S-Video vs Composite Question
 

Alan Bealby wrote:

On Sun, 12 Mar 2006 05:30:59 -0600, wrote:


I just signed up for Comcast cable a couple of weeks ago and am
sending the signal, from the Motorola 6412 Digital Comcast Receiver,
to a standalone Philips Tivo.

After checking and double checking, it seems to me that I'm getting a
better picture, from the Tivo to TV, on composite video than on
S-Video.

Is that normal? I always thought the picture quality would be better
on S-Video.


It is a fairly common misconception that a S-Video connection will
always give a better video signal than a composite video connection.


afaik, if the manufacturers always stuck to
the real specs, s-video video is *always*
superior to composite video

problem is that there's a cheap way to offer
both connects on a unit (for composite and
s-video) which degrades one or the other (afaik,
from one ref that i've seen here in the last year)

in my own firsthand limited knowledge (and experience)
it's best to try both and go with what works best.
for me, so far, that's been s-video (one instance)

bill



Given an equivalent quality video source, then it is usually true that
the quality of the video signal passed will improve as one goes from
composite video , to S-Video, to component video to digital video (
DVI or HDMI). However, this order may change depending on the length
and quality of the particular video cable and in some cases it will be
very hard to notice any difference.

The other reason the generalization is not necessarily true is that
the quality of the source is not always the same. In particular,
cable boxes often have a problem with analog cable channels. The
S-Video, component video and digital video outputs of a cable box
require processing of the analog video signal which would otherwise be
done in the TV or, in your case, by the Tivo. Cable boxes have been
notorious for their poor processing of the analog video channels and,
in a lot of cases, it is better to have the necessary processing of
these signals done in devices with better quality processing such as
the better quality TVs or recorders. This will depend very much on
what devices you have, their video processing capabilities and the
type of video connection you use.

Another factor in this equation is that analog TV displayed on large
screen TV's from the same distance that one would view a smaller TV
means that the large screen will show imperfections in the TV picture
quality more than a smaller screen does. Your cable box is for HD
pictures so if you have a large screen TV then you will be bothered
more by the poorer inherent quality of Standard Definition TV
exasperated by noise introduced by the poor video processing in the
6412 cable box.

Note there are reports that the newer model 6412 cable box with the
HDMI output has better processing of the analog channels so this
problem is eliminated or less significant for those cable boxes.

Unfortunately, you really have to try the particular combinations you
have available to see which connection has the least problem. There
is also the ease of use factor to consider. I have my 6412 cable box
connected with component video and composite video. I use the
component video for SD and HD digital channels and composite video for
analog cable channels. This gives me the best video quality. However
it is a nuisance to change the video source on my TV so I often will
not bother to switch video sources when changing to a analog channel
from a digital channel unless it starts to bother me too much or
unless I know I going to stay on an analog channel for a long time.

Alan Bealby
Remove no_spam from my E-Mail address

S-Video vs Composite Question
 

"Alan" wrote in message
...
Huh? Cable, ANALOG satellite (mostly the big dishes), and laser
discs (not DVDs), source composite signals with luma and chroma
combined. There is, as you say, little advantage to using a cheap
filter in those units instead of a good one in the television.

I was referring to the receiver end. It decodes the MPEG compressed signal
into YUV. To get composite, it has to be converted back to luma and chroma
and combined. The seem to find a way to screw it up at that point. Try it
sometimes. You will often find that the S-video output of a cable box or
sat receiver is worse looking than the composite.

DVD, Dish Network, DirecTV, most other digital satellite signals,
ATSC OTA digital, all have the signals coded separately. The mpeg
decoder outputs components, which have to be converted and combined
to produce composite. In the case of these units, it is almost always
better to *not* combine the signals to composite -- using s-video
would be a preferable choice (though using component would be even
better).

Video is encoded as component. Ideally, one would not want to combine to
composite after converting the YUV to YIQ. In the real world it might look
better using the component outputs. This can be because the processing is
sloppy in the source box, resulting in really lousy results. The bottom
line is that it depends and you have to try it. I have seen enough times
that the composite looks as good or better to not assume that S-video is the
way to go. Sometimes the combined signal comb filtered in the set just
looks better.


The specifics of processing are quite variable with equipment. I would
recommend trying both s and composite connections to see which is better.
When using VHS units which record the luma and chroma discretely there
will
likely be an improvement. With the previsously mentioned sources, it
depends, but the set will usually have the better filtering.

Yes, as you note, vhs, beta, 8mm/hi8, all use color-under recording
so there is some advantage to not combining the chroma and luma back
together for the trip to the display.


Alan

Like I said, it depends. The bottom line is use component when you can and
don't assume that S-video is better than composite.

Leonard

S-Video vs Composite Question
 

Leonard Caillouet wrote:
"Alan" wrote in message
...
Huh? Cable, ANALOG satellite (mostly the big dishes), and laser
discs (not DVDs), source composite signals with luma and chroma
combined. There is, as you say, little advantage to using a cheap
filter in those units instead of a good one in the television.

I was referring to the receiver end. It decodes the MPEG compressed signal
into YUV. To get composite, it has to be converted back to luma and chroma
and combined. The seem to find a way to screw it up at that point. Try it
sometimes. You will often find that the S-video output of a cable box or
sat receiver is worse looking than the composite.

DVD, Dish Network, DirecTV, most other digital satellite signals,
ATSC OTA digital, all have the signals coded separately. The mpeg
decoder outputs components, which have to be converted and combined
to produce composite. In the case of these units, it is almost always
better to *not* combine the signals to composite -- using s-video
would be a preferable choice (though using component would be even
better).

Video is encoded as component. Ideally, one would not want to combine to
composite after converting the YUV to YIQ. In the real world it might look
better using the component outputs. This can be because the processing is
sloppy in the source box, resulting in really lousy results. The bottom
line is that it depends and you have to try it. I have seen enough times
that the composite looks as good or better to not assume that S-video is the
way to go. Sometimes the combined signal comb filtered in the set just
looks better.


The specifics of processing are quite variable with equipment. I would
recommend trying both s and composite connections to see which is better.
When using VHS units which record the luma and chroma discretely there
will
likely be an improvement. With the previsously mentioned sources, it
depends, but the set will usually have the better filtering.

Yes, as you note, vhs, beta, 8mm/hi8, all use color-under recording
so there is some advantage to not combining the chroma and luma back
together for the trip to the display.


Alan

Like I said, it depends. The bottom line is use component when you can and
don't assume that S-video is better than composite.

Leonard

For a moment let's throw out the fact that some manufacturer's do a better job
than others at processing video. Theoretically, what is best?

S-Video vs Composite Question
 

"DanR" wrote in message
. com...
For a moment let's throw out the fact that some manufacturer's do a better
job
than others at processing video. Theoretically, what is best?

Theoretically, FWIW, keeping the luma and chroma apart would be best.

Leonard