From: bf.El_Segundo@XEROX.COM
Newsgroups: rec.video
Subject: Making the S Connection
Date: 14 Oct 92 17:29:32 GMT
Reply-To: bf.el_segundo@xerox.com
Organization: The Internet

I realize this has been answered often and well by many different contributors
to the Digest - but I did a little research and found it in one place

 -This was researched from a recent Stereo Review and is submitted in hopes of
putting the S-VHS/S-Video confusion to rest. :-)

	"The introduction of Super VHS brought with it a new type of multipin
video connector, called S-video or Y/C.  Although the connector itself was a
good idea that has since spread to Hi8 decks and camcorders, its debut in
tandem with S-VHS may not have been, since it has led to some great
misconceptions. Most important among these is the completely erroneous notion
that VCR's equipped with S connectors cannot be used except with similarly
equipped monitors. In fact, all VCR's with S connectors also have the usual
complement of composite-video and RF inputs and outputs and will perform very
nearly as well with those as they will with the S-video inputs and outputs.
	The other important misunderstanding is in the idea that the
performance improvements associated with S-VHS are somehow tied to the S-video
connectors.  In truth, S-VHS's single benefit-higher resolution-has to do only
with the bandwidth of the signal recorded on the tape, which the S connector
doesn't affect at all. The single benefit of the S connector, on the other
hand, is equally applicable to all consumer VCR formats, "super" or otherwise.
	To understand what this is all about, we have to know a little about
how a VCR works. When color was added to television, it was done by putting the
necessary information on a subcarrier plopped into the high-frequency end of
the luminance (black-and-white) signal. Black-and-white receivers ignore this
color (C) subchannel, but color sets extract the information it carries and use
it together with the luminance (Y) information in the baseband signal to
control the intensities of the beams from the three electron guns (for the red,
green , and blue primary colors) in the picture tube.  Performing this
separation is not easy, however, and it almost inevitably results in either a
loss of resolution or the creation of small, distracting artifacts, such as as
the "hanging dots" that you may notice from time to time crawling along sharp
horizontal transitions between areas of color.
	Professional videotape recorders and laserdiscs record the composite
video signal (Y+C, or luminance plus color) directly, but when home VCR's were
developed, bandwidth and other limitations forced a different approach, known
as "color-under" recording. The color information is separated from the
luminance signal and transposed down to a range of frequencies below those used
for recording the luminance. This degrades the resolution somewhat, but it's
better than going without color.
	When a videocassette is played back, the VCR normally recombines the
color and luminance information into a composite-video signal that then goes to
the monitor via a direct-video connection or gets modulated onto an RF carrier
with the audio and sent to the monitor via its antenna terminals.  Either way,
the monitor has to reseparate the color and luminance portions of the video
signal.  All an S-video connector does is to short-circuit this process,
keeping the luminance and color protions of the signal separate so that they
don't have to be combined and pulled apart again.  In most cases, this will
yield a slightly cleaner picture, but the benefit is likely to be marginal, at
best, unless the recorded color and luminance signals have always been
separate, never tangled together in a composite-video signal. Camcorder
recordings fall into this category, but that's about all.
	So why do some laserdisc players, which start with a composite-video
signal, have S-video outputs? To prevent consumers from thinking that they lack
a performance feature available on S-VHS and Hi8 VCR's.
The only way a Y/C output can do any good on a laserdisc player is if its
color-separation circuitry happens to be better than that in your monitor,
which is possible but not likely."


Cheers,
Bill