnect.
Composite
What about if your display device doesn't have an RGB, component or S-Video input?
Well, then we downconvert another notch to composite video. As its name suggests,
composite video is a single video signal that is a composite of the black-and-white
information (Y) and the colour information (C). This is the same type of signal
that at least some of us will have been using prior to the advent of DVD to connect
up our laserdisc players or VCRs.
Composite video signals have a number of unavoidable image problems because
of inherent limitations of the PAL and NTSC systems. The problem is, once the
colour (C) and the black and white (Y) information have been put together, they
can no longer be perfectly separated due to fundamental design limitations of
the two systems. Whilst a detailed description of these image problems is beyond
the scope of this article, there are two specific artifacts which I will mention
which are readily demonstrable.
Dot crawl. This occurs on the boundaries between two colours where you can
see moving blocks of incorrect colour information. The simplest way of demonstrating
this artifact is to look at a test pattern on your TV. If you have access to
either Video Essentials or A Video Standard on DVD or Laserdisc, take a look
at a colour bar pattern. In particular, look at the vertical edges between the
colour bars. You will notice that the edges are smeared, with little blocks of
moving colours throughout in a regular pattern. If you then compare this same
test pattern via an S-Video input, you will see that these blocks have disappeared,
and the edges of the colours are sharp and clear. What applies to a test pattern
also applies to normal images that are displayed with composite video. They,
too, will exhibit dot crawl at the boundaries of different colours on the screen.
Cross-colouration. You may be familiar with this artifact when watching a
black-and-white image on your TV, particularly if it is an older model. Fine
lines in the image result in a purple colour being displayed by the TV. If you
look at the test pattern shown on the right via a composite video output, you
will readily see if your TV is prone to this artifact. If you look at the same
test pattern via an S-Video input, you will not see this artifact.
- Labelled as: Either video, CVBS, composite, or baseband.
Usually in yellow colour.
- All DVD players have standard RCA (Cinch) baseband video
connectors. Connect either directly to a TV or to an AV receiver.
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