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Does S--Video completely bypass the comb filter?


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9 replies to this topic

#1 of 10 Frank@N

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Posted June 25 2004 - 03:54 AM

I'm a little fuzzy on this point.

My recollection is that S-Video keeps two of the picture elements separate (but allows the 3rd to be combined with one of the other signals).

This is a compromise compared to component video (all three separate).

When using a newer set with a superior comb filter, would it be better to just use composite video instead of S-video (assuming no component is available on source)?

Question pertains to VCR & game systems which have S-Video and composite only.

#2 of 10 Don_Berg

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Posted June 25 2004 - 05:39 AM

Yes in many cases using composite can be better than s-video if your display has a good-quality comb filter which is only used with the composite input. Especially if the external source is composite in nature like from an analog source. Just try both of them and compare different scenes if you want to be sure. Look for artifacts like dot crawl to compare.

#3 of 10 Leo Kerr

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Posted June 25 2004 - 06:05 AM

On the other hand, if you're dealing with a 'source' - that is a game machine, it should be starting with component video, even if it only outputs Y/c and composite. If that it the case, the S-video output of that box should be superior to even what your set does.

If you have S-VHS tapes, use the S-video output of the deck. If you have VHS tapes, well, I'd personally recommend the shredder, but.. with respect to your situation, do, by all means, compare the two. In my case, my laserdisc had a superior color seperator to the set it was playing to, so even though it is a composite source, it did a better job than the TV.

Leo Kerr

#4 of 10 Richard Paul

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Posted June 25 2004 - 11:06 PM

For any source that is encoded in component video, or S-Video such as pre-recorded S-VHS, than S-Video will give a far better picture than composite. In fact the leap from composite to S-Video is even greater than the leap from S-Video to component. Every game console since the Dreamcast will have a very noticeable improvement in picture quality when using S-Video instead of composite.

If you have an S-VHS VCR you will get a better signal from it only if it can also record from S-Video (such as from digital cable or DirecTV). If you are receiving analog cable the improvement from outputting your VCR in S-Video will be small.

S-Video keeps the brightness or luma of the signal seperate from the color or chroma of the signal. Though S-Video still has some chroma artifacts it has a far sharper picture than composite. This is because S-Video completely avoids luma artifacts which cause a blurred picture that even the best comb filter can't fix.

#5 of 10 Leo Kerr

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Posted June 26 2004 - 02:21 AM

If you want an excellent explanation as to what is going on and why, consult:


Kookie, Kookie, Lend me your comb.


Leo

#6 of 10 Patrick Sun

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Posted June 26 2004 - 03:46 AM

I usually watch composite video because I tend to not like the honeycomb effect I see when viewing content via the S-video input.
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#7 of 10 Richard Paul

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Posted June 26 2004 - 08:26 AM

Patrick after searching on the forum I've found a reference to a honeycomb effect on this thread. Could it just be that the S-Video input is defective? Or could it be how certain televisions process S-Video signals? A S-Video signal is one step away from component video. As such do you notice the pattern on a component video signal?

#8 of 10 Allan Jayne

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Posted June 26 2004 - 02:59 PM

The S-video input port bypasses the comb filter in that piece of equipment. If the S-video source material was composite in an earlier life, it must have gone through a comb filter (or other Y/C separator such as a notch filter) elsewhere.

The fact that in S-video the third component [of component video] is combined with one of the other two does not mean you should use composite video which essentailly has all three components combined. (In S-video essentially the Pb and Pr are combined while the Y stands alone. Having to separate just the Pb and Pr leads to a much better picture compared with having to separate the Y as well.)

Laserdisk is fundamentally composite so you should try both the composite and (if present) S-video LD player outputs to see which looks better.

All non-digital consumer VCR tapes including regular VHS are recorded with luminance and color separate, and the S-video VCR output (unfortunately not available on regular VHS VCR's) can give a slightly better picture compared with composite. S-VHS VCR's almost always have better Y/C separation filters than regular VHS VCR's and this gives better picture quality on recorded TV shows even when recording in regular VHS mode.

Video hints:
http://members.aol.c...ynejr/video.htm
.

#9 of 10 Richard Paul

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Posted June 27 2004 - 10:47 AM

Allan, I believe that VHS is composite based while S-VHS has luma and chroma recorded separately. There is a post that explains it here.

#10 of 10 Patrick Sun

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Posted June 27 2004 - 11:16 AM

I've seen the honeycomb effect on all three of my TV's s-video inputs (an 8 year old Sanyo RPTV, a 5 year old 27" Toshiba TV, and a 2 year old Panasonic HDTV/RPTV). I don't see the honeycomb effect on the component video input on my newer Panasonic HDTV/RPTV. This issue doesn't bother me much since I'd rarely view video sources via the s-video input anyway and when I watch video from a VCR or my ReplayTV, I am not all that hung up on video quality for time-shifted programming.
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