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Technical Explanation

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Firt, read these snippet of information (source: googling the web) to have a quick and dirty a-b-c in the sector:

S-VIDEO - Is made of 4 pins, 2 signal, 2 ground. The Chroma (C) signal gave you color, the Luminance (Y) signal which gave you black and white, Chroma is an extremely phase-sensitive signal.

Additional cable length or additional adapter meant additional extra delay, additional extra phase shift, and too much of it be resultant of wrong color or no color at all, no color by default is Luminance only which got through and is black and white. The meaning is: color--> one cable with it's own ground, luma--> one cable with it's own ground.

Composite - The Chroma signal is encoded as a color burst (still Phase-sensitive) within the Luminance signal (in the front-porch segment). The end is: all the signal is on one cable.

Scart - is a standard for a cable (not video signal) which can carry multiple signal: audio, video, rgb, composite, s-video and many more. Some where standardized, others are standard de-facto, meaning i build it, so it will work this way [brand_X], and this is not working for Brand_y... when using converters you generally loose audio, so you need separate RCA audio cables (normally, red and white).

Composite is LESS sensitive ("less sensitive" does not mean "impervious") to color loss than S-VIDEO from the fact that Chroma being embeded within Luminance partially compensated for the extra delay or extra phase shift (they shifted together better).

In composite video , the luminance signal is low-pass filtered to prevent crosstalk between high- frequency luminance information and the color subcarrier (essentially like FM receivers, multiple station filtered by your radio, so you can listen to one clear station at once). S-Video, however, separates the two (with two cables), so low-pass filtering is not necessary. This increases bandwidth for the luminance information, and also subdues the color crosstalk problem.

The luminance performance of S-Video is noticeably better than composite video; the chrominance performance with reduced crosstalk also shows noticeable improvement.

S-Video signals tend to degrade considerably when transmitted across more than 5 meters of cable with some cheaper S-Video cables.

Today, S-Video signals can be transferred through SCART connections as well. However the device that has the SCART connector must support S-Video as it is not part of the original SCART standard.

For instance, a VCR that has a SCART connector may not support S-Video, so if you try to connect an S-Video signal through a SCART connector you will get a black and white signal. To get color on devices that does not support S-Video, you can try to join pin 15 and 20 in the SCART-connector as described here (Sometimes the video card is just outputting the wrong signal on the wrong connector).

Basically, the pictures are saying the solutions, DID you see it? clues (cluedo rulez)? pay attention to PIN's functions.

Follow me: Scart Standard doesn't expect S-Video signal they do discard PIN 15 siagnal, BUT there adapters manufactured to do so.

(some) Modern TV are able to "discover" S-Video and handle it properly. Many Tv don'ts.

BUT TVs are (can) expecting Composite signal on PIN 20, that's all. Our S-Video laptop is pumping S-Video LUMA on pin20; ONLY Luma signal, aka gray-B/W images. Our TV is correctly picking up the poor signal on PIN 20 and display it. But, we are missing our C Croma-Color component... so... it is laying alone in PIN15... what if... we do a small bridge to bring C-Color and Y-Luma togheter on PIN20 ??

If we do, we are "creating" a full composite signal on PIN20, we bring the Color channel also on PIN20, our TV Pick it up and say "wow, thats a full regular composite signal, let's separate Luma and Color signal via some filtering" and we have COLOR on Tv !

Well, that's all, really. It wasn't so difficult at all, but someone got to do that.

[ UPDATE 4 gen 2006 ] Here is another view, let's say from the signal side. If you are not technicians don't worry, you may understand !


That's a logic schema of what is happening (only 24Kbit, thank you .PNG) little messy, but follow colored lines

Composite TV expect a dual signal on a single wire. For a composite signal they filter (2. purple square) and generate B/W and color signal. If we feed'em with (a dual signal dual wire) S-Video: they get only the first wire, filter and generate two signal: one B/W and the other is empty because the color signal is phisically on another wire , wire that TV ignores. Tv simply miss the signal, it is looking onto the wrong wire.

This trick is simply replicating color signal on both wires, so wherever Tv is reading and filtering it finds the B/W and Color signal.

That's all, in short:

  • We have in output a composite signal because our Tv can't understand S-video
  • The quality is "composite" because our Tv is composite (with filtering)
  • S-Video and Composite are the same signal, the same, the same but for s-video color and B/W are carried on separate wires; with composite TV need filtering
  • the quality loss is only only only when Tv is filtering. Filtering is a scary beast. Really.
  • remember to stay sgort on cables, commercial 1.5m (around) are ok; custom made are less ok... ;)

Now you can choose to go back to the "How To" or browse for "more file" ;)

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Question, info, suggetion, report ? did it worked, burns? fires? B/W again? totally black? ... maybe... COLORS !!!! mail me ! say something, to ask... or just because it is working :) let me know ! pleaseeeeee ;)