S-Video hack for DTV converter box?

I like the programmable feature of the DTV Pal (Dish Network) converter box. The one drawback is that it doesn't output S-Video.
I haven't received it yet, so I can't crack it open and give component specifics but are the video chips that are common in these boxes capable of both composite and S-Video output? Is it likely that only a connector and a bit of wire is all that is needed for a slightly better signal output?
Thanks,
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DaveC wrote:

It would be much simpler to buy a composite to s-video adapter. Places like MCM Electronics sell them for $4.99 (part number 33-0001 for the "S" male to RCA female version).
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Yeah, but then the image quality is no better than the original composite signal. For a larger TV set, this difference is noticeable.
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Yeah, the whole purpose for adding a S-Video connector isn't for convenience, but to get the video signals (ie separate Y & C signals) "prior" to the composite connector.
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wrote:

Is/was S-video ever really better quality signals than Composite video? My impression is that converting between the two was only a matter of routing the right pin.
Was the alleged higher quality (S-Video over composite) by virtue of the type of cabling as opposed to the signal sent through it?
http://www.mcmelectronics.com/product/DISTRIBUTED-BY-MCM-RGB-322G-/33-0001
$7.89
Features: This high quality adaptor converts composite video to S video and S video to composite video. With a male S VHS connector on one end and a female RCA type connector on the other (#33-0001), only a standard RCA type video cable is required for connection or you can match the S- video adaptor to your cables. The adaptor measures only 13/4" long and 1/2" in diameter allowing it to plug directly into the equipment and solves the problems associated with mixing composite and Svideo inputs and outputs. Note: This unit is a passive device and although it will allow composite video signals to be used in S video inputs the signal will remain the quality of composite video.
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Greegor wrote:

Yes.
http://www.epanorama.net/circuits/svideo2cvideo.html
Nope.
Expensive for a single cap.
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Adrian C

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S-Video sends the color (chroma) and brightness (luminance) information separately. Composite video sends them both as part of the same electrical signal.
A TV or monitor needs to deal with chroma and luminance separately in order to produce a color picture. If they're sent separately (via S-Video) they're pretty much ready to use. If they're sent together (as a composite signal) the TV has to separate them before using them.
Unfortunately, the chroma and luminance parts of a composite-video signal actually overlap (in the frequency domain). This makes it difficult for the TV to separate them cleanly - the process of filtering one out of the other tends to create artifacts (e.g. "dot crawl" at brightly-lit edges).
Many video-source devices (e.g. digital set-top boxes) can and do create the chroma and luminance signals separately. Sending them to the TV via separate wires, and avoiding the "combine them, and then filter them apart" step, eliminates the artifacts-of-filtering-them- apart, and thus gives you a better-looking image.
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> wrote: >
> > > > > > > It would be much simpler to buy a composite to s-video adapter. > > > Yeah, but then the image quality is no better than the original composite > > signal. For a larger TV set, this difference is noticeable. > > Is/was S-video ever really better quality signals than Composite > video? > My impression is that converting between the two was only a > matter of routing the right pin. > > Was the alleged higher quality (S-Video over composite) > by virtue of the type of cabling as opposed to the > signal sent through it?
Yes - provided there was sufficient bandwidth of he components > > http://www.mcmelectronics.com/product/DISTRIBUTED-BY-MCM-RGB-322G-/33 ... > > $7.89 > > Features: > This high quality adaptor converts composite video to S video and S > video to composite video. With a male S VHS connector on one end and a > female RCA type connector on the other (#33-0001), only a standard RCA > type video cable is required for connection or you can match the S- > video adaptor to your cables. The adaptor measures only 13/4" long and > 1/2" in diameter allowing it to plug directly into the equipment and > solves the problems associated with mixing composite and Svideo > inputs and outputs. > Note: This unit is a passive device and although it will allow > composite video signals to be used in S video inputs the signal will > remain the quality of composite video.
The worst thing to happen to composite video is to mix the cubcarrier onto the 'Y' channel because separating them out can bve real easy (cheap trap, poor performance) or difficult (expensive comb). The cheapy adaptor isn't even a trap in that there is still subcarrier on the 'Y' channel. The best separators are the digital 3 line combs which some of the expensive TVs have in them. They come _very_ close to component but cost more.
G
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Thanks, guys.
But i'm talking about a soldering iron hack. I guess what I want to know is whether the Y and C signals are commonly available on pins of a video chip used in many of these TV converter boxes. I have no qualms about running conductors from pins on an IC to an epoxied-in S-video connector.
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It depends on exactly which chip is used for the output of the box. Datasheets are often availalble for many chips on-line as freebies. There are almost always examples of how to use the chip which would likely include S-video if the chip is capable of it. So, it's time to peel off the lid and tell us what chips are actually in the box.
G
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When it arrives, I'll do that.
Thanks,
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DaveC
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Yes S-video is technically better and in real life usually noticeable better than composite video. Especially when the the video source and/or receiver side are not up to be best "professional video" quality, the composite video picture quality is often not the best possible and S-video is considerably sharper especialy on demandign material (for example computer screen graphics to TV). Very good professional video equipment can work with composite video signal from cameras so well that it is hard to tell if composite video or S-video interface is used.

It is more than that. Converting from S-video to composite video is just matter of combining signals from two pins on S-video connector to one signal pin on composite video connector. Simplest as simple as this http://www.epanorama.net/circuits/svideo2cvideo.html
Y-ground------------------+ +---------- RCA/composite ground C-ground------------------+
Y-------------------------+ +--------- RCA/composite video C------------||-----------+ 470pF
The opposite direction, from composite video to S-video, with good image quality is much much more complicated. It can be done with some passive filtering circuitry with not very optimal picture quality (needs different component values for PAL and NTSC video standards). Very good quality will need pretty complicated signal processing circuitry.

I have my doubts on the quality it can do the composite video to S video conversion. With such passivode converter the result could be anything from not so good to useable, but never "crystal clear". With good quality equipment that has composite video input and S-video inputs, wiring the composite vidoe signal to composite video input will give you better image quality than with passive composite video to S-video converter to S-video input. The best image quality would be available if you can get S-video from your signal source to S-video input on display device (or some even better video interface if you have such option).
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| DaveC wrote: |> I like the programmable feature of the DTV Pal (Dish Network) converter box. |> The one drawback is that it doesn't output S-Video. |> |> I haven't received it yet, so I can't crack it open and give component |> specifics but are the video chips that are common in these boxes capable of |> both composite and S-Video output? Is it likely that only a connector and a |> bit of wire is all that is needed for a slightly better signal output? |> |> Thanks, | | It would be much simpler to buy a composite to s-video adapter. Places | like MCM Electronics sell them for $4.99 (part number 33-0001 for the | "S" male to RCA female version).
The whole point of S-video is to avoid ever combining the Y and C signals in the first place, because it is so hard to separate them. You might as well let the TV's composite input separate them, unless the composite to S-video converter you get is a "perfect" design (and this would be very expensive).
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While easier, that is just "not" the same thing.
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There is a list of converters with S-video here: http://www.ezdigitaltv.com/Additional_Features_Matrix.html
John
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